i
A GUIDE TO HUMAN ANATOMY
Emmanuel N. Obikili
ii
A GUIDE TO HUMAN ANATOMY
The aim of this guide is to help students know the course content, anatomical terminologies, and the type of questions to expect and how to prepare for examinations in Anatomy. Lecture notes on selected topics have been included as a guide. Although the guide is primarily meant for students preparing for examinations in Anatomy, it will also be useful to clinical students and resident doctors.
I am very grateful to Dr. C. O. Ohaegbulam for painstakingly going through the manuscripts and for preparing one of the lecture notes. I also wish to express my gratitude to Dr. W. C. Mezue, Rev Dr. T. C. Awuzie, Dr. C. Okpalike, E. O. Ewunonu and the other members of staff of Anatomy Department for their encouragement. Finally, I wish to thank Prof. F. C. Akpuaka who prompted me to write this guide.
This guide is dedicated to my past, present and future students.
All rights reserved. No part of the lecture notes may be reproduced in any form without the written permission of the author.
Emmanuel N. Obikili Senior Lecturer Department of Anatomy University of Nigeria, Enugu Campus 8th December, 1996.
Reprinted, 25 January 2007 E-book, 2 April 2019
Email: [email protected] iii
TABLE OF CONTENTS PREFACE ...... ii
TABLE OF CONTENTS ...... iii
1. INTRODUCTION. ANATOMICAL TERMS ...... 1
2. CLASSIFICATION OF BONES ...... 8
3. CLASSIFICATION OF JOINTS ...... 10
4. OSSIFICATION OF BONES (in collaboration with Dr C.O. Ohaegbulem) ...... 12
5. THE BREAST ...... 19
6. THE BRACHIAL PLEXUS ...... 22
7. THE RADIAL NERVE ...... 25
8. THE ARTERIES OF THE UPPER LIMB ...... 27
9. THE LYMPHATIC DRAINAGE OF THE UPPER LIMB ...... 32
10. THE MEDIASTINUM ...... 34
11. TRACHEA, LUNGS AND PLEURA ...... 36
12. THE AUTONOMIC NERVOUS SYSTEM IN THE THORAX ...... 41
13. THE INGUINAL CANAL AND HERNIAS ...... 44
14. SPLEEN AND COELAC TRUNK ...... 47
15. STOMACH ...... 50
16. DUODENUM ...... 53
17. LIVER ...... 55
18. THE PORTAL VENOUS SYSTEM ...... 59
19. DIAPHRAGM ...... 61
20. THE KIDNEYS ...... 64
21. RECTUM AND ANAL CANAL ...... 67
22. PELVIS ...... 71
23. UROGENITAL TRIANGLE ...... 74
24. THE HIP JOINT ...... 77 iv
25. THE ARCHES OF THE FOOT ...... 80
26. THE LYMPHATIC DRAINAGE OF THE LOWER LIMB ...... 83
27. THYROID GLAND...... 84
28. LARYNX ...... 87
29. FORAMINA OF THE SKULL AND THE STRUCTURES THAT PASS THROUGH THEM .. 92
30. THE PTERYGOPALATINE FOSSA ...... 97
31. FACIAL NERVE ...... 100
32. VAGUS NERVE ...... 102
33. STELLATE OR CERVICOTHORACIC GANGLION ...... 104
34. THE CAVERNOUS SINUS ...... 105
35. TEMPOROMANDIBULAR JOINT ...... 107
36. VISUAL PATHWAY AND VISUAL REFLEXES ...... 109
37. INTERNAL CAPSULE ...... 113
38. FUNCTIONAL COMPONENTS OF THE CRANIAL NERVES ...... 114
39. RECOMMENDED TEXTBOOKS ...... 118
40. LECTURE AND PRACTICAL TOPICS (FROM THE DEPARTMENT) ...... 119
41. PAST ESSAY QUESTIONS ...... 128
42. ESSAY-TYPE QUESTIONS ...... 136
43. OBJECTIVE - TYPE QUESTIONS (FROM THE DEPARTMENT) ...... 141
44. APPENDIX I: VERTEBRAL LEVELS ...... 165
45.APPENDIX II: DIMENSIONS OF SOME STRUCTURES IN THE BODY ...... 167
1 1. INTRODUCTION. ANATOMICAL TERMS
TIT BITS ON HOW TO STUDY ANATOMY
Anatomy is very interesting. However, it is voluminous and volatile. When you stop studying it, it leaves you. It does not waste time on those who do not have time for it. You have to bear with it. It is the foundation of medicine.
Below are pieces of advice which you may find useful.
1. Sleep for about 7 hours everyday. If you do not have enough sleep, even if you read a lot, you are likely to remember very little.
2. Prepare for the lectures by reading up the topics in advance.
3. At the end of the day or at least within the week, read the same topics in your textbooks, correct and enrich the notes you took during the lectures.
DISSECTION:
4. Study in advance the areas that you are going to dissect.
5. You have to train your hands in dissection. The first time you dissect, you may do it awkwardly. Do not worry even if your group mates cajole you. With time your dissection will improve. The group mates should take turns to dissect. Otherwise the good student who does the dissection most of the time will become much better while the bad student will remain bad. It is extremely easy to get stuck in a cycle where you do not dissect because you are not good at it, which of course only gets worse.
6. Learn to identify with reasons the structures you come across. For example, if it is an important muscle you should know its origin, insertion, nerve supply, relations to other structures etc. During dissection, refer to the gross atlas frequently.
7. Periodically, during lunch break or at any other free period, go to the dissection room with a colleague of yours who is 'hot' to have a closer look at the regions you have dissected. Compare the structures you identify in your cadaver with the same structures in other cadavers. In this way, you will get used to normal variations in structures.
8. HISTOLOGY PRACTICAL: Identify the slides with reasons. Draw and label the slides you have studied.
9. OSTEOLOGY: A good knowledge of osteology facilitates the understanding of anatomy. Borrow bones from your friends or from the Department and study them regularly. Have them in front of you when you are studying certain topics like muscle attachments, venous sinuses, fossae and foramina in the skull, etc.
10. DISCUSSION GROUPS: Discussion groups are very helpful. Have a discussion group of about 3 to 5 students. 2
Ensure that at least one member of the group is 'hot'. He will be the pace setter. Discuss regularly throughout the session and more often when the examination approaches. You may still be a member of a large discussion group that meets less regularly.
11. MCQ TEXTBOOKS: Study as many MCQ textbooks as you can lay your hands on. It will help you to pay attention to details that ordinarily you will ignore. To be a good mathematician, you need to solve many mathematical problems because each problem may have a catch. The same thing applies in anatomy.
12. Remember that the surest way to fail anatomy is to hope on 'magomago'. Do not be an accomplice.
CONDUCT IN THE DISSECTING ROOM 1. The bodies for dissection deserve your respect. You may wish to pray for their souls. 2. Unauthorized photography in the dissection room is forbidden. 3. Visitors are not allowed in the dissection room. 4. Every student should wear a laboratory coat. 5. Every dissection group must ensure that the cadaver allocated to it is kept in good condition. At the end of each dissection the cadaver should be covered.
WHAT IS ANATOMY?
Anatomy is the study of the structure of an organism. Human anatomy is the study of the structure of the human organism.
Anatomy is derived from the Greek word anatome which means "cutting up". Its Latin equivalent is dissectio. Anatomy as it is known today has a wider scope than mere cutting up. It is the foundation of the whole art of medicine and it introduces the student to most of the medical terminology.
SUBDIVISIONS OF ANATOMY
1. Gross anatomy or macroscopic anatomy is the study of the structure of the body seen with the naked eye and by means of dissection.
2. Microscopic anatomy or histology is the study of the structure of the body with the aid of a microscope.
3. Embryology is the study of the changes that occur from the time of fertilization to the time of birth.
4. Comparative anatomy is the study of the relationship between the structures of related organisms.
BRIEF HISTORY OF ANATOMY Hippocrates of Cos (460-377 BC) is regarded as the father of medicine and one of the founding fathers of anatomy.
Herophilus (300 BC) is regarded as the founding father of anatomy as a systematic discipline.
Aristotle (384-322 BC) is regarded as the founder of comparative anatomy.
Leonardo da Vinci (1452-1519) was an anatomist and an artist. He prepared models and paintings which were the first correct representations of the various organs of the human body.
Andreas Vesalius (1514-1565) was the first to do a systematic study of the structure of the human body. He corrected over 200 anatomical errors made by Galen. 3
SOME DISCOVERIES MADE BY MEDICAL STUDENTS:
1. Red blood cells (Swammerdan)
2. Islets of pancreas (Langerhans)
3. Collecting tubules of kidney (Bellini)
4. Parotid duct (Stensen)
5. Venae cordis minimae (Thebesius)
ANATOMICAL TERMS
ANATOMICAL POSITION: This is the position in which the body is considered to be standing erect with the eyes directed straight ahead into the horizon, the arms by the side, the palms facing forwards and the toes together and directed forwards. Descriptions in anatomy are based on the anatomical position.
PLANES OF THE BODY
1. Median plane or midsagittal plane is an imaginary vertical plane running from front to back that divides the body into right and left halves. The median plane meets the anterior and posterior surfaces of the body at the anterior and posterior midlines respectively.
2. A sagittal plane is an imaginary vertical anteroposterior plane that divides the body into right and left parts (not halves). It is parallel to the median plane. It derives its name from the sagittal suture of the skull.
3. A coronal plane is a vertical plane running from side to side that divides the body into anterior and posterior parts. It intersects the median plane at right angles. It is named after the coronal suture of the skull.
4. A horizontal or transverse plane is an imaginary plane that divides the body into upper and lower parts. It is at right angles to both the median and the coronal planes.
5. A transverse or cross section of an organ is a section at right angles to the long axis of that organ.
TERMS OF RELATIONSHIPS
General Anterior = nearer to the front surface of the body Posterior = nearer to the back surface of the body
Superior = nearer to the top or upper end of the body or the crown of the head Inferior = nearer to the lower end or the soles of the foot Medial = nearer to the median plane Lateral = farther from the median plane Ipsilateral = on the same side of the body Contralateral = on the opposite side of the body 4 Trunk
Ventral = nearer to the front of the trunk Dorsal = nearer to the back of the trunk
Cephalic or cranial = nearer to the head Caudal = nearer to the tail end
Rostral = nearer to the front end. In the postembryonic period the front end is the region around the nose and the mouth
NB. With reference to the trunk, anterior and ventral are synonymous. Posterior and dorsal are also interchangeable.
Internal = nearer to the centre of an organ or cavity External= farther from the centre of an organ or cavity
Superficial = nearer to the skin or surface of the body Deep = farther from the surface
Invagination = inward bulging of the wall of a cavity Evagination = outward bulging of the wall of a cavity
Proximal = nearer to the root or the attached end of the trunk Distal = farther from the root or the attached end of the trunk
Preaxial border = the thumb or the big toe side of the limb. The preaxial border in the upper limb is the lateral or the radial side while in the lower limb it is the medial or the tibial border Postaxial border = the opposite of the preaxial border
TERMS OF MOVEMENTS Flexion = to flex is to bend or to move forward Extension = to extend is to straighten or to move backward
Adduction = movement towards the median plane Abduction = movement away from the median plane
In the upper limb, the middle finger lies in the axial line of the hand. Ulnar deviation = adduction; radial deviation = abduction. In the lower limb, the 2nd toe lies in the axial line.
Circumduction = a sequence of movement involving flexion, abduction, extension and adduction.
Rotation = a movement in which a part of the body is turned around its own long axis. Rotation may be medial or lateral.
Pronation = to pronate is to rotate the forearm medially so that the palm faces posteriorly. Supination = to supinate is to rotate the forearm laterally so that the palm faces anteriorly.
Supine position = is the position in which the body lies on its back. Prone position = is the position in which the body lies face down.
Protraction = forward movement Retraction = backward movement 5
LATIN NAMES ENGLISH EQUIVALENTS Upper Limb Antebrachium foreaem Axilla armpit Brachium arm Capitate head-like Carpus wrist Cubitus elbow Digiti manus finger Digiti minimi little finger Glenoid socket-like Hamate hooked Humerus shoulder Lunate crescent-shaped Lumbrical like earthworm Manus hand Palma palm Pollex thumb Profundus deep Scaphoid like a small boat Sublimis superficial Trochlea pulley-like
Lower limb
Brevis short Calx heel Coxa hip Clunis or natis buttock Crus leg Digiti pedis toe Dorsum superior surface of foot Femur thigh Gemellus twin Genu knee Gracile slender Hallux big toe Lata wide Longissimus longest Longus long Magna or magnus great Malleolus little hammer Maximus biggest Minimus smallest Pes or pedis foot Planta sole Poples back of the knee Rectus straight Sura calf Talus ankle Tertius third
6 Thorax, Abdomen, Pelvis & Perineum Appendix like a tail Caecum blind Cardia heart Carina keel Costa rib Cauda tail Cervix neck Cornu horn Duodenum twelve each Gaster stomach Helicine like a snail or a coil Hymen membrane Incisura notch Labium lip Os opening Pelvis basin Porta entrance Prepuce foreskin Pudendum external genitalia Pylorus gate-keeper Serratus toothed Sigmoid like the letter 'S' Stoma mouth varicocele dilated vein
Head & Neck & CNS
Ansa loop Antrum cave Buccal of the cheek Buccinator trumpeter Bursa purse Cisterna reservoir, tank Colliculus small hill Collis neck Falciform sickle-shaped Falx sickle Fenestra window Filum thread Fissure cleft Folium leaf Fovea small pit Galea helmet Glossus tongue Ima lowest (e.g., thyroidea ima artery) Lacerum jagged or rough Lacuna lake or hollow Lambda Greek letter 'L' Lamina layer or plate Lingua tongue Lutea yellow Macula spot Malleus hammer 7 Meatus passage Meninges membranes Meninx membrane Motor mover Modiolus A nave Nucha back of the neck Oculomotor mover of the eye Operculum a lid Otic of the ear Petrous stony Plexus network Pons bridge Pterygoid wing-like Ramus branch Raphe seam Rete net Tectum roof Tegmen/Tegmentum covering Tentorium tent Uncus hook Vagus wandering Vermis worm
Prefixes Ambi- on both sides Archaeo- ancient Di- double Endo- inside Ecto- outside Epi- upon Extra- beyond, outside of Hydro- water Hyper- over Hypo- under Infra- beneath Inter- between Intra- within Macro- large Meta- after Micro- small Multi- many Myo- muscle Neo- new Omo- shoulder Paleo- old Pseudo- false Rubro- Red
Suffixes -form shape -glia glue -oid like, resembling, in the form of 8 2. CLASSIFICATION OF BONES
I. Developmentally, bones are divided into:
a) Membranous bones - that develop in membrane b) Cartilaginous bones - that develop in cartilage
II. Regionally, bones are divided into:
a) Axial bones b) Appendicular bones
III. According to their shape, they are divided into:
a) Long bones b) Short bones c) Flat bones d) Irregular bones
A. AXIAL BONES
1. Skull a) Bones of the neurocranium 8 b) Bones of the face 14 c) Auditory ossicles 6 2. Hyoid bone 1 3. Vertebrae 26 4. Sternum 1 5. Ribs 24
B. APPENDICULAR BONES 1. Upper limb bones a) Clavicle 2 b) Scapula 2 c) Humerus 2 d) Ulna 2 e) Radius 2 f) Carpal bones 16 g) Metacarpal bones 10 h) Phalanges 28
2. Pelvic girdle and lower limb a) Hip bones 2 b) Femur 2 c) Tibia 2 d) Fibula 2 e) Tarsal bones 14 f) Metatarsal bones 10 g) Phalanges 28
TOTAL 206 9 1. LONG BONES
These are found in the limbs and their length exceeds their breadth and thickness. A long bone has a body or shaft and two ends. The shaft is called the diaphysis, while the ends are called the epiphyses. In most long bones the shaft has a medullary cavity which contains marrow. The epiphysis is articular, and in a growing bone is separated from the shaft by an epiphyseal cartilage (or disc or plate). The part of the shaft adjacent to the epiphyseal disc is called the metaphysis. With cessation of growth, the epiphyseal disc disappears. The metaphysis then becomes continuous with the epiphysis. The metaphysis has some important characteristics: a) It is the area of greatest growth activity in a long bone b) It has a rich blood supply c) Muscles, tendons, and joint fibrous capsules are attached at or near the metaphysis. A portion of the metaphysis is often within the fibrous capsule of the joint. As a result of this, diseases originating at the metaphysis may easily spread to the joint cavity or vice versa. Long bones develop in cartilage. The clavicle is an exception.
2. SHORT BONES
These are cuboidal in shape. Their length, breadth and thickness are approximately equal, for example, the carpal and tarsal bones. The short bones are surrounded by periosteum except at the articular surfaces. They develop in cartilage.
3. FLAT BONES
These are thin, and are usually curved rather than flat. They consist of two layers of compact bone with an intervening spongy layer. The spongy layer of the skull vault is called the diploe.
4. IRREGULAR BONES
These are bones that do not fit into the above classification scheme. Examples of irregular bones: most bones of the skull, vertebrae, hip bones. They consist of a large spongy layer enclosed by thin layers of compact bone. Pneumatic bones are skull bones that contain air filled cavities. These cavities are extensions of nasal or middle ear cavities, e.g. of pneumatic bones - maxilla, ethmoid.
BLOOD SUPPLY OF A LONG BONE
A long bone receives its blood supply from four sources:
(a) Nutrient artery: it enters the diaphysis obliquely through a nutrient foramen which usually faces away from the growing end of the bone. On entering the bone marrow, it divides into ascending and descending branches to supply the bone as far as the metaphysis.They supply the bone marrow.
(b) Metaphyseal arteries: they are small vessels that are derived from the arteries that supply the adjacent joint.
(c) Epiphyseal arteries: they are derived from periarticular arteries.
(d) Periosteal arteries: they supply the compact bone of the diaphysis.
Some of the epiphyseal arteries may pierce the epiphyseal cartilage and supply the metaphysis. Since the arteries supplying the long bones converge towards the metaphysis, the latter is a highly vascular zone. 10 3. CLASSIFICATION OF JOINTS
A joint is a junction between two or more bones. Joints may be classified into three types based on the type of tissue uniting the bones: I. Fibrous joints: the bones are united by fibrous tissue. II. Cartilaginous joints: the bones are united by cartilage. III. Synovial joints: the joint cavity contains synovial fluid. The degree of movement in a joint is not necessarily related to the type of classification. Although synovial joints are in general the most mobile joints, some fibrous joints are more mobile than some synovial joints.
I. FIBROUS JOINTS / SYNARTHROSIS In these joints, the articular surfaces are joined by fibrous tissue. Usually, little or no movement takes place at these joints. The degree of movement depends on the length of the collagenous fibres uniting the bones. These joints can be classified as: a) Sutures b) Syndesmoses c) Gomphoses
(a) SUTURES These are confined to the skull. The bones are connected by several layers of fibrous tissue. This fibrous tissue is connected externally to the periosteum of the outer surface, and internally to the periosteal layer of the dura mater. Membranous ossification goes on until the two bones become completely fused.
(b) SYNDESMOSES The closely apposed articulating surfaces are united by interosseous ligaments, e.g. the inferior tibiofibular syndesmoses.
(c) GOMPHOSES This is the membranous union between a tooth and its socket.
II. CARTILAGINOUS JOINTS These joints can be classified as: a) Primary cartilaginous joints / synchondroses b) Secondary cartilaginous joints / amphiarthroses a) PRIMARY CARTILAGINOUS JOINTS / SYNCHONDROSES These are temporary joints. The bones are united by a plate of hyaline cartilage. No movement occurs at the joint. The joints disappear by synostosis, e.g. i) Union between the epiphysis and diaphysis of a growing bone. ii) Union between the 1st rib and the manubrium sterni iii) Sphenooccipital joint. b) SECONDARY CARTILAGINOUS JOINTS / AMPHIARTHROSES/SYMPHYSIS The articular surfaces of these joints are covered by a thin layer of hyaline cartilage and connected by a plate of fibrocartilage. Slight movement occurs at these joints; these joints only appear in the median plane, e.g. the symphysis pubis, between the bodies of the vertebrae, the manubriosternal joint, and xiphisternal joint.
III. SYNOVIAL JOINTS / DIARTHROSES The articular surfaces of the adjacent bones in these joints are covered by a thin layer of hyaline cartilage and the bones are connected by a fibrous capsule which is continuous with the periosteum of the bones. The capsule may be strengthened by accessory ligaments. The inner surface of the capsule and the intra-articular structures which are not covered by hyaline cartilage are lined by synovial 11 membrane. This membrane secretes synovial fluid that fills the joint cavity and lubricates the joint. The joint cavity may be partially or completely subdivided into compartments by fibrous or fibrocartilaginous discs, e.g. the menisci of the knee joint. Synovial joints are in general the most mobile joints. CLASSIFICATION The classification of synovial joints may be based on: 1. Organization of the joints 2. Axes of movements that are possible 3. Shape of the articular surfaces 1. Based on the complexity of the organization of the joint, synovial joints may be classified as: a) Simple joints: in these, there are only two articulating surfaces. Most synovial joints are simple joints. b) Compound joints: these are joints that have more the one pair of articulating surfaces, e.g., the elbow joint, where the capitulum and trochlea of the distal end of the humerus articulate with radius and ulna. c) Complex joints: these are joints in which there is an intracapsular disc or meniscus, e.g., the knee joint.
2. Based on the degree of movement, they may be classified as: a) Uniaxial joints: where the movement of the joint is restricted to one axis and the joint is said to have only one degree of movement. b) Biaxial joints: where the movements may occur in two principal axes, and the joint is said to have two degrees of movement. c) Multiaxial joint: where the movements occur in three principal axes.
3. Based on the shape of the articular surfaces, they may be classified as: a) Plane / Arthroidal / Gliding joints: The articular surfaces are flat or almost flat. These joints allow only gliding or sliding movements. E.g., the intercarpal, intermetatarsal and acromioclavicular joints. b) Hinge /Ginglymus joints: these resemble the hinge on a door. One articular surface is concave, while the other is convex. They are uniaxial joints and allow movement along one axis at right angles to the bones. Only flexion and extension occur at these joints. Examples are the elbow, ankle and interphalangeal joints. The knee joint may also be classified as a modified hinge joint. c) Pivot/Trochoid joints: there is a central bony pivot which rotates within a bony-ligamentous ring. They are uniaxial joints and allow only rotation along a longitudinal axis that passes through the centre of the pivot, e.g., atlanto-axial and superior radioulnar joints. d) Condyloid joints: they have two distinct convex surfaces that articulate with two concave surfaces. They are biaxial joints and allow movement in two directions at right to each other. They allow flexion, extension, abduction, adduction and a limited amount of rotation, e.g., metacarpophalangeal joints. e) Ellipsoid joints: they are similar to condyloid joints and may be grouped together with them. The articular surfaces are ellipsoidal and there is no rotation. E.g., wrist joint f) Saddle joints: they are biaxial joints and their apposing articular surfaces are saddle shaped E.g., metacarpophalangeal joint of the thumb. g) Ball and socket joints: they are so named because they have a ball-shaped head fits into a socket-like concavity. They are multiaxial joints and allow flexion and extension, abduction and adduction, medial and lateral rotations, and circumduction. E.g., hip and shoulder joints. 12 4. OSSIFICATION OF BONES
There are two types of ossification: membranous or intramembranous and endochondral or intracartilaginous. In membranous ossification the bone develops in a connective tissue other than a cartilage. In endochondral ossification the bone develops in a preformed cartilage.
Centres of ossification are places where bone begins to be laid down. From these centres, ossification spreads to other parts of the bone. There are two types of centres: primary and secondary. The primary centre appears first and is usually in the body of the bone. There may be more than one primary centre. A primary centre may be the result of fusion of several small centres that are closely located. Usually primary centres appear during the intrauterine life.
Secondary centres appear much later than the primary centres. The part of the bone that develops from a secondary centre is called the epiphysis while the part that develops from the primary centre is called the diaphysis. The part of the diaphysis adjacent to the epiphyseal cartilage is called the metaphysis. Ossification occurs most rapidly at the metaphysis. The cells in the epiphyseal plate proliferate and provide new cells which are responsible for increase in the length of the diaphysis. When the epiphyseal plate disappears, increase in length of the diaphysis ceases. The "growing end" of a long bone is the end that has the epiphysis that grows faster and for a longer period.
General rules of ossification
1. Most primary centres appear during the intrauterine life (IUL) especially between 7 - 12 weeks.
2. Most secondary centres appear after birth. Exceptions include the centre for the distal end of the femur which appears in the 9th month of IUL and the centre for the proximal end of the tibia which may also appear in the 9th month of IUL.
3. The secondary centres for the growing end appear earlier and fuse later. The fibula is an exception to this rule. 4. Secondary centres appear 1-2 years earlier in females than in males. They also fuse earlier in females.
CLAVICLE The ossification is membranous except the ends which are cartilaginous. The clavicle usually has 3 ossification centres: medial and lateral primary centres and one secondary centre. It is the first bone in the body to ossify. The primary centres appear between the 5th and 6th weeks of IUL. The two primary centres fuse soon after, at about the 45th day.
A secondary centre for the sternal end appears in the 16-20th year and fuses about a year after. Occasionally there may be another secondary centre at the acromial end in the 18-20 year. This centre is small and rudimentary and fuses soon after with the rest of the bone.
SCAPULA The ossification is endochondral. It has 8 or more ossification centres: 1 primary and 7 secondary centres. The primary centre appears in the body of the scapula in the 8th week of IUL. The secondary centres appear as follows:
2 in the coracoid process 2 in the acromion 1 in the lower part of the glenoid cavity 1 in the medial border 1 in the inferior angle 13 The first centre in the coracoid process appears in the 1st or 2nd year. In a small proportion of individuals it appears before birth. It unites with the rest of the scapula in the 15th year. The second centre in the coracoid process appears in the root of the coracoid process and it is also called the subcoracoid centre. It also serves the upper third of the glenoid cavity. It appears in the 10th year and fuses with the rest of the bone in the 15th year. Other secondary centres appear after puberty and fuse between the 20th and 25th years.
HUMERUS The ossification is endochondral. It ossifies from 8 centres: 1 primary and 7 secondary. The primary centre appears in the shaft in the middle of the 8th week of IUL. There are 3 secondary centres for the upper end and 4 for the lower end. The centres for the upper end appear as follows: Head 1st year (usually 1-6th month after birth) Greater tubercle 3rd year Lesser tubercle 5th year The above 3 centres fuse into a single centre in the 6-8th year. The fusion with the shaft occurs at about the age of 18-20.
The 4 secondary centres for the lower end appear as follows: Capitulum and the lower part of the trochlea 1-2 year Medial epicondyle 5-8th year Medial part of the trochlea 9-10th year Lateral epicondyle 11-14th year
The centres for the capitulum, trochlea and the lateral epicondyle fuse into a single centre in the 14th year in females and 16th year in males. The centre for the medial epicondyle remains separate. It is completely extracapsular. The centres at the lower end of the humerus unite with the shaft at about the age of 16-18.
RADIUS The ossification is endochondral. It ossifies usually from 3 centres: 1 primary and 2 secondary. The primary centre appears in the shaft in the 8th week. The distal end is the growing end. The secondary centre at this end appears in the 1st or 2nd year and fuses with the shaft at about the age of 18-20. The centre for the proximal end appears in the 4-6th year and fuses at about the age of 16-18. Sometimes there may be an additional centre for the tuberosity of the radius which appears between 14-15th year
ULNA The ossification is endochondral. It ossifies usually from 3 centres: 1 primary and 2 secondary. The primary centre appears in the shaft in the 8th week. The coronoid process and the greater part of the olecranon also ossify from extensions of the primary centre. The distal end is the growing end. The centre for this end appears in 5-6th year and fuses with the shaft in the 18-20th year. The centre for the proximal end appears between the 8-11th year and fuses between the 16-18th years. The proximal part of the olecranon also develops form this centre. The olecranon may also have additional centres. The ossification centres for the olecranon may, therefore, be multipartite.
CARPAL BONES The 8 carpal bones are cartilaginous at birth. Ossification begins after birth. They ossify roughly at yearly intervals and according to their size. Each carpal bone ossifies from one centre. The capitate is the largest carpal bone and is the first to ossify while the pisiform which is the smallest is the last to ossify. 14
The centres appear as follows: Capitate 1st year (Usually in the 2nd month) Hamate 1st year (usually in the 3rd month) Triquetrum 3rd year Lunate 4th year Trapezium 5-6th year Scaphoid 5-6th year Trapezoid 7th year Pisiform 9-12th year
METACARPALS Each metacarpal ossifies form 1 primary centre and 1 secondary centre. The primary centre appears in the shaft in the 9th week. The secondary centre appears at the head of the 2-5 metacarpal and at the base of the 1st metacarpal in the 2nd to 3rd year and fuses at about 16-20. Occasionally there may be an additional centre for the head of the first metacarpal.
PHALANGES They ossify like the first metacarpal. Each phalanx has a primary centre. The primary centre appears in the shaft between 8-12th weeks (distal phalanx... 8-9th week; middle phalanx ...10th week; proximal phalanx ... 11-12th week) The secondary centre for each phalanx appears at the base in the 3rd year and fuses at about 16-20 years of age.
THE HIP BONE The ossification is endochondral. It ossifies from 3 primary centres which appear as follows:
Ilium: A primary ossification centre appears above the greater sciatic notch in the 2nd or 3rd months of IUL.
Ischium: A centre appears in the body of this bone in the 4th or 5th month of IUL.
Pubis: A centre appears in the superior ramus in the 4th or 5th month ofIUL.
The ilium, ischium and the pubis are separated by a Y-shaped acetabular cartilage. The rami of the ischium and the pubis fuse to form the ischiopubic ramus in the 7th or 8th year.
The secondary centres appear at puberty as follows: 2 for iliac crest 2 for acetabular cartilage 1 for anterior inferior iliac spine 1 for symphysial surface of the pubis 1 for ischial tuberosity 1 for pubic tubercle One of the centres for the acetabular cartilage is called the os acetabuli. The secondary centres join between the ages of 20 and 25.
FEMUR The ossification is endochondral. It ossifies from 4 centres: 1 primary and 3 secondary. The primary centre appears in the shaft in the 7th week. The neck of the femur develops from extensions of the primary centre. The secondary centres appear as follows: Distal end 9th month of IUL Head 1st year (usually 1-6 month after birth) Greater trochanter 3-5 years Lesser trochanter 9-12 years 15 The appearance of the secondary centre at the lower end of the femur is medicolegal evidence that the fetus is mature. The lower end, which is the growing end, unites with the shaft at about the age of 18- 20, while the centres at the upper end unite with the shaft at about the age of 16-18.
PATELLA The patella is cartilaginous at birth. It ossifies from 1-3 centres which appear between the 3rd and 6th year. The ossification is usually completed by the age of puberty. Sometimes the superolateral portion of the patella may ossify independently and may remain separate from the rest of the patella. The patella is said to be bipartite. Very rarely the patella has three separate segments and it is said to be tripartite. The segmentation of the patella should be differentiated from fractures.
TIBIA The ossification is endochondral. Usually it ossifies from 3 centres: 1 primary and 2 secondary. The primary centre appears in the shaft in the 7th week of IUL. The centre for the upper end appears shortly after birth. In a small proportion of the population it appears in the 9th month of IUL. An additional centre for the tuberosity of the tibia may appear at puberty. The upper end unites with the shaft at about the age of 18-20. The centre for the distal end appears in the 1st or 2nd year and fuses with the shaft at about the age of 16-18.
FIBULA The ossification is endochondral. It ossifies from 3 centres: 1 primary and 2 secondary. The primary centre appears in the shaft in the 8th week of IUL. The centre for the proximal end appears in the 3- 4th year and fuses at about the 18-20. The centre for the distal end appears in the 1-2nd year and unites with the shaft at about the age of 16-18. The epiphysial lines are extracapsular. The fibula is an exception to the law of ossification. The proximal end which is the growing end ossifies later than the distal end.
TARSAL BONES Each tarsal bone ossifies from one primary centre. The calcaneus has one additional secondary centre. The primary centres appear as follows: Calcaneus 6th month of IUL Talus 7th month of IUL Cuboid 9th month of IUL 3rd or lateral cuneiform 1st year 1st or medial cuneiform 3rd year 2nd or intermediate cuneiform 4th year Navicular 4th year
The secondary centre for the posterior surface of the calcaneus appears about the age of 8-10 and fuses at 18 years. The lateral tubercle of the talus may develop as a separate bone called the os trigonum. The tuberosity of the navicular and the tubercle at the base of the 5th metatarsal may also ossify from separate centres. The medal cuneiform is the largest of the three cuneiforms while the intermediate cuneiform is the smallest.
METATARSALS The ossification is similar to that of metacarpals. Each metatarsal ossifies from 1 primary centre and 1 secondary centre. The primary centre appears in the 3rd month of IUL. The secondary centre appears at the heads of the 2-5th metatarsal and at the base of the 1st metatarsal. The secondary centres appear at about the age of 2-3 and fuse at about the age of 18.
PHALANGES The same as the first metatarsal. 16 SKULL The ossification is mainly membranous except those that form the skull base and those that develop in the olfactory capsule.
FRONTAL BONE It develops in membrane and ossifies from 2 primary centres: one in each half of the frontal bone. The centres appear in the 7th or 8th week of IUL. At birth the two halves are separated by a frontal or metopic suture. The two halves begin to fuse in the 2nd year and the fusion is usually complete by the 6th year. The suture disappears but in some individuals it persists.
ETHMOID It ossifies in the cartilage of the nasal capsule. There are 3 centres of ossification: 1 for the perpendicular plate and 1 each for the left and right labyrinths. The centre for each labyrinth appears in the 4th or 5th month of IUL. The centre for the perpendicular plate and the crista galli appears in the 1st year. The different parts of the ethmoid unite in the 5-6th year. The fusion of the ethmoid and the sphenoid occurs after the 25th year.
SPHENOID The ossification is cartilaginous except the lateral part of the greater wing and the pterygoid process which are membranous in ossification. There are centres for the body, greater wing, lesser wing, pterygoid process and the sphenoid concha. Most of the centres appear in the 2nd month of IUL. The fusion of the body of the sphenoid and the occipital bone occurs by the 25th year.
PARIETAL BONES Each parietal bone develops in membrane from a centre which appears in the 7th or 8th week of IUL in the region of the future parietal eminence.
TEMPORAL BONE The squamous and tympanic parts ossify in membrane in the 7th or 8th week of IUL. The petromastoid part ossifies in cartilage in the 5th month while the styloid process ossifies from the upper part of the cartilage of the 2nd pharyngeal arch in the 9th month. The various parts of the temporal bone unite in the 1st year of life.
OCCIPITAL BONE It ossifies in cartilage except the apical portion of the squamous part which develops in membrane. It has 4 ossification centres which appear in the 2nd or 3rd month. The different parts of the occipital bone unite by the 6th year.
ZYGOMATIC BONE It ossifies in membrane from 1 centre which appears in the 8th week if IUL.
LACRIMAL BONE It ossifies in membrane from 1 centre which appears in the 3rd month of IUL.
NASAL BONE It ossifies in membrane from 1 centre which appears in the 3rd month of IUL.
INFERIOR NASAL CONCHA It ossifies in the cartilage of the lateral part of the nasal capsule. It ossifies from one centre which appears in the 5th month of IUL.
VOMER It ossifies in membrane form 2 centres. The 2 centres unite at puberty.
17 MAXILLA It ossifies in membrane and has 3 primary centres. The centre for the maxilla appears in the 6th week of IUL while the two centres for the premaxilla appear in the 7th week.
PALATINE BONE It ossifies in membrane from 1 centre which appears in the 8th week of IUL.
MANDIBLE It is the 2nd bone in the body to ossify and is mainly membranous in ossification. It ossifies from the mesenchyme surrounding the Meckel's cartilage. Each half of the mandible ossifies from 1 centre which appears in the 6th week of IUL near the mental foramen. The portion below the incisors may develop from the Meckel's cartilage. Accessory cartilages may also form parts of the condyloid and coronoid processes and the symphysis menti. At birth the two halves of the mandible are united by a fibrous joint. In the 2nd year the suture disappears.
STERNUM It ossifies in cartilage and has 6 or more primary centres. There is at least one centre for each of the following: manubrium, each of the four segments of the body, and the xiphoid process. The centres may be paired especially the centres for the manubrium and the 3rd and 4th segments. The centres appear as follows: Appears Fuses Manubrium 5th month of IUL 25th year 1st segment of the body 6th month 25th year 2nd segment of the body 7th month 25th year 3rd segment of the body 8th month 25th year 4th segment of the body 9th month 25th year Xiphoid process 3rd year 30-40th year
Fusion of the segments of the body occurs between puberty and 25th year. Incomplete fusion of the paired centres results in sternal foramen. Fusion of the manubrium with the body occurs in about 10% of the population. Union between the body and the xiphoid process occurs in about 30% of the population.
RIBS Each ossifies in cartilage usually from 4 centres: 1 primary and 3 secondary. The primary centre appears near the angle of the shaft in the 8th week of IUL. The 3 secondary centres are for the head, the articular and the non-articular parts of the tubercle. The secondary centres appear at puberty and unite with the shaft by the 25th year. The first rib has only 3 centres. It does not have a centre for the non-articular part of the tubercle. The 11th and 12th ribs have only 2 centres. They do not have centres for the tubercles.
VERTEBRAE They ossify in cartilage and usually have 3 primary centres: one each for the body, and the left and right halves of the neural arch. The centres appear in the 8th week and fuse by the 3rd year. There are usually 5 secondary centres: 1 for each of the transverse process 1 for the spinous process 1 for the upper surface of the body 1 for the lower surface of the body The centres appear at puberty and fuse by 25th year.
Exceptions to the typical mode of ossification of the vertebrae occur in the 1st, 2nd and 7th cervical vertebrae and the lumbar vertebrae.
18 The atlas ossifies from 2 primary centres, one each for the lateral masses. The primary centres appear in the 7th week and unite in the 3rd of 4th year. A secondary centre for the anterior arch appears in the 1st year and unites with the lateral masses in the 6-8th year.
The axis ossifies from 5 primary centres and 2 secondary centres. The primary centres appear as follows: 1 for each half of the vertebral arch in the 7th week 1 for the centrum in the 4th or 5th month 2 for the dens in the 6th month. The secondary centres appear at the tip of the dens and at the lower surface of the body at the age of 2-6 and unite before puberty.
The 7th cervical vertebra has 2 additional primary centres, one each for the left and right costal elements. They appear in the 6th month and unite with the body and transverse process in the 6th year. The costal elements may remain separate and form cervical ribs. The bifid spine has 2 secondary ossification centres.
The lumbar vertebrae have 2 additional centres one each for the left and right mamillary processes. The 1st lumbar vertebra may have separate primary centres for its transverse process. They may remain separate to form lumbar ribs.
The sacrum has 1 primary centre each for the centrum, the left and right halves of the vertebral arches as well as the left and right costal elements in the upper 2 or 4 sacral vertebrae. Each coccygeal segment ossifies from 1 primary centre. There may be a separate centre for the cornua of the first coccygeal segment. Fusion between the 1st and 2nd coccygeal segments occurs by the 30th year. The coccyx often fuses with the sacrum especially in females.
NB. A detailed knowledge of the ossification of all the bones is not necessary. Concentrate on the important ones. 19 5. THE BREAST
The breast is an accessory female reproductive organ. It consists of glandular, fatty and fibrous tissues, blood and lymph vessels, and nerves. The glandular tissue is the mammary gland proper and is a modified sweat gland that secretes milk instead of sweat. The breast is present in both sexes but in the male it is rudimentary throughout life and consists of a few ducts embedded in the fibrous tissue. The nipple is small but the areola is well developed. In the female, before puberty, the breast is undeveloped and is similar to the male breast. At puberty it enlarges mainly due to deposition of fat.
SIZE AND SHAPE The size and shape of the mature female breast vary in different races. In the same person, they depend on the age and the functional state. The breast is larger during pregnancy and lactation than during the non pregnant state. The increase in size during pregnancy is due to the formation of additional glandular tissue. After menopause it usually undergoes atrophy due to reduction in the glandular and fibrous tissue. Sometimes instead of decreasing in size it enlarges as a result of deposition of fat. Slight inequality in the size of the left and right breasts is normal. The left is usually slightly larger than the right. Gross inequality is usually due to disease, underdevelopment or overdevelopment of one of the breasts. In the young adult nulliparous female the breast is conical or hemispherical in shape while in the older or multiparous female it is pendulous.
LOCATION Although, the shape of the breast varies, the size of the base is fairly constant. It extends from the 2nd to the 6th rib in the midclavicular line, and from the lateral margin of the sternum to the midaxillary line. About two-thirds of the base of the breast lies over the pectoralis major while about one-third lies over the serratus anterior muscle. A small portion lies over the aponeurosis of the external oblique muscle. The retromammary space separates the breast from the fascia covering pectoralis major.
The breast lies in the superficial fascia except a small portion of the upper quadrant which extends upward and laterally beyond the pectoralis major to the axilla where it may pierce the deep fascia. This portion of the breast is called the axillary tail of Spence and it lies in the deep fascia.
NIPPLE AND AREOLA In the young adult nulliparous female the nipple or the mammary papilla is located just below the centre of the breast and it lies at the level of the 4th intercostal space. When the breast becomes pendulous the nipple lies at a lower level. The nipple is surrounded by a dark pigmented area called the areola. The latter is pinkish in nulliparous women and becomes darker during pregnancy. After pregnancy the pigmentation decreases but the areola does not return to its prepregnacy colour.
The areola contains numerous sebaceous glands. These glands enlarge during pregnancy and lactation to form small elevations called Montgomery's tubercles. The tubercles produce an oily secretion that makes the nipple supple and also serves as a protective lubricant for the skin of the areola and nipple during lactation. The nipple does not contain fat but it contains circular and longitudinal smooth muscles. Contraction of the circular muscles causes the nipple to become erect while contraction of the longitudinal muscles causes it to retract. 20
THE LOBES AND LACTIFEROUS DUCTS
The glandular tissues of the breast are arranged into 15-20 lobes and in between them are adipose tissues. Each lobe is subdivided into lobules which consist of clusters of alveoli. The ducts of the lobules unite to form a large lactiferous duct which drains a lobe. The 15-20 lactiferous ducts converge towards the nipple and in the region of the areola each one enlarges to form a lactiferous sinus or ampulla before opening on to the nipple. The sinus serves as a reservoir for milk during lactation. The breast is supported by bands of fibrous tissue called the suspensory ligaments of Cooper. These bands attach the glandular tissues to the overlying skin and the deep fascia covering the pectoralis major. They are more numerous in the upper part of the breast.
BLOOD SUPPLY
The breast has a rich blood supply. It is supplied by the following arteries: 1) The 2nd to 4th perforating branches of the internal thoracic artery. During lactation these perforating branches enlarge. The 2nd and 3rd perforating branches are larger then the 4th. 2) The lateral branches of the lateral thoracic artery. The latter is a branch of the second part of the axillary artery. It is large in the female because it gives branches to the breast. 3) The anterior and lateral cutaneous branches of the anterior intercostal arteries. 4. Pectoral branches of the theriac-acromial artery. They supply the upper lateral part of the breast. VENOUS DRAINAGE They veins follow the arteries. They drain into the axillary, internal thoracic, lateral thoracic and anterior intercostal veins. Through the intercostal veins they communicate with the vertebral venous plexus and the azygos vein. They may be grouped into medial, lateral and posterior venous networks. The medial network accompanies the perforating branches of the internal thoracic artery and drain into the internal thoracic vein. The lateral network drains into the axillary vein while the posterior network drains through the intercostal veins to the vertebral plexus of veins.
LYMPHATIC DRAINAGE Lymphatic drainage of the breast is important because of its relevance in the spread of breast cancer. The lymph vessels originate from the interstitial plexus in the interlobular connective tissue and the walls of the lactiferous ducts. There is also a cutaneous plexus below the areola called the subareola plexus of Sapey and a submammary plexus in the deep fascia covering the pectoralis major and serratus anterior. There is communication between these plexuses.
In the past it was thought that lymph vessels from the superficial parts of the breast first drain to the subareolar plexus while those from the deeper parts drain to the submammary plexus before draining into the regional lymph nodes. It is now believed that these plexuses are not very important and that most of the lymph vessels drain directly into the regional lymph nodes. Lymph vessels from the lateral and inferior parts of the breast tend to drain to the axilla while those from the medial part drain to the parasternal lymph nodes.
About 75% of the lymph vessels of the breast drain to the axillary group of lymph nodes especially the anterior group of lymph nodes. A few of the lymph vessels from the upper part of the breast drain to the apical group of lymph nodes while those from the axillary tail drain to the subscapular group of axillary lymph nodes. About 20% of the lymph vessels accompany the perforating branches of the internal thoracic artery and drain to the parasternal (internal thoracic) lymph nodes that lie along the internal thoracic artery. Of the remaining 5%, some follow the posterior intercostal arteries and drain to the posterior intercostal lymph nodes. Those from the lower part of the breast may drain through the rectus abdominis to the hepatic lymph nodes especially in diseased states while those from the medial part of the breast may cross the midline to communicate with the submammary plexus of the opposite breast.
21 NERVE SUPPLY The breast is supplied by the anterior and lateral branches of the 2nd to 6th intercostal nerves. These nerves also convey sympathetic fibres to the breast from the thoracic sympathetic trunk. The secretory activities of the breast are primarily under the control of ovarian and the pituitary hormones rather than by the sympathetic fibres. The nipple and the areola have a rich nerve supply.
APPLIED ANATOMY Amastia: the breast is absent or poorly developed. Polymastia: there are supernumerary or accessory breasts. They occur along the mammary ridge. Polythelia: there are accessory nipples. Gynaecomastia: this is abnormal enlargement of the male breast due to imbalance between estrogens and androgens.
Incisions of the breast: radial incisions should be made to avoid damaging the lactiferous ducts.
CANCER OF THE BEAST: It is very common in females and rare in males. The commonest site is the superolateral quadrant because it contains more glandular tissue than any other quadrant. Cancer in this quadrant has the best prognosis. The inferomedial quadrant is the least common site and has a poor prognosis because of its proximity to the abdominal cavity. DIMPLING of the skin of the breast is due to infiltration of the suspensory ligaments by the cancer cells causing the ligaments to shorten. Blockage of the lymphatics draining the skin of the breast causes the skin to be thickened and oedematous and to have a pea d'orange (orange skin) appearance.
RETRACTION of the nipple is due to infiltration of the lactiferous ducts by the cancer cells causing shortening of these ducts. Retraction of the nipple may also be congenital or inflammatory in origin.
METASTASES: the axillary lymph nodes are the commonest site of metastases from the breast cancer. Through the communication between the intercostal veins and the vertebral venous plexuses, cancer of the breast spreads to the bones and the brain. MAMMOGRAPHY: this is a radiographic examination of the breast in order to detect cancer cells.
THERMOGRAPHY: this is another method for the detection of breast cancer. It is based on the measurement of heat radiation emitted by the breast tissue. Breast tumours emit more heat than normal breast tissue.
MASTECTOMY: this is the removal of the breast. During mastectomy care should be taken to avoid damage to the long thoracic nerve. In simple mastectomy only the breast is removed. In radical mastectomy the breast, the axillary lymph nodes and fascia, pectoralis major and minor muscles and parts of the thoracic wall are removed. In modified radical mastectomy the breast and the axillary lymph nodes are removed. The muscles are not removed.
22 6. THE BRACHIAL PLEXUS
The brachial plexus is the main nerve plexus supplying the upper limb. It is formed by the ventral rami of C5 to T1 and there may be contributions from the ventral rami of C4 and T2. These ventral rami constitute the roots of the brachial plexus. The roots are equal in size.
TYPES OF BRACHIAL PLEXUS There are pre-fixed and post-fixed types of brachial plexus. In the prefixed type, the contribution from C4 is large; the branch from T1 is small, while that from T2 is usually absent. In the post-fixed type, the branch from C4 is small or absent, the branch from T1 is large and the branch from T2 is always present.
FORMATION OF THE BRACHIAL PLEXUS The ventral rami of the 5th and 6th cervical nerves unite to form the upper or superior trunk at the lateral border of the scalenus medius. The ventral ramus of the 7th cervical nerve continues as the middle trunk. The ventral rami of the 8th cervical and 1st thoracic nerves unite behind the scalenus anterior to form the lower or inferior trunk. This trunk leaves a groove on the superior surface of the first rib.
Just above or behind the clavicle, each trunk divides into an anterior and a posterior division. The anterior division supplies the flexor compartment, while the posterior division supplies the extensor compartment of the upper limb. The anterior divisions of the upper and middle trunks unite to form the lateral cord, while the anterior division of the lower trunk continues as the medial cord. The posterior divisions of the three trunks unite to form the posterior cord. The posterior division of the lower trunk is the smallest of the posterior divisions.
RELATIONS OF THE BRACHIAL PLEXUS The supraclavicular part of the brachial plexus lies in the neck while the infraclavicular part lies in the axilla. In the neck, the brachial plexus lies in the lower part of the posterior triangle, that is, between the clavicle, the lower part of the neck and the posterior border of sternocleidomastoid. It emerges between scalenus anterior and scalenus medius, and the divisions pass behind the medial 2/3 of the clavicle. The cords then enter the axilla.
In the axilla, the lateral and posterior cords are lateral to the first part of the axillary artery, while the medial cord lies behind it. The cords surround the 2nd part of the axillary artery and are named after their relationships to this part - the medial cord is medial, the lateral cord is lateral and the posterior cord is posterior to the 2nd part of the axillary artery. In the lower part of the axilla, the cords divide into several branches. The branches, with the exception of the medial head of the median nerve, maintain the same relationships to the 3rd part of the axillary artery.
BRANCHES OF THE BRACHIAL PLEXUS These may be divided into: I. Supraclavicular II. Infraclavicular
I. Supraclavicular branches
A. Branches from the roots of the plexus 1. Dorsal scapular nerve (C5). It supplies the rhomboid major and minor and levator scapulae muscles. 2. Long thoracic nerve (C5, 6, 7). It descends behind the brachial plexus and supplies the serratus anterior muscle. 23 B. Branches from the trunks 3. Nerve to subclavius (C5, 6). It is a small nerve arising from the junction between C5 and C6. It supplies the subclavius and may give rise to the accessory phrenic nerve. 4. Suprascapular nerve (C5, 6). This is a large nerve, which enters the supraspinous fossa by passing below the superior transverse scapular ligament. It supplies the supraspinatus and infraspinatus, as well as the shoulder and acromioclavicular joints.
II. Infraclavicular branches A. Branches from the lateral cord 1. Lateral pectoral nerve (C5, 6,7). This is larger than the medial pectoral nerve. It pierces the clavipectoral fascia and supplies pectoralis major. It also supplies pectoralis minor through a filament or communication it sends to medical pectoral nerve. 2. Musculocutaneous nerve (C5, 6,7). This pierces coracobrachialis. It supplies coracobrachialis, biceps brachii and brachialis and continues as the lateral cutaneous nerve of the forearm. 3. Lateral head of the median nerve (C5, 6, 7).
B. Branches of the medial cord 1. Medial pectoral nerve (C8, T1). It supplies pectoralis major and minor. 2. Medial cutaneous nerve of the arm (C8, T1). It supplies the skin of the lower one-third of the medial side of the arm. It is the smallest branch of the brachial plexus. It descends along the medial side of the axillary vein. It may be connected to the intercostobrachial nerve. 3. Medial cutaneous nerve of the forearm (C8, T1). This lies between the axillary artery and vein, medial to the axillary artery. 4. Ulnar nerve (C8, T1). 5. Medial root of median nerve (C8, T1).
C. Branches of the posterior cord 1. Upper subscapular nerve (C5, 6) supplying subscapularis 2. Thoracodorsal nerve (C6, 7, 8) arising between the upper and lower subscapular nerves, accompanying the subscapular artery and supplying the latissimus dorsi. 3. Lower subscapular (C5, 6) supplying the subscapularis and teres major. 4. Axillary nerve (C5, 6) 5. Radial nerve (C5, 6, 7, 8, T1)
The musculocutaneous, ulnar, median, radial and axillary nerves are the five major terminal branches of the brachial plexus. The letter M may be used to identify the following terminal branches of the brachial plexus: musculocutaneous nerve, median nerve and its lateral and medial roots, and ulnar nerve.
Ulnar nerve (C8, T1). It may also receive fibres from C7. It is the largest branch of the medial cord and it runs between the axillary artery and vein, and continues downwards on the medial side of the brachial artery. It pierces the medial intermuscular septum and descends on the groove behind the medial epicondyle and enters the forearm between the two heads of flexor carpi ulnaris. Its muscular branches supply the following: a) Flexor carpi ulnaris b) Medial half of flexor digitorum profundus c) Superficial terminal branch to the palmaris brevis d) Deep terminal branch. It supplies most of the short muscles of the hand: hypothenar muscles, 3 & 4 lumbricals, , interossei, adductor pollicis, and often the deep head of flexor pollicis brevis. It also provides cutaneous innervation to the front and back of the medial half of the hand
The Median Nerve (C5,6,7,8,T1). It arises by 2 heads, medial and lateral heads or roots, which unite anterior or lateral to the 3rd part of the axillary artery. It supplies all the flexor muscles of the forearm except flexor carpi ulnaris and the lateral half of flexor digitorum profundus. It also supplies the lateral two lumbricals, and some of the thenar muscles (opponens pollicis, abductor pollicis brevis 24 and superficial part of flexor pollicis drevis). In addition, it supplies the elbow joint and the skin of the lateral part of the palm.
Axillary Nerve (C5, 6) This nerve is also called the circumflex humeral nerve. It supplies nothing in the axilla and winds round the surgical neck of the humerus. It passes through the quadrangular space where it lies in contact with the surgical neck. It divides into anterior and posterior branches. The anterior branch supplies the deltoid muscle, while the posterior branch supplies the teres minor and deltoid. It then becomes cutaneous and continues as the upper lateral cutaneous nerve of the arm.
The Radial nerve This is the continuation of the posterior cord of the brachial plexus. It is the largest branch of the brachial plexus. It passes through the lower triangular space of the arm and supplies the extensor muscles of the arm and forearm. It divides into superficial and deep branches. The former supplies the skin of the back of the arm, forearm and hand. The posterior interosseous nerve, the continuation of the deep branch, supplies the extensor carpi radialis longus and brevis, supinator, extensor digitorum, extensor indicis, abductor pollicis longus and extensor pollicis brevis.
APPLIED ANATOMY 1. Erb palsy or Erb-Duchenne palsy It is an upper brachial plexus injury and is due to damage to the upper trunk (C5, 6). The nerves that are derived solely from C5 and C6 roots are affected: suprascapular nerve, nerve to subclavius, musculocutanoeus nerve and axillary nerve. There is paralysis of supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor. The arm is adducted and medially rotated, and the forearm is extended and pronated. This is because the abductors and lateral rotators of the shoulder joint, and the flexors and supinators of the forearm are affected. This position of the upper limb is called Porter’s tip, Waiter’s tip or Policeman’s tip hand. It occurs when there is excessive increase in the angle between the neck and the shoulder. It may due to traction of the head in a breech delivery or direct compression of the nerves during forceps delivery. In the adult, it may be due to motorcycle accidents, fall from a height, or anaesthesia.
2. Klumpke's palsy or paralysis It is a lower brachial plexus injury and is due to injury to the lower trunk (C8, T1) as a result of excessive abduction of the arm. The T1 roots of ulnar and median nerves are damaged and there is paralysis of the intrinsic muscles of the hand. It leads to claw hand, anaesthesia and analgesia, and there may also be Horner’s syndrome. Klumpke’s palsy is not as common as Erb’s palsy.
3. Crutch paralysis The brachial plexus in the axilla may be damaged by pressure from a crutch. The radial nerve is most frequently involved; the ulnar nerve may also be damaged.
4. 'Sleep palsy or 'Saturday night palsy It is usually due to prolonged compression of the radial nerve at the spiral groove of the humerus, while the patient is in deep sleep under the influence of alcohol or drugs. Unusual sleep positions may also cause sleep palsies involving other nerves. The ulnar nerve may undergo sleep palsy from prolonged pressure at cubital tunnel behind the medial epicondyle
5. Winged scapula This is caused by injury to the long thoracic nerve and it results in weakness or paralysis of serratus anterior muscle. The inferior angle of the scapula is drawn medially by the unopposed actions of the rhomboids and levator scapulae. The scapula is drawn away from the thoracic cage and it has a winged-like appearance. Elevation of the arm above the head is impaired unless the inferior angle of the scapula is pushed anterolaterally. Winged scapula is best demonstrated when the affected individual pushes forward against resistance.
25
7. THE RADIAL NERVE
The radial nerve is the continuation of the posterior cord of the brachial plexus. It is derived from the posterior divisions of the ventral rami of C5-T1 and is the largest branch of the brachial plexus.
COURSE AND RELATIONS In the axilla it descends in front of the subscapularis and the tendons of latissimus dorsi and teres major and behind the third part of the axillary artery and the upper part of the brachial artery. It then inclines posteriorly to enter the spiral groove of the humerus by passing through the triangular space between the long and medial heads of triceps brachii, and the humerus. It then runs obliquely across the back of the humerus above the medial head and deep to the lateral head of triceps. In the groove, it is accompanied by the profunda brachii artery. At the lateral side of the humerus, it pierces the lateral intermuscular septum and enters the anterior compartment of the arm along with the radial collateral artery, which is a descending branch of the profunda brachii artery. In the anterior compartment of the arm, it first lies between the brachialis and the extensor carpi radialis longus. In front of the lateral epicondyle, it divides into a deep and a superficial branch.
BRANCHES Branches in the axilla (before entering the spiral groove). They are three in number: 1. The posterior cutaneous nerve of the arm. This is the first branch of the radial nerve. It supplies a strip of skin along the extensor compartment of the arm. 2. Two muscular branches to the long and medial heads of triceps brachii. The branch to the medial head accompanies the ulnar nerve as far as the distal one-third of the arm and was formerly called the ulnar collateral nerve.
Branches in the spiral groove - they are four in number. 1. Two muscular branches to the lateral and medial heads of triceps brachii. The branch to the medial head also supplies anconeus. 2. The lower lateral cutaneous nerve of the arm. This is given off just before the radial nerve pierces the lateral intermuscular septum. It supplies skin over the lateral surface of the arm. 3. The posterior cutaneous nerve of the forearm. This supplies a strip of skin over the extensor surface of the forearm.
Branches after the spiral groove - they are 3 in number 1. Muscular branch to the lateral part of brachialis 2. Muscular branch to brachioradialis 3. Muscular branch to extensor carpi radialis longus
Deep terminal branch (posterior interosseous nerve): It spirals around the upper end of the radius and gives a branch to the extensor carpi radialis brevis and to supinator. It then pierces supinator and enters the extensor compartment of the forearm. It may be called the posterior interosseous nerve when it emerges from the supinator muscle. At first, it descends between the superficial and deep muscles of the extensor compartment. In the distal part of the forearm, it runs on the dorsal aspect of the interosseous membrane and ends on the dorsum of the carpus. Its termination is expanded and is sometimes referred to as a pseudoganglion. In the extensor compartment, it supplies 7 muscles, viz: extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis.
It is also sensory to the interosseous membrane and the periosteum of the radius and ulna. It gives articular branches to the wrist and carpal joints. 26 Superficial terminal branch: It is smaller than the deep terminal branch but it is the direct continuation of the radial. It lies superficial to supinator and deep to brachioradialis, and lateral to the radial artery. In the middle third of the forearm, it comes closer to the lateral side of the artery. About 7cm above the radial styloid process of the radius, it leaves the artery and winds around the lateral side of the radius to pierce the deep fascia.
At the dorsum of the hand, it divides into 4 or 5 dorsal digital nerves. The first branch supplies the lateral side of the thumb and the adjoining part of the thenar eminence, and communicates with the lateral cutaneous nerve of the forearm. The second branch supplies the medial side of the thumb, while the third supplies the lateral sides of the index fingers. The fourth supplies the adjoining sides of the index and middle fingers. The fifth supplies adjoining sides of the middle and ring fingers, and communicates with the dorsal branch of the ulnar nerve which may, in some cases, replace it entirely. The dorsal digital nerves supply only as far up as the nail bed of the thumb, the middle of the middle phalanx and the index finger and the bases of the middle phalanx of the middle finger and part of ring fingers. The parts of the fingers distal to these points are supplies by the palmar cutaneous branches of the median nerve.
EFFECTS OF SECTIONING THE RADIAL NERVE AT VARIOUS LEVELS
1. At the wrist joint: There is only sensory loss in the areas supplied by the dorsal digital nerves.
2. At the elbow, just proximal to the origin of the posterior interosseous nerve: a) Sensory loss as for a cut at wrist level. b) Motor loss / paralysis of all the extensor muscles of the forearm except brachioradialis and extensor carpi radialis longus. The paralysis produces a `wrist drop' in which the wrist is flexed. When an attempt is made to extend the fingers, the interossei and lumbricals extend the middle and distal phalanges, but not the proximal phalanx.
3. At the spiral groove: a) Sensory loss essentially as for a cut at the wrist level. There is only a small sensory loss in the forearm and arm because of extensive overlap in supply with other nerves. b) Motor loss similar to that produced by a cut in the nerve at the elbow, with added paralysis of brachioradialis, extensor carpi radialis longus, the lateral part of brachialis and anconeus.
4. At the axilla: a) Sensory loss as for a cut at the spiral groove b) Motor loss as for a cut at the spiral groove, with added loss of extension of the elbow because of complete paralysis of triceps.
27 8. THE ARTERIES OF THE UPPER LIMB
The subclavian artery is the stem artery of the upper limb. The right subclavian artery arises from the brachiocephalic trunk behind the right sternoclavicular joint. The left arises directly from the arch of the aorta and ascends behind the left sternoclavicular joint. The subclavian artery arches over the apex of the lung and at the outer border of the first rib becomes the axillary artery. The latter becomes the brachial artery at the lower border of teres major. The subclavian artery is divided into three unequal parts by the scalenus anterior. The first part is proximal to the scalenus anterior, the second part deep to the muscle while the third part is distal to it.
BRANCHES OF THE SUBCLAVIAN ARTERY 1. Vertebral artery 2. Thyrocervical trunk 3. Internal thoracic artery 4. Costocervical trunk 5. Descending scapular artery
The first three arise from the first part of the subclavian artery. The costocervical trunk arises from the second part. Sometimes the left costocervical trunk arises from the first part of the subclavian artery. The descending scapular artery arises from the third part of the subclavian artery. Sometimes, it is replaced by the deep branch of the transcervical artery.
Thyrocervical trunk
This arises from the first part of the subclavian artery. It is a short trunk and almost immediately divides into three branches: a. Inferior thyroid artery b. Transverse cervical artery c. Suprascapular artery
The transverse cervical artery runs laterally towards the levator scapulae. At the anterior border of the latter, it divides into a superficial or ascending branch which supplies the trapezius and a deep or descending branch which descends along the medial border of the scapula. Occasionally, The deep branch arises directly from the third part of the subclavian artery and is then called the dorsal or descending scapular artery. The branch from the thyrocervical trunk is then called the superficial cervical artery.
The suprascapular artery runs towards the superior border of the scapula. It passes above the superior transverse scapular ligament and enters the supraspinous fossa from where it passes to the infraspinous fossa through the spinoglenoid notch. Its branches are the : a) Suprasternal branch - supplying skin over the suprasternal region b) Acromial branch - supplying skin over the acromion c) Articular branch - supplying the acromioclavicular and shoulder joints d) Nutrient arteries - supplying the clavicle and scapula
The Costocervical trunk This arises from the first part of the left subclavian and the second part of the right subclavian. It arches upwards and backwards over the apex of the pleura to the neck of the first rib and divides into two: a) The highest intercostal artery: This gives off the first posterior intercostal artery and continues as the second posterior intercostal artery. b) The deep cervical artery which, along with the descending branch of the occipital artery, is the main arterial supply to the muscles of the back of the neck. 28
The descending scapular artery When present, this artery replaces the deep branch of the transverse cervical artery. It arises from the third part of the subclavian artery and runs downwards towards the superior angle of the scapula. It passes deep to the levator scapulae and descends along the medial border of the scapula accompanied by the dorsal scapular nerve.
THE AXILLARY ARTERY
This is the continuation of the subclavian artery. It begins at the outer border of the first rib and ends at the lower border of the teres major.
For descriptive purposes, the axillary artery is divided into 3 parts by pectoralis minor - the first part lies proximal to the muscle, the second part lies posterior, and the third part distal to pectoralis minor.
The first part of the axillary artery, the axillary vein and the brachial plexus are enclosed in the axillary sheath. The cords of the brachial plexus are named according to their relationship to the second part of the axillary artery.
BRANCHES OF THE AXILLARY ARTERY
From the first part 1. Supreme or superior or highest thoracic artery
From the second part 1. Thoraco-acromial artery - this pierces the clavipectoral fascia. Deep to the pectoralis major, it divides into 4 branches: a) Pectoral branch - passing between pectoralis major and minor and supplying the breast b) Acromial branch - running towards the acromion c) Clavicular branch - running towards the sternoclavicular joint d) Deltoid branch - accompanying the cephalic vein.
2. Lateral thoracic artery - it descends along the lateral border of pectoralis minor and supplies the pectoral muscles and the serratus anterior. In the female, it is large and gives branches to the breast.
From the third part 1. Anterior circumflex humeral artery - this is the smallest branch, and arises from the lateral part of the axillary artery. It runs beneath the biceps and coracobrachialis and winds around the surgical neck of the humerus.
2. Posterior circumflex humeral artery - this is larger than the anterior branch. It runs posteriorly in the company of the axillary nerve, and passes through the quadrangular space. It winds around the surgical neck of the humerus and gives off the descending branch which anastomoses with the profunda brachii artery. The terminal part anastomoses with the anterior circumflex humeral artery.
3. Subscapular artery- It is the largest branch of the axillary artery and it descends along the lateral border of subscapularis muscle. It divides into circumflex scapular and thoracodorsal arteries.
Anastomoses around the scapula There is an extensive arterial anastomoses around the scapula. They bring the first part of the subclavian artery into communication with the third part of the axillary artery.
29
The major vessels concerned are: 1. Subscapular and circumflex scapular arteries along the lateral border of the scapula.
2. Transverse cervical, descending scapular and posterior intercostal arteries along the medial border of the scapula.
3. Suprascapular artery descending along the upper border.
The transverse cervical and suprascapular arteries, both branches of the thyrocervical trunk, communicate freely on the surface of the scapula with branches of the subscapular artery.
The presence of the anastomoses makes it safe to tie either the subclavian artery or the axillary artery between the thyrocervical trunk and the subscapular artery.
Anastomoses around the acromion There are anastomoses between the acromial branches of 1. Suprascapular 2. Thoraco-acromial, and 3. Posterior circumflex humeral arteries
The corresponding veins form corresponding anastomoses.
Anastomoses on the thoracic wall These are between transverse cervical, superior thoracic, lateral thoracic and subscapular arteries.
Anastomoses along the medial border of scapula These are between descending scapular and posterior intercostal arteries.
Anastomoses in infraspinous fossa These are between the suprascapular and circumflex scapular.
THE BRACHIAL ARTERY This is the continuation of the axillary artery. It begins at the lower border of teres major, and ends in the cubital fossa opposite the neck of the radius by dividing into radial and ulnar arteries. It lies first on the medial side of the humerus, and later passes in front of it to lie midway between the medial and lateral epicondyles.
BRANCHES OF THE BRACHIAL ARTERY 1. The profunda brachii artery This arises from the postero-medial aspect of the brachial artery near its origin. It descends in the spiral groove of the humerus along with the radial nerve. At the lateral side of the humerus, it divides into two descending branches: a) Radial (or anterior) collateral artery b) Middle (or posterior) collateral artery
The radial collateral artery accompanies the radial nerve to the elbow. The middle collateral passes to the back of the lateral epicondyle.
Other branches are: c) Nutrient artery (occasional) d. Ascending or deltoid branch which anastomoses with the descending branch of the posterior circumflex humeral artery. 2. Nutrient artery 30 This supplies the humerus, and arises near the middle of the arm and enters the nutrient canal.
3. Muscular branches
4. Superior ulnar collateral artery This arises near the middle of the arm and accompanies the ulnar nerve to the back of the medial epicondyle.
5. Inferior ulnar collateral artery This arises just 5cm above the elbow. It divides into 2 branches - anterior and posterior. The anterior branch passes in front of the medial epicondyle and anastomoses with the anterior ulnar recurrent artery, while the posterior branch passes posterior to the medial epicondyle to anastomose with the posterior ulnar recurrent artery.
THE RADIAL ARTERY This is the smaller of the terminal branches of the brachial artery. It is overlapped proximally by brachioradialis, and lies between the flexor and extensor groups of muscles.
It is accompanied in the middle third of the forearm by the superficial branch of the radial nerve. In the distal part of the forearm, it becomes superficial and lies on the lateral side of the flexor carpi radialis tendon. It crosses to the back of the wrist by passing below the styloid process of the radius. It may be absent.
BRANCHES OF THE RADIAL ARTERY 1. The radial recurrent artery - arises below the elbow 2. Muscular branches - to the radial side of the forearm 3. Superficial palmar branch - contributes to the formation of the superficial palmar arch 4. Palmar carpal branch 5. Dorsal carpal branch 6. 1st dorsal metacarpal artery 7. Arteria princeps pollicis 8. Deep palmar arch
THE ULNAR ARTERY This is the larger terminal branch of the brachial artery. It passes obliquely downwards to the wrist. It passes anterior to the flexor retinaculum to enter the palm and form the superficial palmar arch with a contribution from the radial artery.
BRANCHES OF THE ULNAR ARTERY 1. Anterior ulnar recurrent artery 2. Posterior ulnar recurrent artery 3. Common interosseous artery - this is a short trunk which divides at the upper border of the interosseous membrane into: a) Anterior interosseous artery b) Posterior interosseous artery - this gives off the interosseous recurrent artery. 4. Muscular branches 5. Palmar carpal branches 6. Dorsal carpal branch 7. Deep palmar branch - joins the deep palmar arch 8. Superficial palmar arch 31 Anastomoses around the elbow In front of the medial epicondyle: Anterior ulnar recurrent artery anastomoses with the anterior branch of inferior ulnar collateral artery.
Behind the medial epicondyle: Posterior ulnar recurrent artery anastomoses with the posterior branch of inferior ulnar collateral and superior ulnar collateral arteries.
In front of the lateral epicondyle: Radial recurrent artery anastomoses with the radial collateral artery.
Between the lateral epicondyle and the olecranon: Interosseous recurrent artery anastomoses with the descending branch of profunda brachii artery (or middle collateral artery) and inferior ulnar collateral artery.
Anastomoses at the wrist These are the anastomoses between the anterior and posterior carpal branches of radial and ulnar arteries.
Anterior carpal arch This lies transversely across the wrist joint. It supplies the carpal bones and sends branches distally to anastomose with the deep palmar arch.
Posterior carpal arch This lies transversely across the distal row of carpal bones. It gives off a dorsal metacarpal artery to each metacarpal space. These arteries divide to supply the fingers and they anastomose through the interosseous spaces with the palmar digital and metacarpal branches of the palmar arches. There are free anastomoses between the radial and ulnar arteries through the carpal and palmar branch. 32 9. THE LYMPHATIC DRAINAGE OF THE UPPER LIMB
The lymph vessels of the upper limb drain into the axillary lymph nodes either directly or indirectly after passing through other lymph nodes.
These lymph vessels can be grouped into: a) Superficial lymph vessels: the superficial lymph vessels of the upper limb begin in the superficial lymphatic plexuses in the skin of the hand. The plexuses are finer and more numerous on the palm and palmar surface of the digits than on the dorsum. They accompany the large superficial veins. Those on the medial side accompany the basilic vein while those on the lateral side accompany the cephalic vein. b) Deep lymph vessels - these accompany the deep vessels e.g. the brachial, radial, ulnar and interosseous arteries. There is free communication with superficial lymph vessels.
The lymph nodes are also divided into two groups: a) Superficial lymph nodes - these are few in number, and lie in the superficial fascia. b) Deep lymph nodes - these lie deep to the superficial fascia.
SUPERFICIAL LYMPH NODES 1. Cubital or supratrochlear lymph nodes: they may be one or two in number and are located just above the medial epicondyle, and medial to the basilic vein. The afferents drain the medial three fingers and the ulnar side of the hand and forearm. The efferents accompany the basilic vein and drain into the lateral group of axillary lymph nodes.
2. Infraclavicular (deltopectoral) lymph nodes: They may be one or two in number and are located in the deltopectoral triangle along the cephalic vein. The afferents accompany the cephalic vein and they drain the thumb and its web, and the "vaccination" area. The efferents pierce the clavipectoral fascia and drain into the apical lymph nodes (and sometimes to the lower deep cervical lymph nodes)
DEEP LYMPH NODES
A) Axillary lymph nodes: They are about 20-30 in number and are distributed in the axilla. They may be divided into five groups.
1. Lateral group: This has 4-6 nodes. They lie posteromedial to the axillary vein. Their afferents are the lymph vessels that drain the entire upper limb except those that accompany the cephalic vein. The efferents drain into the central and apical groups of axillary lymph nodes, as well as the lower deep cervical lymph nodes.
2. Anterior or pectoral group: It has 4-6 nodes which lie along the lateral thoracic vein near the lower border of pectoralis minor. The afferents drain: a) The skin and muscles of the anterior and lateral walls of the trunk above the level of the umbilicus. b) The central and lateral parts of the mammary gland.
The efferents drain to the central and apical nodes.
3. Posterior or scapular group: It has 6-7 nodes. They are located along the subscapular vessels at the lateral border of the scapula.
33 The afferents drain: a) Skin and muscles of the lower part of the back of the neck. b) Skin and muscles of the dorsal aspect of the trunk as far down as the iliac crest. c) Tail of the breast.
The efferents drain into central and apical nodes.
4. Central group: It has 3-4 nodes. They are located near the base of the axilla. They have no specific drainage area. Their afferents are the efferents of the lateral, posterior and anterior groups of lymph nodes. The efferents drain into the apical nodes.
5. Apical group: It has the largest group of axillary lymph nodes. There are about 16-20 nodes in this group. They are the most commonly palpated axillary lymph nodes. It is the only group of axillary lymph nodes that lies above the pectoralis minor. It lies at the apex of the axilla, medial to the axillary vein. Their afferents are: a) Efferents of the other axillary lymph nodes b) Lymph vessels that accompany the cephalic vein c) Lymph vessels that drain the upper part of the breast
The efferents mostly unite to form the subclavian lymph trunk which drains into any of the following: a) Junction of the internal jugular and subclavian veins b) Jugular lymphatic trunk c) Thoracic duct
B) A few deep lymph nodes may be found along the brachial, radial, ulnar and interosseous arteries.
Lymphatics are important because they form an important route for the spread of infection and cancer. Infections of the upper limb and parts of the neck and trunk may lead to enlargement of the axillary lymph nodes, as may cancer of the breast. The lymph vessels when inflamed may appear as red lines in fair-skinned people.
34 10. THE MEDIASTINUM
The mediastinum is the area or space in the thorax between the two pleural sacs. It extends from the thoracic inlet above to the diaphragm below and from the sternum in front to the 12 thoracic vertebrae behind. It is a mobile structure because some of its contents are constantly changing in volume and position.
For descriptive purposes, the mediastinum is divided into a superior mediastinum and an inferior mediastinum by an imaginary horizontal plane passing between the sternal angle (of Louis) in front and the disc between 4th and 5th thoracic vertebrae behind.
The inferior mediastinum is further subdivided into three parts: a) Anterior mediastinum b) Middle mediastinum c) Posterior mediastinum
SUPERIOR MEDIASTINUM
This lies between the manubrium sterni in front and the upper 4 thoracic vertebrae behind. It extends from the thoracic inlet above to an imaginary horizontal plane passing through the sternal angle and the disc between T4 and T5. It is bounded laterally by the mediastinal pleura. It is wedge shaped and the base of the wedge lies posteriorly. The posterior boundary is longer than the anterior because of the obliquity of the thoracic inlet. The manubrium is connected to the upper part of the pericardium by loose connective tissue referred to as the superior sternopericardial ligament.
CONTENTS 1. Muscles: i) The origins of the sternohyoid and sternothyroid muscles. These are the most ventral structures in the superior mediastinum. ii) The lower part of the longus colli muscle. This is the most dorsal structure in the superior mediastinum.
2. The superior portion of the thymus gland: the thymus is relatively large and active in childhood. It regresses during adolescence.
3. Veins: They lie in front of the arteries. i) Upper part of the superior vena cava ii) Arch of the azygous vein iii) Left and right brachiocephalic veins iv) Left superior intercostal vein
4. Arteries: Arch of the aorta and its three main branches - brachiocephalic, left common carotid and left subclavian arteries.
5. Nerves: i) Right and left vagus nerves ii) Left recurrent laryngeal nerve, which hooks around the ligamentum arteriosum, then ascends in the groove between the trachea and the oesophagus.
6. The thoracic and lymphatic ducts. The former lies behind the arch of the aorta and the left subclavian artery.
7. Lymph nodes of the paratracheal and tracheobronchial groups. 8. The viscera: 35 i) Trachea: it lies in the midline and dorsal to the great vessels. ii) Oesophagus: it lies dorsal and slightly to the left of the trachea.
THE ANTERIOR MEDIASTINUM This lies between the body of the sternum in front, and the pericardium behind. It is a narrow space. It is continuous, through the superior mediastinum, with the pretracheal space of the neck. Loose connective tissue connects the xiphoid process to the inferior part of the pericardium.
CONTENTS 1. The remnants of the lower part of the thymus gland. This is the main content of this space. 2. Areolar tissue. 3. Branches of the internal thoracic vessels. 4. Lymphatics and a few lymph nodes. 5. Transversus thoracis muscle.
THE MIDDLE MEDIASTINUM This is the largest compartment of the mediastinum.
CONTENTS 1. The pericardium and the heart 2. The roots of the great vessels: i) Lower half of the superior vena cava ii) Terminations of right and left brachiocephalic veins iii) Azygous vein iv) Right and left pulmonary veins v) Ascending aorta vi) Pulmonary trunk with its left and right branches 3. The bifurcation of the trachea. 4. The phrenic nerves and the deep cardiac plexus. 5. Tracheobronchial lymph nodes.
POSTERIOR MEDIASTINUM This is the portion of the mediastinum posterior to the pericardium and the diaphragm. The upper part of the anterior boundary is formed by the pericardium (the left atrium), while the lower part is formed by the diaphragm. The posterior boundary is formed by the lower eight thoracic vertebrae. Through the superior mediastinum, it communicates with the retropharyngeal space and the spaces lateral to the trachea and oesophagus.
CONTENTS 1. Thoracic aorta and its intercostal branches. 2. Inferior vena cava 3. Azygos and hemiazygos veins. 4. Thoracic duct and the right lymphatic duct. 5. Left and right vagus nerves 6. Sympathetic trunk and the splanchnic nerves 7. Oesophagus. 8. Posterior mediastinal lymph nodes.
APPLIED ANATOMY Infections in the neck can spread to the mediastinum, causing mediastinitis. Lateral displacement of the mediastinum by increased pressure in one of the pleural cavities, or as a result of fibrosis or collapse, can be detected clinically by lateral deviation of the trachea in the jugular notch and by alteration of the position of the apex beat of the heart. 36 11. TRACHEA, LUNGS AND PLEURA
THE TRACHEA The trachea is a cartilaginous and membranous tube that extends downwards from the lower end of the larynx. It begins at the level of the lower border of C6, and ends at the level of the sternal angle (level of the disc between T4 and T5) by bifurcating into right and left principal bronchi. The trachea moves upwards during swallowing and downwards in deep inspiration. The level of bifurcation varies with the phase of respiration, the position of the body, and the age of the individual. In deep inspiration, the bifurcation may descend to the level of T6. In the cadaver, the bifurcation is at the level of the upper border of T5. At birth the bifurcation is at the level of T3.
The trachea is about 10-15cm long and may increase or decrease in length. The posterior surface is flattened. Its external diameter is 2cm in males and 1.5cm in females. In children, the trachea is smaller, more deeply placed and more mobile than in the adult. The trachea lies mainly in the median plane but near its bifurcation, it deviates slightly to the right. At the bifurcation, there is an antero- posterior ridge called the carina. This ridge lies to the left of the midline.
RELATIONS Anteriorly: thymus, left brachiocephalic vein, the arch of the aorta, the brachiocephalic artery and the common carotid artery, the isthmus of the thyroid gland. Posteriorly: oesophagus, left recurrent laryngeal nerve.
Left side: arch of the aorta, left common carotid artery, left subclavian artery, left vagus and phrenic nerves, pleura and upper lobe of the left lung. Right side: arch of azygos vein, right vagus nerve, pleura and the upper lobe of right lung.
At the bifurcation: the pulmonary trunk (dividing into left and right pulmonary arteries. This division lies more to the left principal bronchus), the deep cardiac plexus, the tracheobronchial group of lymph nodes.
THE RIGHT MAIN BRONCHUS This is shorter, wider and more vertical than the left bronchus. It is about 2.5cm long and slopes about 25 degrees off the vertical. Foreign bodies are, therefore, more likely to enter the right main bronchus.
Before entering the hilum of the right lung, the main bronchus gives off the superior lobar bronchus. On entering the hilum, it divides into a middle and inferior lobe bronchus.
THE LEFT MAIN BRONCHUS This is longer, narrower, and more horizontal than the right. It is about 5cm long and 45 degrees off the vertical (40 degrees in the male and 50 degrees in the female).
Unlike the right bronchus, it enters the hilum before dividing into superior and inferior lobar bronchi.
The bronchi are supplied by the bronchial arteries. The right bronchial vein drains into the azygos vein while the left drains into the accessory hemiazygos vein.
THE LUNGS The lungs are the organs of respiration and are located on either side of the mediastinum. They are soft, spongy and very elastic. In the child, they are pink in colour, but with age, they become mottled because of accumulation of dust particles. Each lung is covered with visceral pleura and is suspended free in the pleural cavity except at its root where it is attached to the mediastinum. The right lung is wider and heavier. Each lung is conical in shape and has an apex, three surfaces and three borders.
37 SURFACES The surfaces are medial, costal and diaphragmatic (base). The apex is rounded and projects superiorly into the neck. The summit is 2.5cm above the medial third of the clavicle or 3cm above the 1st costal cartilage.
The base is also referred to as the diaphragmatic surface. It is related to the dome of the diaphragm. The base of the right lung is more concave than that of the left lung. This is because the right dome of the diaphragm is pushed higher up by the right lobe of the liver.
The costal surface is related to the sternum and the ribs and their costal cartilages.
The medial surface is divided into two parts: the posterior or vertebral part and the anterior or mediastinal part. The vertebral part is related to the borders of the vertebrae while the mediastinal part is related to the mediastinum. The mediastinal part has a deep concavity called the cardiac impression for the pericardium. It is deeper on the left lung because the heart projects more to the left. Above and behind the cardiac impression, there is another impression called the hilum or hilus. Here, the structures that form the root of the lung enter or leave the lung.
BORDERS It has anterior, posterior and inferior borders. The anterior border is sharp and separates the medial and costal surfaces. The anterior border of the left lung has a notch called the cardiac notch.
The inferior border separates the base from the costal surface.
The posterior border is rounded and separates the costal surface from the medial surface.
SURFACE MARKINGS In the supraclavicular region and the costal wall, the surface marking coincides with that of the pleura. The anterior border of the left lung curves laterally from the 4th costal cartilage to the apex beat in the mid-clavicular line. From this point, the lower borders of the lungs lie horizontally 2 ribs higher than the pleura - 6th rib in the mid-clavicular line, 8th rib in the mid-axillary line and the 10th rib posteriorly.
LOBES AND FISSURES OF THE LUNGS The right lung is divided by the oblique and horizontal fissures into 3 lobes - superior, middle and inferior.
The oblique fissure begins at the posterior border of the lung at the level of the spine of T4 or slightly lower. In the mid-axillary line, it crosses the 5th intercostal space and then follows the course of the 6th rib to the 6th costo-chondral junction. It is marked by the vertebral order of the scapula when the arm is abducted above the head.
The horizontal fissure separates the superior and middle lobes. It runs horizontally from the oblique fissure near the mid-axillary line to the anterior border of the lung at the level of the 4th costal cartilage.
The left lung is divided by an oblique fissure into superior and inferior lobes. The course of the left oblique fissure is similar to that of the right one, except that it starts at a higher level - in the interval between the spines of T3 and T4, and is more vertical.
38 ROOTS OF THE LUNGS The root of the lung connects the medial surface of the lung to the heart and trachea. It lies opposite the bodies of T5 to T7 vertebrae and is formed by structures which enter or leave the hilus. These structures are the principal bronchus, the pulmonary artery, the two pulmonary veins, the bronchial arteries and veins, the pulmonary lymph nodes and areolar tissue. These structures are enveloped in a sleeve of pleura. The "sleeve" is too big for the root of the lung and it hangs inferiorly as an empty fold called the pulmonary ligament. This serves as dead space for the expansion of the root of the lung.
The root of the left lung lies within the concavity of the arch of the aorta. The upper part of the root is occupied by the left pulmonary artery. Below and behind the left pulmonary artery is the left main bronchus. There are two pulmonary veins; one is in front of the main bronchus while the other is below it. There are two bronchial arteries.
The root of the right lung lies within the concavity of the azygos vein. The arrangement of the structures within it is similar to that on the left. The main difference is the existence of the superior lobar bronchus arising above the hilus. Usually there is only one bronchial artery.
The arrangement of the structures that constitute left and right roots is similar from anterior to posterior; the pulmonary vein is in front, the pulmonary artery is in the middle and the main bronchus behind. The bronchial vessels are posterior to the bronchus. From above downwards, the arrangement on the right differs from that on the left. On the left side, from above downwards are the pulmonary artery, the main bronchus and the lower pulmonary vein. On the right side, from above downwards are the superior lobe or eparterial bronchus, the pulmonary artery, the right principal bronchus and the lower pulmonary vein.
BRONCHOPULMONARY SEGMENTS A bronchopulmonary segment is a portion of the lung supplied by a tertiary or segmental bronchus. It is a structural and functional unit of the lung.
The segments are pyramidal in shape, with their apices directed towards the hilum and their bases towards the surface of the lung. They are given the same names as their segmental bronchi. The segments differ in the two lungs only in the different positions of the two segments of the middle lobe. There are ten segments in each lung. The segments are:
RIGHT LUNG LEFT LUNG
Upper lobe Upper lobe 1. Apical 1 & 2 Apicoposterior 2. Posterior 3. Anterior 3.Anterior
Middle lobe Lingula 4. Lateral 4. Superior 5. Medial 5. Inferior
Lower lobe Lower lobe 6. Apical basal 6. Apical (superior) basal 7. Medial basal 7. Medial basal 8. Anterior basal 8. Anterior basal 9. Lateral basal 9. Lateral basal 10. Posterior basal 10.Posterior basal
39 Importance Diseases may be restricted to one or more segments of the lungs. A segment may be excised without damage to the other segments. Knowledge of the bronchopulmonary is also important in postural drainage of the lung, bronchoscopy, interpretation of bronchograms, and in the determination of appropriate position for the postural drainage of an infected segment.
BLOOD SUPPLY The bronchi, connective tissue and visceral pleura receive their blood supply from the bronchial arteries, which are direct branches of the aorta. There are usually two on the left and one on the right.
Bronchial veins drain into the azygos vein on the right and the accessory azygos vein on the left. They communicate with the pulmonary vein.
There is no anastomosis between the bronchial and pulmonary arteries, though peripherally there is some overspill of bronchial capillaries into the alveolar capillaries of the pulmonary arteries. The alveoli receive deoxygenated blood from the terminal bronchioles.
LYMPHATIC DRAINAGE Lymph drainage is towards the hilum from the pleura, along the bronchi and pulmonary artery.
The lymph vessels originate in the superficial and deep plexuses. The vessels from the deep plexus drain into the pulmonary lymph nodes which are located close to the hilum. The lymph vessels from the superficial plexus and from the pulmonary lymph nodes drain into the bronchopulmonary lymph nodes at the hilum. Lymph vessels from the bronchopulmonary lymph nodes drain into the bronchomediastinal lymph trunks. The latter drain into the brachiocephalic vein, the right lymphatic trunk or the thoracic duct.
NERVE SUPPLY The lungs are supplied by the pulmonary plexus, which is formed by branches of the sympathetic trunk and fibres from the vagus nerve.
Vagal efferents are motor (constrictor) to the smooth muscle of the bronchi and the pulmonary arterioles, and secretomotor to the glands.
Sympathetic efferents are dilator to the pulmonary arterioles and to the bronchi.
THE PLEURA The pleura is a serous membrane that invests or surrounds each lung. It consists of two layers - visceral and parietal.
The parietal pleura lines the thoracic wall and covers the thoracic surface of the diaphragm. The visceral pleura covers the surface of the lungs and lines the fissures between the lobes. It is intimately related to the lung surface. The visceral and parietal layers are continuous with each other around the root of the lung. The potential space between them is called the pleural cavity. It is a completely closed cavity, and contains a thin film of fluid which lubricates the pleura and facilitates movement of the lungs.
The parietal pleura is given different names according to the region which it lines or the surface it covers. The portion covering the internal aspects of the ribs and the transversus thoracis is called the costal pleura and is separated from these structures by a layer of loose areolar tissue called the endothoracic fascia. The latter corresponds to the transversalis fascia of the abdominal wall. The costal pleura is the strongest part of the parietal pleura. The diaphragmatic pleura covers the thoracic surface of the diaphragm. The cervical pleura or dome of the pleura is the portion that ascends into the neck. It is strengthened by a thickening of endothoracic fascia called the suprapleural membrane (Sibsons fascia). The mediastinal pleura is the portion that covers the lateral wall of the mediastinum. 40
In quiet respiration the lower limit of the lung is about 5cm above the lower limit of the pleura, the lower portions of the costal and diaphragmatic pleurae are in apposition. The narrow slit between the latter two layers is called the costo-diaphragmatic recess. A similar slit between the costal and mediastinal parts of the parietal pleura is called the costomediastinal recess.
The cuff of pleura that projects around the root of the lung is too big for it. It hangs down as an empty fold called the pulmonary ligament. This is a misnomer, as it is not a ligament and has nothing to do with the lung. It serves as a dead space for the expansion of the pulmonary veins when there is increased venous return, as during exercise. The pulmonary ligament also allows for the descent of the root of the lung.
SURFACE MARKING OF THE PLEURA The pleura projects into the neck. The surface marking of the cervical pleura is a curved line from the sternoclavicular joint to a point 2.5cm above the junction between the medial and intermediate thirds of the clavicle. From behind the sternoclavicular joint, the pleura runs downwards behind the sternum to meet its fellow at the sternal angle, i.e. the level of the 2nd rib. The right and left pleurae may overlap at this level. The pleura then passes vertically behind the sternum down to the level of the 4th costal cartilage. Here, the right pleura continues vertically downwards, while the left arches out and laterally half-way to the apex of the heart.
At the 6th costal cartilage, each pleura turns laterally, crossing the mid-clavicular line at the 8th rib, the mid-axillary line at the 10th rib and the lateral border of sacrospinalis at the 12th rib. It then passes horizontally to the lower border of the 12th thoracic vertebra.
NERVE SUPPLY OF THE PLEURA The costal pleura is segmentally supplied by intercostal nerves. The mediastinal pleura is supplied by the phrenic nerve while the diaphragmatic pleura is supplied over the domes by the phrenic nerves, and around the periphery by the intercostal nerves.
The visceral pleura has only an autonomic vasomotor supply. It is insensitive to ordinary sensations such as pain and touch. 41 12. THE AUTONOMIC NERVOUS SYSTEM IN THE THORAX
The autonomic nervous system supplies the thoracic viscera via the vagal nerves and the sympathetic trunk.
The autonomic nervous system differs structurally from the somatic nervous system in that the nerve fibres which exit the CNS are not pre-ganglionic fibres and they synapse in ganglia, or in the visceral walls (in the case of parasympathetic fibres) with the post-ganglionic fibres.
THE SYMPATHETIC NERVOUS SYSTEM IN THE THORAX The sympathetic outflow to the entire body is derived from spinal segments T1 to L2 or L3. The pre- ganglionic fibres have their cell bodies in the lateral horn of the thoracic spinal cord and pass in the ventral roots of their corresponding ganglia via white rami communicantes which are so coloured because of the myelinated nature of these fibres. In the ganglia, these pre-ganglionic fibres may: a) Synapse with post-ganglionic fibres b) Pass up or down in the sympathetic trunk to reach ganglia at other levels c) Pass out of the ganglia without synapsing via visceral nerves
There are usually 3 cervical, 11 thoracic, 4 lumbar and 4 sacral sympathetic ganglia. The lowest cervical and 1st thoracic may fuse to form the cervicothoracic or stellate ganglion. Sympathetic fibres to the thoracic viscera are derived from spinal segments T1 to T5. Some of these pre-ganglionic fibres ascend in the sympathetic trunk to the cervical sympathetic ganglia, while the rest synapse in the upper thoracic ganglia. From these ganglia, post-ganglionic fibres are distributed in: a) Cardiac branches of the superior middle and inferior cervical ganglia to the cardiac plexuses b) Visceral branches from the upper five thoracic ganglia to the aortic, pulmonary and oesophageal plexuses
The sympathetic trunk in the thorax lies on the necks of the ribs, just lateral to their heads. It passes down into the abdomen behind the medial arcuate ligament, to lie on the psoas major muscle. All the ganglia give off visceral branches, but those from the 5th to the 12th give off contributions to the: a) Greater splanchnic nerve - from 5th to 9th or 10th ganglia b) Lesser splanchnic nerve - from 9th or 10th to 11th ganglia c) Least splanchnic nerve - from the 12th ganglion
These splanchnic nerves descend medial to the sympathetic trunk to supply abdominal viscera, the former two with the sympathetic trunk behind the medial arcuate ligament, and the latter through the corresponding crus of the diaphragm.
THE PARASYMPATHETIC NERVOUS SYSTEM IN THE THORAX Pre-ganglionic parasympathetic fibres to the thoracic viscera all arise from the dorsal motor nucleus of the vagus(cranial nerve X), while the afferent fibres have their cell-bodies in the inferior vagal ganglia. They are distributed to the thoracic. a) Superior cardiac branches arising high in the neck and joining the cervical cardiac branches of the sympathetic ganglia. b) Inferior cardiac branches arising in the root of the neck and running directly to cardiac plexuses. c) Cardiac branches of the vagus and recurrent laryngeal nerves in the thorax. d) Anterior and posterior pulmonary branches to the respective pulmonary plexuses, e. oesophageal branches to the oesophageal plexuses.
The vagi also carry branchial motor fibres which are distributed via the recurrent laryngeal nerves to the laryngeal musculature. 42
The two vagi do not follow identical courses in the thorax. The right vagus enters the thorax lying on the trachea and descends posterior to the hilum of the right lung to then lie on the oesophagus where, together with the left vagus and sympathetic fibres, it breaks up to form the oesophageal plexus.
The left vagus is separated from the trachea by the arch of the aorta upon which it lies, and then leaves to pass onto the posterior aspect of the hilum of the left lung and then the oesophagus. As the left vagus crosses the arch of the aorta, it gives off a substantial branch, the left recurrent laryngeal nerve, which hooks upward beneath the ligamentum arteriosum to ascend in the groove between the trachea and the oesophagus into the neck. The right recurrent laryngeal nerve performs a similar manoeuvre, but around the subclavian artery in the root of the neck.
VISCERAL PLEXUSES IN THE THORAX There are several plexuses supplying the viscera with autonomic fibres in the thorax.
Cardiac Plexuses There are two cardiac plexuses traditionally described - superficial and the larger deep plexuses. However, both are functionally a single unit. They distribute sympathetic and parasympathetic fibres to the heart, and extend onto the coronary arteries as the smaller coronary plexuses.
The superficial cardiac plexus lies inferior to the aortic arch, and receives: a) Inferior cervical branch of the left vagus nerve - carrying parasympathetic fibres b) Cardiac branch of the left superior cervical ganglion - carrying sympathetic fibres.
The deep cardiac plexus lies between the arch of the aorta and the bifurcation of the trachea, and receives contributions from the superficial plexus, as well as from: a) Superior cervical cardiac branch of the left vagus nerve b) Both cervical cardiac branches of the right vagus nerve c) Branches of both recurrent laryngeal nerves d) Branches from the remaining five cervical sympathetic ganglia
The preganglionic parasympathetic fibres arise in the dorsal nuclei of the vagi, and synapse with post-ganglionic fibres in the myocardium. The vagi also contain afferent fibres concerned with cardiovascular reflexes which relay in the inferior vagal ganglia in the brainstem.
The sympathetic preganglionic fibres arise from cell bodies in the lateral horn of thoracic segments of T1 to T5, and these fibres ascend in the sympathetic trunk to synapse with post-ganglionic fibres in the cervical sympathetic ganglia which they then leave in their cardiac branches. The sympathetic nerves also carry afferent fibres subserving pain to cervical and upper two or three thoracic ganglia which they leave via the white rami on their way to the spinal cord and then the inferior vagal ganglia. It is these fibres that are responsible for the referral of cardiac pain along cervical and thoracic spinal nerves to the arm, chest and neck. The coronary arteries are provided with vasomotor fibres, while the SA node is supplied with cardio- inhibitor and cardio-accelerator fibres.
Pulmonary Plexus The pulmonary plexuses exit at the roots of the lungs sending autonomic nerve fibres into the lungs along the bronchial tree. As the vagi descend behind the hila of the two lungs they give off numerous twigs to the plexus which are sometimes described as having anterior and posterior parts.
The pulmonary plexuses also receive contributions from the cardiac plexuses, and visceral nerves of the upper thoracic sympathetic ganglia (T1 to T4). The parasympathetic afferents end in cell bodies in the inferior vagal ganglia, and subserve the response to bronchial stimulation (important in the clinical diagnosis of brain death), and also to pain. The preganglionic efferent fibres have their cell 43 bodies in the dorsal motor nucleus of the vagus and are motor to the smooth muscle of the bronchi and the pulmonary arteries/arterioles (broncho-and vaso-constrictor).
The spinal connections for the sympathetic preganglionic fibres actually lie at levels T2 to T6, despite the origins of the post-ganglionic fires from the 1st to 4th thoracic ganglia. The sympathetic efferents are dilator to the bronchial smooth muscle and pulmonary vasculature, to accommodate increase cardiac output and allow increased pulmonary ventilation in excited states.
Oesophageal Plexus While the upper oesophagus is supplied with branchial motor fibres via the recurrent laryngeal nerves, and sympathetic nerve fibres from the middle cervical ganglion running along the inferior thyroid artery, the lower part is supplied by the anterior and posterior oesophageal plexuses.
As the vagal nerves descend on their respective sides of the oesophagus, they wind around it: the left nerve to the anterior surface and the right nerve posteriorly. They then split into numerous twigs forming a widely enmeshed network encircling the oesophagus below the level of the lung roots and collecting into anterior and posterior vagal trunks over the last few centimetres of the thoracic oesophagus. The anterior trunk consists predominantly of fibres from the left vagus, while the posterior trunk has mostly right vagal fibres.
The plexus receives postganglionic sympathetic fibres from the visceral branches of the upper five sympathetic ganglia, as well as indirectly via the greater splanchnic nerve.
The parasympathetic fibres are motor to the smooth muscle of the lower oesophagus with the cell bodies in the dorsal motor nucleus of the vagus (note that the upper skeletal muscle is also supplied by the vagus nerves, but by branchial motor fibres via the recurrent laryngeal nerves having their cell bodies in the nucleus ambiguus). The secretomotor fibres of the vagus have their cell bodies in the inferior salivary nucleus. Afferent parasympathetic fibres pass to their cell bodies in the inferior vagal ganglion. The sympathetics are vasomotor with preganglionic cell bodies at spinal levels T5 and T6. 44 13. THE INGUINAL CANAL AND HERNIAS
The inguinal canal is an oblique passage in the lower part of the anterior abdominal wall. It is about 3-5cm long and passes downwards and medially from the deep or internal inguinal ring to the superficial or external inguinal ring. It lies parallel to and about 1cm above the medial half of the inguinal ligament. It represents the path of descent of the testis and spermatic cord in the male, or the round ligament of the uterus in the female.
The superficial inguinal ring is a V-shaped slit or gap in the external oblique aponeurosis. It lies above and medial to the pubic tubercle. The base is formed by the pubic crest and the margins by the medial and lateral crura. The medial crus is attached to the pubic symphysis while the lateral crus is attached to the pubic tubercle. Intercrural fibres help to strengthen the apex and prevent the crura from spreading out. The deep ring is an oval area of evagination in the transversalis fascia. It lies 1- 2cm above the mid-inguinal point (midpoint between the anterior superior iliac spine and the pubic symphysis), just lateral to the epigastric vessels.
RELATIONS OF THE INGUINAL CANAL
Anterior relations/wall a) The canal is bounded throughout its entire length by skin, superficial fascia, and the external oblique aponeurosis. b) It is also bounded in its lateral third by the internal oblique aponeurosis.
Posterior relations/wall a) The posterior wall is formed throughout its entire length by transversalis fascia. b) It is reinforced medially by the conjoint tendon - which is the fused common insertion of the internal oblique and transversus abdominis.
Roof This is formed by the lowest fibres of the internal oblique and transversus abdominis that arch medially across the canal.
Floor The floor is formed by the inguinal ligament, and on its medial end by the lacunar ligament.
CONTENTS OF THE INGUINAL CANAL The canal transmits the spermatic cord and ilioinguinal nerve in the male, and the round ligament of the uterus and ilioinguinal nerve in the female.
The spermatic cord itself consists of the following structures: 1. 3 layers of fascia: a) External spermatic fascia - derived from external oblique muscle. b) Cremasteric fascia and muscle - derived from internal oblique muscle. c) Internal spermatic fascia - derived from transversalis fascia
2. 3 arteries: a) Testicular artery - from aorta b) Cremasteric artery - from inferior epigastric artery c) Artery of the vas deferens - from inferior vesical artery. This artery is homologous to the uterine artery. 45 3. 3 nerves: a) Ilioinguinal nerve b) Nerve to cremasteric muscle - a branch of the genitofemoral nerve. c) Sympathetic nerve fibres
4. Other structures: a) Vas deferens. b) Pampiniform plexus of veins: they coalesce to form the testicular veins. The left testicular vein drains into the left renal vein while the right drains into the inferior vena cava. The pampiniform plexus creates a countercurrent heat exchange mechanism which helps to keep the testis at about 3 degrees below the body temperature. Varicosities of the pampiniform plexus is called varicocele. It is more common on the left side. c) Lymphatic vessels from the testis.
HERNIAS Hernias are abnormal protrusions of an organ or part of an organ through a defect in the walls of the cavity it lies in. There are different types, but the commonest ones are inguinal, femoral and umbilical hernias.
A hernia usually has: a) Sac - of parietal peritoneum b) Neck - the proximal end of the sac c) Contents - the protruding viscus d) Coverings - structures separating the sac from the exterior
Hernias may be acquired or congenital.
Inguinal Hernias These occur in the inguinal region, and are commoner in males than in females, because the inguinal canal is wider in males. The testis and spermatic cord traverse the inguinal canal in the male while only the round ligament of the uterus traverses the inguinal canal in the female. These hernias are commoner on the right side because of the later descent of the testis on that side.
There are two types of inguinal hernia:
Indirect inguinal hernias These begin in the lateral inguinal fossa behind the deep ring, enter the deep ring and pass through the canal to emerge from the superficial ring. They then descend into the scrotum. They lie superior and medial to the pubic tubercle.
During its passage, the indirect hernia receives a number of coverings: 1. Parietal peritoneum - the sac 2. Extraperitoneal fat 3. Internal spermatic fascia 4. Cremasteric fascia and muscle 5. External spermatic fascia 6. Superficial fascia 7. Skin
Predisposing factors for these hernias include: 1. Congenital weakness 2. Causes of increased intraabdominal pressure such as chronic cough, constipation, pregnancy, urinary obstruction. 46 The sac may become constricted at the neck with consequent impairment of the blood supply. This leads to strangulation.
When an inguinal hernia is reduced, it can be completely controlled by pressure over the deep ring - 1.5cm above the midinguinal point. An indirect inguinal hernia may be associated with a congenital defect in which the processus vaginalis (which is the peritoneal pouch accompanying the testis during its descent) remains patent.
Direct inguinal hernias These usually follow an acquired weakness in the posterior wall of the inguinal canal. The sac pushes directly forwards through Hasselbach's triangle in the lower anterior abdominal wall. This triangle is bounded medially by the lateral border of the rectus abdominis, inferiorly by the medial half of the inguinal ligament, and laterally by the inferior epigastric vessels. The direct inguinal hernia descends medial to the inferior epigastric vessels and does not usually enter the scrotum. The risk of strangulation is low.
Umbilical Hernias 1. Congenital umbilical hernias - due to failure of complete reentry of the umbilical loop during intrauterine life. 2. Paraumbilical hernias - due a defect in the lower part of the linea alba. It is commoner in obese patients. 3. Infantile umbilical hernias - due to stretching of scar tissue in the umbilical region.
Femoral Hernia This is a protrusion through the femoral ring. It is commoner in females because they have a wider pelvis. The hernia descends in the femoral canal and emerges through the saphenous opening and is directed superiorly. The risk of strangulation is high because of the ligamentous boundaries through which the hernia emerges. The hernia may pass medial or lateral to an aberrant obturator artery.
The coverings include: 1. Parietal peritoneum - the sac 2. Femoral septum - extraperitoneal tissue 3. Femoral sheath 4. Cribriform fascia 5. Superficial fascia and skin
A femoral hernia lies inferior and lateral to the pubic tubercle. 47 14. THE SPLEEN AND COELAC TRUNK
THE SPLEEN [LEN (L) OR SPLEN (GR)]
The spleen is the largest single mass of lymphoid tissue in the body. The size varies with age and the amount of blood it contains. It measures about 12cm long, 7cm wide and 3.5cm thick. On the average it weighs 150g (the range is 50-250g). The spleen increases in size during digestion. It diminishes in size and weight with advancing age.
The shape depends on the surrounding structures especially the stomach and the left colic flexure. It is roughly tetrahedral in shape when the colon is full. The spleen may also be described as having the size and shape of a clenched fist or cupped hand. It is located in the left hypochondrium between the stomach in front and the upper part of the left kidney behind and is related to the 9 to 11th ribs. The long axis is along the 10th rib.
SURFACES The spleen has two surfaces: diaphragmatic and visceral. The diaphragmatic surface is convex and smooth and is directed postero-laterally. It is related to the left dome of the diaphragm which separates it from the lower parts of the lung, the pleura and 9th to 11th ribs.
The visceral surface has 4 impressions: a) Gastric impression: this is the largest impression and it is concave. It is separated from the posterior wall of the stomach by the omental bursa. Near its lower part, there is a long fissure or cleft called the hilus. The splenic artery enters while the splenic vein leaves the spleen through the hilus. b) Renal impression: this lies below the hilus and is related to the upper and lateral part of the anterior surface of the left kidney. In children, it is also related to the suprarenal gland. c) Colic impression: this is located near the anterior end of the spleen. It is flat, and is related to the left or splenic flexure of the colon. It is also related to the phrenico-colic ligament. d) Pancreatic impression: this is located between the colic impression and the lateral part of the hilus. It is directly related to the tail of the pancreas. It is not always present.
BORDERS It has two borders: superior and inferior.
The superior (or anterior) border is convex and it separates the diaphragmatic surface from the gastric impression. Near its lateral end, it has one or two notches which indicate the lobular nature of the spleen in intrauterine life. The notches become palpable when the spleen enlarges and help to differentiate the spleen from the kidney during palpation.
The inferior border is blunter and more rounded than the superior border. It separates the diaphragmatic surface from the renal impression.
THE ENDS OR EXTREMITIES The upper, medial or posterior end is about 4cm from the dorsal midline at the level of the 10th thoracic spine.
The lower, lateral or anterior end is more expanded than the upper end, and it reaches as far as, or just medial to the midaxillary line. It is related to the phrenico-colic ligament. 48
PERITONEAL REFLECTIONS (LIGAMENTS OF THE SPLEEN) The spleen is surrounded by peritoneum, except at the hilar area. The peritoneum which surrounds the spleen is firmly adherent to its capsule, and it is continuous with the peritoneal reflections, where the peritoneum is reflected onto the surrounding structures to form gastrosplenic and splenorenal ligaments.
The gastrosplenic ligament is a double fold of peritoneum from the left portion of the greater curvature of the stomach to the visceral surface of the spleen. The short gastric and left gastroepiploic arteries lie within it.
The splenorenal or lienorenal ligament is a double fold of peritoneum extending from the hilus of the spleen to the anterior surface of the left kidney. It contains the splenic vessels and the tail of the pancreas. The phrenicocolic ligament is related to the anterior end of the spleen. It helps to support the spleen.
BLOOD SUPPLY The spleen is very vascular. It is supplied by the splenic artery. The latter passes between the layers of the lienorenal ligament, and at the hilus divides into 6 or more branches.
The splenic vein is formed by the union of 6 or more veins that arise from the hilus of the spleen. It runs in the groove between the dorsal surface of the pancreas by joining the superior mesenteric vein to form the portal vein.
NERVE SUPPLY The spleen receives only sympathetic fibres from the greater splanchnic nerve via the coeliac plexus. They are confined to the blood vessels and the smooth muscle of the capsule and trabeculae.
LYMPHATIC DRAINAGE The lymph vessels of the spleen are few and they arise from the capsule and trabeculae. They pass along the splenic vessels and drain into the pancreaticolienal lymph nodes, and then into the coeliac nodes.
APPLIED ANATOMY There may by one or more accessory spleens, which are encapsulated nodules of splenic tissue found most commonly in the hilus, but also on the tail of the pancreas, the mesentery or omentum. They may or may not be connected to the spleen. In therapeutic splenectomy for thrombocytopenic purpura, for example, it is important to remove the accessory spleens otherwise the symptoms may persist. The spleen is not essential to life. When it is removed its function is taken over by other reticuloendothelial organs.
Splenomegaly (enlargement of the spleen) occurs in a number of diseases. The spleen enlarges towards the right iliac fossa because the phrenico-colic ligament prevents it from enlarging towards the left iliac fossa. The anterior end and superior border become palpable, only when the spleen has enlarged to at least twice its normal size.
The different lobes of the spleen retain separate blood circulations. There is no anastomosis between the smaller branches of the splenic arteries. Blockage of these arteries leads to infarction.
The capsule of the spleen is tense; consequently the spleen is the most commonly ruptured intraabdominal organ as a result of trauma. Rupture of the spleen may lead to massive intraabdominal haemorrhage. The spleen may have to be removed to prevent further loss of blood. 49 THE COELIAC TRUNK
The coeliac trunk is the largest of the 3 unpaired branches of the abdominal aorta. It arises from the anterior surface of the aorta at the level of the 12th thoracic vertebra. It is about 1.25cm and is directed horizontally.
RELATIONS It lies behind the omental bursa, below the caudate lobe of the liver and above the upper border of the pancreas and splenic vein. It is surrounded by the coeliac plexus of nerves. On each side of the trunk, there is a coeliac ganglion. The coeliac trunk divides into 3 branches - the left gastric, the hepatic and splenic arteries.
THE LEFT GASTRIC ARTERY This is the smallest of the 3 branches of the coeliac trunk, but it is the largest of the 5 arteries that supply the stomach. It passes upwards and to the left towards the cardiac end of the stomach. Near the cardiac end, it gives off 2 or 3 oesophageal branches, and descends along the lesser curvature of the stomach and anastomoses with the right gastric artery.
THE SPLENIC ARTERY This is the largest branch of the coeliac trunk. It runs a tortuous course along the upper border of the body and tail of the pancreas. It lies at a higher level than the splenic vein and passes behind the stomach and omental bursa. Thereafter, it passes in front of the suprarenal gland and the kidney and enters the lienorenal ligament and divides into 5 or more branches which enter the hilus. The branches are end arteries.
Its branches are: i) Numerous pancreatic branches ii) Short gastric arteries; 5-7 in number, supplying the fundus iii) Left gastroepiploic artery: the largest branch of the splenic artery, running in the gastrosplenic ligament.
THE HEPATIC ARTERY It runs forwards and to the right and then ascends between the two layers of the lesser omentum. At the porta hepatis, it divides into left and right hepatic arteries. In the lesser omentum, the hepatic artery lies in front of the portal vein and to the left of the bile duct.
Its branches are: i) Right gastric artery: from the hepatic artery ii) Gastroduodenal artery: passes behind the duodenum. At the lower border of the superior part of the duodenum it divides into right gastroepiploic and superior pancreaticoduodenal arteries (anterior and posterior) iii) Ssupraduodenal artery: may arise from the gastric or hepatic arteries iv) Right gastroepiploic artery: the largest terminal branch of the gastroduodenal artery v) Cystic artery: arises usually from the right hepatic artery, to pass behind the common hepatic and cystic duct.
For descriptive purposes the portion of the hepatic artery from the coeliac trunk to the origin of gastroduodenal artery is called the common hepatic artery while the remaining portion before the bifurcation into left and right hepatic arteries is called the proper hepatic artery. 50 15. STOMACH
The stomach is a muscular bag that serves as a reservoir and blender of food. It is the most dilated part of the alimentary tract.
Its size and shape vary from one individual to another. In the same individual the shape depends on: i) Volume of its contents - the degree of "fullness" ii) Posture - whether the person is standing or lying down iii) Phase of respiration iv) Surrounding structures The stomach is roughly J-shaped when it is empty. The capacity in the adult is about 1500mls. It can accommodate more. The capacity at birth is about 30-35mls (about the size of a hen's egg).
The stomach extends from the lower end of the oesophagus to the beginning of the duodenum. It lies in the epigastrium, the umbilical region and the left hypochondrium. It is fixed at both ends and mobile in between. It has two openings, two borders or curvatures and two surfaces.
ORIFICES The openings are the cardiac and pyloric orifices.
The cardiac orifice is the opening through which the stomach communicates with the oesophagus. It is the most fixed part of the stomach and lies to the left of the median plane. It lies behind the 7th costal cartilage and is about 2.5cm from the costosternal junction. This orifice is at the level of the 11th thoracic vertebra, and is about 10cm from the anterior abdominal wall.
The pyloric orifice is the opening through which the stomach communicates with the duodenum. It lies about 1-2cm to the right of the median plane. In the supine position, it lies at the level of the lower border of L1 vertebra,(the transpyloric plane). This opening is marked by a groove on the surface of the stomach called the pyloric constriction. The prepyloric vein (of Mayo) vertically crosses the region of this orifice anteriorly.
BORDERS OR CURVATURES The two borders are the lesser and greater curvatures. The stomach tends to become tubular when it is full, and the curvatures are then less marked.
The lesser curvature is concave and extends from the cardiac orifice to the pyloric orifice. It descends as a direct continuation of the right border of the oesophagus. The most dependent part of the lesser curvature presents a constant notch - the incisura angularis. The lesser curvature then bends upwards and to the tight to become continuous with the duodenum. The lesser curvature gives attachment to the lesser omentum.
The greater curvature is convex and is about 4 to 5 times as long as the lesser curvature. It begins at the left border of the cardiac orifice. It is directed first upwards and to the left (around the fundus) and then downwards. It has a bulge opposite the angular notch of the lesser curvature. This bulge marks the left extremity of the pyloric part of the stomach. The greater omentum is attached to this curvature.
SURFACES When the stomach is empty, the surfaces are almost superior and inferior. When it is full, the surfaces become anterior and posterior respectively. The surfaces are often referred to as anterosuperior and posteroinferior surfaces respectively. 51 The anterosuperior surface is completely covered by the peritoneum of the greater sac. It is in contact with the left dome of the diaphragm and the anterior abdominal wall.
The posteroinferior surface is almost completely covered with peritoneum except near the cardia, where a small triangular area of it is in direct contact with the left crus of the diaphragm. The structures on which the posteroinferior surface of the stomach lies constitute the "stomach bed". These structures include: i) Diaphragm ii) Left suprarenal gland iii) Upper part of the left kidney iv) Spleen and the splenic artery v) Body and tail of the pancreas vi) Left colic flexure, and vii) A part of the transverse mesocolon
The stomach is separated from these structures by posterior wall of the lesser sac except the gastric surface of the spleen which is separated by a part of the greater sac.
PARTS OF THE STOMACH
1. The cardia: This is the area around the cardiac orifice. It is ill defined anatomically 2. The fundus is the part of the stomach above the level of the cardiac orifice. It is the most superior part of the stomach and is related to the left dome of the diaphragm. In the upright position it usually contains gas. 3. The body extends from the fundus to the level of the incisura angularis. 4. The pyloric part consists of: i) Pyloric antrum: it is the dilated part with a thin wall. ii) Pylorus: it is the narrow part and is surrounded by the pyloric sphincter. Its cavity is called the pyloric canal. The fundus and the upper part of the body are fairly constant in shape and size. The lower part of the body and the pyloric antrum are more variable in shape.
BLOOD SUPPLY The stomach has a profuse blood supply. All the arteries that supply it are from the coeliac trunk. 1. The left gastric artery: this is a direct branch of the coeliac trunk of which it is the smallest branch, but it is the largest artery to the stomach. It reaches the lesser curvature of the stomach, and near the cardiac orifice it gives off 2 or 3 oesophageal branches. It supplies both surfaces of the stomach and anastomoses with the right gastric artery.
2. The right gastric artery: this is a branch of the proper hepatic artery. It reaches the lesser curvature and anastomoses with the left gastric artery. 3. The right gastroepiploic artery: this is a branch of the gastroduodenal artery. It runs along the greater curvature of the stomach. 4. The left gastroepiploic artery: this is a branch of the splenic artery. It runs along the greater curvature and anastomoses with the right gastroepiploic artery
5. The short gastric arteries (or vasa brevia): these are branches of the splenic artery and they are about 4 or 5 in number. They supply the fundus. They anastomose with the left gastric and left gastroepiploic arteries.
The veins accompany the arteries. The left and right gastric veins drain directly into the portal vein. The left gastroepiploic and short gastric veins drain into the splenic vein while the right gastroepiploic vein drains into the superior mesenteric vein. 52 NERVE SUPPLY The nerve supply to the stomach is mainly parasympathetic but there are also sympathetic fibres. The parasympathetic supply is derived from the vagus nerves. They constitute the motor and secretory supply to the stomach. The vagus nerves enter the abdomen through the oesophageal hiatus. The left vagus nerve is smaller than the right and it lies anterior and closer to the stomach wall. The right vagus nerve lies posterior. The vagus nerves control the secretion of acid by the parietal cells of the stomach.
Vagotomy (cutting of the vagus nerves) abolishes reflex neurogenic secretion. It also renders the stomach atonic (the stomach cannot empty properly). Vagotomy is usually performed with a drainage procedure such as pyloroplasty. The sympathetic nerve supply is mainly from the coeliac plexus. It carries pain sensation in the stomach. In vagotomy pain is not abolished while in sympathectomy it is.
LYMPHATIC DRAINAGE The lymph vessels accompany the blood vessels. They may be arranged in four sets which ultimately drain into the coeliac group of lymph nodes. 1. The lymph vessels of the 1st set accompany the branches of the left gastric artery. They receive tributaries from a large part of the anterior and posterior surfaces of the stomach in the region of the lesser curvature. It is the largest area of lymphatic drainage. They drain into the left gastric group of lymph nodes.
2. The 2nd set of vessels drains the fundus and a part of the body to the left of a vertical line drawn from the oesophagus. They accompany short gastric and left gastroepiploic arteries end in the pancreaticosplenic group of lymph nodes. 3. The 3rd set of vessels drains the right part of the greater curvature up to the pyloric region. They terminate in the right gastroepiploic group of lymph nodes. 4. The 4th set of vessels drains the pyloric region and passes to hepatic, pyloric and left gastroepiploic lymph nodes.
The lymphatic drainage may also be grouped into three areas:
Area I: The superior two-thirds of the stomach, draining along the left and right gastric arteries mainly to the left gastric lymph nodes and partly to the hepatic nodes.
Area II: The right two-thirds of the inferior third, draining along the gastroepiploic vessels to the right gastroepiploic and pyloric lymph nodes.
Area III: The left third of the inferior third, draining along short gastric and splenic arteries to pancreaticosplenic lymph nodes.
53 16. DUODENUM
The duodenum is the first, the shortest, the widest and the most fixed part of the small intestine. It is about 25cm long. The duodenum is located in the epigastric and umbilical regions of the abdomen and extends from the pylorus to the duodenojejunal junction. It is C-shaped and has 3 flexures - the superior duodenal, the inferior duodenal, and the duodenojejunal. It is retroperitoneal except the first 2.5cm which has a mesentery.
For descriptive purposes, the duodenum is divided into 4 parts - superior, descending, horizontal and ascending.
SUPERIOR OR FIRST PART This part is about 5cm long. It begins at the pylorus and ends at the neck of the gall bladder. It runs upwards and backwards on the right side of L1 vertebra. It is the most mobile part of the duodenum. The first 2.5cm of the superior part is called the duodenal cap. It has a mesentery and lies between the peritoneal folds of the greater and lesser omenta. The remaining part of the duodenum is covered with peritoneum only on its anterior aspect.
Anteriorly: the first part of the duodenum is related to the quadrate lobe of the liver and the gall bladder. Posteriorly: it is related to the gastroduodenal artery, the bile duct, the portal vein and the inferior vena cava. Superiorly: it is related to the epiploic foramen - the entrance to the lesser sac. Inferiorly: it is related to the head and neck of the pancreas.
DESCENDING OR SECOND PART This is about 7.5cm long and runs vertically downwards on the right side of L2 and L3 vertebrae. It is crossed by the attachment of the mesocolon. As a result of this, the upper half of it is in the supracolic compartment, while the lower half is in the infracolic compartment. The relations are as follows: Anteriorly: it is related to the transverse colon and mesocolon, coils of small intestine, the fundus of the gall bladder and the right lobe of the liver. Posteriorly: it is related to the hilum of the right kidney and the ureter, the renal vessels, psoas major. Medially: it is related to the head of the pancreas and the bile duct. Laterally: it is related to the right colic flexure.
The bile duct and the pancreatic duct unite in the posteromedial wall of the duodenum to form the hepatopancreatic ampulla. The ampulla opens on the summit of the major papilla (the papilla of Vater). The papilla is surrounded by sphincter of Oddi. It lies about half-way along the 2nd part of the duodenum. About 2cm proximal to the major papilla is a minor duodenal papilla, on which opens the accessory pancreatic duct of Santorini.
HORIZONTAL OR THIRD PART This is about 10cm long. It runs horizontally from right to left along the subcostal plane, at the level of L3 vertebra. Its anterior surface is covered with peritoneum, except near the median plane where it is crossed by the superior mesenteric vessels and the root of the mesentery. The relations are as follows: Anteriorly: it is related to the root of the mesentery of the small intestine, the superior mesenteric vessels which are contained in it, and coils of jejunum. Posteriorly: it is related to inferior vena cava, the aorta, psoas major and the right ureter. Superiorly: it is related to the head of the pancreas. Inferiorly: it is related to coils of jejunum. 54 ASCENDING OR FOURTH PART
This is about 2.5cm long. It runs upwards and to the left, and turns forwards at the duodenojejunal flexure. The terminal part of the duodenum and the duodenojejunal flexure are fixed to the psoas fascia by a fibromuscular band called the suspensory ligament (muscle) of the duodenum or the muscle of Treitz. It extends from the duodenojejunal flexure to the right crus of the diaphragm. The upper part of the suspensory ligament contains striated muscle; the intermediate part contains elastic tissue while the lower part consists of smooth muscles. The ligament helps to support and widen the duodenojejunal flexure.
Anteriorly: it is related to the root of the mesentery and coils of jejunum. Posteriorly: it is related to the aorta and the left psoas major. Medially: it is related to the head of pancreas. Superiorly: it is related to the body of the pancreas.
PERITONEAL FOLDS AND RECESSES There are a number of peritoneal folds and recesses that are related to the terminal part of the duodenum. a) Superior duodenal recess. It lies to the left of the upper portion of the ascending duodenum and behind the superior duodenal fold. It opens inferiorly and is not always present. b) Inferior duodenal recess. It lies to the left of the lower portion of the ascending duodenum and behind the inferior duodenal fold. It opens superiorly and is not always present. c) Retroduodenal recess. It lies behind the duodenojejunal flexure between the superior and inferior duodenal recesses. d) Paraduodenal recess. It lies to the left of the duodenojejunal flexure and behind the paraduodenal fold which is formed by the inferior mesenteric artery.
All the recesses may unite to form a large recess. The recesses are of surgical importance because they may become sites of internal hernia. The hernia may become strangulated. The paraduodenal fossa proper is the most surgically important.
BLOOD SUPPLY The duodenum is supplied by branches from the coeliac and superior mesenteric arteries. The upper half of the duodenum receives blood supply from the superior pancreaticoduodenal artery. The 1st 2.5cm of the duodenum also receives blood from the hepatic and gastroduodenal arteries. The lower half receives blood from the inferior pancreaticoduodenal artery, a branch of superior mesenteric artery. The superior and inferior pancreoticoduodenal arteries form arterial arcades. The duodenum is drained by corresponding veins which end in the splenic and superior mesenteric veins, and ultimately the portal vein. Most of the veins drain into the superior mesenteric vein. Some drain directly into the portal vein.
LYMPHATIC DRAINAGE Lymph from the duodenum drains into the paraduodenal nodes and then to the coeliac and superior mesenteric groups of preaortic lymph nodes.
NERVE SUPPLY The nerves to the duodenum are derived from sympathetic and parasympathetic (vagal) nerves from the coeliac and mesenteric plexuses.
APPLIED ANATOMY Duodenal ulcers are usually located in the duodenal cap. Ulcers may erode the gastroduodenal artery causing severe haemorrhage into the peritoneal cavity. This artery is a posterior relation of the first part of the duodenum. Duodenal ulcers may also erode the pancreas causing severe pain. 55 17. LIVER (HEPAR)
The liver is the largest gland and the largest visceral organ in the body. It is both endocrine and exocrine in function, and is a highly vascular organ. It accounts for about 2% of the body weight in the adult, and 5% in the infant. The average weight is 1.5kg in the adult male and 1.3kg in the adult female.The shape is determined by the surrounding structures but it is usually wedge-shaped. The base of the wedge lies to the right, while the apex is to the left.
SURFACE ANATOMY It occupies almost the entire right hypochondrium, the greater part of the epigastrium and a part of the left hypochondrium (to the mid-clavicular line). It conforms to the concavity of the right dome of the diaphragm. Most of it is covered by the 5th to 10th ribs. The superior aspect of the liver is at level of 5th rib on the right side and the 5th intercostal space on the left side. The inferior edge may be palpated below the costal margin in some normal people.
SUPPORT It is maintained, or held, in position mainly by the hepatic veins. The hepatic ligaments, and the intra- abdominal pressure produced by the abdominal muscles play a minor role in the support of the liver. The ligaments can be cut without any appreciable change in the position of the liver.
SURFACES The liver has two surfaces: visceral and diaphragmatic. The diaphragmatic surface is convex and is related to the diaphragm. It has anterior, posterior, superior and right aspects. The visceral surface is related to the suprarenal gland, kidney, stomach, duodenum and transverse colon (and hepatic flexure). The right part of the left lobe is called the tuber omentale. It is separated from the tuber omentale of the neck of the pancreas by the lesser omentum.
BORDERS Only the inferior border of the liver is sharp and well defined. It separates the diaphragmatic surface from the visceral surface. Just to the right of the median line, the inferior border presents a notch for the ligamentum teres hepatis. The other borders of the liver are indistinct and rounded.
FISSURES AND FOSSAE The visceral surface is marked by a H-shaped group of fissures and fossae. The left limb (left sagittal fissure) is incomplete and consists of the fissure for the ligamentum teres hepatis in front and the fissure for the ligamentum venosum behind. The right sagittal fossa is formed by the fossa for the gallbladder in front and the fossa for the IVC behind. The cross-bar of the "H" is the porta hepatis or the hilus of the liver - through it the portal vein and hepatic artery enter, and the bile duct leaves. It also contains hepatic nerve plexus and lymph vessels.
LOBES AND SEGMENTS Traditionally, the liver was considered as having two anatomical lobes - a large right lobe and a small left lobe. The two lobes are separated by the attachment of the falciform ligament on the diaphragmatic surface, and by the fissures for ligamentum venosum and ligamentum teres hepatis on the visceral surface. The caudate and quadrate lobes belong to the right anatomical lobe. Nowadays, based on the subdivisions of the hepatic artery, the portal vein and hepatic ducts within the liver, the latter is divided into right and left physiological or functional lobes. The plane of division is along the centres of the fossae for the gall bladder and the inferior vena cava. The plane is demarcated on the visceral surface by the right sagittal fissure and on the diaphragmatic surface by an imaginary line called the Cantlie line which runs from the notch of the gallbladder to the inferior vena cava. The middle hepatic vein lies in this plane. The caudate and quadrate lobes belong to the left physiological lobe. 56 Each physiological lobe receives its own arterial and portal supply and has its own venous drainage. The right and left branches of the hepatic artery and the portal vein as well as the left and right hepatic ducts are almost equal in size and they supply or drain almost equal amounts of liver tissue but the right functional lobe is still slightly larger than the left.
The physiological lobes are further divided into four divisions or sectors or sections. The left physiological lobe is divided into left lateral and left medial divisions or sectors, while the right physiological lobe is divided into right lateral and right medial divisions or sectors. The left lateral division lies to the left of the attachment of the falciform ligament on the diaphragmatic surface and corresponds to the traditional or anatomical left lobe. The left medial division lies to the right of the falciform ligament and corresponds to the quadrate lobe and the caudate lobe. There is no external marking separating the right lateral and right medial divisions.
The right hepatic vein lies between the right lateral and right medial divisions while the left hepatic vein lies between the left lateral and left medial divisions. Each of the four hepatic divisions is further subdivided into anterior and posterior segments along a transverse plane that passes through the bifurcation of the the portal vein. There are eight hepatic segments. On the visceral surface, starting with the caudate lobe, they are named in an anticlockwise direction around the porta hepatis. Segment I: posterior segment of the left medial division; it corresponds to the caudate lobe. Segment II: posterior segment of the left lateral division. Segments III and IV are the anterior segments of the left lateral and left medial divisions respectively. Segment IV corresponds to the quadrate lobe. Segments V and VI are the anterior segments of the right medial and right lateral divisions respectively while segments VII and VIII are the posterior segments of the right lateral and right medial divisions respectively.
The segments are of surgical importance. They form the basis for the different types of hepatic resection. There is little or no arterial, portal and biliary communication across the segments. The major tributaries of the hepatic veins unlike the arterial and portal branches are intersegmental: they drain adjacent segments.
Although the caudate lobe belongs to the left physiological lobe, it is an independent segment. It receives blood supply from the right and left branches of the hepatic artery and portal vein and its biliary drainage is into the right and left hepatic ducts. The venous drainage is by minor hepatic veins that drain into the inferior vena cava. The caudate lobe is the only part of the liver enclosed in the omental bursa, and is bounded: Superiorly: by the superior surface of the liver Inferiorly: by the porta hepatis On the right: by the fossa for the IVC On the left: by the fissure for ligamentum venosum. The lower end has two projections - the papillary process and the caudate process. The latter is a narrow projection from the right part of the lower end of the caudate lobe that connects it to the right lobe of the liver. The caudate process forms the superior border or limit of the epiploic foramen. The papillary process projects from the left part of the lower end of the caudate lobe.
PERITONEAL ATTACHMENTS AND LIGAMENTS OF THE LIVER The liver is almost completely covered by peritoneum - the exceptions are the "bare area" and the lines of attachment of the ligaments. It is connected to the stomach, duodenum, diaphragm and anterior abdominal wall. The ligaments of the liver are: the falciform, the right and left triangular, the coronary and the lesser omentum. They help to subdivide the upper part of the abdominal cavity into left and right subphrenic spaces.
The falciform ligament This is a sickle-shaped fold of peritoneum that connects the liver to the diaphragm and anterior abdominal wall. It extends from the inferior surface of the diaphragm and the midline of the supraumbilical part of the anterior abdominal wall to the notch for ligamentum teres hepatis and the 57 anterior and superior aspects of the liver. It bears the ligamentum teres hepatis and paraumbilical veins in its free lower edge. On the superior aspect of the liver, the two layers of the falciform ligament separate from each other. The right layer continues as the superior layer of the coronary ligament, while the left continues as the anterior layer of the left triangular ligament.
The coronary ligament This is a double fold of peritoneum extending from the diaphragm to the superior and posterior aspects of the liver. It consists of a superior and an inferior layer. The superior layer is continuous with the right layer of the falciform ligament, while the inferior layer is continuous with the right layer of the lesser omentum. The two layers surround the "bare area" of the liver, and meet at the right end of the liver to form the right triangular ligament. The latter connects the posterior surface of the liver to the diaphragm.The "bare area" of the liver is an area on the posterosuperior surface of the liver that is not covered with peritoneum and in which the liver and the diaphragm are in direct contact. It is triangular in outline. The sides are formed by the superior and inferior layers of the coronary ligament. Its base is formed by the groove for the IVC while its apex is formed by the right triangular ligament.
The left triangular ligament This is larger than the right triangular ligament. It has anterior and posterior layers. The anterior layer is continuous with the left layer of the falciform ligament while the posterior layer is continuous with the left layer of the lesser omentum.
The lesser omentum This extends from the lesser curvature of the stomach and the proximal part of the duodenum to the porta hepatis and the fissure for ligamentum venosum. Its attachment to the liver is L-shaped: the horizontal limb of the "L" corresponds to the porta hepatis while the vertical limb corresponds to the fissure for ligamentum venosum. The left layer of the lesser omentum is continuous with the posterior layer of the left triangular ligament. The right layer is indirectly continuous with the inferior layer of the coronary ligament.
BLOOD SUPPLY The liver receives blood from two sources: a) The hepatic artery - it accounts for 20-30% of the blood supply of the liver and carries oxygenated blood. b) The portal vein - it accounts for 70-80% of the blood supply of the liver and carries blood rich in products of digestion. The hepatic artery and portal vein divide at the porta hepatis into right and left branches. The right lobe of the liver receives blood from the intestines, while the left lobe receives blood from the spleen and stomach. The hepatic arteries are end arteries. There are no anastomoses between the left and right hepatic arteries. Within each half of the liver, the branches of the arteries are also end arteries.
VENOUS DRAINAGE The venous drainage is different from the arterial supply. There is mixing of venous blood between both halves of the liver and between the segments. The liver is drained by hepatic veins. They are formed by the union of the central veins of the liver lobules. The hepatic veins are arranged into superior and inferior groups. The superior group consists of right, middle and left hepatic veins. These veins are intrahepatic in their course and drain into the inferior vena cava. Consequently access to these veins during surgery especially for the control of traumatic bleeding is difficult. The right hepatic vein drains most parts of the right lobe. The middle hepatic vein drains the medial segment of the left lobe and a part of the anterior segment of the right lobe. In about 80% of the population it joins the left hepatic vein. The exact site of union varies. The left hepatic vein drains the left lateral segment of the left lobe. The inferior group vary in number and are small in size. They drain into the inferior vena cava below the openings of the superior group. NERVE SUPPLY 58 Sympathetic innervation of the liver is derived from the coeliac plexus while parasympathetic innervation is from fibres of the left vagus nerve. Vagal stimulation causes contraction of the gall bladder. The sympathetic fibres are vasoconstrictors. LYMPHATIC DRAINAGE Lymph vessels from most parts of the liver drain into hepatic nodes which lie at the porta hepatis. Lymph from these nodes drains alongside the hepatic arteries to retropyloric then to coeliac nodes. Lymph vessels from the bare area of the liver drain into lymph nodes in the posterior mediastinum.
APPLIED ANATOMY Liver biopsy is usually done through the right 7th, 8th or 9th intercostal space in the midaxillary line. The patient holds his breath in full expiration in order to reduce costophrenic recess and consequently reduce the risk of damage to the pleura. 59 18. THE PORTAL VENOUS SYSTEM
The portal venous system drains blood to the liver from the following areas: 1. The abdominal parts of the alimentary tract except the lower part of the anal canal. 2. The pancreas. 3. The spleen. 4. The gall bladder.
In the liver, the portal vein breaks up into branches which end in capillary-like vessels called sinusoids. From these sinusoids which also receive blood conveyed to the liver by the hepatic artery, the hepatic veins arise and open into the inferior vena cava; thus, the portal blood reaches the general circulation. In adults, the veins of the portal system have no valves (the valves present at birth undergo atrophy).
FUNCTIONS 1. The portal system acts as a reservoir of blood for the needs of the general circulation.
2. It conveys the products of digestion from the intestine, and the products of red blood cell destruction from the spleen.
THE PORTAL VEIN
The portal vein is formed by the union of the superior mesenteric vein and the splenic vein. The union occurs behind the neck of the pancreas and in front of the inferior vena cava. The portal vein begins at the level of L1 vertebra and may be considered as an upward continuation of the superior mesenteric vein, after it has received the splenic vein. It is about 8cm long and passes upwards behind the pancreas and the superior part of the duodenum. Just above the superior part of the duodenum, it passes forwards and enters the lesser omentum, where it ascends in its free border and lies behind the common bile duct and hepatic artery, and in front of the epiploic foramen.
At the right border of the porta hepatis, it divides into right and left branches. The right branch is shorter and wider. It receives the cystic vein before entering the right lobe. The left branch gives branches to the caudate and the quadrate lobes and the left lobe of the liver. Before entering the left lobe, it receives on its anterior surface the ligamentum teres hepatis, and the para-umbilical veins which accompany the ligament. The ligamentum venosum also connects the posterior surface of the left branch to the inferior vena cava.
Although the portal vein contains blood from the splenic and superior mesenteric veins, there is little mixing of blood from these two veins because of the sluggish flow of blood in the portal vein. Consequently, the right branch of the portal vein receives blood mainly from the superior mesenteric vein, while the left branch receives blood mainly from the splenic vein and its tributaries.
TRIBUTARIES OF THE PORTAL VEIN
1. The splenic vein: this in turn receives the: i) Short gastric ii) Left gastroepiploic iii) Pancreatic iv) Inferior mesenteric veins (sometimes it empties into the superior mesenteric vein or the junction between the latter and the splenic vein). 60 2. The superior mesenteric vein: this receives the: i) Right gastroepiploic ii) Pancreaticoduodenal veins
3. The left gastric vein
4. The right gastric vein
5. The paraumbilical veins
6. The cystic vein
THE PORTOSYSTEMIC ANASTOMOSES
There are anastomoses between the portal and systemic circulations. These anastomoses become important when there is obstruction of the portal vein. Through these communications, blood from the portal vein reaches the heart via the vena cavae.
There are portocaval anastomoses at the following areas:
1. At the lower end of the oesophagus (gastro-oesophageal junction): There are anastomoses between the oesophageal tributaries of the left gastric vein (portal) and the oesophageal veins of the azygous system (systemic). In portal obstruction, these anastomoses become engorged. This condition is called oesophageal varices. The veins may rupture resulting in haematemesis.
2. Around the umbilicus: There are anastomoses between the paraumbilical veins which accompany the ligamentum teres hepatis (portal) and the epigastric veins around the umbilicus (systemic). Enlargement of these anastomoses may produce a bunch of enlarged veins radiating from the umbilicus. This condition is called caput medusae.
3. In the anorectal region: There are anastomoses between superior rectal vein, a tributary of the inferior mesenteric vein(portal) and the middle and inferior rectal veins (systemic). The middle rectal vein is a tributary of the internal iliac vein while the inferior rectal vein is a tributary of the internal pudendal vein. Enlargement of the submucous veins in the terminal part of the rectum is called internal haemorrhoids while in the anal canal is called external haemorrhoids.
4. The bare area of the liver: Across the bare area of the liver, there are anastomoses between portal branches in the liver and the phrenic veins (systemic).
5. Behind the colon: There are anastomoses between the veins of the ascending colon, pancreas and the duodenum (portal) and the renal and lumbar veins (systemic). 61 19. DIAPHRAGM
The diaphragm is a fibromuscular septum that separates the thoracic cavity from the abdominal cavity. It consists of two parts: a central fibrous part called the central tendon and a peripheral muscular part. The central tendon is depressed by the heart and consequently the diaphragm has left and right domes or cupulae. The right dome is usually higher than the left one because the heart depresses the left dome.
TOPOGRAPHY On full expiration the right dome is at the level of the 4th intercostal space while the left is at the level of the 5th intercostal space. The diaphragm is at a higher level in stocky subjects than in slender subjects. It is also higher in the supine position than in the erect position. The anterior attachment of the diaphragm is superior to the posterior attachment.
ORIGIN The muscle fibres of the diaphragm are grouped into three parts according to their origin. a) The sternal part: It arises by two fleshy slips from the posterior surface of xiphoid process. The slips arch upward and backward and are inserted into the central tendon. They are the shortest of the muscular fibres of the diaphragm. b) The costal part: It arises by slips from the internal surface of each of the lower 6 costal cartilages and the adjoining portions of the ribs. The costal slips interdigitate with the slips of the transversus abdominis. They are inserted into the lateral and anterior portions of the central tendon. c) The lumbar or vertebral part: It arises by: i) The left and right crura ii) The left and right medial and lateral arcuate ligaments
The right crus is larger and longer than the left. It arises from the anterior surfaces of the upper three lumbar vertebrae and the discs between them. The left crus arises from the upper two lumbar vertebrae and the disc space between them. The medial sides of the left and right crura are fibrous and are united superiorly by a tendinous band called the median arcuate ligament. Muscle fibres do not arise from this ligament.
Medial arcuate ligament or medial lumbosacral arch: It is a thickened band of the fascia covering the upper part of the psoas major. It is connected medially to the transverse process of L1 or L2 and laterally to the lateral arcuate ligament.
Lateral arcuate ligament or lateral lumbosacral arch: It is a thickened band of the fascia covering the upper part of quadratus lumborum. It is connected medially to the arcuate ligament and laterally to the 12th rib.
Central tendon: It receives the insertion of the muscular fibres. It is C-shaped or club- or trefoil- shaped and blends with the fibrous capsule.
ORIFICES OR OPENINGS IN THE DIAPHRAGM The diaphragm is pierced by a number of structures. The three major openings in the diaphragm are: 62
1. Vena caval opening: it is located in the central tendon. It is square shaped and is at the level of the 8th thoracic vertebra. It is 2cm to the right of the midline and lies behind the 6th costal cartilage. The following structures pass through it. a) Inferior vena cava b) Right phrenic nerve c) Lymph vessels from the liver
2. Oesophageal opening: it is located in the muscular part of the diaphragm. It is oval or elliptical in shape and is at the level of the 10th thoracic vertebra. It is about 2cm to the left of the midline and lies behind the 7th costal cartilage. The opening is strengthened by the crura surrounding it. The phrenico-oesophageal ligament attaches the oesophagus to the right crus. The opening transmits the following structures: a) Oesophagus b) Right and left vagus nerves. The right passes through the anterior angle of the opening while the left passes through the posterior angle. c) Oesophageal branches of the left gastric vessels. d) Lymphatic vessels.
3. Aortic opening: it lies behind the median arcuate ligament. It is at the level of the 12th thoracic vertebra and is slightly to the left of the median plane. It transmits the following structures: a) Aorta b) Thoracic duct: it lies to the left of the aorta. c) Azygos vein: it lies to the left of the thoracic duct. d) Lymph vessels.
Other smaller openings in the diaphragm are: 4. Between the sternal slip and the slip from the 7th costal cartilage: it transmits the superior epigastric vessels and lymph vessels.
5. Between the slips from the 7th and 8th costal cartilages: it transmits the musculophrenic vessels.
6. Between the remaining costal slips: each of these openings transmits one of the lower 5 intercostal vessels and nerves.
7. Behind the lateral arcuate ligament: it transmits the subcostal nerves and vessels.
8. Behind the medial arcuate ligament: it transmits the sympathetic trunk.
9. The crus is pierced by the greater, lesser and least splanchnic nerves.
10. The left crus is also pierced by the hemiazygos vein.
11. The left dome of the diaphragm is pierced by the branches of the left phrenic nerve.
BLOOD SUPPLY 1. Inferior phrenic artery from the abdominal aorta. It is the main arterial supply to the diaphragm. 2. Superior phrenic artery from the thoracic aorta. 3. Superior epigastric artery from the internal thoracic artery. 4. Musculophrenic artery from the internal thoracic artery. 5. Pericardiacophrenic artery from the internal thoracic artery. 6. The lower 5 posterior intercostal arteries. The venous drainage is mainly through the inferior phrenic vein. The latter drains into the inferior vena cava.
63 NERVE SUPPLY The phrenic nerve (C3, 4, 5) provides motor innervation to the diaphragm and sensory innervation to the pleura and peritoneum covering the upper and lower surfaces of the central tendon respectively. The sensory innervation to the peripheral part of the diaphragm is from the branches of the lower 6 thoracic nerves. ACTION 1. The diaphragm is the principal muscle of inspiration. It is passive during expiration. When it contacts, the volume of the thoracic cavity increases while the pressure decrease decreases. 2. It increases the intra-abdominal pressure during expulsive acts like defecation, micturition, parturition, etc.
APPLIED ANATOMY 1. Effects of contraction of the diaphragm: a) The intra-abdominal pressure rises. b) The vena caval opening in the central tendon is pulled open. As a result of this, the venous return through the inferior vena cava increases. c) The oesophageal orifice is pinched off to prevent regurgitation of gastric contents. d) The aortic opening is not affected because strictly speaking it is not an opening in the diaphragm. It is an opening between the diaphragm and the vertebral column. 2. Pain sensations from the pleura or peritoneum covering the central tendon of the diaphragm are referred to the shoulder region. The root value of the phrenic nerve is C3, 4, 5. The supraclavicular nerves which supply the shoulder region have a similar nerve root value viz.C3, 4. Pain sensations from the peripheral part of the diaphragm are referred to the lower thoracic and upper abdominal regions. 3. Clonic spasmodic contraction of the diaphragm results in hiccup.
DIAPHRAGMATIC HERNIAS They may be congenital or acquired. 1. Hernia through the pleuroperitoneal hiatus or foramen of Bochdalek. It is the commonest type of congenital hernia of the diaphragm and is due to failure of the pleuroperitoneal membrane to fuse with the dorsal mesentery of the oesophagus. It is located in the posterolateral part of the diaphragm and is more common on the left. 2. Retrosternal or parasternal hernia, or hernia through the sternocostal hiatus or foramen of Morgagni. It is a hernia through the gap between the sternal and costal origins of the diaphragm. It is due to inadequate development of the muscles around the sternocostal orifice. It is more common on the right side. 3. Hernia through the oesophageal hiatus. There are two types: a) Congenital type also called rolling hernia b) Acquired type also called the sliding hernia.
In the congenital type, the cardio-oesophageal junction is at its normal position but the fundus of the stomach herniates through the oesophageal hiatus into the thorax. This type of hernia may be due: i) Congenital shortening of the oesophagus ii) Weakness of the muscle fibres that surround the oesophageal hiatus. iii) Abnormal widening of the oesophageal hiatus. In the acquired type, the lower part of the oesophagus and the cardia herniate through the oesophageal hiatus into the thorax. It may be due to: a) Weakness of the phrenico-oesophageal membrane, e.g. after surgery. b) Increase in intra-abdominal pressure e.g. in obesity. 64 20. THE KIDNEYS
The kidneys are a pair of bean-shaped retroperitoneal organs that lie on the upper part of the posterior abdominal wall. Each kidney is about 12cm long, 6cm wide and 3cm thick. It weighs about 150g in the male and 130g in the female. The left kidney tends to be longer than the right kidney.
The kidneys are oblique in position with their long axes directed inferolaterally and parallel to the lateral surface of psoas major. The right kidney is about 1.5cm lower than the left because of its downward displacement by the right lobe of the liver. The hilus of the left kidney lies just above the transpyloric plane, while that of the right lies just below.
POLES, SURFACES AND BORDERS The kidney has: Two poles -- upper and lower Two surfaces -- anterior and posterior Two borders -- medial and lateral The upper pole is thicker and nearer the median plane than the lower pole. The upper pole of the left kidney lies along the 11th rib while that of the right kidney is along the 11th intercostal space. In both kidneys the upper is at T12 vertebral level, the hilus at L1 and the lower pole at L3.
The anterior surface faces anterolaterally while the posterior surface faces posteromedially. The lateral border is uniformly convex. The intermediate third of the medial border presents a vertical cleft called the hilum. This leads into a cavity called the renal sinus. The pelvis of the ureter, renal vessels, sympathetic nerves and lymph vessels pass through the hilum.
CAPSULES The kidney has three capsules: 1. Fascial capsule or renal fascia 2. Fatty capsule or perinephric fat 3. True capsule or fibrous capsule
The fascial capsule or renal fascia encloses both the kidney and the suprarenal gland. It is formed by the splitting of the transversalis fascia into anterior and posterior layers. This fascia is continuous: Superiorly with the diaphragmatic fascia Medially with the fascia around the renal vessels Laterally with the transversalis fascia. Inferiorly, the layers are separate. Consequently, perinephric abscess tends to spread downwards and the kidneys move about 3cm downwards in deep inspiration.
The fatty capsule or perirenal fat fills the space between the true capsule and renal fascia. At body temperature the fat is in a liquid state. The true capsule or fibrous capsule encloses each kidney; it is easily stripped from the kidney surface (except when there is scaring as a result of inflammation). The capsule passes through the hilum to line the renal sinus and becomes continuous with the walls of the calyces. It helps to limit spread of infection. The pararenal fat is the fat outside the renal fascia. It is more abundant posteriorly than anteriorly. The pararenal and perinephric fat provide the main support of the kidneys. The renal vessels and capsules also contribute in the support of the kidneys.
RELATIONS The posterior relations of the left and right kidneys are the same. Superiorly: the diaphragm Medially: the lateral side of psoas major Intermediately: quadratus lumborum muscle covered by the anterior layer of the thoracolumbar fascia Laterally: aponeurosis of the transversus abdominis. 65 The subcostal vessels and nerves, iliohypogastric and ilioinguinal nerves lie diagonally between the posterior surface of the kidney and the anterior layer of the thoracolumbar fascia which covers the quadratus lumborum. Anteriorly, the relations of both kidneys differ. 1. Right kidney: Superior part of medial border: suprarenal gland Region around the hilus: 2nd part of the duodenum Upper two-thirds of remaining surface: the hepatorenal recess separates it from the posterior surface of liver. Lower one-third of remaining surface: hepatic flexure of colon laterally and the small intestine medially. 2. Left kidney: Superior part of medial border: suprarenal gland Upper two-third of lateral half: spleen Lower one-third of lateral half: splenic flexure of colon Upper portion of medial half: stomach Middle portion of medial half: body of pancreas and splenic vessels. Lower portion of medial half: jejunum
BLOOD SUPPLY The kidneys have a rich blood supply and they receive about one fifth of the cardiac output. They are supplied by the renal arteries. These arteries arise at right angles from the abdominal aorta at about the level of the disc between L1 and L2 vertebrae and pass behind the renal veins.
The kidney has a segmental blood supply. The organ is divided into 5 segments: apical, upper, middle, lower and posterior. Each segment is supplied by a segmental artery. The anterior and posterior halves of the kidney also tend to have separate arterial supply. Consequently, coronal and intersegmental sections are usually bloodless. The renal artery divides into 5 segmental arteries that enter the hilus of the kidney, 4 in front and 1 behind the renal pelvis.
The segmental arteries divide into lobar arteries one for each renal pyramid. Each lobar artery divides into 2 or 3 interlobar arteries which run between the pyramids. Near the junction of the medulla and cortex the interlobar arteries give off the arcuate arteries. The latter arch over the bases of the pyramids and give off a number of interlobular arteries which pass into the cortex. The afferent arterioles that supply the glomeruli arise from the interlobular arteries.
Aberrant or accessory renal arteries are seen in about 30% of individuals. The aberrant arteries arise from the aorta and supply the upper or lower pole of the kidney. The accessory artery to the lower pole is usually anterior to the ureter and may compress it.
The veins from the renal segments communicate with each other profusely and eventually form 5 or 6 vessels that unite at the hilum to form a single renal vein. The left renal vein is longer than the right one. It empties into the IVC at a higher level than the right renal vein. It passes anterior to the aorta and receives blood from left suprarenal and gonadal veins. It also communicates with the azygos veins. The right renal vein does not receive any important tributary.
NERVE SUPPLY The nerves are derived mainly from the coeliac plexus.
LYMPHATIC DRAINAGE Lymphatics from the kidney drain directly to para-aortic lymph nodes. 66 STRUCTURE The kidney consists of an outer cortex and an inner medulla. The medulla is arranged into pyramid- shaped units called the medullary pyramids. These are separated by extensions of the cortex called the renal columns. There are about 14 pyramids. The apex of the pyramid is called a papilla.
The nephron is the functional unit of the kidney. There are about 1 million nephrons in each kidney. Each consists of 2 main parts - the renal corpuscle and the renal tubule.The renal corpuscle is the part of the nephron responsible for ultra-filtration. It consists of the Bowman's capsule, which is the blind end of the nephron, and the glomerulus, which invaginates the Bowman's capsule. The glomerulus is a coiled network of capillaries. The renal tubule is mainly responsible for selective reabsorption of water, ions, etc. from the glomerular filtrate. It consists of 4 parts: Proximal convoluted tubule Loop of Henle (with thin and thick limbs) Distal convoluted tubule, and Collecting tubule
THE URETERS The ureter is a muscular duct that conveys urine from the kidney to the urinary bladder. It lies posterior to the renal vein and artery at the hilus. The pelvis of the ureter is the expanded funnel- shaped superior end of the ureter. It is formed by the union of 2 or 3 major calyces. The upper half of the ureter lies in the abdominal cavity, while the lower half lies in the pelvis.
The ureter is retroperitoneal throughout its entire length. It lies along the medial edge of psoas major which separates it from the tip of the transverse processes of L2 to L5. It crosses into the pelvis at the bifurcation of the common iliac artery in front of the sacro-iliac joint. The right ureter is crossed by the gonadal, right colic and ileocolic vessels. The left ureter is crossed by the gonadal and left colic vessels.
The pelvic part runs on the lateral wall of the pelvis, anterior to the internal iliac artery, and just in front of the iliac spine. In the female, it passes 2.5cm lateral to the supravaginal portion of the cervix.
It is narrowed at 3 sites: a) Pelvi-ureteric junction. b) Pelvic brim c) Ureteric orifice - the narrowest part
Along its course the ureter is supplied with blood segmentally from all available sources - the aorta, renal, gonadal, common and internal iliac, superior and inferior vesical, uterine, and middle rectal arteries. 67 21. RECTUM AND ANAL CANAL
The rectum is the part of the large intestine that is continuous above with the sigmoid colon, and below with the anal canal. It is about 12 cm long and extends from the pelvic surface of the 3rd sacral vertebra to slightly below the tip of the coccyx. There is no change of structure at the recto-sigmoid junction. This junction is indicated by the lower end of the sigmoid mesocolon. The rectum has no mesentery, appendices epiploicae, sacculations or taeniae coli. The taeniae coli of the sigmoid colon spread and form a complete coat over the rectum. The rectum ends at the anorectal junction. There, the muscle coats are replaced by anal sphincters. The U-shaped loop of puborectalis forms a sling around the junction. The upper part of the rectum has the same diameter as the sigmoid colon. It is usually empty. The lower part is dilated to form the rectal ampulla and it rests on the pelvic floor. It contains flatus and faeces. FLEXURES In man, the rectum is not straight (rectus means straight). It follows the curvature of the sacrum and coccyx. It passes downwards and backwards, and then downwards and finally forwards forming two antero-posterior curves. The 1st of these curves is called the sacral flexure of the rectum and is concave anteriorly. The 2nd is called the perineal flexure and is convex anteriorly.
In addition to the antero-posterior curves, the rectum has 3 lateral curves: two on the left side and one on the right side. The upper and lower ends of the rectum are in the midline, but the ampulla is convex to the left. The curvatures are due to the presence of transverse folds of mucosa, submucosa and circular muscle fibres that are called the rectal valves of Houston. The upper and lower valves lie on the left side, and the middle valve on the right between the other two. The valves vary in position, but they are always present. They probably separate flatus from faeces.
Some of the longitudinal muscle fibres from the lower part of the ampulla pass anteriorly towards the apex of the prostate and the beginning of the membranous urethra to form the rectourethralis (a surgical landmark).
PERITONEAL RELATIONSHIPS The upper one-third of the rectum is covered with peritoneum on its anterior and lateral aspects. The middle one-third has peritoneal covering only on its anterior surface; the lower one-third is not covered with peritoneum. In the male, the peritoneum is reflected from the anterior surface of the middle one-third of the rectum to the posterior wall of the bladder to form the rectovesical porch. In the female, it is reflected to the uterine cervix and the posterior wall of the vagina to form the rectouterine pouch, or pouch of Douglas. The peritoneal covering of the sides of the upper one-third is reflected laterally to the posterior pelvic wall to form the pararectal fossae.
RELATIONS Anteriorly, the relations of the rectum differ in both sexes. In the male, above the peritoneal reflections, it is related to the upper part of the base of the bladder and seminal vesicles. It is separated by the rectovesical septum from the lower part of the base of the bladder, seminal vesicles, vas deferens and the prostate. In the female, above the peritoneal reflection, the rectum is separated by coils of intestine in the rectouterine pouch from the uterine cervix and the posterior fornix of the vagina. Below the 68 peritoneal reflection, it is separated by the rectovaginal septum from the posterior vaginal wall.
Posteriorly, the relations are the same in both sexes. It is related in the median plane to the lower 3 sacral vertebrae, the coccyx, the median sacral vessels, the ganglion impar and branches of the superior rectal vessels. On either side of the midline, particularly on the left side, it is related to piriformis, coccygeus, levator ani, lower sacral and coccygeal nerves, sympathetic trunks and lower lateral sacral vessels.
Laterally, the upper part is related to the pararectal fossa of peritoneum and its contents (the sigmoid colon and terminal ileum). The lower part is related to fat and fascia over levator ani and coccygeus.
THE FASCIA OF THE RECTUM 1. The fascia of Waldeyer is an avascular sheath of fascia that extends from the anterior surface of the lower part of the sacrum to the posterior aspect of the anorectal junction. It encloses the superior rectal vessels. 2. The lateral ligament of the rectum is a condensation of areolar tissue that passes from the posterolateral wall of the pelvis at S3 to the rectum. It encloses the middle rectal vessels and branches from the hypogastric plexus. 3. The fascia of Denonvilliers lies between the rectum and the prostate.
BLOOD SUPPLY 1. The principal blood supply is the superior rectal artery. It supplies the mucous membrane down to the muco-cutaneous junction of the anal canal. It divides at the commencement of the rectum into left and right branches. The right in turn divides into anterior and posterior branches. These three lie at the 4, 7 and 11 o'clock positions at proctoscopy.
Other arteries that supply the rectum are: 2. Middle rectal artery. It is a branch of the internal iliac artery and supplies the middle and inferior parts of the rectum. 3. Inferior rectal artery. It is a branch of the internal pudendal artery and supplies the inferior part of the rectum and the anal canal. 4. Median sacral artery. It is the attenuated continuation of the abdominal aorta and supplies the posterior surface of he rectum.
The venous drainage follows the arterial supply. There are free anastomoses between the tributaries of the venous system. A submucous plexus of veins in the rectum and anal canal drains into a plexus that surrounds the ampulla. This plexus is called the external rectal plexus. It communicates with vesical plexus in the male and the uterovaginal venous plexus in the female. The internal rectal plexus lies deep to the epithelium of the rectum. The external rectal plexus is external to the muscular coat. The veins drain into the portal system by the superior rectal veins and into the systemic venous system by the middle rectal veins via the internal iliac veins.
Lymphatic drainage follows the arterial supply to para-aortic nodes.
NERVE SUPPLY The nerve supply of the rectum is derived from both parts of the autonomic nervous system.
The sympathetic supply is derived from the hypogastric plexus and from branches of the coeliac plexus that accompany the inferior mesenteric and superior rectal arteries. The parasympathetic supply is derived from S2, 3,4 by the nervi erigentes which pass via the hypogastric plexus. The nervi erigentes are motor to the detrusor muscle. They also carry pain and general sensation from the rectum. They can distinguish between flatus and faeces. 69 THE ANAL CANAL The anal canal begins at the anorectal junction where the lower end of the ampulla of the rectum suddenly narrows and ends at the anus. It is about 4 cm long and is directed downwards and backwards.
RELATIONS Anteriorly, in the male, it is separated by the perineal body from the membranous urethra and the bulb of the penis. In the female, it is separated by the perineal body from the lower part of the vagina. Posteriorly, it is in contact with a mass of fibromuscular tissue called the anococcygeal ligament which extends from it to the tip of the coccyx. Laterally, it is related to the ischiorectal fossa.
MUSCULATURE At the anorectal junction, the circular muscle coat of the rectum becomes thickened to form the sphincter ani internus. This sphincter surrounds the upper one-thirds of the anal canal.
Sphincter ani externus surrounds the entire length of the anal canal. It is striated muscle and consists of 3 parts: 1. Subcutaneous part: surrounds the lower part of the canal (below the white line). Anteriorly, some of the fibres are attached to the perineal body while posteriorly some are attached to the anococcygeal ligament.
2. Superficial part: lies deep to the subcutaneous part; it is the only part of the external sphincter that has a bony attachment. Posteriorly, it arises from the posterior surface of the terminal piece of the coccyx by an aponeurosis called the anococcygeal raphe. It surrounds the lower part of the internal sphincter and is inserted mainly into the perineal body.
3. Deep part: surrounds the upper part of the internal sphincter. Its deeper fibres fuse with the puborectalis muscle (a part of levator ani). The puborectalis, deep part of sphincter ani externus and the sphincter ani internus form the anorectal ring of muscle which can be felt during rectal examination. Division of this ring, for example during surgery, leads to rectal incontinence.
THE LINING OF THE ANAL CANAL The upper half of the anal canal is lined by columnar epithelium. This mucous membrane is thrown into 6-10 vertical folds called the anal columns (well marked in children). Each column contains a terminal branch of the superior rectal artery and vein.
The lower ends of the anal columns are joined together by crescentic folds of mucosa called the anal valves. Above each valve lies a small recess called an anal sinus. The sinuses are deepest on the posterior wall. The valves may be torn by hard faeces resulting in anal fissure. In the region of the anal sinus, anal glands may be found. These glands open into the anal sinuses and may become infected with formation of abscesses.
The line along which the anal valves are situated is called the pectinate line. It lies opposite the middle of the internal sphincter. It marks the junction between the endodermal and ectodermal parts of the anal canal mucosa. The region immediately below the pectinate line is called the transitional zone or pecten. It extends for 15mm. It has thin stratified squamous epithelium and lacks sweat glands. It is hairless. The submucosa contains dense connective tissue, unlike in the upper half of the anal canal. This transitional zone ends at a narrow wavy line called the white line (of Hilton). This line is situated at the level of the interval between the subcutaneous part of the external sphincter and the lower border of the internal sphincter. 70
Endodermal part Arterial supply: Mainly the superior rectal artery. Vein: Superior rectal vein: tributary of inferior mesenteric vein. Nerve: Sympathetics from the inferior hypogastric plexus. The cloacal part is insensitive to pain but sensitive to stretching. Lymphatics: They pass upwards and join those of the rectum. They drain into the para-aortic nodes.
Ectodermal part Arterial supply: Inferior rectal artery. It is a branch of internal pudendal artery. The middle rectal artery also assists in the supply of the anal canal. Vein: Inferior rectal vein. It drains into the internal pudendal vein. Nerve: Somatic nerves from the inferior rectal branch of the pudendal nerve. The skin in this part is sensitive to pain and touch. Lymphatics: They drain along with the perianal region to medial group of superficial inguinal nodes.
APPLIED ANATOMY Rectal examination is important in medicine, especially in surgery. Some conditions that affect the rectum and the anal canal are: a) Rectal prolapse: rectal prolapse may be partial or complete. In partial prolapse the rectal mucous membrane and submucous coat protrude outside the anus. In complete prolapse, the whole thickness of the rectal wall protrudes through the anus. Damage to the levatores ani muscles is one of the contributory factors in rectal prolapse. b) Haemorrhoids: these may be internal or external haemorrhoids. Internal haemorrhoids are varicosities of the tributaries of the superior rectal veins. They are covered by mucous membrane. External haemorrhoids are varicosities of the tributaries of the inferior rectal vein. They are covered by skin. c) Fissure-in-ano: rupture of the anal valves. This occurs mostly in the posterior wall because of the insertion of the superficial part of the external sphincter. 71 22. PELVIS
"Pelvis" means basin. The skeleton of the pelvis is formed by the two hip bones, the sacrum and the coccyx. In the anatomical position, the anterior superior iliac spines and the pubic tubercles lie in the same frontal plane. The upper border of pubic symphysis, the ischial spine, the tip of the coccyx, the head of the femur and the tip of the greater trochanter lie in the same horizontal plane.
The linea terminalis divides the pelvis into greater (or false) pelvis and lesser (or true) pelvis. The linea terminalis is formed by the pubic crest, pecten pubis, arcuate line of the ilium, ala of the sacrum and the sacral promontory.
The true pelvis has a superior aperture or pelvic brim (or inlet), a cavity and an inferior aperture or pelvic outlet. The apertures and the cavity have 3 main diameters viz. anteroposterior (conjugate), transverse and oblique diameters.
THE SUPERIOR APERTURE It lies in the plane of the linea terminalis. It slopes downwards and forwards from the sacral promontory to the pubic symphysis and makes an angle of 50-60 degrees with the horizontal.
The anteroposterior (or conjugate) diameter: it extends from the upper margin of the pubic symphysis to the mid-point of the sacral promontory. In the male it is about 10 cm, while in the female, it is 11.2 cm.
Obstetric conjugate diameter: it extends from the posterior surface of the pubic symphysis to the mid-point of the sacral promontory.
Diagonal conjugate diameter: it is the distance between the inferior margin of the pubic symphysis and the mid-point of the sacral promontory. It is the only diameter of the pelvis that can be measured per vaginam.
The transverse diameter: it is the distance across the widest part of the pelvic inlet.
Oblique diameter: it is the distance from the sacroiliac joint of one side to the iliopubic eminence of the opposite side.
THE CAVITY It extends from the superior aperture to the inferior aperture and is directed posteroinferiorly. The anterior wall is shorter than the posterior wall.
The anteroposterior diameter is the distance between the midpoints of the posterior surface of the body of the pubic symphysis and the pelvic surface of the third sacral vertebra. The transverse diameter is the distance across the widest part of the cavity.
The oblique diameter is the distance from the end of the sacroiliac joint to the centre of the obturator membrane of the opposite side.
THE INFERIOR APERTURE OR PELVIC OUTLET It is diamond-shaped and is formed by the pubic arch, the ischiopubic rami, the ischial tuberosities, sacrotuberous ligament and the coccyx.
The anteroposterior diameter extends from the lower margin of the pubic symphysis to the tip of the coccyx.
The transverse diameter is the distance between the ischial tuberosities. 72 The oblique diameter is the distance between the midpoint of the sacrotuberous ligament (point of crossing of the sacrotuberous ligament and the sacrospinous ligament) of one side and the junction between the ischial and pubic rami of the opposite side.
AXIS OR PLANE OF THE PELVIS It is an imaginary plane that passes through the centres of the anteroposterior diameters of the superior aperture, the cavity and the inferior aperture of the pelvis. It is parallel to the sacrum and the coccyx. It is the path that the fetus follows during parturition.
CLASSIFICATION OF THE PELVIS There are two main types of classification: 1. Classification based on the pelvic brim index (anteroposterior diameter/transverse diameter x 100). a) Mesatipellic pelvis: the anteroposterior diameter and the transverse diameter are approximately equal. b) Dolichopellic pelvis: the anteroposterior diameter is longer than the transverse diameter. c) Brachypellic pelvis: the transverse diameter is slightly longer than the anteroposterior diameter. d) Platypellic pelvis: the transverse diameter is much longer than the anteroposterior diameter.
2. Classification based on the shape of the pelvic inlet. Caldwell and Moloy (1933) classified the pelvis into 4 types: a) Gynaecoid pelvis: the pelvic inlet is round. It corresponds to the mesatipellic pelvis and is seen in about 42% of females. b) Anthropoid pelvis: the pelvic inlet is long, narrow and oval in shape. It corresponds to the dolichopellic pelvis. It is seen in about 41% of Negro females and 24% of white females. c) Android pelvis: The pelvic inlet is heart-shaped. It corresponds to the brachypellic pelvis and is seen in 16% of Negro females and 33% of white females. d) Platypelloid or Flat pelvis: The pelvic inlet is oval with the long axis lying transversely. It corresponds to the platypellic type and is seen in 2-3% of both Negro and white females.
SEX DIFFERENCES IN THE PELVIS Sex differences are more marked in the pelvis than in any other bone. They are due to the fact that:
1. The female pelvis is adapted for easier passage of the fetal head during parturition.
2. The male pelvis is more heavily built and has larger joints and more muscular markings. 73 MALE FEMALE
1. General appearance thick and heavy thin and light 2. Muscular markings distinct less distinct 3. Joint surfaces large small 4. Pelvic inlet heart-shaped rounded 5. Pelvic cavity long and funnel-shaped short with parallel sides 6. Pelvic outlet smaller than the pelvic almost as large as the pelvic inlet inlet 7. Ilium less vertical more vertical 8. Iliac crest rugged and more curved less curved 9. Iliac fossa deep shallow 10. Preauricular sulcus frequently absent or less frequently present and better distinct marked 11. Sacrum long, narrow and short, wide, flat except the uniformly curved lower part which is curved forwards 12. Body of S1 wider than the ala (more narrower than the ala (less than one-third of the than one-third of the transverse diameter of transverse of the sacrum) the sacrum) 13. Auricular surface extends to the middle or extends only to the upper lower border of S3 border of S3 14. Greater sciatic notch narrower, about 50o about a right angle 15. Ischial spine inverted everted or in the plane of the body of the ischium 16. Ischial tuberosities in - turned and closer everted and further apart to each other
17. Distance from the pubic equal to or less than the more than the tubercle to the anterior margin transverse transverse diameter of the of the acetabulum diameter of the acetabulum acetabulum 18.Outer border of more everted less everted ischiopubic ramus 19. Subpubic angle acute, about 55o right angle `angle `angle between the index between the thumb and middle fingers.' and the index finger.' 20. Pubic tubercle less widely separated more widely separated 21. Obturator foramen oval triangular 74 23. UROGENITAL TRIANGLE
The urogenital triangle or region is the anterior portion of the perineum. It extends from the pubic symphysis in front to the perineal body behind. The perineal body is a fibromuscular tissue at the centre of the perineum to which several muscles are attached.
The triangle is bounded posteriorly by and imaginary transverse line that passes between the anterior parts of the ischial tuberosities and anterolaterally by the ischiopubic rami. The apex is at the pubic symphysis. The urogenital triangle has 3 layers of fascia separated by 2 spaces or pouches.
Its contents differ in both sexes. The male urogenital diaphragm is pierced by the urethra, while in the female it is pierced by the urethra and the vagina.
THE MALE UROGENITAL TRIANGLE This is pierced by the urethra and contains the following structures from superficial to deep:
1. Skin
2. Superficial perineal fascia (fatty and membranous layers)
3. Superficial perineal space or pouch
4. Inferior fascia of the urogenital diaphragm (the perineal membrane)
5. Deep perineal space or pouch
6. Superior fascia of the urogenital diaphragm
The superficial perineal fascia This is the subcutaneous tissue of the urogenital region. It consists of a superficial fatty layer and a deep membranous layer. The fatty layer contains fat and smooth muscle. As it passes anteriorly over the scrotum, it is replaced by large amounts of smooth muscle fibres which form the dartos muscle. It is continuous laterally with the fatty layer of the medial side of the thigh and posteriorly with the subcutaneous tissue around the anus. In the median lane, it is attached to the skin and membranous layer.
The membranous layer of the superficial layer or the Colles fascia is continuous anteriorly with the dartos muscle of the scrotum, the fascial sheath of the penis and the Scarpa's layer of the lower abdominal wall. Laterally, it is attached to the everted lip of the ischiopubic ramus along a line lateral to the crus penis, and to which the fascia lata is also attached. Posteriorly, it turns superiorly and fuses with the posterior margins of fasciae of the urogenital diaphragm and the perineal body.
The superficial perineal space This is a space which is bounded below by the membranous layer of the perineal fascia and above by the perineal membrane. It is incompletely divided into left and right sides by a median septum. It is closed posteriorly by the union of its upper and lower layers, and laterally by their attachments to the sides of the pubic arch. Anteriorly, it is continuous with the submembranous potential space of the anterior abdominal wall - the space between Scarpa's layer and the anterior wall of the rectus sheath. Rupture of the penile urethra leads to extravasation of urine into this space and distension of the tissues of the penis and scrotum. 75 The space contains: 1. 3 pairs of superficial muscles 2. 3 pairs of arteries 3. 3 pairs of nerves 4. Root and bulb of the penis The testes, spermatic cord and penis are located in this space.
MUSCLES OF THE SUPERFICIAL PERINEAL POUCH
There are 3 muscles on each side:
1. The superficial transverse perineal muscle. This arises from the medial side of the ischial tuberosity and inserts into the perineal body. It is usually poorly developed and may be absent. It is supplied by the perineal branch of the pudendal nerve. When both muscles contract, they help to fix the perineal body.
2. Bulbospongiosus or bulbocavernosus. This consists of 2 symmetrical parts. It arises from the perineal body and the median fibrous raphe below the bulb of the penis. Its most posterior fibres insert into the perineal membrane, intermediate fibres into the dorsal surface of the corpus spongiosum, and the most anterior fibres meet on the dorsum of the penis and blend with the deep fascia of the penis. It is supplied by the perineal branch of the pudendal nerve. Acting together, both muscles assist in expelling the last drops of urine or semen from the urethra, and some of the fibres help in maintaining erection of the penis (by compressing the erectile tissue of the bulb or the deep dorsal vein of the penis).
3. Ischiocavernosus. This arises from the medial side of the ischial tuberosity behind the crus penis, and covers the latter. It inserts into the lower and medial aspects of the crus penis. It is supplied by perineal branches of the pudendal nerve. The muscle helps to maintain erection of the penis by compressing the crus penis and thereby retarding venous return from the penis.
ARTERIES & NERVES IN THE SUPERFICIAL POUCH The 3 superficial arteries are: a) 2 pairs of posterior scrotal arteries b) Transverse perineal artery Both are branches of the perineal artery.
The 3 superficial nerves are: a) 2 pairs of posterior scrotal branches of the perineal nerve b) 1 perineal branch of the posterior cutaneous nerve of the thigh. It may lie in the subcutaneous fascia.
THE UROGENITAL DIAPHRAGM
The inferior and superior fasciae of the urogenital diaphragm as well as the deep perineal space and its contents constitute the urogenital diaphragm. It is a musculofascial sheath that separates the perineum from the pelvis anteriorly. The muscles of the urogenital diaphragm are the deep transverse perineal and the sphincter urethrae muscles.
The Inferior Fascia of the Urogenital Diaphragm This is a strong layer of fibrous tissue that stretches horizontally across the pubic arch. It is attached laterally to the ischiopubic ramus. Posteriorly, its margin fuses with the Colles' fascia. Its apex is thickened to form the transverse perineal ligament. The deep dorsal vein and the dorsal nerve of the penis pass through the interval between the arcuate pubic ligament and the transverse perineal ligament. 76
The Superior Fascia of the Urogenital Diaphragm This is not well developed as the inferior fascia. It stretches across the pubic arch. It is continuous with the perineal fascia, the perineal body and the Colles fascia. Anteriorly, it fuses with the inferior fascia at the transverse perineal ligament. Superiorly, it is pierced by the urethra and blends with the prostatic fascia.
The deep perineal space This is the space between the superior and inferior fasciae of the urogenital diaphragm. It is completely closed and contains the following structures: 1. Deep transverse perineal and sphincter urethrae muscles 2. Membranous urethra 3. A pair of bulbourethral (Cowper's) glands and their ducts 4. Internal pudendal vessels 5. Dorsal nerve of the penis 6. Artery of the bulb of the penis and a plexus of veins
The deep transverse perineal muscle arises from the inner surface of the ischial ramus and inserts into the tendinous perineal raphe and the perineal body. It helps to fix the perineal body. When the muscle is well developed, it may fuse with the posterior margin of the sphincter urethrae muscle to form a single muscle.
The sphincter urethrae arises from the inferior ramus of the pubis. Some of its fibres surround the urethra. It is inserted into the perineal body. When the muscles of both sides act simultaneously, they act as a sphincter. They also constrict the membranous urethra, and help to expel the last drops of urine and semen.
THE FEMALE UROGENITAL TRIANGLE The urogenital region in the female contains the urethra, as well as the lower end of the vagina and the female external genital organs. The superficial transverse perineal muscle is smaller, but similar to that in the male.
The Bulbospongiosus surrounds the orifice of the vagina. Its origin is the same as in the male, but it inserts into the side of the pubic arch and the root and dorsum of the clitoris. Acting together, they constrict the orifice of the vagina. The anterior fibres contribute to the erection of the clitoris by compressing the deep dorsal vein of the clitoris.
The ischiocavernosus is smaller than its male counterpart. It arises from the inner surface of the ischial ramus, embraces the crus of the clitoris and inserts into the medial aspect of the clitoris. It helps to maintain erection of the clitoris by compressing the crus of the clitoris and thereby retarding venous return from the clitoris.
The urogenital diaphragm in the female is not as complete as in the male because it is divided into 2 sides by the urethra and vagina. The deep transverse perineal muscles and the sphincter urethrae are much less developed than those of the male. The 2 muscles are often described as a single muscle which is called the deep transverse perineal muscle. It arises from the inner surface of the ischial rami. Its most anterior fibres are inserted into the perineal body. The sphincter urethrae arises from the inner surface of the ischial ramus and is mostly inserted into the lateral walls of the vagina. The remaining fibres pass in front of the urethra or between the urethra and vagina.
The perineal body is the central tendon of the perineum. It is a fibromuscular node in the median plane about 1.25cm anterior to the anus. Eight muscles converge and are attached to it. 77 24. THE HIP JOINT
The hip joint is a synovial joint of the "ball and socket" variety. The ball is the head of the femur, while the socket is the acetabulum. It is multiaxial.
It is adapted both for stability and a wide range of movement. In general, the stability of a joint and the range of movement are in inverse proportion to each other. The stability of the hip joint is primarily due to its bony configuration, i.e., the good adaptation between the articulating surfaces of the head and the acetabulum. The ligaments and muscles also contribute to the stability of the joint.
The wide range of movement is due to the fact that the neck of the femur is much narrower than the equatorial diameter of the head.
ARTICULAR SURFACES
The head of the femur is two-thirds of a spheroid. It is not a perfect sphere, as it is flattened above where the acetabulum rests on it. It is directed upwards, forwards and medially, and fits into the concavity of the acetabulum. It is covered with hyaline cartilage which encroaches slightly onto the anterior surface of the neck for articulation with the acetabulum when the hip is flexed. The fovea capitis, a depression below and behind the centre of the head, is non-articular and is not covered with cartilage. The ligament of the head of femur, ligamentum teres femoris, is attached to it. The other end of this ligament is attached to the transverse acetabular ligament.
The acetabulum is a cup-shaped cavity on the lateral aspect of the hip bone. The inferior margin of it is deficient and is called the acetabular notch. This notch is converted into a foramen by the transverse acetabular ligament. The acetabulum is formed by the fusion of the ilium, pubis and ischium. The three bones meet at a Y-shaped epiphyseal cartilage which fuses after puberty. The stem of the Y is vertical and passes through the acetabular notch to the obturator foramen. The pubis forms the upper and anterior one-fifth of the acetabulum, the ilium less than two-fifth and the ischium forms more than the lower two-fifth including the acetabular fossa.
The floor of the acetabulum is rough and non-articular, and is called the acetabular fossa. It is occupied by the Haversian fat pad. The c-shaped part that surrounds the acetabular fossa is called the lunate surface, and it is articular. The acetabulum is deepened by a rim of fibrocartilage called the acetabular labrum which is attached to its margin and the transverse acetabular ligament.
FIBROUS CAPSULE AND LIGAMENTS
The fibrous capsule of the hip joint is loose but strong and is attached proximally to the rim of the acetabular labrum and the transverse acetabular ligament. It extends downwards in a spiral or oblique manner to surround the neck of the femur. Distally, it is attached anteriorly to the entire length of the intertrochanteric line, posteriorly to just about 1cm above the intertrochantric crest.
From its distal attachment, longitudinal fibres are reflected backwards along the neck of the femur. They blend intimately with the periosteum of the neck and are attached to the articular margin of the head of the femur. These reflected fibres are called the retinacular fibres. They contain the arteries that supply the head of the femur, which arise from the trochanteric anastomosis.
The fibrous capsule of the hip joint is thick anteriorly, inferiorly and superiorly. Its posterior and inferior aspects are thin. It is strengthened by 3 ligaments: iliofemoral, pubofemoral and ischiofemoral ligaments. These ligaments wind around the long axis of the neck of the femur. 78 The iliofemoral ligament (ligament of Bigelow) is the strongest of the 3 ligaments, and one of the strongest ligaments in the body. It lies in front of the joint and has the shape of an inverted "Y". The stem of the Y is attached to the lower half of the anterior inferior iliac spine and the acetabular margin. The limbs diverge and are attached to the upper and lower ends of the intertrochanteric line. It limits hyperextension and excessive lateral rotation of the hip joint. It forms the axis along which the neck of the femur rotates in dislocation of the hip joint.
The pubofemoral ligament is triangular in shape and extends from the iliopubic eminence and obturator crest to the lower part of the intertrochanteric line. It blends with the fibrous capsule and the medial band of the iliofemoral ligament and helps to strengthen the anterior and inferior parts of the fibrous capsule. It becomes taut when abduction and extension occur together. It prevents overabduction and extension.
The part of the fibrous capsule between the iliofemoral and pubofemoral ligaments is often deficient and permits communication between the hip joint and the psoas bursa.
The ischiofemoral ligament is the weakest of the 3 ligaments. It arises from the posteroinferior margin of the acetabulum. The fibres run in a spiral manner upwards and laterally over the back of the neck. Most of these fibres running transversely across the neck form the zona orbicularis which causes a constriction in the fibrous capsule. The remaining fibres of the ischiofemoral ligament reach the femur. Since most of the fibres are inserted into the femur, the ligament is more accurately referred to as the ischiocapsular ligament.
The other ligaments of the hip joint are the ligament of the head of the femur, the transverse acetabular ligament and the acetabular labrum.
THE SYNOVIAL MEMBRANE The synovial membrane of the hip joint is extensive. As in all joints, it is attached to the articular margins of the joint. It lines the fibrous capsule and covers the acetabular labrum. It is reflected back along the neck of the femur where it invests the retinacular fibres. It also invests the Haversian fat pad and the ligament of the head of the femur. The synovial membrane is thin anteriorly between the iliofemoral and pubofemoral ligaments. Occasionally there is a communication between the joint cavity and the psoas bursa.
RELATIONS OF THE HIP JOINT The hip joint is surrounded by muscles.
Anteriorly: Pectineus, the tendon of psoas major, and iliacus separate the joint from the femoral vein, artery and nerve respectively. Superiorly: Reflected head of rectus femoris and gluteus minimus.
Inferiorly: Obturator externus.
Posteriorly: Obturator internus, gemelli and quadratus femoris separate the joint from the sciatic nerve. 79 BLOOD SUPPLY The head and the intracapsular part of the neck are supplied by:
1. The artery of the ligament of the head: this is a branch of the obturator artery. In the young, it supplies the ligament and the greater part of the head. It shrinks with age and in the adult, supplies only the area around the fovea capitis.
2. Arteries in the retinacula of the posterosuperior and posteroinferior parts of the neck of the femur: they are branches of the trochanteric anastomosis.
3. Terminal branches of the medullary artery to the shaft of the femur.
NERVE SUPPLY Hilton's law states that the nerve crossing any joint supplies that joint and the muscles acting on it. The nerves supplying the hip joint are:
1. Femoral nerve, via the nerve to rectus femoris 2. Obturator nerve, via the anterior division 3. Sciatic nerve, via the nerve to quadratus femoris 4. Some twigs from the superior gluteal nerve
MOVEMENTS A wide range of movements occurs at the hip joint - flexion, extension, adduction, abduction, circumduction (which is a combination of the above four movements), medial and lateral rotation.
Flexion is performed mainly by psoas major and iliacus. These are assisted by rectus femoris, pectineus, sartorius and tensor fascia latae. The adductors may participate in early stages of flexion. Flexion is limited by the thigh touching the abdomen or by tension in the hamstrings if the knee is extended.
Extension is performed by gluteus maximus and the hamstrings. The gluteus maximus is active at the extremes of movement. The hamstrings are active in the intermediate stages of extension. Extension is limited by the iliofemoral ligament.
Adduction is performed by the adductor muscles - adductor longus, adductor brevis and part of the adductor magnus. These are assisted by pectineus and gracilis. Adduction is limited by contact of the thigh with the opposite limb.
Abduction is performed by gluteus medius and minimus and assisted by tensor fasciae latae, sartorius and piriformis. This movement is important for stabilizing the pelvis while walking. The pelvis would normally tend to fall on the side with the raised limb i.e. the unsupported side. The abductors of the opposite side by contracting prevent this from happening. Abduction is limited by the pubofemoral ligament.
Medial rotation is produced by iliacus, psoas, tensor fasciae latae and the anterior fibres of gluteus medius and minimus. Any muscle whose line of pull passes in front of the joint produces medial rotation of the extended thigh.
Lateral rotation is produced by gluteus maximus and the small muscles of the back of the thigh - the obturators, the gemelli, quadratus femoris and piriformis. These small muscles, the so called lateral rotators of the thigh act as stabilizers of the hip joint. Lateral rotation is limited by the pubofemoral ligament. 80 25. THE ARCHES OF THE FOOT
The human foot is built to perform 3 main functions: 1. To support the weight of the body in the erect position. In order to perform this function, the foot is able to adapt to various positions and to uneven surfaces.
2. To propel the body during movement for example in walking, running and jumping. To perform this function, the foot is able to be transformed into a rigid lever springboard that will withstand stress and will not collapse.
3. To act as a shock-absorber for the propulsive mechanism of the foot for example when landing from a height.
In order to perform the above functions, the foot is built in the form of an arch with many segments. A segmented structure can bear weight only if it is built in the form of an arch.
There are 3 arches in the foot: 1. Medial longitudinal arch 2. Lateral longitudinal arch 3. Transverse arch
The imprint of a wet foot on the floor made when a person is standing shows that the heel, lateral margin of the foot, the pads under the metatarsal heads and the pads of the distal phalanges are in contact with the floor. The medial margin of the foot from the heel to the head of the 1st metatarsal is arched above the ground.
On standing, the arches flatten slightly under the weight of the body, the individual bones lock together, the ligaments become taut and maximally tensed and the foot becomes an immobile lever.
On walking, the body weight is released from the arches, the individual bones unlock and the arches become a mobile lever system.
MECHANISM OF ARCH SUPPORT This is similar to that of a stone bridge, the strength of which is maintained by:
1. Shape of the stones: the stones are wedge-shaped with the thin edge of the wedge lying inferiorly.
2. Inferior edges of the stones are tied together by staples: this prevents the inferior edges of the stones from separating when the arch is weight-bearing.
3. The ends of the bridge, that is, the pillars, are tied together by a tie-beam to prevent separation of the pillars and consequent sagging of the arch.
4. The arch may be suspended from above.
The medial longitudinal arch It is formed by the calcaneus, the talus, the navicular, the 3 cuneiforms and the medial 3 metatarsal bones. It is the most important arch of the foot. It is higher, stronger, more mobile and more resilient than the lateral longitudinal arch. It is a long arc of a small circle and bears most of the body weight.
The 2 pillars or extremities on which it rests in the erect position are the plantar surface of calcaneus posteriorly and the heads of the medial 3 metatarsals anteriorly. The summit of the arch is the superior articular surface of the talus. The head of the talus is the keystone of the arch.
81 The arch is maintained by:
1. The shape of the bones: this plays a minimal role. The head of the talus is supported by the sustentaculum tali and is received by the concave proximal surface of the navicular. The concave surface of the medial cuneiform receives the navicular.
2. The edges of the bones are tied together by the plantar ligaments. The plantar calcaneonavicular (or spring) ligament is the most important support of the medial longitudinal arch. The tendinous insertions of tibialis posterior also play a role in uniting the edges of the bones.
3. The ends or pillars of the medial arch are tied together in the form of a tie-beam by the plantar aponeurosis which stretches like a bow-string between the pillars of the arch; and by some muscles and tendons, namely the medial part of flexor digitorum brevis, abductor hallucis, flexor hallucis brevis, the tendons of flexor digitorum longus and flexor hallucis longus. The flexor hallucis longus is the most important muscle for the maintenance of the medial longitudinal arch.
4. The arch is suspended from above by tibialis anterior and posterior and the medial (deltoid) ligament of the ankle.
The short muscles are not very active when standing. They come into play during walking.
The navicular and talus are bones of the medial longitudinal arch that are most prone to fracture.
The lateral longitudinal arch It is formed by the calcaneus, cuboid and the lateral two metatarsal bones. It is a small arc of a big circle (it is a low arch). It is less mobile and more in contact with the ground than the medial longitudinal arch. Its summit is the inferior articular surface of the talus, that is, the subtalar articulation. The chief joint is the calcaneocuboid and the keystone is the cuboid. The calcaneus is the bone of this arch that is most prone to fracture.
It is maintained by:
1. The shape of the bones, especially between the distal end of calcaneus and the proximal end of the cuboid. The bony factors play little or no role.
2. The inferior edges of the bones are tied together by the long and short plantar ligaments and the origins of the short muscles of the forepart of the foot. The long plantar ligament is the main support of the lateral longitudinal arch.
3. The pillars of the arch are tied together in the form of a tie-beam by the plantar aponeurosis, abductor digiti minimi and the lateral parts of flexor digitorum brevis and longus.
4. The arch is suspended from above by the peroneus longus and brevis.
The transverse arch This is formed by the bases of the 5 metatarsal bones, and the adjacent cuboid and the three cuneiform bones. The heads of the 5 metatarsals lie flat on the ground. This arch is best marked at the tarsometatarsal joints. Each foot constitutes 1/2 of the transverse arch with its base on the lateral side. A complete transverse arch is formed when the medial borders of the 2 feet are placed together. The arch is maintained by: 1. The intermediate and lateral cuneiforms and the bases of the 3rd to 4th metatarsals which are wedge-shaped.
82 2. The inferior edges of the bones are tied together by the deep transverse ligament, plantar ligaments, dorsal interossei and transverse head of adductor hallucis.
3. The pillars of the arch are tied together by peroneus longus.
4. The arch is suspended from above by the peroneus longus and brevis.
Weight distribution The weight of the body is transmitted to the talus through the tibia. From the talus the weight is transmitted to the calcaneus and the heads of the metatarsals.
Of the 50% of the body weight transmitted to each foot, 25% of it passes through the tuberosity of the calcaneus while the remaining 25% passes through the metatarsal heads as follows: 10% passes through the head of the 1st metatarsal or through the sesamoid bones, and 15% to the other metatarsal heads.
80% of the support of the arches is contributed by ligaments while 20% is contributed by muscles. The shape of the interlocking bones plays a minor role.
Pes Planus Pes planus (or flat foot) may be congenital or acquired. It is a condition in which the medial longitudinal arch is depressed. It may be due to malalignment of the bones or overstretching of the ligaments. The head of the talus is not supported and the weight of the body forces it down. The forefoot becomes everted.
The bones of a child are arched as in the adult, but the foot appears flattened because the concavity of the sole is filled with fat.
When the muscles supporting the arches are fatigued, for example, as a result of exercise, prolonged standing or excessive weight, the muscular support may give way. The ligaments become overstretched and the patient feels pain. This condition is called fallen arches.
Pes cavus Pes cavus (or claw foot, high-arched foot) is a condition in which the medial longitudinal arch is unduly high. It is usually due to muscle imbalance which in many cases may be as a result of poliomyelitis, cerebral palsy, spina bifida, etc. 83 26. THE LYMPHATIC DRAINAGE OF THE LOWER LIMB
The lower limb is drained by superficial and deep lymph vessels. The superficial lymph vessels accompany the superficial veins while the deep lymph vessels accompany the deep veins. Most of the superficial lymph vessels accompany the great saphenous vein while those from the posterolateral aspect of the foot and leg accompany the small saphenous vein. The sole has a rich lymph plexus. The lymph nodes of the lower limb may be grouped into: a) Superficial inguinal lymph nodes b) Deep inguinal lymph nodes c) Popliteal lymph nodes. Small and inconstant lymph nodes may also be found along the anterior tibial vessels.
THE SUPERFICIAL INGUINAL NODES The superficial inguinal lymph nodes lie in the subcutaneous tissue. They are arranged in 2 chains like the letter "T". The horizontal limb (or proximal chain or set) lies below and parallel to the inguinal ligament while the vertical limb (or the distal chain or set) lies along the terminal part of the great saphenous vein.
The horizontal chain consists of 5-6 nodes divided into medial and lateral groups. The medial group lies below the medial part of the inguinal ligament. It receives lymphs from the area of the trunk below the umbilicus, and the perineum including the distal part of the anal canal, and the external genitalia (the penis, scrotum and urethra in the male; the vulva and lower part of the vagina in the female). In the female, it also receives lymph vessels from the fundus of the uterus that accompany the round ligament of the uterus. The lymph vessels from the testes do not drain into the medial group of lymph nodes. They drain into the para-aortic nodes. The lateral group lies below the lateral part of the inguinal ligament. It receives lymph from the buttock and gluteal region i.e. the area below the iliac crest.
The vertical chain consists of about 4 nodes, and it receives lymph from the skin and superficial fascia of the lower limb with the exception of the posterolateral aspect of the leg. The afferents are lymph vessels that accompany the long saphenous vein.
The efferents of both chains converge towards the saphenous opening and pass through the cribriform fascia to enter the deep inguinal nodes. Their passage gives the fascia its sieve-like appearance, hence the name "cribriform".
THE DEEP INGUINAL NODES The deep inguinal lymph nodes lie deep to the fascia lata, along the medial side of the femoral vein. They vary in number between 1 and 3. One of them lies in the femoral canal and is the most constant and is referred to as the gland of Cloquet or the node of the femoral canal. These nodes drain the tissue of the lower limb beneath the deep fascia. They receive as afferents: a) Deep lymph vessels that accompany the femoral vessels b) Lymph vessels from the glans penis or glans clitoris c) Some afferent vessels from superficial inguinal lymph nodes The efferent vessels end in the external iliac nodes. The deep inguinal lymph vessels of the perineum and gluteal regions drain into the internal iliac lymph nodes.
THE POPLITEAL LYMPH NODES The popliteal lymph nodes are small deep lymph nodes, about 6 to 7 in number, which are embedded in the fat of the popliteal fossa, at the sides of the popliteal vessels. Their afferents accompany the small saphenous vein and the anterior and posterior tibial vessels. They receive lymph from the skin of the posterolateral aspect of the foot and leg, and also from the deep structures.Their efferents accompany the femoral vessels and drain mostly into the deep inguinal lymph nodes. A few accompany the great saphenous vein and end in the superficial inguinal nodes. 84 27. THYROID GLAND
The thyroid gland is the largest endocrine gland. It is located in the anterior and lateral aspects of the neck at the level of C5 to T1. It weighs about 20-30g. The size, however, varies with age, sex and nutritional status of the individual. It is relatively larger in the youth, in women and in the well nourished. In women, the size is larger during menstruation and pregnancy.
The thyroid gland consists of 2 lobes, the left and the right. The two lobes are connected across the median plane by a narrow band of thyroid tissue called the isthmus. Each lobe is conical in shape and is about 5cm long, 3cm wide and 2cm thick. It has an apex, a base and 3 surfaces. The apex extends superolaterally up to the level of the oblique line of the thyroid cartilage. The base is directed inferomedially to the level of the 6th tracheal ring. The 3 surfaces are the medial, posterolateral and anterolateral (superficial).
RELATIONS OF THE LOBES The anterolateral surface is covered by sternothyroid, sternohyoid and belly of omohyoid muscle. More laterally, it is overlapped by sternocleidomastoid muscle. The attachment of the sternothyroid muscle to the oblique line of the lamina of the thyroid cartilage prevents extension of the thyroid gland beyond this line.
The medial surface is related superiorly to two cartilages: the thyroid and the cricoid; two muscles: the inferior constrictor and the cricothyroid muscle; and a nerve: external laryngeal. Inferiorly, it is related to 2 tubes: the trachea and the oesophagus; and a nerve: the recurrent laryngeal.
The posterolateral surface is related to the longus colli muscle and the carotid sheath. Near the posterior border it is related to the parathyroid glands. The anterior border is closely related to the anterior branch of the superior thyroid artery. The posterior border is more rounded than the anterior border and is related to the inferior thyroid artery and an anastomosing branch between the inferior thyroid artery and the posterior branch of the superior thyroid artery. The lower portion of the posterior border of the left lobe is also related to the thoracic duct.
THE ISTHMUS The isthmus is a band of glandular tissue that unites the lower parts of the right and left lobes. It is about 1.25cm both in length and width and overlies the 2nd to 4th tracheal rings. It may be located at a higher or lower level. Anteriorly, it is related to the sternothyroid and sternohyoid muscles and the anterior jugular vein. The anastomotic branch between the left and right superior thyroid arteries is related to the upper border of the isthmus. The inferior thyroid veins leave the thyroid gland at the lower border of the isthmus.
In about 40% of the population a third lobe called the pyramidal lobe extends from the isthmus towards the hyoid bone. Sometimes it may be anchored to the hyoid bone by a fibrous band or a fibromuscular band called levator glandulae thyroidea. The pyramidal lobe seldom lies in the median plane. Usually it lies more to the left than to the right. Occasionally, it may be double. Small detached masses of thyroid tissue may be found near this lobe. They are called accessory thyroid glands.
THE CAPSULES The thyroid gland has two capsules: a true and a false capsule. The true capsule is formed by condensation of the connective tissue at the periphery of the thyroid gland while the false capsule is derived from the pretracheal fascia. The venous plexus lies between the capsules. The lateral ligament of the thyroid gland (suspensory ligament of Berry) is a thickening of the pretracheal fascia. It extends from the posteromedial aspect of each lobe to the cricoid cartilage. 85 The left and right lateral ligaments form a sling that helps to anchor the thyroid gland to the larynx. Consequently, the thyroid gland moves with the larynx during swallowing.
BLOOD SUPPLY
ARTERIAL SUPPLY The thyroid gland has a rich blood supply. It is supplied by the following:
1. Superior thyroid artery: It is usually the first branch of the external carotid artery and is accompanied by the external laryngeal nerve. It pierces the pretracheal fascia as a single trunk, and runs towards the apex of the lateral lobe. There it divides into an anterior branch and a posterior branch. The anterior branch runs down to the upper border of the isthmus where it anastomoses with that of the opposite side. The posterior branch runs down the posterior surface of the lobe where it anastomoses with the ascending branch of the inferior thyroid artery.
2. Inferior thyroid artery: This is a branch of the thyrocervical trunk of the subclavian artery. It enters the thyroid gland from its posterior surface. It divides into 4 or 5 branches before piercing the pretracheal fascia and supplies more glandular tissue than the superior thyroid artery. It supplies the lower pole and the posterior aspect of the gland. It also supplies the parathyroid glands.
3. Thyroidea ima artery: In about 2-12% of the population an additional artery called the thyroidea ima artery supplies the isthmus. It arises from the brachiocephalic trunk, the right common carotid or directly from the arch of the aorta.
4. Accessory thyroid arteries: The thyroid gland also receives blood supply from arteries to the oesophagus and trachea. These arteries provide enough blood to the gland when the superior and inferior thyroid arteries are tied off.
VENOUS DRAINAGE 1. The superior thyroid vein accompanies the superior thyroid artery. It drains the upper pole and empties into the internal jugular vein. It may also drain into the common facial vein.
2. The middle thyroid vein is short and wide and drains the middle portion of the thyroid gland. It passes anterior to common carotid artery at the level of the cricoid cartilage and drains into the internal jugular vein.
3. The inferior thyroid veins unlike the superior ones do not accompany the artery of the same name. They arise as two or more trunks from the inferior thyroid venous plexus which is located in the pretracheal fascia. They usually drain into the corresponding brachiocephalic veins or they may unite to form a single trunk which usually drains into the left brachiocephalic vein.
4. According to Kocher, there may be a 4th thyroid vein between the middle and inferior thyroid veins.
Thyroid veins do not have valves. They bleed profusely when cut. During thyroidectomy they should be doubly ligated before they are cut.
LYMPHATIC DRAINAGE The lymph vessels of the thyroid gland accompany the arterial supply. They run in the interlobular connective tissue. Those from the upper part of the gland accompany the superior thyroid artery and drain into the anterosuperior group of deep cervical lymph nodes. Those from the lower parts of the gland accompany the inferior thyroid artery and drain into the posteroinferior group of cervical lymph nodes. A few lymph vessels accompany the thyroidea ima artery and drain into the pretracheal lymph nodes. 86 NERVE SUPPLY The thyroid gland is supplied by postganglionic sympathetic fibres from the superior, middle and inferior cervical ganglia. Most of these fibres are from the middle cervical ganglion and they accompany the inferior thyroid artery. Some fibres from the superior cervical ganglion accompany the superior thyroid artery. The sympathetic fibres are distributed mainly to the blood vessels and are vasoconstrictors. A few are distributed to the follicular cells. A small number of the vagal fibres may accompany the arteries to the thyroid gland. Their function is unknown.
APPLIED ANATOMY Enlargement of the thyroid gland is called goitre. The attachment of the sternothyroid muscle and the fascial sheath to the the oblique line of the lamina of the thyroid cartilage prevents the enlarged thyroid gland from extending superiorly. It enlarges posteriorly or inferiorly into the thorax. An enlarged thyroid gland may compress the trachea causing difficulty in respiration. It may also compress the nerves associated with it causing loss of voice.
Thyroidectomy is the removal of the thyroid gland. The posterior part of each lobe is usually left behind during thyroidectomy to avoid removal of the parathyroid glands and to prevent the occurrence of myxoedema. The latter occurs when the thyroid gland is completely removed.
The superior thyroid artery and the external laryngeal nerve (a branch of the superior laryngeal nerve) lie close to each other. However, near the upper pole of the thyroid gland they separate. In order to reduce the risk of damaging the external laryngeal nerve during thyroidectomy, the superior thyroid artery is tied close to the thyroid gland. On the contrary, the inferior thyroid artery comes very close to the recurrent laryngeal nerve near the posterior aspect of the gland. In most cases the nerve lies behind the branches of the inferior thyroid artery. Sometimes, it may pass between the branches before they pierce the pretracheal fascia. It is usually posterior to the pretracheal fascia. In other to avoid damage to the recurrent laryngeal during thyroidectomy, it is safer to ligate the inferior thyroid artery further away from the gland before it divides.
87 28. LARYNX
The larynx is an organ that connects the lower part of the pharynx with the trachea. It is located in the anterior part of the neck and is about 5cm long in males, and 4cm long in females. It extends from the tip of the epiglottis at the level of C3 vertebra to the lower border of the cricoid cartilage at the level of C6.
FUNCTIONS 1. It serves as a valve to prevent food and foreign bodies from entering the lower respiratory passages during swallowing or vomiting. 2. It allows the passage of air from the pharynx to the trachea and lungs. 3. It serves for vocalization or phonation by regulating the flow of air to and from the lungs. 4. It closes the glottis during valsava manoeuvres, e.g., coughing and defecation.
RELATIONS Anteriorly, it is superficial and is covered only by skin and fascia. Posteriorly, it is related to the laryngopharynx, pretracheal fascia and prevertebral muscles. Laterally, it is related to the carotid sheaths and their contents, infrahyoid muscles, the thyroid gland and the sternocleidomastoid muscles.
CARTILAGES It has 3 single cartilages: thyroid, cricothyroid and epiglottis, and 3 paired ones: arytenoid, corniculate and cuneiform. The thyroid, cricoid and most parts of the arytenoid are of hyaline cartilage. The other cartilages together with the apices and vocal processes of the arytenoids are of elastic cartilage.
THYROID CARTILAGE This is the largest of the laryngeal cartilages. It consists of 2 laminae or plates which are fused anteriorly but diverge posteriorly. The angle of union of the thyroid laminae is about 90 degrees in the male and 120 degrees in the female.
The superior borders of the laminae curve inferiorly in the midline to form the laryngeal notch. Below the notch, where the lower parts of the anterior borders of the lamina fuse, there is median projection called the laryngeal prominence which is also referred to as the "Adam's Apple". It is more prominent in the male than in the female. The posterior border of each lamina projects upwards and downwards to form the superior and inferior horns respectively. The lateral surface of each lamina is crossed by an oblique line which gives attachment to the sternothyroid, the thyrohyoid and the inferior pharyngeal constrictor muscles.
CRICOID CARTILAGE This is shaped like a signet ring and is the only complete cartilage of the larynx. It consists of a narrow anterior part called the arch, and a large posterior part called the lamina. The superior border is connected to the thyroid cartilage by the cricothyroid membrane while the lower border is connected to the 1st ring of the trachea by the cricotracheal ligament.
EPIGLOTTIS It is a leaf-like cartilage. It is located behind the root of the tongue and the body of the hyoid bone, and in front of the inlet of the larynx. The upper end projects above the hyoid bone. The lower part is attached to the back of the thyroid cartilage by the thyroepiglottic ligament. The hyoepiglottic ligament attaches the epiglottis to the hyoid bone. The sides of the epiglottis are connected to the arytenoid cartilages by the aryepiglottic folds. These folds separate the larynx from the piriform recesses of the pharynx. They also run posteriorly to form the margins of the laryngeal inlet or aditus.
The mucous membrane covering the epiglottis is reflected anteriorly to the base of the tongue to form a median and two lateral glossoepiglottic folds. The depression on each side of the median 88 glossoepiglottic fold is called the vallecula. A small elevation in the lower part of the posterior surface of the epiglottis is called epiglottic tubercle.
ARYTENOID CARTILAGES These articulate with the upper border of the lamina of the cricoid cartilage. Each has a base and an apex. The base has a muscular and a vocal process. The vocal process gives attachment to the vocal ligament and the vocalis muscle while the muscular process gives attachment to the posterior and lateral cricoarytenoid muscles as well as the thyroarytenoid muscle.
CORNICULATE CARTILAGES These are attached to the apices of the arytenoid cartilages and are located in the aryepiglottic folds of the mucous membrane.
CUNEIFORM CARTILAGES They are small rod-like cartilages that lie in the aryepiglottic folds anterior to the corniculate cartilages.
JOINTS AND LIGAMENTS OF THE LARYNX The joints of the larynx are the cricothyroid and cricoarytenoid joints. They are synovial joints. The ligaments and menbranes of the larynx are divided into two: extrinsic and intrinsic.
Extrinsic ligaments: they connect the cartilages of the larynx to the hyoid and the trachea. 1. The thyrohyoid membrane: It extends from the upper margin of the thyroid cartilage to the posterior surface of the body and greater cornu of the hyoid bone. The median part of this membrane is thickened to form the median thyrohyoid ligament. The posterior margins are thickened to form the lateral thyrohyoid ligaments. This membrane is pierced by the superior laryngeal vessels and the internal laryngeal brnches of the superior laryngeal nerves. 2. The cricotracheal ligament: It connects the inferior border of the cricoid cartilage to the first tracheal ring. 3. The hyoepiglottic ligament: It attaches the upper end of the epiglottis to the hyoid.
Intrinsic ligaments: they connect the laryngeal cartilages to each other. 1. Quadrate or quadranglar membrane: This is the upper portion of the fibroelastic membrane that lies beneath the mucous membrane of the larynx. It extends between the epiglottis and the arytenoid cartilages; its lower margin forms the vestibular ligament while its upper margin forms the aryepiglottic fold. 2. The conus elasticus or cricovocal membrane or cricothyroid membrane or ligament: This is the lower portion of the fibroelastic membrane. It connects the thyroid, cricoid and arytenoid cartilages. It consists of a thick anterior part called the median cricothyroid ligament and two lateral portions called the lateral cricothyroid ligaments. 3. The vocal ligament: It is the free upper margin of the conus elasticus. It extends from the junction of the laminae of the thyroid cartilage to the vocal process of the arytenoid cartilage.
4. The vestibular (ventricular) ligament: It is the free lower margin of the quadrangular ligament. It extends from the thyroid cartilage in front to the arytenoid cartilage behind. It is loosely covered with mucosa to form the vestibular fold. 5. The thyroepiglottic ligament: It connects the epiglottis to the thyroid cartilage.
THE LARYNGEAL CAVITY The laryngeal cavity extends from the laryngeal inlet to the level of the inferior border of the cricoid cartilage. The inlet or aditus is the opening through which the larynx communicates with the laryngopharynx. It is set obliquely and is bounded anteriorly by the epiglottis, posteriorly and inferiorly by the arytenoid cartilages, and laterally by the aryepiglottic folds with the corniculate and cuneiform cartilages. Between the aryepiglottic fold and the inner wall of the thyroid cartilage is the piriform recess of the pharynx. 89 The cavity of the larynx is divided into 3 compartments by 2 pairs of horizontal folds: the vestibular and vocal folds. The superior compartment is called the laryngeal vestibule. It extends from the laryngeal inlet to the vestibular folds. The middle compartment is called the laryngeal ventricle. It lies between the vestibular folds above and the vocal folds below. It is the smallest of the compartments and it bulges laterally between the two folds to form the laryngeal sinus. Anteriorly, each sinus extends superiorly between the vestibular fold and the lamina of the thyroid cartilage to form a pouch called the laryngeal saccule. The saccule contains mucous glands which lubricate the vocal cords. The latter do not contain glands. The inferior compartment is called the infraglottic compartment. It extends from the vocal folds to the lower border of the cricoid cartilage.
The vestibular (ventricular) folds or false vocal cords are thick folds of mucous membrane that cover the vestibular ligament. This ligament is the thickened lower margin of the quadrangular membrane. They help to close the larynx during swallowing and so prevent food particles or foreign bodies from entering into it. They do not play any role in phonation, coughing, sneezing, etc. The rima vestibuli is the interval between the two vestibular folds.
The vocal folds or true vocal cords extend from the angle of the thyroid cartilage to the vocal process of the arytenoid cartilage. Each vocal cord consists of the vocal ligament, the conus elasticus and muscle fibres, and is covered by mucous membrane. The interval between the vocal cords is called the rima glottidis and is the narrowest part of the laryngeal cavity. The vocal cords play a very important role in phonation because they control the stream of air passing through the rima glottidis. The vocal cords, the rima glottidis and the part of the larynx around the vocal cords constitute the glottis. The vocal cords alter the shape and size of the rima glottidis in order to facilitate respiration and phonation.
During breathing the vocal cords are held open and their length do not change. The rima glottidis is narrow and wedge shaped. During speaking, prior to a cough or sneezing, or during abdominal contraction, the vocal cords are closed and their length can change. The rima glottidis becomes a narrow slit. Changes in the pitch of voice are as a result of variation in the tension and length of the vocal cords, the shape of the rima glottidis and the force of expiration. Men have a lower pitch of voice than women because they have longer vocal cords. The quality of voice depends on the structures above the larynx.
CLOSURE OF THE LARYNX There are 2 levels in the larynx that can be closed by sphincter muscles. These levels are: laryngeal inlet and the rima glottidis. Closure of the laryngeal inlet during swallowing prevents food particles or foreign bodies from entering the respiratory passages. Closure of the rima glottidis helps to trap air below and increases the intrathoracic pressure (as in coughing) or intraabdominal pressure (as in defecation or micturition).
MUCOUS MEMBRANE OF THE LARYNX The larynx is lined by pseudostratified columnar epithelium except at the areas that are subject to greater wear and tear viz. the vocal cords, the vestibular folds, the margins of the aryepiglottic folds and the upper part of the epiglottis. These areas are covered by stratified squamous epithelium. Inflammation of the larynx may give rise to oedema above the vocal cords. Since the mucous membrane is adherent to the larynx at the level of the vocal cords, the oedema does not extend inferior to the vocal cords.
MUSCLES OF THE LARYNX The muscles of the larynx are divided into two groups: the extrinsic and the intrinsic. The extrinsic muscles move the larynx as a whole while the intrinsic muscles move parts of the larynx and are concerned with changes in the laryngeal inlet and rima glottidis. The extrinsic laryngeal muscles: 90 1. Depressors of the larynx: omohyoid, sternohyoid, sternothyroid. These muscles are infrahyoid muscles. 2. Elevators of the larynx: stylohyoid, digastric, mylohyoid and stylopharyngeus. These muscles are suprahyoid muscles except stylopharyngeus. The thyrohyoid muscle may be considered as the superior continuation of the sternothyroid muscle. It elevates the larynx but unlike the other elevators, it depresses the hyoid bone.
The intrinsic muscles are divided into two: those that control the aperture of the laryngeal inlet and those that move the vocal cords. All the intrinsic laryngeal muscles are supplied by the recurrent laryngeal nerve except the cricothyroid muscle which is supplied by the exlaryngeal branch of the superior laryngeal nerve Muscles that control the laryngeal inlet: 1. Muscles that close the laryngeal inlet: Oblique arytenoids and the aryepiglottic muscles. The latter is a prolongation of the oblique arytenoid muscle. During swallowing, the inlet is closed to prevent food particles from entering the respiratory passages. 2. Muscle that widen the laryngeal inlet: Thyroepiglotticus.
Muscles of the vocal cords: 1. Adductors: Lateral cricoarytenoids, the transverse arytenoid, cricothyroids, and the thyroarytenoids. They close the rima glottidis. The transverse arytenoid muscle is the only unpaired intrinsic muscle of the larynx. 2. Abductors: Posterior cricoarytenoid muscle is the only abductor of the vocal folds. It widens the rima glottidis and is the most important muscle of the larynx. 3. Tensors: Cricothyroid muscle. It increases and tightens the vocal ligaments and consequently raises the pitch of the voice. 4. Relaxers: Thyroarytenoid muscle. Vocalis muscle is a portion of this muscle. It arises from the vocal ligament and is attached to the vocal process of the arytenoid cartilage. It adjusts the vocal ligaments during whispering.
BLOOD VESSELS Two pairs of arteries supply the larynx: superior and inferior laryngeal arteries. The superior laryngeal artery is a branch of the superior thyroid artery. It pierces the thyrohyoid membrane along with the internal branch of the superior laryngeal nerve and supplies the larynx up to the vocal folds. The inferior laryngeal artery is a branch of the inferior thyroid artery. It runs with inferior laryngeal nerve and supplies the mucous membrane and muscles of the inferior part of the larynx, i.e., below the vocal folds. The corresponding veins accompany the arteries and drain into the superior and inferior thyroid veins.
LYMPH VESSELS The lymph vessels accompany the arterial supply. The lymph vessels superior to the vocal cords accompany the superior thyroid artery and drain into upper deep cervical lymph nodes, while those that are inferior to the vocal cords accompany the inferior thyroid artery and drain into the lower deep cervical nodes, and the supraclavicular nodes. NERVE SUPPLY The larynx is supplied by sympathetic fibres and the vagus nerves. The sympathetic fibres follow the arteries. The fibres supplying the upper half of the larynx are from the superior cervical ganglion while those supplying the lower half are from the middle cervical ganglion.
The superior laryngeal and recurrent laryngeal nerves are branches of the vagus nerve. The superior laryngeal nerve has external and internal laryngeal branches. The external laryngeal branch accompanies the superior thyroid artery and supplies the cricothyroid muscle. The internal laryngeal branch pierces the thyrohyoid membrane and gives sensory and secretomotor fibres to the upper half of the larynx, the piriform recess, mucous membrane of the epiglottis and the most posterior part of the tongue. 91
The terminal branch of the recurrent laryngeal nerve enters the larynx close to the inferior thyroid artery. It supplies all the intrinsic muscles of the larynx except cricothyroid muscle which is supplied by the external branch of the superior laryngeal nerve. It also gives sensory and secretomotor fibres to the lower half of the larynx. Injury to the recurrent laryngeal nerve results in paralysis of the vocal folds, loss of voice and some difficulty in swallowing. Damage to the superior laryngeal nerve is seldom bilateral and does not usually give rise to any distinctive symptoms.
AGE CHANGES IN THE LARYNX The larynx is relatively large at birth. Thereafter, the growth gradually diminishes. For a short time at puberty there is an abrupt increase in the size of the larynx especially in males. The rapid increase in length of the vocal cords in boys is responsible for the breaking of their voice. Breaking of voice does not occur in the absence of testosterone as in:
i) Agonadal males- the testes fail to develop ii) Castrated males- the testes are removed during childhood iii) Klinefelter's syndrome- there is inadequate production of testosterone.
The thyroid, cricoid and parts of the arytenoid cartilages may calcify with age.
92 29. FORAMINA OF THE SKULL AND THE STRUCTURES THAT PASS THROUGH THEM The skull consists of: Neurocranium and viscerocranium (facial skeleton). There are twenty-two bones in the skull. The neurocranium has 8 bones while the viscerocranium has 14 bones.
A. ANTERIOR CRANIAL FOSSA FORAMEN CAECUM: This lies between the frontal bone and the crista galli and usually ends blindly in adult life. When it is patent, as in early life, it transmits an emissary vein from the nasal mucosa to the superior sagittal sinus. ANTERIOR ETHMOIDAL CANAL: This is a slit along the suture between the orbital part of the frontal bone and the cribriform plate of the ethmoid bone. It transmits: 1. Anterior ethmoidal vessels (the artery is a branch of ophthalmic artery) 2. Anterior ethmoidal nerve (a branch of nasociliary nerve) POSTERIOR ETHMOIDAL CANAL: This opens at the posterolateral corner of the cribriform plate. It transmits: 1. Posterior ethmoidal vessels (the artery is a branch of ophthalmic artery) 2. Posterior ethmoidal nerve (a branch of nasociliary nerve) CRIBRIFORM PLATE OF ETHMOID: The numerous small foramina here transmit the minute olfactory nerves from the nasal mucosa to the olfactory bulb.
B. MIDDLE CRANIAL FOSSA a) MEDIAN PART OPTIC CANAL: This lies between the two roots of the lesser wing of the sphenoid, with the body of the sphenoid medially. It transmits: 1. Optic nerve 2. Ophthalmic artery b) LATERAL PART i) GREATER WING OF SPHENOID
SUPERIOR ORBITAL FISSURE: This is a comma-like slit bounded above by the lesser wing, below by the greater wing and medially by the side of the body of the sphenoid. It leads into the orbit and transmits: 1. Oculomotor nerve (III) 2. Trochlear nerve (IV) 3. Terminal branches of the ophthalmic nerve (V) a) Nasociliary nerve b) Frontal nerve c) Lacrimal nerve 4. Abducent nerve (VI) 5. Sympathetic nerve fibres from the internal carotid artery 6. Orbital branch of the middle meningeal artery 7. Meningeal branch of the lacrimal artery 8. Superior and inferior ophthalmic veins
FORAMEN ROTUNDUM: This pierces the greater wing of the sphenoid immediately below the medial end of the superior orbital fissure. It leads forwards into the pterygopalatine fossa to which it transmits the maxillary nerve (V2).
FORAMEN OVALE: This passes through the greater wing of the sphenoid about 1cm posterolateral to the foramen rotundum. It leads downwards into the infratemporal fossa, to which it transmits: 1. Mandibular nerve (V3) 2. Accessory middle meningeal artery 3. Emissary veins between the pterygoid plexus and the cavernous sinus. 93 ± 4. Lesser petrosal nerve
FORAMEN SPINOSUM: This lies immediately posterolateral to the foramen ovale, and derives its name from its close relationship with the spine of the sphenoid. It transmits: 1. Middle meningeal vessels 2. Nervous spinosus (meningeal branch of V3)
Three inconstant foramina are: LACRIMAL FORAMEN: This lies lateral to the apex of the superior orbital fissure and allows the lacrimal artery to anastomose with the anterior branch of the middle meningeal artery.
EMISSARY SPHENOIDAL FORAMEN (OF VESALIUS): This lies between the foramen rotundum and foramen ovale. When present, it transmits an emissary vein from the cavernous sinus, and lymph vessels.
CANALICULUS INNOMINATUS: This lies on the medial side of the foramen spinosum. When present, it transmits the lesser petrosal nerve. ii) PETROUS TEMPORAL BONE FORAMEN LACERUM: This lies between the apex of the petrous temporal bone and the attachment of the greater wing to the body of the sphenoid. It is large and irregular in shape. In life, the lower part of it is closed by a fibrocartilage. Only small structures pass through the entire length of the foramen:
1. Meningeal branches of the ascending pharyngeal artery 2. Emissary veins from the cavernous sinus 3. Lymph vessels
Structures that do not pass through the entire extent of the foramen, but are related to it include: 1. Internal carotid artery and its accompanying sympathetic and venous plexuses. The artery pierces the posterior wall of the foramen and emerges through its upper opening.
2. Greater petrosal nerve. It enters the foramen upon emerging from the hiatus. Here it unites with the deep petrosal nerve to form the Vidian nerve (nerve of the pterygoid canal). Just above the inferior opening of the foramen lacerum, the Vidian nerve leaves the foramen and enters the pterygoid canal.
OTHERS: Two foramina open about 0.5cm and 1cm respectively to transmit: 1. Lesser petrosal nerve 2. Greater petrosal nerve
C. POSTERIOR CRANIAL FOSSA
FORAMEN MAGNUM: This is in the floor of the posterior fossa and is the largest foramen in the skull. It transmits the: 1. Spinal cord 2. Spinal roots of the accessory nerve (XI) 3. Vertebral arteries 4. Sympathetic nerves associated with vertebral arteries 5. Anterior spinal artery 6. Posterior spinal artery 7. Vertebral venous plexus 94 HYPOGLOSSAL CANAL/ANTERIOR CONDYLAR CANAL: This is located at the antero- lateral margin of the foramen magnum. It transmits the: 1. Hypoglossal nerve (XII) 2. Meningeal branch of the ascending pharyngeal artery
JUGULAR FORAMEN: This is an interosseous foramen between the occipital and the petrous temporal bones. The posterior and lower borders are smooth and regular. The upper border is sharp and may be interrupted by a notch. The ends of the notch together with two transverse septa of fibrous dura mater, which may ossify, sometimes divide the foramen into three compartments. a) Anterior compartment: It transmits: 1. Inferior petrosal sinus 2. Glossopharyngeal nerve (XI) - there may be a notch for this nerve at the upper border of the foramen. b) Middle compartment: 1. Vagus nerve (X) 2. Accessory nerve (XI) c) Posterior compartment: 1. Terminal part of the sigmoid sinus 2. Meningeal branches of the occipital and ascending pharyngeal arteries
INTERNAL ACOUSTIC MEATUS: This lies about 1cm above the jugular foramen, and it transmits the: 1. Facial nerve (VII) 2. Vestibulocochlear nerve (VIII) 3. Labyrinthine artery and accompanying vein
MASTOID CANALICULUS: This is a minute canal in the lateral wall of the jugular fossa. It transmits: the auricular branch of the vagus nerve (X) CONDYLAR CANAL/POSTERIOR CONDYLAR CANAL: This is located in the posterolateral margin of the foramen magnum and opens behind the condyle. It is sometimes a fossa. When it is a canal, it transmits: emissary veins between the sigmoid sinus and the vertebral/suboccipital venous plexus.
MASTOID FORAMEN: This is located about midway along the sigmoid sulcus. It pierces the mastoid portion of the temporal bone above the base of the mastoid process. It is near or on the occipitomastoid suture. It transmits: 1. Emissary vein from the sigmoid sinus to the posterior auricular vein 2. Meningeal branch of the occipital artery
II FORAMINA OF THE EXTERIOR OF THE SKULL A. NORMA BASALIS The inferior of the skull may be divided by two lines: a) Anterior transverse line passing through both mandibular notches b) Posterior transverse line passing through the anterior margins of both mastoid processes
These lines divide the inferior aspect into three areas: i) Anterior ii) Intermediate iii) Posterior 95 i) Anterior area and anterior transverse line
INCISIVE FOSSA: This is a deep fossa lying in the midline at the front of the hard palate. It receives the ends of the two lateral incisive canals from both sides which lead upwards to the corresponding side of the nasal septum and transmits:
1. Nasopalatine nerves 2. Ascending branch of the greater palatine artery
GREATER PALATINE FORAMEN: This is the lower orifice of the canal of the same name, and opens close to the lateral border of the palate immediately behind the palatomaxillary suture. It transmits: 1. Greater palatine vessels 2. Great (anterior) palatine nerve
LESSER PALATINE FORAMINA: There are usually two (sometimes one or even three) of these tiny foramina lying behind the greater palatine foramen, and transmitting: 1. Lesser (middle and posterior) palatine nerves.
PALATOVAGINAL CANAL: This canal is enclosed by the articulation between the palatine bone and the vaginal process of the medial pterygoid plate. It opens posteriorly in the vault of the nose. It transmits:
1. Pharyngeal branch of the pterygopalatine 2. A minute pharyngeal branch from the third part of the maxillary artery
VOMEROVAGINAL CANAL: This inconstant canal may be present on the medial side of the palatovaginal canal, and lies between the ala of the vomer and the upper surface of the vaginal process of the medial pterygoid plate. It transmits: the minute pharyngeal branch of the sphenopalatine artery. ii). Intermediate Area
CAROTID CANAL: The petrous temporal bone is perforated anterior to the jugular foramen by the carotid canal. It transmits: 1. Internal carotid artery 2. Numerous sympathetic nerve fibres
TYMPANIC CANALICULUS: This small foramen lies in the ridge between the jugular fossa and the carotid canal. It transmits: 1. Tympanic branch of the glossopharyngeal nerve
Other small foramina on the same ridge transmit: 1. Caroticotympanic branches of the internal carotid artery 2. Sympathetic filaments from the carotid plexus
EXTERNAL AUDITORY MEATUS: This leads into the external auditory canal.
PETROTYMPANIC FISSURE: This is the posterior part of the medial part of the squamotympanic fissure whose anterior part is the petrosquamous fissure. The division is by the edge of the tegmen tympani. It transmits: 1. Chorda tympani 2. Stylomastoid branch of the posterior auricular artery 96 B. NORMA LATERALIS/INFRATEMPORAL FOSSA
PTERYGOMAXILLARY FISSURE: This lies between the lateral pterygoid plate and the back of the maxilla. It is through this fissure that the infratemporal fossa communicates with the pterygopalatine fossa. Its upper end is continuous with the posterior end of the inferior orbital fissure. It transmits:
1. Terminal part of the maxillary artery
2. Maxillary nerve in its uppermost part
SPHENOPALATINE FORAMEN: This is formed by the articulation between the sphenopalatine notch of the palatine bone with the lower part of the ethmoid bone. In life, it is covered by the mucous membrane of the lateral wall of the nose, immediately behind the posterior end of the middle concha. It transmits:
1. Lateral posterior superior nasal nerves and vessels
2. Nasopalatine (long sphenopalatine) nerve
3. Sphenopalatine artery (it is the termination of the maxillary artery)
INFERIOR ORBITAL FISSURE: This provides communication between the orbit and the infratemporal and pterygopalatine fossae. Its lower lip is notched by the infraorbital groove, which passes forwards to become the infratemporal canal. The fissure transmits: 1. Maxillary nerve 2. Infra-orbital vessels 3. A few minute twigs from the pterygopalatine ganglion to the orbital periosteum 4. Zygomatic nerve (a branch of maxillary nerv) 5. Communicating veins between the inferior ophthalmic vein and the pterygoid plexus.
ZYGOMATICOTEMPORAL FORAMEN: This pierces the temporal surface of the zygomatic bone in the anterior wall of the temporal fossa to transmit: 1. Zygomaticotemporal nerve 2. A minute artery
MENTAL FORAMEN: This is an irregular opening, just above the centre of the medial surface of the ramus of the mandible. It transmits inferior alveolar nerve and vessels
C. NORMA VERTICALIS
PARIETAL FORAMEN: This lies in the posterior part of the bone, and close to the sagittal plane. It transmits: 1. A vein from the superior sagittal sinus
2. Sometimes, a small branch of the occipital artery. 97 30. THE PTERYGOPALATINE FOSSA
The pterygopalatine fossa is a pyramidal space below and behind the apex of the orbit. It is bounded: anteriorly: by the upper part of the posterior surface of the maxilla posteriorly: by the root of the pterygoid process and the adjoining part of the greater wing of the sphenoid superiorly: by the body of the sphenoid and the orbital process of the palatine bone medially: by the perpendicular plate of the palatine bone laterally: it is open.
Openings into the pterygopalatine fossa
There are several openings into this fossa: 1. The pterygopalatine fissure: this is a triangular interval at the lateral side of the pterygopalatine fossa. Through it, the fossa communicates with the infratemporal fossa.
2. The sphenopalatine foramen: This is an opening in the medial wall of the pterygopalatine fossa. It is bounded above by the body of the sphenoid and below by he upper border of the perpendicular plate of the palatine bone. It transmits the nasopalatine nerve and accompanying vessels.
3. The inferior orbital fissure: It is located in the superior wall of the pterygopalatine fossa. Through it, the fossa communicates with the orbit. It transmits the infraorbital nerves and vessels, zygomatic nerve and a communicating vein between the inferior ophthalmic vein and the pterygoid plexus.
4. The greater and lesser palatine canals: These are found at the junction between the inferior and posterior walls of the pterygopalatine fossa. Through them, the fossa communicates with the palate. They transmit the greater and lesser palatine nerves as well as the greater and lesser palatine vessels.
5. The foramen rotundum: This is located on the posterior aspect of the pterygopalatine fossa, and through it the fossa communicates with the middle cranial fossa. The maxillary nerve enters the fossa through this foramen.
6. The pterygopalatine canal: It is located on the posterior aspect of the fossa, and lies medial to the foramen rotundum. It transmits the nerve of the pterygoid canal and the accompanying artery.
7. The palatovaginal canal: It is located on the posterior aspect of the fossa. It transmits the pharyngeal nerve and artery from the pterygopalatine ganglion to the roof of the pharynx.
Contents of the pterygopalatine fossa
1. Pterygopalatine ganglion
2. Terminal part of the maxillary nerve
3. Third part of the maxillary artery and vein
The pterygopalatine (sphenopalatine) ganglion
This is the largest peripheral ganglion of the parasympathetic system. It is located in the pterygopalatine fossa where it lies in front of the pterygoid canal, and close to the sphenopalatine foramen. 98 It serves as a relay station between the superior salivatory nucleus in the pons, and the lacrimal gland, the palatine glands, the nose and the paranasal air sinuses.
Roots of the pterygopalatine ganglion The pterygopalatine ganglion has autonomic and sensory roots.
The autonomic (sympathetic and parasympathetic) roots reach the ganglion through the nerve of the pterygoid canal (Vidian nerve). The Vidian nerve is formed by the greater petrosal nerve from the geniculate ganglion of the facial nerve, and the deep petrosal nerve from the sympathetic plexus that accompanies the internal carotid artery. The greater petrosal nerve contains parasympathetic secretomotor fibres while the deep petrosal nerve contains sympathetic vasoconstrictor fibres.
The sensory root is from the maxillary division of the trigeminal nerve. The parasympathetic fibres relay in the pterygopalatine ganglion, while the sensory and sympathetic fibres do not.
Branches of the pterygopalatine ganglion
There are 5 branches from the pterygopalatine ganglion, and these are distributed to the nose and palate. Each branch carries a mixture of sensory, secretomotor and sympathetic fibres.
The secretomotor fibres to the lacrimal gland leave the pterygopalatine ganglion and join the maxillary nerve. They pass through the zygomatic branch of the maxillary nerve into the orbit, where they leave to join the lacrimal branch of the ophthalmic nerve to reach the lacrimal gland.
The branches of the pterygopalatine ganglion are:
1. Orbital branches: There are 2 or 3 of these. They enter the orbit through the inferior orbital fissure. They are distributed to the periosteum, orbital muscles, sphenoidal and posterior ethmoidal sinuses.
2. Naso-palatine (long sphenopalatine) nerve: It passes through the sphenopalatine foramen and descends along the posterior aspect of the nasal septum to reach the hard palate through the median incisive foramen. It supplies parts of the roof and floor of the nasal cavity and the nasal septum.
3. Lateral posterior superior nasal nerves: They supply the mucous lining of the posterior parts of the superior and medial nasal conchae as well as the posterior ethmoidal sinuses.
4. Palatine branches: They supply the roof of the mouth, the soft palate, the tonsils and the lining membrane of the nasal cavity. There are 2 of these nerves: a) Greater (anterior) palatine nerve: It passes through the greater palatine canal and emerges from the greater palatine foramen. It supplies the gums, the mucous membrane and glands of the hard palate. While in the greater palatine canal, it gives off the posterior inferior nasal branches. b). Lesser (middle and posterior) palatine nerves: They pass through the greater palatine canal and emerge from the lesser palatine foramina. They supply the tonsil and soft palate. Taste fibres from the palate pass through the palatine nerves to the pterygopalatine ganglion.
5. Pharyngeal nerve: It passes through the palatovaginal canal with the pharyngeal branch of the maxillary artery to supply the mucous membrane of the nasopharynx. 99 The Maxillary Artery The third part of the maxillary artery lies in the pterygopalatine fossa lateral to the pterygopalatine ganglion. It enters the fossa through the pterygomaxillary fissure. It gives off 5 branches that accompany the 5 branches of the pterygopalatine ganglion:
1. The posterior superior alveolar artery: It supplies the upper premolar and molar teeth and the maxillary sinus.
2. The infraorbital artery: It enters the orbit through the inferior orbital fissure and runs along the inferior orbital canal with the infraorbital nerve. In the canal it gives off: a) Orbital branches which supply the lacrimal sac, and the inferior rectus and inferior oblique muscles. b) Anterior superior alveolar branches which supply the upper incisor teeth and the mucous membrane of the maxillary sinus.
3. The greater palatine artery: It descends through the greater palatine canal along with the greater palatine nerve and gives off 2-3 branches which accompany the lesser palatine nerve. It may also give off the artery of the pterygoid canal. Sometimes, this artery may arise from the maxillary artery.
4. The pharyngeal branch: It passes through the palatovaginal (pharyngeal) canal with the pharyngeal branch of the pterygopalatine ganglion.
5. The sphenopalatine artery: It is the terminal branch of the maxillary artery. It passes through the sphenopalatine foramen into the nasal cavity and gives off the lateral nasal branches and ends in the posterior septal artery which accompanies the nasopalatine nerve.
The Maxillary Nerve The maxillary verve enters the pterygopalatine fossa through the foramen rotundum and leaves the fossa through the inferior orbital fissure to enter the orbit where it is called the infraorbital nerve. The branches of the maxillary nerve in the pterygopalatine fossa are:
1. Ganglionic branches: There are 2 of these, and they connect the pterygopalatine ganglion to the maxillary nerve.
2. The zygomatic nerve: It enters the orbit through the inferior orbital fissure and splits into zygomaticotemporal and zygomaticofacial branches.
3. The posterior superior alveolar nerve: It pierces the posterior surface of the maxilla and supplies the maxillary sinus.
The meningeal branch is given off just before the maxillary nerve enters the pterygopalatine fossa. The middle superior and anterior superior alveolar nerves are given off from the infraorbital nerve, which is the continuation of the maxillary nerve within the infraorbital canal. 100 31. FACIAL NERVE
The facial nerve is the seventh cranial nerve and it supplies the structures derived from the 2nd pharyngeal arch. It has two roots - a large motor root and a small sensory root. The sensory root is also called the nervus intermedius. The latter contains taste fibres from the submandibular and sublingual salivary glands, the lacrimal gland and the glands of the nose and palate.
ORIGIN The motor nucleus of the facial nerve lies in the reticular formation of the lower part of the pons. The nucleus receives fibres from the left and right cortico-nuclear tracts in the lower parts of the pons. The fibres to the part of the nucleus supplying the upper half of the face are bilateral in origin, while those to the lower part of the face are contralateral in their origin. Some of the efferent fibres emerging from the facial nerve also come from the superior salivary nucleus.
The fibres emerging from the facial nucleus follow an unusual course. They first pass dorsally and medially to reach the caudal end of the abducent nucleus. They then ascend on the medial side of the nucleus, and at its cranial end they bend forwards and medially. The abducent nucleus and the facial nerve fibres looping around it form a surface elevation called the facial colliculus that is located in the floor of the fourth ventricle. The fibres of the facial nerve then pass between the facial nucleus medially and the spinal nucleus of the trigeminal nerve laterally.
COURSE The motor and sensory roots of the facial nerve emerge from the brain in the groove between the lower border of the pons and the pyramid of the medulla oblongata. They pass anterolaterally in the posterior cranial fossa with the vestibulocochlear nerve to the internal acoustic meatus. The sensory root lies between the motor root and the vestibulocochlear nerve. At the lateral end of the internal acoustic meatus, the facial nerve enters the facial canal and runs laterally above the vestibule of the internal ear until it reaches the medial wall of the tympanic cavity.
Above the promontory on the medial wall of the tympanic cavity, the facial nerve becomes expanded to form the geniculate ganglion which contains the bulk of the cell bodies of origin of the taste fibres. The facial nerve now bends sharply backwards over the promontory. The bend is called the geniculum. It arches downwards and backwards in the medial wall of the tympanic cavity. On emerging from the stylomastoid foramen, the facial nerve runs forwards within the substance of the parotid gland and divides into five terminal branches.
BRANCHES A. Branches of communication i) In the internal auditory meatus, it communicates with the vestibulocochlear nerve. ii) At the geniculate ganglion, it communicates with: 1. Pterygopalatine ganglion through the greater petrosal nerve. 2. Sympathetic plexus on the middle meningeal artery through the external petrosal nerve. iii) In the facial canal, it communicates with the auricular branch of the vagus. iv) As it emerges from the stylomastoid foramen, it communicates with: 1. Glossopharyngeal nerve 2. Vagus nerve 3. Great auricular nerve 4. Auriculotemporal and lesser occipital nerves. 101 B. Branches of distribution i) Within the facial canal: 1. Nerve to stapedius 2. Chorda tympani nerve ii) As it emerges from the stylomastoid foramen: 1. Posterior auricular nerve - supplying the muscles of the auricle. 2. Nerve to posterior belly of digastric.
iii) Within the substance of the parotid gland: 1. Temporal branches - supplying the anterior and superior auricular muscles, the frontal belly of occipitofrontalis, corrugator supercili and the orbicularis oculi. 2. Zygomatic branches - supplying the orbicularis oculi. 3. Buccal branches - emerging below the parotid duct and supplying the buccinator and muscles of the nostril and upper lip. 4. Marginal mandibular branches - supplying the muscles of the lower lip. 5. Cervical branches - passing below the mandible and supplying the platysma and depressor anguli oris muscles.
APPLIED ANATOMY
Facial paralysis may be due to supranuclear or infranuclear lesions.
Supranuclear lesions may be as a result of a cortical lesion or lesion of the internal capsule. This may result in total paralysis of the lower part, and partial paralysis of the upper part of the face on the contralateral side. The upper part of the face, unlike the lower part, is supplied by both sides of the cerebral cortex. In cortical lesions movements of facial expression are lost, whereas in lesions of the internal capsule they are retained.
In infranuclear and nuclear lesions, the effects depend on the exact site of the lesion:
A) Lesion at the entrance into the internal auditory meatus: i) Paralysis of all motor function ii) Taste fibres are affected iii) Hyperacusis (a ringing sensation in the ear) which results from paralysis of the stapedius muscle iv) Loss of the corneal reflex v) Loss of the movements of facial expression
B) Lesion in the internal auditory meatus after the nerve to stapedius has been given off: the effects are similar to those in (A) above, except for the absence of hyperacusis.
C) Lesion at the stylomastoid foramen: the same effects as in (B) above, except that the taste fibres are not affected.
Bell's palsy is the commonest cause of facial nerve palsy. There is inflammation of the facial nerve close to the stylomastoid foramen. The cause of the inflammation is unknown, but it results in oedema that compresses the facial nerve fibres in the facial canal near the stylomastoid foramen. The muscles of the upper and lower parts are equally paralysed on the ipsilateral side of the face.
Facial nerve paralysis may also occur in the newborn. At this age, the mastoid process is poorly developed and, therefore, provides little protection for the nerve. The nerve is quite superficial at its exit from the skull and may be damaged during forceps delivery. 102 32. VAGUS NERVE
The vagus nerve is the 10th cranial nerve. It is a mixed nerve (consisting of motor and sensory fibres) and has a more extensive course and distribution than any other cranial nerve. It supplies:
1. Structures derived from the 4th and 6th branchial arches.
2. Foregut and midgut with the structures derived from them.
ORIGIN It arises by about 10-12 rootlets from the posterolateral sulcus of the medulla oblongata (i.e., the groove between the olive and the inferior cerebellar peduncle). The rootlets are in series with the 9th cranial nerve above, and the 11th cranial nerve below. The rootlets unite and leave the skull through the middle part of the jugular foramen. The nerve shares the same dural sheath with the 11th cranial nerve, while the 9th cranial nerve has a separate dural sheath. The vagus has a small superior ganglion in the jugular foramen and a large inferior ganglion immediately below the foramen.
COURSE The nerve passes vertically down the neck within the carotid sheath, between the internal jugular vein and the internal carotid artery, and then between the vein and the common carotid artery.
At the root of the neck, the right vagus passes anterior to the 1st part of the subclavian artery and behind the brachial plexus, and then descends into the superior mediastinum at the right side of the trachea. It descends in the thorax initially posterolateral to the brachiocephalic artery and later lateral to the trachea and medial to the terminal part of the azygous vein. It passes behind the root of the right lung.
The left vagus nerve passes between the left common carotid artery and the left subclavian artery and behind the left brachiocephalic vein. It descends in the superior mediastinum and crosses the left side of the arch of the aorta.
Both nerves descend posterior to the roots of their corresponding lungs. The right lies on the trachea, while the left passes first between the left common carotid and left subclavian arteries, and later on the left side of the arch of the aorta. The vagus is then crossed anteriorly by the left phrenic nerve.
At the root of the lung, each nerve gives branches to the pulmonary plexuses, and also 2 or more branches which reach the corresponding branches of the opposite vagus to form the oesophageal plexus. The plexus also receives contributions from the greater splanchnic nerve. The oesophageal plexus separates into right and left vagal trunks. They enter the abdomen through the oesophageal opening. The right vagal trunk is anterior to the oesophagus while the left is posterior.
BRANCHES A) In the jugular fossa 1. Meningeal branch: It arises from the superior ganglion and supplies the dura mater in the posterior cranial fossa.
2. Auricular branch: It arises from the superior ganglion in the skull and emerges from the tympanomastoid fissure (behind the external acoustic meatus). It supplies the medial side of the auricle, the floor of the external auditory meatus and the inferior part of the tympanic membrane. 103 B) In the neck 1. Pharyngeal branch: It arises from the inferior ganglion and contains motor fibres from the cranial part of the 11th cranial nerve. It passes between the internal and external carotid arteries to reach the pharyngeal wall. It joins the branches from the 9th cranial nerve and the sympathetic trunk to form the pharyngeal plexus. The pharyngeal plexus supplies all the muscles of the pharynx except the stylopharyngeus (which is supplied by the 9th cranial nerve). It also supplies all the muscles of the soft palate except the tensor veli palatini which is supplied by the mandibular division of the 5th cranial nerve.
2. Branches to carotid body: They are minute branches which form a plexus with those from the 9th cranial nerve.
3. Superior laryngeal nerve: It arises from the inferior ganglion and descends posterior to the internal carotid artery where it divides into external and internal laryngeal nerves. The external laryngeal nerve is small and descends along the superior thyroid artery. It supplies cricopharyngeus and cricothyroid muscles. The internal laryngeal nerve is sensory. It pierces the thyrohyoid membrane along with the superior laryngeal artery and is distributed to the floor of the piriform fossa and the membrane of the larynx as far down as the vocal cords.
4. Right recurrent laryngeal nerve: It arises from the right vagus nerve in front of the right subclavian artery. It winds backwards around the artery and ascends in the groove between the trachea and the oesophagus. It passes deep to the lobe of the thyroid gland and comes into close relationship with the inferior thyroid artery passing either in front or behind the artery. The nerve supplies the muscles of the larynx except the cricothyroid which is supplied by the external laryngeal branch of the superior laryngeal nerve. It also supplies the mucous membrane of the upper part of the trachea.
5. Cardiac branches: There are 2 or 3 branches arising from the vagus at the upper and lower parts of the neck. The upper branches are small and they join the cardiac branches of the sympathetic trunk and end in the deep part of the cardiac plexus.
C. In the thorax 1. Cardiac branches: The lower cardiac branches arise at the root of the neck and join the cardiac plexus. 2. Left recurrent laryngeal nerve: It arises from the left vagus as the latter crosses the arch of the aorta. It hooks around the arch of the aorta behind the ligamentum arteriosum and then ascends into the neck in the groove between the trachea and the oesophagus. 3. Pulmonary branches: There are anterior and posterior pulmonary branches. They join the filaments from the sympathetic trunks to form the anterior and posterior pulmonary plexuses respectively. 4. Oesophageal branches: They form the oesophageal plexus which is distributed to the oesophagus.
D. In the abdomen 1. Gastric branches: to the stomach 2. Hepatic branches: join the hepatic plexus 3. Renal branches: join the renal plexus 4. Pancreatic branches 5. Branches to the intestine: as far down as the left colic flexure 104 33. STELLATE OR CERVICOTHORACIC GANGLION
It is formed by the fusion of the inferior cervical ganglion and the first thoracic ganglion. The middle cervical ganglion and the second thoracic ganglion are sometimes involved in the fusion. The size of the stellate ganglion is variable. It is about 2cm long and 0.5cm wide. It lies anterior to the transverse process of the 7th cervical vertebra and the neck of the first rib, and posterior to the vertebral vessels. The suprapleural membrane separates it from the cervical pleura. The lateral side of the ganglion is related to the superior intercostal artery.
BRANCHES: 1. Gray rami communicantes to the anterior rami of the 7th and 8th cervical nerves and 1st thoracic nerve.
2. Arterial branches to the subclavian and vertebral arteries.
3. The inferior cardiac branch: it descends behind the subclavian artery and joins the deep part of the cardiac plexus.
APPLIED ANATOMY Destruction or removal of the stellate ganglion results in Horner's Syndrome. The sympathetic supply to the ipsilateral side of the head and neck is lost. The syndrome is characterized by: a) Constriction of the pupil: this is as a result of the unopposed action of the constrictor pupillae. The sphincter pupillae is paralysed because of loss of its sympathetic supply. b) Partial ptosis (drooping of the eyelid): the sympathetic supply to the levator palpebrae is lost. The ptosis is partial because apart from the sympathetic innervation, the levator palpebrae is also supplied by the oculomotor nerve. c) Anhidrosis (absence of sweating) on the face and neck of the affected side. It is due to loss of sympathetic supply to the sweat glands. d) Nasal congestion and redness of the conjunctiva: there is dilatation of the blood vessels because of loss of the vasoconstrictor supply. e) Enophthalmos (recession of the eyeball): is due to loss of the sympathetic supply to the orbitalis muscle. 105 34. THE CAVERNOUS SINUS
The cavernous sinus is one of the paired dural venous sinuses. Unlike the other sinuses, it is traversed by numerous interlacing filaments. The trabeculae divide the sinus into a series of tiny "caves" hence the sinus is called cavernous sinus. It lies in the space between the periosteum of the body of the sphenoid and the folds of the fibrous dura mater.
The cavernous sinus extends from the superior orbital fissure in front, to the apex of the petrous temporal bone behind. It is about 2cm long and 1cm wide.
RELATIONS OF THE CAVERNOUS SINUS Anteriorly: the apex of the orbit.
Posteriorly: the cerebral peduncle.
Medially: the body of the sphenoid and the hypophysis cerebri.
Laterally: the uncus (medial side of the temporal lobe of the brain). The posteroinferior part of the lateral wall is related to the trigeminal cave.
Superiorly: the internal carotid artery and the uncus.
Inferiorly: the greater wing of the sphenoid bone.
CONTENTS OF THE CAVERNOUS SINUS 1. The internal carotid artery: this is accompanied by a plexus of sympathetic fibres from the superior cervical ganglion. The plexus is called the cavernous plexus and gives branches to the ciliary ganglion. The internal carotid artery forms a siphon on the cavernous sinus and grooves the medial wall of the sinus.
2. The abducent nerve: this runs anteriorly in the lateral side of the internal carotid artery. Further anteriorly, it lies inferior to the artery.
3. The oculomotor and trochlear nerves, as well as the ophthalmic and maxillary divisions of the trigeminal nerve: these enter the roof of the cavernous sinus and run forwards in the lateral wall. They lie in that order from top to bottom on the lateral wall. The trigeminal nerve is the most lateral in location.
AFFERENTS OF THE CAVERNOUS SINUS 1. Superior ophthalmic vein: this passes through the superior orbital fissure and enters the anterior part of the cavernous sinus. 2. Inferior ophthalmic vein: it empties into the cavernous sinus. However, before it does so, most of the blood drains through the inferior orbital fissure to the pterygoid venous plexus. 3. Superficial middle cerebral vein: this pierces the roof and drains into the cavernous sinus. 4. Sphenoparietal sinus: this runs along the lesser wing of the sphenoid and empties into the anterior part of the cavernous sinus. 5. A tributary of the middle meningeal vein. 6. Central vein of the retina. 7. Some of the inferior cerebral veins. 106 EFFERENTS OF THE CAVERNOUS SINUS 1. Superior petrosal sinus: It runs along the petrous ridge and empties into the sigmoid sinus.
2. Inferior petrosal sinus: It begins in the posteroinferior part of the cavernous sinus beneath the petroclinoid ligament and empties into the internal jugular vein. It is larger than the superior petrosal sinus.
3. An emissary vein: It drains the cavernous sinus through the foramen ovale or foramen of Vesalius to the pterygoid plexus of veins.
4. Basilar plexus: The cavernous sinus is connected to the basilar plexus through an emissary vein.
5. Anterior and posterior intercavernous sinuses: They connect the left and right cavernous sinuses.
APPLIED ANATOMY The cavernous sinus communicates with the `dangerous' area of the face (the area between the upper lip, lateral nasal wall and the medial cheek). This may lead to spread of infection from the face to the cavernous sinus, and then to the meninges and brain. The communication occurs through:
1. Supratrochlear and supraorbital veins communicating with the angular vein of the face. They drain into the superior ophthalmic vein. The latter drains into the cavernous sinus.
2. Deep facial vein communicating with the pterygoid plexus. The latter communicates with the cavernous sinus through the inferior ophthalmic vein or emissary veins.
Infection in the upper parts of the nasal cavities and in certain paranasal sinuses may also spread to the cavernous sinus.
Arteriovenous communication between the cavernous sinus and the internal carotid artery may occur, causing a pulsating swelling of the orbit. This may occur following stab or bullet wounds. 107 35. TEMPOROMANDIBULAR JOINT
Temporomandibular joint is a synovial joint of the condyloid variety. It is the only moveable joint in the skull. The articular surfaces are the condyle of the mandible and the mandibular fossa of the temporal bone and they are covered by a layer of fibrocartilage. There is no hyaline cartilage in this joint. The joint is separated into upper and lower cavities by a fibrous disc which lies within the joint.
FIBROUS CAPSULE It surrounds the joint. Superiorly, it is attached to the articular tubercle anteriorly, the margins of the malleolar fossa medially and laterally, and the squamotympanic fissure posteriorly. Inferiorly it is attached to the neck of the mandible. It is also attached to the periphery of the disc. The fibrous capsule is loose above the disc and taut below it.
SYNOVIAL MEMBRANE It lines the fibrous capsule and fuses with the periphery of the articular disc. It does not cover the superior and inferior surfaces of the articular disc.
ARTICULAR DISC It is roughly oval in shape and completely divides the joint into superior and inferior cavities. The superior surface of the disc is saddle-shaped or concavo-convex from anterior to posterior. This shape is to accommodate the mandibular fossa and articular tubercle which are reciprocally shaped. The inferior surface is concave to accommodate the head of the mandible which is convex in shape. The articular disc is thinnest at its centre and thickest at its periphery. The anterior margin of the disc and the adjoining fibrous capsule receive the insertion of the upper fibres of the lateral pterygoid muscle.
LATERAL TEMPORAL MANDIBULAR LIGAMENT It is a stout band of fibrous tissue that extends from the lower border and tubercle of the zygoma to the lateral surface and posterior border of the neck of the mandible. The fibres run obliquely downwards and backwards. The deep fibres blend with the fibrous capsule. The ligament limits the posterior movement of the mandible and consequently protects the external auditory meatus. It is most loose when the mandible is in the rest position.
SPHENOMANDIBULAR LIGAMENT It is a thin band of fibrous tissue that extends downwards and forwards from the spine of the sphenoid to the lingula of the mandibular foramen. It is an accessory ligament of the temporomandibular joint. It lies on the medial side of the joint and is completely separated from the articular disc. It is separated from the mandible from above downward by the auriculotemporal nerve, lateral pterygoid muscle, maxillary vessels and the inferior alveolar nerve and vessels.
NERVE SUPPLY The joint is supplied by the auriculotemporal nerve and nerve to masseter. Both nerves are branches of mandibular nerve.
ARTERIAL SUPPLY The joint is supplied by the superficial temporal and maxillary arteries.
STABILITY OF THE JOINT The stability of the joint is mainly due to the bony configuration. The joint is more stable when the jaw is closed than when it is open. In the occluded position, the teeth stabilize the mandible on the maxilla. Forward movement of the mandible is prevented by the prominence of the articular tubercle and by the contraction of the posterior fibres of temporalis. Backward movement is prevented by the obliquity of the temporomandibular ligament and the contraction of the lateral pterygoid muscle. 108
MOVEMENTS The movements that occur in the joint are depression, elevation, protrusion, retraction and side to side movements.
Depression: Depression of the mandible is either passive or active. Passive depression is by gravity while active depression is by muscle contraction. The muscles that depress the joint are the lateral pterygoids. When the mouth is opened wide or against resistance, the lateral pterygoids are assisted by the digastric, geniohyoids and mylohyoids.
Elevation: Temporalis, masseter and medial pterygoids.
Protrusion: Lateral pterygoids assisted by the medial pterygoids.
Retraction: Posterior fibres of temporalis assisted by the deep fibres of masseter, the digastrics and the geniohyoids.
Side to side movements: Medial and lateral pterygoids of opposite sides acting alternately.
RELATIONS OF THE JOINT Anteriorly: mandibular notch and the masseteric nerve and vessels.
Posteriorly: the tympanic plate of the external auditory meatus and the parotid gland.
Laterally: parotid gland.
Medially: maxillary vessels and auriculotemporal nerve.
APPLIED ANATOMY Forward dislocation is the commonest type of dislocation. When the mouth is open, the condyles of the mandible are on the articular eminence. In forward dislocation, sudden contraction of the elevators pushes the condyles anteriorly beyond the articular tubercle. The condyles lie in the infratemporal fossa. The patient is unable to close the mouth. Reduction of the dislocation is achieved by depressing the jaw with the thumbs placed on the last molar teeth and at the same time elevating the chin. The depression of the mandible overcomes the spasm of the masseter and temporalis while the elevation of the chin helps to push the head of the mandible into the mandibular fossa.
The temporomandibular joint is less stable in the edentulous. Dislocation of the joint is consequently commoner in the edentulous. 109 36. VISUAL PATHWAY AND VISUAL REFLEXES
VISUAL PATHWAY
The visual field is the area of vision seen by only one eye. The visual fields of both eyes overlap to a large extent. For descriptive purposes, each visual field is divided into right and left halves. Each half is further divided into upper and lower quadrants. Similarly, each retina has corresponding halves and quadrants. The medial half of each retina is referred to as the nasal half, while the lateral half is the temporal half. Because of the convex nature of the cornea and lens, images are inverted in the eye. As a result, image of objects in the nasal half of the visual field are formed on temporal halves of the retinae, and vice versa.
THE RETINA The retina contains the cones and the rods, which are the photoreceptive cells that convert light stimuli into nervous impulses. There are about 7 million cones and 120 million rods in each human retina. The cones respond maximally to bright light and are responsible for sharp vision and colour discrimination. There is a large concentration of cones in the central region of the retina especially at the macula lutea. The centre of the macula lutea has a depression called the fovea centralis which contains only cones. The rods respond to poor light and movement across the field of vision. They are concentrated in the peripheral parts of the retina.
The peripheral processes of the cones and rods are cone-and rod-shaped respectively. They end on the pigment cells of the retina. The pigment cells, which form the outermost layer of the retina, are important in the support and spacing of the cones and rods. The central processes of the cones and rods synapse with the peripheral processes of the bipolar cells of the retina. The central processes of these bipolar cells synapse with the dendrites of the ganglion cells, the innermost cell layer of the retina.
THE OPTIC NERVE, CHIASMA AND TRACTS The optic nerve is the nerve of vision. It is formed by the central processes of the ganglion cells of the retina and is about 4-5cm long. Unlike other cranial and spinal nerves, it is not a true nerve, but a prolongation of the white matter of the brain. Like the white matter, it does not have Schwann cells, and does not regenerate when it is cut.
From the innermost layer of the retina, the axons of the ganglion cells converge towards the optic disc and pierce the layers of the retina, choroid coat and lamina cribrosa of the sclera.
The fibres arising from the nasal halves of each retina pass through the optic chiasma, and enter the optic tract of the opposite side. Fibres from the temporal halves of each retina continue in the otic tract of the same side; they do not pass through the optic chiasma. As a result of the decussation of the nasal fibres of the optic nerves, each optic tract contains fibres from the ipsilateral field of vision. For example, the right optic tract contains fibres from right halves of both retinae (the temporal half of the right retina and the nasal half of the left retina).
The optic tracts pass posteriorly around the cerebral peduncles to the thalamus where each divides into a large and a small branch. The fibres in the large branch are the visual fibres and they synapse in the lateral geniculate ganglion. The fibres in the small branch are those mediating visual reflexes. They constitute the superior brachium, pass between the lateral and medial geniculate bodies and synapse in the superior colliculi and pretectal nuclei. 110
THE LATERAL GENICULATE BODY, OPTIC RADIATION AND VISUAL CORTEX
The lateral geniculate body has 6 layers. The nasal fibres (of the contralateral retina) synapse in layers 1, 4 and 6 while temporal fibres (of the ipsilateral retina) synapse in layers 2, 3 and 5. Specific points on the retina project to specific points of the lateral geniculate body and the visual cortex. Fibres from the upper part of the retina are represented in the medial side of the lateral geniculate body, while fibres from the lower part of the retina are represented in the lateral side.
The right visual cortex therefore receives impulses from the right halves of both retinae and the left visual cortex from the left halves of the both retinae. The upper quadrants of the retinae are represented above the calcarine sulcus, while the lower halves are represented below the calcarine sulcus.
APPLIED ANATOMY Loss of vision in one half of the visual field is called hemianopia. If the same halves of both visual fields (e.g. left halves of both retinae) are lost, the defect is called homonymous hemianopia. If different halves are affected, the defect is called heteronymous hemianopia.
1. Complete lesion of the optic nerve results in: a) Blindness of the affected eye b) Loss of direct reflexes on the affected eye c) Lloss of consensual reflexes on the contralateral eye
2. Lesion of the central part of the optic chiasma, e.g. from an enlarged pituitary gland, destroys fibres from the nasal halves of both retinae. This results in bitemporal heteronymous hemianopia. Hemianopia is named in relation to the affected part of the visual field, and not in relation to the retina. It is called bitemporal because the nasal fibres of both retinae that are destroyed subserve the temporal halves of both visual fields. It is also called heteronymous because the left half of one visual field and the right side of the other visual field are affected.
3. Lesion of both lateral parts of the optic chiasma results in binasal heteronymous hemianopia. This is because the uncrossed temporal fibres from both retinae subserving the nasal halves of both visual fields are destroyed.
4. Complete lesion of the optic tract results in: a) Homonymous hemianopia of the opposite side. It is homonymous because the same halves of both visual fields are lost, e.g., if the right optic tract is destroyed, the temporal fibres of the right retina and the nasal fibres of the left retina, both subserving the left halves of each visual field, are affected resulting in left homonymous hemianopia. b) Loss of pupillary reflexes in the contralateral visual field, for the same reason as above.
5. Lesion of the visual cortex results in homonymous hemianopia, as with lesions of the optic tract. However, the eye reflexes are maintained as the fibres in the superior brachium passing to the midbrain are unaffected. 111 VISUAL REFLEXES
PUPILLARY LIGHT REFLEX When one eye is exposed to a bright light both pupils contract. The contraction of the pupil exposed to light is called direct pupillary reflex while the simultaneous contraction of the pupil of the other eye is called consensual pupillary light reflex.
Pathway for the pupillary light reflex Impulses from the retina of the eye exposed to light pass through the optic nerve, optic chiasma, optic tract to the lateral geniculate body. Near the lateral geniculate body, fibres concerned with light reflexes pass to the midbrain and end in the pretectal nuclei of both sides. The axons arising from each of the pretectal nucleus pass to the Edinger Westphal nucleus of both sides. Preganglionic fibres from the Edinger Westphal nucleus pass through the oculomotor nerve and its branch to the inferior oblique muscle and end in the ciliary ganglion. The postganglionic fibres from the ciliary ganglion pass through the short ciliary nerves to the sphincter pupillae muscle.
The consensual reflex is as a result of the crossing of fibres along the pathway of the pupillary light reflex viz: a) Crossing of fibres at the optic chiasma. b) Fibres from the optic chiasma reach both pretectal nuclei. c) Each pretectal nucleus receives fibres from the Edinger Westphal nucleus of both sides.
ACCOMMODATION REFLEX The eyes converge when we look at a near object. At the same time, the ciliary muscle contracts to modify the shape of the lens, and the pupil constricts to make the focus sharp. The pathway for the accommodation reflex is different from that of the light reflexes. It comprises the optic nerve, optic chiasma, optic tract, lateral geniculate body, optic radiation and the visual area.
The visual cortex is connected via the superior longitudinal fasciculus to the eye field in the medial frontal gyrus. Efferent fibres from the frontal eye field pass through the internal capsule to the oculomotor nuclei. Preganglionic fibres from the Edinger Westphal nucleus relay in the ciliary ganglion from where the postganglionic fibres arise to supply the ciliary muscle and the sphincter pupillae. Fibres from the ventral part of the oculomotor pass to the medial recti muscles. Contraction of these muscles results in convergence of the eyes.
ARGYLL ROBERTSON PUPIL
In this condition, accommodation reflex is present but pupillary reflex is absent. The lesion is in the pretectal area between the Edinger Westphal nucleus and the lateral geniculate body. It is seen in certain diseases of the central nervous system e.g. tabes dorsalis caused by syphilis.
GENERAL LIGHT REFLEXES are reflex movements of the eyes, head, neck, trunk or the limbs in response to visual stimuli e.g. a flash of light. Fibres responsible for these reflexes pass from the optic tract to superior colliculus through the superior brachium. Some of the fibres from the superior colliculus pass through the following:
1. Tectobulbar tract to the motor nuclei of the brain stem. These fibres are responsible for the movements of the eyes.
2. Tectospinal tracts to the spinal anterior horn cells. These fibres are responsible for the movements of the neck, trunk and limbs. 112
CONJUNCTIVAL OR CORNEAL REFLEX When the conjunctiva or cornea is touched with say a cotton wool, both eyelids blink. This is called corneal or conjunctival reflex.
The pathway is as follows:
Afferent impulses from the cornea pass through the branches of the ophthalmic division of trigeminal nerve to the sensory nuclei of the nerve. Secondary fibres from the sensory nuclei of the trigeminal nerve are connected to the motor nuclei of the facial nerves. Efferent fibres from the facial nuclei reach orbicularis oculi and the facial muscles.
In paralysis of the ophthalmic division of trigeminal nerve, corneal reflex is not elicited from the affected side but stimulation of the cornea of the unaffected side results in blinking of both eyes. In facial nerve paralysis, only the unaffected eye blinks. 113 37. INTERNAL CAPSULE
Internal capsule is a band of white fibres between the thalamus and the caudate nucleus medially and the lentiform nucleus laterally. It consists of afferent fibres passing from the cell bodies in the thalamus to the cortex, and efferent fibres from the cell bodies in the cortex to the crus cerebri of the midbrain. The internal capsule is continuous superiorly with the corona radiata and inferiorly with the crus cerebri. It can be divided into anterior limb, posterior limb, genu, retrolentiform part and sublentiform part.
THE ANTERIOR LIMB: It lies between the head of the caudate nucleus medially and the anterior part of the lentiform nucleus laterally. It contains frontopontine fibres which arise in the cortex of the frontal lobe. The fibres pass through the middle third of the crus cerebri and synapse in the pontine nuclei. The anterior thalamic radiation fibres that arise from the thalamus and end in the frontal lobe also pass through the anterior limb.
THE GENU: It is the junction between the anterior and posterior limbs. It contains the corticonuclear fibres which arise mainly from Brodmann's area 4 of the cerebral cortex. Some of these fibres also arise from the motor nuclei of the cranial nerves in the brain stem.
THE POSTERIOR LIMB: It lies between the thalamus medially and the posterior part of the lentiform nucleus laterally. It contains the corticospinal fibres which constitute the pyramidal tracts. The fibres occupy the middle third of the crus cerebri. The fibres to the head lie close to the genu while those to the perineum and the lower limb lie more posteriorly. The superior thalamic radiation (which is formed by ascending fibres from the ventroposterior nucleus of the thalamus to the somatosensory area of the cortex) passes through both the posterior limb and the genu.
THE RETROLENTIFORM PART: It is formed by fibres that lie behind the posterior end of the lentiform nucleus. It contains fibres that pass to and from the occipital lobe and the posterior part of the parietal lobe. These fibres include parietopontine, occipitopontine and occipitotectal fibres. The ascending fibres that pass through the retrolentiform nucleus constitute the posterior thalamic radiation. The latter passes from the thalamus to the occipital lobe. It includes the optic radiation which passes from the lateral geniculate body to the visual cortex.
THE SUBLENTIFORM PART: it is formed by fibres that pass below the lentiform nucleus. It contains the temporopontine, temporothalamic and a few parietopontine fibres. The ascending fibres that pass through this part of the internal capsule constitute the inferior thalamic radiation. These ascending fibres arise from the thalamus and end in the temporal lobe. It includes the auditory radiation which arises from the medial geniculate body and ends in the auditory area of the cerebral cortex.
ARTERIAL SUPPLY OF THE INTERNAL CAPSULE The internal capsule receives its blood supply from the medial and lateral striate branches of the medial cerebral artery, the recurrent branches of the anterior cerebral artery, anterior choroidal artery and the posterior communicating artery. One of the lateral striate branches is larger than the others and is called the artery of cerebral haemorrhage or Charcot's artery. It is the artery in the brain that is most susceptible to rupture. 114 38. FUNCTIONAL COMPONENTS OF THE CRANIAL NERVES
The nerve fibres are broadly divided into two: afferent and efferent.
1. Afferent Fibres carry impulses from peripheral structures to the CNS. The afferent fibres that carry impulses that make us conscious of sensations like pain, touch, etc. are called sensory fibres. Other afferent fibres carry impulses that we do not perceive, but are necessary for the reflex control of various body activities. 2. Efferent or motor fibres carry impulses from the CNS to the effector tissue or organ.
The tissues or organs of the body may be divided into two main types: somatic and efferent. 1. Somatic structures are those that are related to the body wall (soma - body wall). These structures include the skin, bones, joints, muscles of the limbs and body wall. 2. Visceral structures are the internal organs such as the heart, lungs, smooth muscles, gastrointestinal tract as well as striated muscles derived from the branchial arches.
NB. Special nerve fibres are those that are associated with the special senses such as vision, smell, taste, hearing and equilibrium as well as the striated muscles derived from the branchial arches.
Based on the above preamble, cranial nerve fibres may be divided into 7 functional components:
1. SOMATIC EFFERENT (SE) FIBRES These supply striated muscles of the limbs and body wall, extraocular muscles and the intrinsic muscles of the tongue. The SE nuclei are represented by: a) Oculomotor (III) and trochlear (IV) in the midbrain b) Abducent (VI) in the pons c) Hypoglossal (XII) in the medulla
2. SPECIAL VISCERAL EFFERENT (SVE) FIBRES These supply striated muscles derived from the branchial arches. The branchial muscles are classified as visceral because they develop from the visceral mesoderm. They are also referred to as special to distinguish them from smooth muscles which are supplied by the general visceral efferent. The SVE nuclei are represented by: a) Motor nucleus of trigeminal (V) in the upper pons b) Nucleus of facial (VII) in the lower pons c) Nucleus ambiguus (IX, X, XI) in the medulla oblongata
3. GENERAL VISCERAL EFFERENT (GVE) FIBRES These are neurons that constitute the autonomic nervous system. The preganglionic fibres arise from the nucleus and relay in a peripheral ganglion. The postganglionic fibres supply smooth muscles and glands. The nerves that supply glands are called secretomotor fibres. The GVE nuclei are represented by: a) Edinger-Westphal nucleus (accessory nucleus of oculomotor) in the midbrain. b) The superior and inferior salivatory nuclei. These lie in the pons. c) Dorsal nucleus of vagus. It lies in the medulla. 115
4. GENERAL VISCERAL AFFERENT (GVA) FIBRES They carry visceroceptive sensations such as pain from the viscera. The GVA fibres are carried by VII, IX and X cranial nerves and they end in the nucleus of tractus solitarius.
5. SPECIAL VISCERAL AFFERENT (SVA) FIBRES These fibres carry sensations of taste and they are found in the VII, IX and X cranial nerves. They end in the gustatory nucleus, which is the upper part of the nucleus of tractus solitarius. Both GVA and SVA nuclei are represented by the nucleus of tractus solitarius which lies in the medulla.
6. GENERAL SOMATIC AFFERENT (GSA) FIBRES These fibres carry: i) Exteroceptive sensations namely pain and temperature from the skin. ii) Proprioceptive sensations i.e. sensations that convey information about the movement and position of joints. The GSA nuclei column is represented by the sensory nucleus of trigeminal nerve which has three parts: a) Mesencephalic nucleus of V which lies in the midbrain b) Main nucleus of V which lies in the pons c) Spinal nucleus of V which lies in the medulla. This nerve extends from the main sensory nucleus to the upper two segments of the spinal cord. Its lower end is continuous with the substantia gelatinosa of the spinal cord.
7. SPECIAL SOMATIC AFFERENT (SSA) FIBRES The SSA fibres are carried by I, II and VIII cranial nerves. There are 2 cochlear nuclei (dorsal and ventral) and 4 vestibular nuclei (medial, lateral, interior and superior). They lie at the junction of the pons and the medulla.
FUNCTIONAL COMPONENT OF EACH CRANIAL NERVE
I. OLFACTORY NERVE SSA. The central processes of the bipolar olfactory cells constitute the olfactory nerve, the nerve of smell. It is classified as SSA. It is special because it supplies a special sense and somatic because the olfactory mucosa is ectodermal in origin. It may also be classified as SVA because of the close relationship between smell and taste.
II. OPTIC NERVE SSA. It is the nerve of vision. The fibres arise from the ganglion cells of the retina. It is a special because it supplies a special sense, and somatic because the retina is ectodermal in origin.
III. OCULOMOTOR NERVE a) SE. The fibres arise from the oculomotor nucleus and supply all the extraocular nucleus except the lateral rectus and superior oblique (LR6SO4). b) GVE. The preganglionic fibres arise from the accessory oculomotor (Edinger-Westphal) nucleus and relay in the ciliary ganglion. The postganglionic fibres supply the sphincter pupillae and the ciliaris muscle. c) GSA. They carry proprioceptive fibres from the muscles supplied by the oculomotor nerve. They end in the sensory nucleus of V. 116 IV. TROCHLEAR NERVE a) SE. The fibres arise from the trochlear nucleus and supply the superior oblique. b) GSA. They carry proprioceptive sensations from the superior oblique. They end in the sensory nucleus of V.
V. TRIGEMINAL NERVE a) SVE. These fibres arise from the motor nucleus, pass in the mandibular nerve and supply the muscles derived from the 1st branchial arch. b) GSA. They carry the following: i) Exteroceptive sensations from the skin of the face and parts of the scalp. ii) Mucous membrane of the mouth, nose, paranasal sinuses as well as the dura mater of the anterior and middle cranial compartments.
Another group of fibres carry proprioceptive impulses from the muscles of mastication. The GSA fibres end in the sensory nucleus of trigeminal nerve.
VI. ABDUCENT NERVE a) SVE. The fibres arise from the motor nucleus of facial nerve and supply the muscles derived from the 2nd pharyngeal arch. b) GVE. The preganglionic fibres arise from the superior salivatory nucleus and relay in the submandibular ganglion. The postganglionic fibres supply the submandibular and the sublingual salivatory glands. Some fibres that arise close to the salivatory nucleus relay in the pterygopalatine ganglion and supply the lacrimal gland through the lacrimal nerve, and the nasal and paranasal glands through the nasal and palatine nerves. c) SVA. They are peripheral processes of cells located in the geniculate ganglion. They carry taste sensations from the anterior two-thirds of the tongue except the circumvallate papillae. Sometimes they receive taste sensations from the soft palate. They reach the taste buds via the chorda tympani nerve. The central processes end in the gustatory nucleus. d) GVA. The fibres carry sensations from the deep face. e) GSA. They are the peripheral processes of the geniculate ganglion. They carry impulses from the skin of the external auditory meatus, the tympanic membrane and a small area behind the pinna. The central processes end in the spinal nucleus of the trigeminal nerve.
VIII. VESTIBULO-COCHLEAR NERVE a) SSA. It is the nerve of hearing and balancing. It is one of the special senses and is classified as somatic because the membranous labyrinth is ectodermal in origin. The cochlear nerve fibres are the central processes of bipolar cells in the spiral ganglion. The peripheral processes supply the organ of corti. The vestibular nerve fibres are the central processes of bipolar cells in the vestibular ganglion. The peripheral processes supply the semicircular canal, the saccule and the utricle.
IX. GLOSSOPHARYNGEAL NERVE a) SVE. The fibres arise in the nucleus ambiguus and supply stylopharyngeus. b) GVE. The preganglionic fibres arise from the inferior salivatory nucleus and relay in the otic ganglion. The postganglionic fibres supply the parotid gland. 117 c) GVA. These fibres are the peripheral processes of the cells in the inferior ganglion of glossopharyngeal. They carry general sensations such as pain, touch and temperature from the pharynx and the posterior one third of the tongue. The central processes end in the nucleus of the solitary tract. d) SVA. The fibres are the peripheral processes of cells in the inferior ganglion. They carry sensations of taste from the posterior one third of the tongue. The central processes end in the nucleus of the solitary tract. e) GSA. They carry exteroceptive sensations from the skin of the ear and proprioceptive sensations from stylopharyngeus.
X. VAGUS NERVE a) SVE. The fibres arise in the nucleus ambiguus and supply the muscles of the pharynx and the larynx. b) GVE. The preganglionic fibres arise in the dorsal (motor) nucleus of vagus and end in ganglia. The postganglionic fibres supply the smooth muscles and glands of the thoracic viscera and the gastrointestinal tract up to the right two-thirds of the transverse colon. c) GVA. They are peripheral processes of cells in the inferior ganglion. They carry general sensations from the pharynx, larynx, trachea, oesophagus, etc. The central processes end in the nucleus of the solitary tract. d) SVA. They are the peripheral processes of neurons in the inferior ganglion. They carry sensations of taste from the epiglottis and the most posterior part of the tongue. The central processes end in the nucleus of the tractus solitarius. e) GSA. They are the peripheral processes of neurons in the superior ganglion. They supply a small area of skin in the external auditory meatus and the dura mater of the posterior cranial fossa. The central processes end in the spinal nucleus of trigeminal nerve.
XI ACCESSORY NERVE
It has cranial and spinal components. The cranial component is accessory to the vagus and joins the vagus nerve. The spinal accessory arises from the upper 5 or 6 spinal segments.
Cranial Accessory: a) SVE. The fibres arise in the nucleus ambiguus supply the muscles of the pharynx, larynx and the soft palate except the tensor veli palatine which is supplied by the mandibular nerve. b) GVE. The preganglionic fibres arise from the nucleus ambiguus and relay in ganglia. The postganglionic fibres supply the smooth muscles and glands of thoracic and abdominal viscera.
Spinal Accessory: supplies the sternocleidomastoid and trapezius muscles.
XII. HYPOGLOSSAL NERVE
A) SE. The fibres arise from the hypoglossal nucleus and supply the muscles of the tongue except palatoglossus. b) GSA. The fibres carry proprioceptive impulses from the muscles of the tongue. 118 39. RECOMMENDED TEXTBOOKS
GROSS ANATOMY DISSECTION 1. Cunningham's Manual of Practical Anatomy: Volumes I, II and III --G. J. Romanes
GROSS ANATOMY TEXTBOOKS
1. Clinically Oriented Anatomy-- Keith Moore & Arthur Dalley
2. BD Chaurasia’s Human Anatomy: Volumes 1-3
3. Textbook of Anatomy: Volumes 1-3 -- Indebir Singh
4. Clinical Anatomy for Medical Students -- R. S. Snell
5. Last's Anatomy: Regional and applied – Chummy S. Sinnatamby
6. Textbook of Human Anatomy -- W. J. Hamilton
ATLAS 1. Grant's Atlas of Anatomy -- J. C. Grant 2. A Colour Atlas of Human Anatomy -- R. M. H. McMinn
NEUROANATOMY 1. A Textbook of Human Neuroanatomy -- Inderbir Singh 2. The Human Nervous System -- Murray L. Barr
HISTOLOGY 1. A Textbook of Human Histology -- Inderbir Singh 2. Functional Histology -- Wheater, Burkitt and Daniels 3. Textbook of Histology -- E. F. Hiver
EMBRYOLOGY 1. Langman's Medical Embryology. -- T. W. Sadler 2. Clinical Embryology for Medical Students -- R. S. Snell 3. Textbook of Human Embryology -- Inderber Singh
REFERENCE TEXTS 1. Gray's Anatomy 2. Textbook of Human Embryology -- Hamilton, Boyd & Mossman 3. A Textbook of Histology -- Bloom & Fawcett
MCQ'S IN ANATOMY 1. Multiple Choice Questions in Anatomy -- Medicus Anatomicus 2. Anatomy: 1600 Multiple Choice Questions -- Fitzgerald, Golden & Fitzgerald. 3. Medical Examination Review in Anatomy --- Sidney A. Cohn & Marvin I. Gottlieb. 4. Medical Examination Reviews in: - Embryology - Histology - Gross Anatomy 5. Human Anatomy Review -- Montgomery & Singleton. 6. Anatomy: Pretest Self-Assessment and Review -- April. 119 40. LECTURE AND PRACTICAL TOPICS
COURSES IN ANATOMY
2ND YEAR ANATOMY
SEMESTER I
1. ANA201 Gross Anatomy I (Upper limb, Thorax, Abdomen).
2. ANA213 General Embryology
3. ANA225 General Histology & Cytology
SEMESTER II
1. ANA202 Gross Anatomy II (Pelvis, Perineum and Lower Limb)
2. ANA214 Systemic Embryology I
3. ANA226 Systemic Histology I
3RD YEAR ANATOMY
SEMESTER I
1. ANA301 Gross Anatomy III (Head & Neck, Neuroanatomy)
2. ANA311 Systemic Embryology II
3. ANA323 Systemic Histology II
IN COURSE ASSESSMENTS
1. 1st semester examinations
2. 2nd semester examinations
3. Mock examinations
4. Histology practical manual assessment.
120 GROSS ANATOMY LECTURES
UPPER LIMB - 7 WEEKS
WEEK TOPICS
1. 1. General Introduction 2. Anatomical positions, terms, movements, etc. 3. Pectoral Region/ Axilla
2. 4. Mammary gland 5. Brachial plexus 6. Shoulder Region
3. 7. Classification of joints 8. Shoulder joint 9. Anatomy of the arm
4. 10. Classification of bones 11. Anatomy of the forearm (flexor compartment) 12. Extensors of the forearm / Dorsum of the hand
5. 13. Radial and median nerves 14. Palm I (muscles of the palm) 15. Palm II (flexor retinaculum, palmar aponeurosis, fascial spaces of hand)
6. 16. Elbow and wrist joints 17. Radio-ulnar joints (movements of supination and pronation) / Ulnar nerve 18. Arteries of the upper limb / Anastomoses around the shoulder, elbow and wrist
7. 19. Cutaneous / Segmental innervation of upper limb 20. Lymphatic and venous drainage of upper limb
THORAX - 3 WEEKS
WEEK 1 1. The thoracic wall / Intercostal nerves and vessels 2. The pleura and lungs 3. Roots of the lungs / Broncho-pulmonary segments
WEEK 2 4. Mediastinum 5. Borders, surfaces and blood supply of the heart 6. Interior of the heart
WEEK 3 7. Thoracic duct / Azygos and hemiazygos veins 8. The oesophagus 9. Thoracic part of autonomic nervous system
121 ABDOMEN & PELVIS - 7 WEEKS
WEEK 1 1. Anterior abdominal wall / Rectus sheath 2. Inguinal canal and hernias 3. Peritoneum - peritoneal cavity and omental bursa
WEEK 2 4. Spleen - coeliac artery and its branches 5. Stomach 6. Small intestine / Mesentery proper / Superior mesenteric artery
WEEK 3 7. Large intestine / Inferior mesenteric artery 8. Portal vein / Portal venous system / Porto-caval anastomosis 9. Duodenum / Pancreas
WEEK 4 10. Liver / Gall bladder 11. Kidneys / Suprarenal glands 12. Diaphragm
WEEK 5 13. Rectum / Anal canal 14. Urinary bladder 15. Prostate / Male and female urethrae
WEEK 6 16. Uterus / vagina 17. Posterior abdominal wall / Vessels, nerves and muscles of lesser pelvis 18. Ovaries / Female external genitalia
WEEK 7 REVISION
PERINEUM AND LOWER LIMB - 7 WEEKS
WEEK 1 1. Male external genital organs 2. Perineum - Anal triangle 3. Perineum - Urogenital triangle
WEEK 2 4. Front of thigh / Femoral triangle 5. Medial side of thigh / Adductor canal 6. Lumbar plexus: Femoral and obturator nerves 7. Gluteal region WEEK 3 8. Sacral plexus: tibial and common peroneal nerves 9. Femoral artery and anastomoses in the gluteal, thigh and knee regions
WEEK 4 10. Hip joint 11. Back of thigh and popliteal fossa 12. Front and lateral sides of leg / Dorsum of foot
WEEK 5 13. Back of leg 14. Knee joint 15. Sole of foot
WEEK 6 16. Ankle, subtalar and midtarsal joints 17. Arches of foot 18. Lymphatic and venous drainage of lower limb WEEK 7 19. Cutaneous / Segmental innervation of lower limb
122 HEAD AND NECK
1. The scalp and the face 2. Triangles of the neck
3. Course and distributions of external and internal carotid arteries 4. The thyroid and parathyroid glands
5. Cranial nerves V & VII 6. Cranial nerves IX, X and XI
7. Parotid gland 8. Temporomandibular joint: muscles of mastication
9. Submandibular region & Pterygopalatine fossa 10. Pharynx
11. Nasal Cavity & Paranasal air sinuses 12. Larynx
13. Tongue 14. The ear
15. The eye 16. Contents of the vertebral canal
NEURO-ANATOMY
1. Receptors, effectors and synapses
2. External features and internal structure of the spinal cord
3. External features and internal structure of the brain stem
4. External features and internal structure of the cerebellum
5. External features of cerebrum and cerebral cortex
6. White matter of cerebrum / Basal ganglia
7. Diencephalon
8. Tracts of spinal cord and brain stem
9. Auditory and vestibular pathways / Olfactory pathway
10. Visual pathway
11. Ventricles of the Brain / CSF
12. Blood supply of the CNS 123 HISTOLOGY LECTURE AND PRACTICAL TOPICS
1ST SEMESTER 1. Introduction, histotechniques 2. Protective and glandular epithelium
3. Fibrous connective tissue 4. Cartilage
5. Bone, bone formation 6. Muscle tissue
7. Nervous tissue (fibres, cells, ganglions) 8. Blood and lymphatic vessels
9. Trachea, lung 10. Lymph node, tonsil, thymus, spleen
11. Skin 12. Lip, tongue, tooth
13. Salivary glands, oesophagus
2ND SEMESTER 14. Stomach 15. Small intestine
16. Large intestine, appendix, rectum 17. Liver
18. Gall bladder, pancreas 19. Kidney
20. Ureter, urinary bladder 21. Pituitary gland, islets of Langerhans
22. Thyroid and suprarenal glands 23. Testis, epididymis
24. Vas deferens, seminal vesicle, prostate
3RD SEMESTER 25. Penis, urethra 26. Ovary
27. Uterine tube, uterus, vagina 28. Mammary gland
29. Spinal cord 30. Cerebellum
31. Cerebrum 32. Eye 124 EMBRYOLOGY LECTURES
1ST SEMESTER 1. Introduction, testis, spermatogenesis 2. Ovary and oogenesis
3. Female reproductive cycles 4. Fertilization
5. Cleavage, blastocyst formation and implantation 6. Early embryogenesis
7. Late embryogenesis 8. Placenta I
9. Placenta II 10. Development of the larynx, trachea and lung
11. Development of the heart I 12. Development of the heart II
13. Development of the heart III
2ND SEMESTER 14. Development of the arteries 15. Development of the veins
16. Foetal and neonatal circulation 17. Development of the diaphragm
18. Development of the gut I 19. Development of the gut II
20. Development of the liver and pancreas 21. Development of the urinary system
22. Development of the genital system I 23. Development of the genital system II
24. Development of the genital system III
3RD SEMESTER 25. Pharyngeal arches 26. Pharyngeal pouches and clefts 27. Development of face, nose and palate 28. Development of spinal cord 29. Development of medulla oblongata, cerebellum and pons 30. Development of mesencephalon 31. Development of prosencephalon 32. Development of eye 33. Development of ear 125 DISSECTION SCHEDULE FOR MEDICAL AND DENTISTRY STUDENTS
REF. CUNNINGHAM'S MANUAL OF PRACTICAL ANATOMY, VOL.1-3, 15TH ED
UPPER LIMB - 7 WEEKS
TOPICS PAGES WEEK
1. General introduction, the pectoral region, the axilla 1 - 32
2. The brachial plexus, the superficial muscles and nerves of the 33 - 41 back
3. The superficial tissues of the upper limb, the shoulder region 41 - 66 and shoulder joint
4. The arm, cubital fossa
5. The flexor compartment of the forearm, 73 - 80 the palm
6. The palm (continued), the carpal tunnel, the wrist joint, the 81 - 98 thenar & hypothenar eminences, the extensor compartment of the forearm
7. The dorsal aspect of the hand, the intrinsic muscles of the hand. The joints of the upper limb
THORAX - 3 WEEKS
WEEK TOPICS PAGES
1. The walls of the thorax, the pleura, the sympathetic trunk, the 1 - 29 azygos system of veins, the veins, the vagal and phrenic nerves
2. The roots of the lungs, the anterior mediastinum, the 30- 56 pericardium, the chambers of the heart
3. The superior mediastinum, the remaining chamber of the 57- 82 heart (left atrium), the base of the heart, the posterior mediastinum, the joints of the thorax
126 ABDOMEN - 5 WEEKS
WEEK TOPICS PAGES
1. The anterior abdominal wall, the inguinal canal, the rectus 83- 104 sheath (The male external genitalia to be dissected with the perineum), the spermatic cord
2. The loin, the abdominal cavity, the visceral peritoneum, the 115- 125 omental bursa, lesser omentum
3. The spleen, the coeliac trunk, the stomach, the small intestine 124- 146 & mesentery, the caecum and colon
4. The pancreas, the duodenum, the portal vein, the liver, the gall bladder
5. The coeliac ganglion, the kidneys, the suprarenal glands, the 166- 186 ureter, the diaphragm, the posterior abdominal wall (the sacro-iliac and lumbosacral areas to be dissected with gluteal regions). The perineum to be dissected after the pelvis
PELVIS - 2 WEEKS
WEEK TOPICS PAGES
1. Urinary bladder, prostate, uterus, vagina 213 - 218
2. Rectum, anal canal, vessels, nerves and muscles of lesser 218 - 241 pelvis
PERINEUM / LOWER LIMB - 7 WEEKS
WEEK TOPICS PAGES
1. The male external genitalia (Vol.2) 104 - 111 The urogenital & anal triangles of the perineum (Vol.2) 195 - 210
2. The front of the thigh (Vol. 1)
3. The medial side of the thigh, the gluteal region 147 - 160
4. The popliteal fossa, the back of the thigh, the hip joint 160 - 174
5. The front of the leg, the dorsum of the foot, the lateral side 175 - 190 of the leg, the back of the leg
6. The back of the leg (continued), the sole of the foot 190 - 204
7. The sole (continued), the joints of the lower limb 205 - 234 127
HEAD AND NECK - 9 WEEKS
WEEK TOPIC PAGES
1. The scalp, superficial temporal region, facial muscles 11 - 20
2. The side of the neck and the dissection ofthe back 21 - 35
3. The anterior triangle of the neck 35 - 43
4. (The cranial cavity will be dissected later) 43 -64 The deep dissection of the neck 64 -93
5. The prevertebral region and the deeper dissection of the 93 - 104 face. (The orbit will be dissected later) The parotid region 104 - 115 115 - 118
6. The temporal and infratemporal regions 118 - 127
7. The submandibular region 123 - 135 The mouth and the pharynx 135 - 149
8. The cavity of the nose. 149 - 157 The larynx 157 - 166 The tongue 166 - 171
9. The organs of hearing and equilibration. Orbital cavity 171 - 183 and its contents. The eyeball.The contents of the vertebral 183 - 192 column
NEUROANATOMY - 4 WEEKS
WEEK TOPIC PAGES
1. Removal of the brain/dura mater/cranial fossae 43 - 64 Orbital cavity 104- 115
2. Meninges and vessels of the brain. The base of the brain 212 - 224 Hindbrain and cerebellum 224 - 245
3. The midbrain/the cerebrum 245 - 274
4. The thalamus and optic tract. The deep dissection of 274 - 300 cerebral hemisphere. The deep nuclei of the telencephalon. Nuclei and connexions of the thalamus
REVISION 128 41. PAST ESSAY QUESTIONS
DEPARTMENT OF ANATOMY COLLEGE OF MEDICINE UNIVERSITY OF NIGERIA, ENUGU CAMPUS SEPTEMBER 1980 2ND PROFESSIONAL (RESIT) EXAMINATIONS FOR MB.BS DEGREES PAPER II - (ESSAY)
ANSWER ALL FIVE QUESTIONS
1. Give an account of the gross anatomy of the broncho-pulmonary segments and their clinical significance. Briefly describe the development of the bronchial tree.
2. Describe the lateral wall of the nasal cavity.
3. Describe the gross anatomy and microscopic structure of the vermiform appendix.
4. Give an account of the origin, course and distribution of the femoral nerve.
5. Write short notes on the following: a) Ligamentum arteriosum b) Internal capsule c) Omental bursa d) Synovial sheath of the flexor tendons of hand.
APRIL 1981
1. Describe the factors responsible for the strength and stability of the hip joint.
2. Describe the origin, course, relations and distribution of the left recurrent laryngeal nerve.
3. Describe the microscopic structure of the kidney. Add a note on the topography of the left kidney.
4. Describe the neuronal structure of the hypothalamo-hypophyseal system.
5. Write short notes on the following: a) Anastomoses around the elbow joint b) The parietal pleura c) Microscopic anatomy of the intestinal villi d) Membranous labyrinth. 129 SEPTEMBER 1981 (RESIT)
1. Describe the gross anatomy of the ankle (talocrural) joint.
2. Describe the extra-hepatic parts of biliary apparatus. Add a note on the histology of the gall bladder.
3. Give an account of the anatomy of the azygos system of veins. Add a note on its development.
4. Describe the anatomical structure of the fourth ventricle of the brain.
5. Write short notes on the following: a) Deep palmar arch b) Microscopic anatomy of the suprarenal gland c) Carotid sheath d) Cornea
MAY 1982 - (MAIN)
1. Describe the formation of the brachial plexus. Briefly enumerate its branches and add a note on its applied anatomy.
2. Draw diagrams to show the relations of the mediastinal surfaces of the right and left lungs. Describe the microscopic structure of the lung.
3. Describe the anatomy of the uterus. Add a note on its development.
4. Give an account of the structure and connections of the cerebellum.
5. Write short notes on the following: a) Great saphenous vein b) Development of the suprarenal gland c) Submandibular gland d) Medial wall of the tympanic cavity
APRIL 1983 - (MAIN)
1. Describe the structural formation of the knee joint and explain its movements.
2. Describe the microscopic structure of the liver. Add a note on its anatomical relations.
3. Describe the gross anatomy and microscopic structure of the trachea. Add a note on its development.
4. Give an account of the extra-ocular muscles and explain their function in the movements of the eye ball.
5. Write short notes on the following: a) Anastomoses around the scapula b) Development of the uterus c) Pudendal canal d) Internal capsule
130 DECEMBER 1983
1. Describe the anatomy of the mammary gland with special reference to its lymphatic drainage.
2. Describe the gross anatomy of urinary bladder. Add a note on its microscopic structure.
3. Describe the gross anatomy of right atrium of heart. Add a note on its development.
4. With the help of suitable diagrams describe the structure of the medulla oblongata.
5. Write short notes on the following: a) Plantar arterial arch b) Development of pancreas c) Cricoid cartilage d) Histology of parotid gland
APRIL 1984
1. Describe the structure and function of the shoulder joint.
2. Describe the topographical anatomy and histology of the thyroid gland.
3. Give an account of the gross anatomy and development of the stomach.
4. Give an account of the composition and course of the spinothalamic tract.
5. Write short notes on: a) Femoral sheath b) Oblique sinus of pericardium c) Skeletal muscle d) Development of anal canal
APRIL 1985
1. Describe the venous drainage of the lower limb. Add a note on its clinical significance.
2. With the help of diagrams describe the general arrangements of the fasciae in the male perineum.
3. Describe the microscopic anatomy of the liver. Add a note on its topographical relationships.
4. Give an account of the neuronal structure and connections of the cerebellum. Add a note on its development.
5. Write short notes on the following: a) Anastomoses around the scapula b) Cervical plexus c) Histology of the male urethra d) Development of the paramesonephric duct.
131 DECEMBER 1985 - (RESIT)
1. Describe the structural formation of the hip joint and explain its movements.
2. With the help of suitable diagrams, describe the gross anatomy of the lungs. Add a note on its development.
3. Describe the extra-hepatic biliary apparatus. Add a note on the histology of the gall bladder.
4. Give an account of the general composition of the visual pathway.
5. Write short notes on: a) Carpal tunnel b) Mitral valve c) Development of chorion frondosum d) Cardiac muscle
APRIL 1986 - (MAIN)
1. Describe the morphological features of the shoulder joint. Briefly explain its movements.
2. Give an account of the gross anatomy of the right atrium. Add a note on its development.
3. Describe the anatomy of the suprarenal gland. Add a note on its microscopic anatomy.
4. Describe the neuronal structure of the hypothalamo-hypophyseal system. Add a note on the mechanism of neurosecretion.
5. Write short notes on the following: a) Smooth muscle b) Graafian follicle c) Paranasal air sinuses d) Hyaline cartilage
SEPTEMBER 1986 - (RESIT)
1. Describe the origin, distribution and relations of the axillary artery. Add a note on its histological features.
2. Describe the anatomy of the inguinal canal. Give an account of the hernias associated with it.
3. Describe the morphological features and applied anatomy of the bronchopulmonary segments.
4. Give an account of the movements of the eyeball and the axes on which they take place.
5. Write short notes on: a) Arches of the foot. b) Ductus venosus c) Basal ganglia d) Somites
132 APRIL 1987 (MAIN)
1. Describe the formation and distribution of the brachial plexus. Add a note on its applied anatomy.
2. Give an account of the thoracic part of the sympathetic nervous system.
3. Describe the anatomy of the thyroid gland. Briefly explain its development.
4. Describe the horizontal disposition of peritoneum, with special reference to omental bursa.
5. Write short notes on: a) Features of a typical synovial joint b) Ductus arteriosus c) Femoral sheath d) Hyaline cartilage.
SEPTEMBER 1987 - (RESIT)
1. Describe the gross anatomy of the stomach. Add a note on its development.
2. Describe the venous drainage of the lower limb. Add a note on its clinical significance.
3. With the aid of suitable diagrams describe the general arrangements of the fasciae in the male perineum.
4. Give an account of the origin and distribution of a typical spinal nerve.
5. Write short notes on the following: a) Islets of Langerhans b) Bronchopulmonary segments c) Microscopic anatomy of the breast d) Membranous labyrinth
APRIL 1988 (MAIN)
1. Describe the gross anatomy of the scrotum and its contents. Add a note on the descent of the testis.
2. Describe the lateral wall of the nasal cavity.
3. Give an account of the microscopic structure of the liver. Add a note on its anatomical relations.
4. Describe the formation of the brachial plexus. Enumerate its major branches and muscles they supply. Add a note on its applied anatomy.
5. Write short notes on the following: a) Development of the greater omentum b) Great saphenous vein c) Chorda tympani nerve d) The conducting system of the heart.
133 APRIL 1989 (MAIN)
1. Describe the anatomy of the axilla. How is this area drained?
2. Give an account of the external features and attachments of the heart. Add a note on the microscopic appearance of the aorta.
3. Describe the anatomy of the midbrain with special reference to the level of the exit of the oculomotor nerve.
4. Give an account of the gross anatomy of the male urinary bladder. Add a note on its development.
5. Write concise notes on the following: a) Peritoneal reflections on the anterior abdominal wall. b) Blood vessels of the kidney c) Deep muscles of the posterior compartment of the leg d) The palate
OCTOBER 1989 (RESIT)
1. Describe the gross and developmental anatomy of the pancreas.
2. Give an account of the origin, course, distribution and applied anatomy of the sciatic nerve and its major branches.
3. Give an account of the structure and contents of the orbit.
4. Describe the anatomy of the root of the lung. Briefly describe the histology of the bronchial tree.
5. Write short notes on the following: a) Lumbar vertebrae b) Intra-embryonic coelom c) Hyoid muscles d) Draw the coronal section of the male pelvis and perineum.
MAY 1990 (MAIN)
1. Give an account of the portal vein and the porto-systemic anastomoses.
2. Discuss the anatomical basis of chewing.
3. Describe the levator ani muscle, mentioning the important anatomical relations. What are the functions of this muscle?
4. Describe the anatomy of the shoulder joint and its movements.
5. Write short notes on: a) The circle of Willis (circulus arteriosus cerebri) b) Microscopic anatomy of the pancreas c) Tight junctional complex d) The fate of aortic arch arteries 134 SEPTEMBER 1990 (RESIT)
1. Discuss the anatomical basis of hearing.
2. Give an account of the gross anatomy of the spinal cord. Add a note on its congenital malformations.
3. Describe the anatomy of the pleura of the lungs. Add a note on the bronchopulmonary segments, and its significance.
4. Write a concise essay on the gross and applied anatomy of the brachial plexus.
5. Write short notes on the following: a) Retropubic space b) Implantation c) Talocalcaneonavicular joint d) T-lymphocytes
APRIL 1991 (MAIN)
1. Define and give a brief classification of the glands of the body. Discuss the salient features of the suprarenal gland.
2. Outline and describe the white matter of the cerebrum.
3. Give an account of the anatomy of the adductor group of muscles of the thigh.
4. Describe the anatomy of the mammary gland. Add a note on its applied anatomy.
5. Write short notes on the following: a) Proximal radio-ulnar joint b) Parathyroid gland c) First pharyngeal arch d) Lymphatic drainage of the stomach
SEPTEMBER 1991
1. Describe the histological features of a lymph node. Outline the anatomical groups of lymph nodes in the axilla.
2. Describe the gross anatomy and movements of the hip joint.
3. Draw and label fully the sternocostal surface of the heart and the great vessels. Add a note on the histology of the aorta.
4. Discuss the anatomy of the parotid gland. Add a note on its applied anatomy.
5. Write short notes on the following: a) Blood supply of the hindgut b) Implantation c) Applied anatomy of the brachial plexus d) Internal capsule
135 APRIL 1992 (MAIN)
1. Give an account of the gross anatomy of the tongue.
2. Describe the shoulder joint.
3. Give an account of the gross and microscopic anatomy of the duodenum.
4. Describe the gross anatomy of the right atrium. Add a note on its development.
5. Write short notes on: a) Internal capsule b) Gross anatomy of anal canal c) The tooth d) Longitudinal arches of the foot.
SEPTEMBER 1992 (RESIT)
1. Give an account of the origin, course, relations and distribution of the radial nerve. Add a note on its applied anatomy.
2. Give an account of the visual pathway. Add a note on its applied anatomy.
3. Describe the gross anatomy of the prostate gland. Add a note on its histology,
4. Give an account of the development of the diaphragm. Add a note on its anomalies.
5. Write short notes on: a) Omental bursa b) Paranasal air sinuses c) Basal ganglia d) Ankle joint
APRIL 1993 (MAIN)
1. Give an account of: a) Auditory pathway b) The development of the internal ear
2. Describe the gross anatomy of the hip joint. What factors account for the stability of this joint?
3. Describe the anatomy of the suprarenal gland. Add a note on microscopic anatomy.
4. Give an account of the gross anatomy of the bronchopulmonary segments and the pleurae.
5. Write short notes on: a) Carpal tunnel b) Microscopic structure of the cerebellar cortex c) Cavernous sinus d) Development of the urinary bladder.
136 42. ESSAY-TYPE QUESTIONS
UPPER LIMB 1. Describe the shoulder joint. What factors lend stability to the joint?
2. Describe the anatomy of the elbow joint. Add a note on the ossification of the bones of the joint.
3. Describe the radioulnar joints and the movements that occur on them.
4. Describe the anatomy of the mammary gland. Add a note on its applied anatomy.
5. Describe the anatomy of the axilla.
6. Outline the anatomical groups of lymph nodes in the axilla. Describe the histological features of a lymph node.
7. Describe the formation, relations and distribution of the brachial plexus. Add a note on its applied anatomy.
8. Give an account of the origin, course, relations and distribution of the radial nerve. What deformities may result from damage to the nerve at various levels?
9. Describe the formation and distribution of the median nerve.
10. Describe the formation and distribution of the ulnar nerve. What deformities may result from damage to the nerve at various levels?
11. Describe the anatomy of the palmar spaces in the hand.
12. Give an account of the origin, relations and branches of the axillary artery.
13. Give and account of the dermatomes of the upper limb.
WRITE SHORT NOTES ON:
1. The anastomoses around the scapula.
2. The anastomoses around the elbow joint.
3. The deep palmar arch.
4. The cubital fossa.
5. Lymphatic drainage of the breast.
6. Applied anatomy of the brachial plexus.
7. The carpal bones.
8. Claw hand.
9. Synovial sheaths of the flexor tendons of the hand.
10. The wrist joint. 137 THORAX 1. Give an account of the gross anatomy of the bronchopulmonary segments and their clinical significance. Add a note on the histology of the bronchial tree. 2. With the help of suitable diagrams, describe the gross anatomy of the lungs. 3. Describe the anatomy of the pleura. 4. Describe the gross anatomy of the right atrium of the heart. Add a note on its development. 5. Give an account of the arterial supply and venous drainage of the heart. 6. Describe the gross anatomy of the oesophagus. Add a note on its development. 7. Describe the origin, course, relations and distribution of the left and right recurrent laryngeal nerves. 8. Describe the gross anatomy and microscopic structure of the trachea. Add a note on its development. 9. Give an account of the thoracic part of the sympathetic nervous system. 10. Give an account of the origin and distribution of a typical thoracic spinal nerve
WRITE SHORT NOTES ON: 1. The root of the lung. 2. The first rib. 3. Surface anatomy of the lung and pleura. 4. Ligamentum arteriosum. 5. The oblique sinus of pericardium. 6. Surface anatomy of the heart. 7. Azygos system of veins. 8. Bronchopulmonary segments. 9. The superior mediastinum. 10. The conducting system of the heart. 11. Gross and developmental anatomy of the arch of the aorta. 12. The thoracic duct.
ABDOMEN 1. Give an account of the gross and developmental anatomy of the stomach. 2. Give an account of the gross and developmental anatomy of the duodenum. 3. Describe the gross and developmental anatomy of the pancreas. 4. Give an account of the portal vein, and the porto-systemic anastomosis. 5. Give an account of the gross and microscopic anatomy of the spleen. 6. Describe the anatomy of the kidney, and the anomalies that may be associated with its development. 7. Give an account of the lesser sac of the peritoneum. Add a note on its development. 8. Describe the gross and microscopic anatomy of the vermiform appendix. 9. Describe the anatomy of the suprarenal gland. Add a note on its microscopic anatomy. 10. Describe the extrahepatic biliary apparatus. Add a note on the histology of the gall-bladder. 11. Give an account of the gross anatomy of the liver. 12. Describe the gross anatomy of the inguinal canal. Compare and contrast the anatomy of direct and indirect inguinal herniae. 13. Give an account of the gross anatomy of the diaphragm. What developmental anomalies occur in this organ? 138 WRITE SHORT NOTES ON: 1. Peritoneal reflections on the anterior abdominal wall. 2. Blood vessels of the kidney. 3. Lymphatic drainage of the stomach. 4. The microscopic anatomy of the pancreas. 5. The microscopic anatomy of the liver. 6. The microscopic anatomy of the intestinal villi. 7. The development of the midgut.
PELVIS AND PERINEUM 1. Give an account of the gross anatomy of the male urinary bladder. Add a note on its development. 2. Give an account of the gross and microscopic anatomy of the male urethra. Add a note on its development. 3. Describe the gross anatomy of the prostate gland. Add a note on its histology. 4. Describe the gross anatomy of the uterus. Add a note on its development. 5. Give an account of the gross and microscopic anatomy of the ovary. 6. Describe the gross anatomy of the scrotum and its contents. Add a note on the descent of the testis. 7. With the aid of diagrams, describe the general arrangement of the fasciae in the male perineum. 8. Describe the gross and microscopic anatomy of the rectum.
WRITE SHORT NOTES ON: 1. The ischiorectal fossae. 2. Levator ani. 3. The pudendal canal. 4. Development of the anal canal. 5. Development of the vagina.
LOWER LIMB 1. Describe the gross anatomy of the hip joint. What factors contribute to the stability of the joint? 2. Describe the gross anatomy of the knee joint. 3. Describe the gross anatomy of the ankle joint. 4. Describe the femoral triangle and its contents. 5. Give an account of the venous drainage of the lower limb. Add a note on its clinical significance. 6. Describe the lymphatic drainage of the lower limb. 7. Describe the arches of the foot. 8. Describe the course and relations of the obturator nerve. 9. Give an account of the origin, course and distribution of the femoral nerve. 10. Give an account of the origin, course, relations, distribution and applied anatomy of the sciatic nerve.
139 WRITE SHORT NOTES ON: 1. The ankle joint.
2. The great saphenous vein.
3. The femoral sheath.
4. The popliteal fossa.
5. The longitudinal arches of the foot.
6. The profunda femoris artery.
7. The second muscular layer of the foot.
8. The fourth muscular layer of the foot.
9. The patella.
10. Blood supply to the head of femur.
11. Describe the femoral artery and the anastomoses at the gluteal region, back of the thigh and the knee region.
HEAD AND NECK 1. Describe the gross and microscopic anatomy of the thyroid gland.
2. Describe the anatomy of the tongue.
3. Describe the gross and microscopic anatomy of the palatine tonsil. How does it develop?
4. Describe the anatomy of the parotid gland.
5. Describe the lateral wall of the nasal cavity
6. Give an account of the extra-ocular muscles.
7. Give an account of the orbital cavity and its contents.
8. Describe the temporomandibular joint and the muscles of mastication.
9. Give an account of the origin, course and distribution of the facial nerve. Add a note on the lesion of the nerve at various sites.
10. Give an account of the origins, courses and distributions of the external and internal carotid arteries.
11. Describe the gross anatomy of the pharynx.
12. Describe the gross anatomy of the larynx. 140
WRITE SHORT NOTES ON: 1. The pterygopalatine fossa. 2. The cavernous sinus. 3. Paranasal air sinuses. 4. The carotid sheath. 5. The submandibular gland. 6. The cervical plexus. 7. Chorda tympani nerve. 8. The hyoid muscles. 9. The external carotid artery. 10. The internal carotid artery. 11. The circle of Willis. 12. The palate. 13. The tooth.
NEUROANATOMY 1. Give an account of the gross anatomy of the spinal cord. Add a note on its congenital malformations.
2. With the aid of suitable diagrams, describe the structure of the medulla oblongata.
3. Describe the internal structures of the midbrain at the levels of the superior and inferior colliculi.
4. Describe the auditory pathway.
5. Describe the visual pathway. Add a note on its applied anatomy.
6. Give an account of the structure and connections of the cerebellum.
7. With the aid of suitable diagrams, describe the white matter of the cerebrum.
8. Describe the anatomy of the ventricles and the formation and circulation of cerebrospinal fluid.
9. Describe the gross and developmental anatomy of the pituitary gland.
10. Describe the anatomy of the hypothalamus or thalamus.
11. Describe the tracts of the spinal cord and brain stem.
12. Describe the arterial supply and venous drainage of the brain.
13. Describe the functional components of the cranial nerves.
WRITE SHORT NOTES ON: 1. The internal capsule. 2. The basal ganglia. 3. The spinothalamic tracts. 4. Pupillary reflexes. 5. Corneal reflex. 6. Functional areas of the cerebral cortex. 141 43. OBJECTIVE - TYPE QUESTIONS
DEPARTMENT OF ANATOMY, UNIVERSITY OF NIGERIA 1ST SEMESTER EXAMINATION FOR 2ND YEAR MEDICAL STUDENTS
TIME ALLOWED: 1hr
Indicate whether the following statements are TRUE or FALSE by writing the alphabet "T" or "F" on the left hand side of the question. Each correct answer scores one point. For each wrong answer you lose one point. There is no score for questions not attempted.
1. Cartilage increases in size by both appositional and interstitial growth. 2. The lamina propria consists mainly of the type III collagen. 3. The adipocytes of the brown adipose tissue have a larger amount of cytoplasm than those of the white adipose tissue. 4. Sinusoids are present in the liver and spleen but not in the bone marrow.
5. Type C- fibres are thin and unmyelinated. 6. The organic matter of bone matrix is predominantly composed of collagen. 7. The circumvallate papillae are irregularly scattered over the dorsum of the tongue. 8. In the spleen, the red pulp contains more lymphatic nodules than sinusoids. 9. The epithelial lining of the vagina is stratified squamous of the keratinized type.
10. The red fibres found in the skeletal muscle have high concentration of myoglobin and cytochrome. 11. The glassy appearance of hair is derived from the Huxley's layer due to the presence of trichohyaline. 12. The alveoli of lings are lined by a single layer of squamous cells. 13. The areolar connective tissue of the trachea contains collagen, elastic and reticular fibres. 14. The Sebaceous glands are holocrine in their mode of secretion.
15. In the closed theory of splenic circulation, blood passes through the parenchyma of the organ to reach the sinusoids. 16. The Sarcomere of the skeletal muscle contains more than one A band. 17. DNA duplication occurs during the S phase. 18. The gingiva of the teeth is lined by stratified squamous epithelium. 19. The cells of stratum basale of skin are cuboidal in shape.
20. Osteoblasts are converted into osteocytes in spaces called canaliculi. 21. In elastic arteries, the tunica intima is predominantly composed of elastic fibres. 22. Parietal cells secrete the intrinsic factor which is required for the absorption of vitamin B 12 23. The sebaceous glands are good examples of simple branched acinar glands. 24. The basement membrane is characterized by type IV collagen.
25. The enamel is characterized by the presence of Retzius lines. 26. Most of the somites are formed in the 5th week of intrauterine life. 27. The luteinizing hormone has direct stimulating effect on the interstitial cells of the testis. 28. There is decreased cornification of vaginal smears at the time of ovulation. 29. Transport of the fertilized ovum through the uterine tube to the uterus takes 3 days.
30. Placenta previa may be caused by delayed rupture of the zona pellucida. 31. During cleavage there is increase in DNA content and protoplasm. 32. Intraembryonic mesoderm is formed from proliferation of ectoderm and endoderm. 142 33. The amniotic sac is temporarily connected to the secondary yolk sac by the neuroenteric canal. 34. Human chorionic gonadotropin is first produced two weeks after fertilization.
35. Erythrocyte mosaicism may be seen in monozygotic twins. 36. The most common type of monozygotic twinning results from division of the inner cell mass. 37. Oligohydramnios is commoner in first pregnancies than in subsequent pregnancies. 38. The placenta synthesizes somatotropin. 39. Variations in the menstrual cycle are due to variations in the luteal phase.
40. Mitotic features are seen in the syncytiotrophoblast. 41. The placental membrane is most efficient in the first few months of pregnancy. 42. The floor of the fossa ovalis is formed by the septum secundum. 43. The suprarenal artery is derived from a lateral splanchnic artery. 44. The pulmonary trunk is derived from the sixth aortic arch.
45. The pars anterior of the pituitary gland is ectodermal in origin. 46. The most characteristic event in the fourth week of development is the formation of the primitive streak. 47. At puberty there are about two million follicles in both ovaries. 48. The cuneiform cartilages develop in the aryepiglottic folds. 49. The respiratory portion of the bronchial tree is formed during the glandular stage.
50. Mittelsmerz pains occur in some women during menstruation. 51. The upper lateral cutaneous nerve of the arm is a branch of radial nerve. 52. The axillary nerve has no cutaneous branches. 53. The carpal bones are cartilaginous at birth. 54. The motor nerve supply to the intrinsic muscles of the hand is from the first thoracic nerve.
55. The basilic vein in the cubital fossa is superficial to the bicipital aponeurosis. 56. The radial collateral ligament extends from the styloid process of the radius to the scaphoid bone and is crossed by the radial artery. 57. The floor of the cubital fossa is formed by supinator and brachialis. 58. The superficial palmar arch is deep to the digital branches of the median nerve. 59. The ulnar nerve lies medial to the hook of hamate.
60. The shaft of the humerus begins to ossify in the 7th week of fetal life. 61. Trapezius forms the lateral border of the triangle of auscultation. 62. The ulnar artery lies medial to the ulnar nerve. 63. The medial two lumbricals arise by a single head from the tendons of flexor digitorum profundus. 64. The subscapularis extends and medially rotates the shoulder joint.
65. In the cubital fossa the brachial artery lies medial to the median nerve. 66. The interosseous recurrent artery anastomoses with the median collateral artery. 67. The deep palmar arch lies 1 - 2cm proximal to the superficial palmar arch and it gives off the palmar digital arteries. 68. The palmar cutaneous branch of the median nerve passes deep to the flexor retinaculum. 69. The pisiform bone may be considered as a sesamoid bone in the tendon of flexor carpi ulnaris and appears about the 10th year of life.
70. Thoracodorsal nerve is cutaneous to the dorsal surface of the thorax. 71. The extensor pollicis longus grooves the dorsal tubercle of the radius. 72. The infraspinatus is the chief lateral rotator of the arm. 73. Compression of the median nerve in the carpal tunnel will produce clawing of the index and middle fingers. 74. The epiphysis of the first metacarpal bone is at its proximal end. 143
75. In carpal tunnel syndrome there is loss of sensation over the thenar eminence. 76. The left superior intercostal vein drains into the superior vena cava. 77. During inspiration the bronchi become linger and wider. 78. The opening of the coronary sinus into the right atrium has a valve. 79. The right coronary supplies the sinu-atrial node.
80. The left vagus nerve is anterior to the left brachiocephalic vein. 81. The thoracic sympathetic trunk lies in front of the necks of the ribs. 82. The lung tissue has no lymph vessels. 83. The root of the lung lies opposite the bodies of the 4th, 5th and 6th thoracic vertebrae. 84. The left coronary artery supplies the atrioventricular node.
85. The serous pericardium forms the epicardium. 86. The left ureter is posterior to the uterine artery as the lie lateral to the cervix of the uterus. 87. The right suprarenal gland is anterior to the inferior vena cava. 88. The Meckel's diverticulum receives blood supply from the branches of superior mesenteric artery. 89. The paranephric fat helps to maintain the kidney in position.
90. The middle rectal artery is a branch of the internal iliac artery. 91. The vascular caecal fold contains the anterior caecal artery. 92. The fibrous fascial of the kidney is derived from the transversalis fascia. 93. Transversus abdominis contributes to the coverings of the spermatic cord. 94. Referred pain from the appendix is felt around the umbilicus.
95. The pyloric orifice is the most fixed part of the stomach. 96. The mucous membrane of the anal canal presents six to ten horizontal folds called anal columns in the adult. 97. The para-umbilical veins anastomose with the veins of the anterior abdominal wall. 98. The sac of the inguinal hernia lies inferomedial to the pubic tubercle. 99. The anterior superior iliac spine is at the level of L5. 100. The kidney moves about 2.5cm in the vertical direction during inspiration.
144 2ND SEMESTER EXAMINATION
TIME ALLOWED: 1hr
Indicate whether the following statements are TRUE or FALSE by writing the alphabet "T" or "F" on the left hand side of the question. Each correct answer scores one point. For each wrong answer you lose one point. There is no score for questions not attempted.
1. Paneth cells are characteristic of the crypts of Lieberkuhn. 2. Lamina propria consists mainly of the type III collagen. 3. Sebaceous glands are holocrine in their mode of secretion. 4. Golgi type II neurons have very long projecting axons.
5. The sour taste sensation is distributed to the dorsum of the tongue. 6. A hepatic lobule contains one portal canal at its centre. 7. A portal lobule contains one central vein at its centre. 8. Auerbach's plexus is found in the submucosa of the duodenum. 9. Transitional epithelium does not lie on a basement membrane.
10. The sarcomere of the skeletal muscle contains two A-bands. 11. The neuroglia do not participate in the myelination process of neuron. 12. Sweat glands are good examples of simple coiled tubular glands. 13. The fasciculi of the skeletal muscles are covered by the endomysium. 14. The renal columns of Bertin do not extend into the renal medulla.
15. The submucosa of jejunum contains more Peyer's patches than the ileum. 16. The red pulp of the spleen contains more lymphatic nodes than sinusoids. 17. The mucosa of ureter has no muscularis mucosa. 18. The epithelial lining of vagina is stratified squamous of the keratinized type. 19. The space of disse separates the Kupffer cells from the sinusoids.
20. The exocrine portion of the pancreas forms a simple tubuloacinar gland. 21. Chorionic gonadotropins reach a peak level in the urine in the third trimester of pregnancy. 22. Completion of the secondary maturation division occurs on fertilization. 23. In the sixth month of intrauterine life there are about six million follicles in both ovaries. 24. Premature rupture of zona pellucida results in placenta previa.
25. Melanocytes of the skin are derived from the neural crest. 26. The chorion consists of trophoblast and extraembryonic gonadotropin. 27. The placenta secretes estrogen, progesterone and chorionic gonadotropin. 28. Oligohydramnios is associated with renal agenesis. 29. Meckel's diverticulum may contain pancreatic tissue.
30. The septum transversum contributes to the formation of the fibrous pericardium. 31. Pleuropericardial membrane participates in the formation of the diaphragm. 32. The junction between the excretory and collecting sections of the kidney is at the proximal end of distal convoluted tubule. 33. In Tetralogy of Fallot there is shunting of blood from left to right. 34. Crista terminalis of the adult heart is derived from the right venous valve. 145
35. The renal artery is derived from a lateral splanchnic artery. 36. Coronary sinus develops from the left horn of the sinus venosus. 37. The medial umbilical ligament is formed by the urachus. 38. A double aortic arch is due to persistence of right fourth aortic arch. 39. The original epithelium of the trigone of the bladder is mesodermal in origin.
40. The respiratory bronchioles are formed during the canalicular stage. 41. The scaphoid, lunate and triquetrum present a uniformly convex surface for articulation at the radio-carpal joint. 42. At the level of insertion of coracobrachialis, the median nerve crosses deep to brachial artery to become medial. 43. Pronation occurs at the elbow and wrist joints. 44. The following muscles medially rotate the arm: latissimus dorsi, teres major and infraspinatus.
45. The female breast lies entirely beneath the deep fascia. 46. The cords of the brachial plexus are named after their relationship to the 3rd part of the axillary artery. 47. The musculocutaneous nerve passes deep to the Deltoid muscle. 48. In pronation, the ulna rotates over the radius. 49. The pectoralis major muscle can act as a muscle of respiration when the arms are fixed.
50. The radial bursa encloses the tendon of flexor pollicis longus. 51. In relation to the radius and ulna, the radius is the principal weight or force transmitting bone of the forearm. 52. The muscle pair that elevates the arm above the head is levator scapulae and serratus anterior. 53. Regarding the segmental cutaneous supply of the upper limb, C4 supplies the skin over the shoulder tip. 54. The mid-palmar space lies in front of the 3rd, 4th and 5th metacarpals.
55. The "Erb's" point is where C5 and C6 unite to form the upper trunk. 56. Serratus anterior rotates the scapula medially. 57. The ulnar artery at the wrist lies deep to the flexor retinaculum. 58. The accessory hemi-azygos vein is formed by the 4th to 8th intercostal veins. 59. The pleurae cross the mid-axillary line at the level of 8th rib.
60. The inferior vena cava (IVC) pierces the central tendon of the diaphragm at the level of 6th chondrosternal joint. 61. The cisterna chyli lies on the bodies of the 1st and 2nd lumbar vertebrae. 62. The Highest intercostal artery gives rise to the 1st and 2nd anterior intercostals arteries. 63. The superior vena cava (SVC)is formed at the level of the sternal angle behind the right 2nd costal cartilage. 64. The azygos vein drains into the right brachiocephalic vein.
65. The coronary sinus is about 3cm long. 66. The right coronary artery supplies the sinu-atrial node. 67. The mitral valve lies behind the sternal end of the 3rd costal cartilage. 146 68. The Costal pleura and the peripheral parts of the diaphragm are innervated by the phrenic nerve. 69. Ossification of calcaneus begins in the 6th month of intrauterine life.
70. Deep external pudendal artery is a branch of external iliac artery. 71. Anterior division of obturator nerve supplies pectineus. 72. The posterior wall of the femoral sheath is pierced by the femoral branch of the genitofemoral nerve. 73. The trochanteric anastomosis provides the main blood supply to the head of the femur in the adult. 74. Zona orbicularis is formed by the ischiofemoral ligament.
75. The sciatic nerve is supplied by the inferior gluteal artery. 76. The Tibialis posterior is the bulkiest and most powerful of the three deep muscles of the calf. 77. Flexor hallucis brevis is a muscle of the third layer of the sole and is supplied by the lateral plantar nerve. 78. The posterior talofibular ligament is attached to malleolar fossa. 79. The spring ligament has attachment to sustentaculum tali.
80. Inversion and eversion occur mainly at the subtalar joint. 81. In the female, the transverse diameter of the acetabulum is less than the distance from the pubic tubercle to the acetabular margin. 82. The proximal epiphysis of the fibula appears before the distal epiphysis. 83. The internal oblique muscle is associated with the falx inguinalis and cremasteric muscle. 84. The cremaster muscle is innervated by the iliohypogastric nerve.
85. The uncinate process of the pancreas lies in front of the superior mesenteric artery. 86. The supracristal plane is at the level of the fourth lumbar vertebra. 87. The genital branch of the genitofemoral nerve and the ilioinguinal nerve traverse the inguinal canal. 88. The cremasteric artery is a branch of inferior epigastric artery. 89. The portal vein begins behind the neck of the pancreas.
90. The left gonadal vein drains into the inferior vena cava. 91. The renal fascia encloses both the kidney and suprarenal gland. 92. The ureter lies inferior and posterior to the uterine artery. 93. The inferior fascia of the urogenital diaphragm is the perineal membrane. 94. The interosseous sacro-iliac ligaments are the strongest ligaments of the sacro-iliac joint.
95. Indirect inguinal herniae pass medial to the inferior epigastric artery. 96. The posterior labial nerves are branches of the obturator nerve. 97. The prostatic venous plexus communicates with the vertebral venous plexus. 98. The paraurethral ducts open into the vestibule of the female genitalia. 99. The stomach is separated from the liver by the lesser sac. 100. The root of the mesentery is about 25cm long. 147 2ND PROFESSIONAL EXAMINATIONS FOR MB.BS/BDS DEGREES PAPER 1 - MULTIPLE CHOICE QUESTIONS (MCQ) ANSWER ALL 250 QUESTIONS TIME ALLOWED - 3 HOURS SECTION A: (1-100) SELECT THE MOST APPROPRIATE ANSWER AND CIRCLE IT IN INK 1. Pronation: a) Occurs at the wrist joint b) Produced by pronator teres only c) The dorsal surface of the radius and hand face anteriorly and the thumb lies medially d) Occurs at the elbow and wrist joints e) All are correct
2. The bicipital aponeurosis passes obliquely over : a) Brachial artery b) Median nerve c) Radial nerve d) Cephalic vein e) 'A' and 'B'
3. The Anatomical snuff box contains: a) Cutaneous branch of the radial nerve b) Ulnar nerve c) The Radial artery d) (A) and (B) e) (A) and (C)
4. The muscle pair which elevates the arm above the head: a) Trapezius and pectoralis minor b) Levator scapulae and serratus anterior c) Trapezius and serratus anterior d) Rhomboid major and serratus anterior (e) Levator scapulae and pectoralis minor
5. The Femoral Canal: a) Is the lateral compartment of the femoral sheath b) Is about 2.5cm in length c) Contains the femoral branch of the genito-femoral nerve d) Is posterior to the inguinal ligament at its proximal end e) 'B' and 'D' are correct
6. The Obturator nerve: a) Is from the dorsal offshoot of ventral rami L2, 3 and 4 b) Supplies both the hip and knee joints c) Has no cutaneous branches d) Has an anterior branch which is anterior to the adductor magnus muscle e) Both 'A' and 'C' are correct
7. Tibia: a) Its articulations with the fibula are both synovial b) The extensor hallucis longus muscle is attached to its antero- lateral surface c) The flexor hallucis longus is attached to its posterior surface d) There may be a separate epiphysis for the tuberosity e) 'A' and 'D' 148 8. All of the following muscles insert on the greater trochanter of the femur except: a) Gluteus medius b) Inferior gemellus c) Quadratus femoris d) Gluteus minimus e) Obturator internus
9. Severing the femoral nerve would result in: a) Impairment of flexion of the hip and extension of the knee b) Total loss of extension of the hip and flexion of the knee c) Total loss of flexion of the hip and impairment of extension of the knee d) Total loss of flexion of the hip and extension of the knee e) Impairment of flexion of the hip and total loss of extension of the knee
10. The epiphysis for the lower end of femur appears at: a) 7th month of intrauterine life b) 8th month of intrauterine life c) 9th month of intrauterine life d) Within one year after birth e) Second year of life
11. Which of the following arteries do not participate in the cruciate anastomosis around the hip joint? a) Inferior gluteal b) Superior gluteal c) Transverse branch of the medial circumflex femoral d) Transverse branch of the lateral circumflex femoral e) First perforating branch of the profunda femoris
12. Dorsiflexion and eversion of the foot are totally lost. The toes cannot be extended. The nerve that is damaged is: a) Femoral b) Common peroneal c) Superficial peroneal d) Obturator e) Tibial
13. The following branches arise from the radial nerve in the spiral groove except: a) Nerve to lateral head of triceps b) Nerve to anconeus c) Nerve to brachioradialis d) Posterior cutaneous nerve of forearm e) Lower lateral cutaneous nerve of arm
14. The nerves to the knee joint are typically derived from the: a) Femoral b) Obturator c) Tibial d) Common peroneal e) All of the above
149 15. The greater sciatic notch transmits all of the following except the: a) Piriformis muscle b) Superior gluteal nerve c) Obturator externus d) Posterior femoral cutaneous nerve e) Internal pudendal artery
16. Which of the following statements is correct in comparing the male and female pelves: a) The pubic arch is wider and more rounded in males b) The pubic tubercles are more widely separated in males c) The greater sciatic notches are wider in males d) The distance from the pubic tubercle to the acetabular margin is greater than the diameter of the acetabulum in the female e) None of the above is correct
17. The following are true of ligamentum arteriosum except: a) It is a vestigial structure b) It connects the left pulmonary artery with the arch of the aorta c) The left recurrent laryngeal nerve hoods around it d) It develops from proximal part of sixth left arch artery e) All the statements are correct
18. At surgery, anticipate finding the following structures behind the first part of the duodenum a) Gastroduodenal artery b) Common bile duct c) Portal vein d) "A" and "C" only e) "A", "B" and "C"
19. The duodeno-jejunal flexure is held in place by the: a) Falciform ligament b) Suspensory muscle of the duodenum c) Greater omentum d) Lesser omentum e) Hepatoduodenal ligament
20. All the statements below are true of the lacunar ligament except: a) Is at the medial end of the inguinal ligament b) In the erect position has the spermatic cord on its posterior inferior surface c) Is rolled under the spermatic cord and attached along the perineal fascia d) Has its apex medially at the pubic tubercle e) Is closely associated with the medial wall of the femoral canal
21. The dorsal root of the spinal cord contains: a) Only myelinated fibres b) Only unmyelinated fibres c) Only small myelinated fibres and large unmyelinated fibres d) Only small unmyelinated fibres and large myelinated fibres e) None of the above is correct
150 22. An important receptor for temperature in the body a) Naked nerve fibres on the skin b) End bulb of Krause c) Peritrichial ending d) Spindle fibres e) The organ of Corti
23. The term "Decussation" means: a) A chain of neurons leading from a receptor to a higher centre b) Fibres that cross the midline to terminate in an area that is not equivalent to their origin c) That the origin and termination of the crossing fibres are equivalent areas on opposite sides of the midline plane d) Lemniscus e) None of the above definitions is correct
24. Unilateral lesion of the medial meniscus will result in: a) Loss of pain and temperature on the same side of the body b) Contralateral deficit of proprioception c) Loss of pain temperature on the other side of the body d) Ipsilateral deficit of proprioception e) All of the above
25. The cell bodies of the trigeminal afferent fibres are located in: a) The descending nucleus of V b) Main sensory nucleus of V c) Motor nucleus of B d) Geniculate ganglion e) Semilunar ganglion
26. The secondary oocyte contains: a) First polar body; 2n-chromosome; 2n DNA b) Second polar body; n-chromosome; n DNA c) First polar body; n-chromosome; 2n DNA d) First polar body; n-chromosome; n DNA e) Second polar body; n-chromosome; n DNA
27. The blastocyst: a) Is usually located in the uterus b) Contains fluid c) Encloses a cavity d) Only "A" and "B" are correct e) All are correct
28. Sacrotuberous ligament is a degenerate part of: a) Coccygeus b) Biceps femoris c) Adductor magnus d) Semitendinosus e) Semimembranosus
151 29. A pregnant woman began her last normal menstrual period on 20 November 2006. Her expected date of delivery (EDD) is: a) 27 August 2007 b) 20 August 2007 c) 25 August 2007 d) 20 September 2007 e) None of the above
30. The following statements about inferior epigastric artery are true except: a) A branch of external iliac artery b) Arises near the midinguinal point c) Ascends lateral to the deep inguinal ring d) Forms the lateral boundary of the inguinal triangle e) Anastomoses with the superior epigastric artery
31. Lacteals are: a) Venules b) Arterioles c) Milk channels in the small intestine d) Lymphatic vessels e) None of the above
32. The so-called "Zone of Exclusion" is the area of cytoplasm that is devoid of other cytoplasmic components and is closely associated with the: a) Nucleolus b) Mitochondrion c) Golgi apparatus d) Smooth endoplasmic reticulum e) Granular endoplasmic reticulum
33. "Herring bodies" are elaborated at the: a) Parafollicular cells of the thyroid gland b) Zona fasciculata of the adrenal cortex c) Supra-optic and paraventricular nuclei of the hypothalamus d) Oxyphil cells of the parathyroid gland e) None of the above
34. An enzyme secreting cell of the stomach: a) Chief cell b) Paneth cell c) Oxyntic cell d) Goblet cell e) All of the above
35. Columns of Morgagni are diagnostic of the : a) Rectum b) Colon c) Stomach d) Caecum e) Vermiform appendix
152 36. All are true of the elbow joint except: a) The capitulum and the trochlea of the humerus take part in the formation of the joint. b) The joint is a synovial joint of hinge variety c) The capsular ligament is strengthened by anterior, posterior medial and lateral ligaments. d) The synovial membrane of the elbow joint is continuous with synovial membrane of superior radio-ulnar joint e) All the above are correct
37. In the radio-ulnar joints: a) The superior radio-ulnar joint is a synovial joint of the pivot variety. b) In the middle radio-ulnar joint, the fibres of the interosseous membrane pass downwards and laterally. c) The middle radio-ulnar joint transmits pressure and shocks from the radius to the ulna. d) The anterior surface of the interosseous membrane is related to deep flexors e) In the inferior radio-ulnar joint, the head of the ulna articulates with the ulnar notch of the radius
38. All are true of pronation and supination except: a) They are rotatory movements around a vertical axis b) During movement, the head of ulna rotates within the annular ligament c) Brachioradialis acts most effectively in the semi-prone position d) In pronation the radius lies forwards e) In supination the ulna lies medially
39. All are true of radio-carpal (wrist) joint except: a) The proximal surface of this joint is formed by the lower articular surface of radius and articular disc b) The distal face of the joint is formed by scaphoid, lunate and triquetral bones c) The joint has a capsular ligament d) The distal end of ulna does not take part in this joint e) Palmaris longus and extensor carpi ulnaris extend the wrist
40. The Sacral plexus: a) Is composed of dorsal rami of the lumbar and sacral spinal nerves b) Is composed of only motor fibres c) Innervates the lower limb d) Is the only important nerve plexus in the body e) Contains motor fibres whose cell bodies of origin are within the dorsal root ganglion
41. The descending genicular artery is usually a branch of the a) Obturator artery b) Femoral artery c) Profunda femoris artery d) Posterior tibial artery e) Anterior tibial artery
42. Which of the following structures emerge from pelvis via the lesser sciatic foramen? a) Superior gluteal artery b) Obturator internus muscle c) Posterior femoral cutaneous nerve d) Pudendal nerve e) Sciatic nerve
43. The posterior cruciate ligament functions primarily to limit______movement of the femur on the tibia: 153 a) Anterior b) Posterior c) 'A' and 'B' d) Medial e) Lateral 44. The following structures lie in front of scalenus anterior except: a) Suprascapular artery b) Transverse cervical artery c) Costocervical trunk d) Phrenic nerve e) Subclavian vein 45. The cortical branches of middle cerebral artery supply: a) All of the precentral gyrus b) All of the primary auditory cortex c) A small part of primary visual cortex d) The cingulate gyrus e) All of the above 46. All these muscles are innervated by the medial plantar nerve except: a) Flexor hallucis brevis b) Flexor digitorum brevis c) First lumbrical d) Abductor hallucis e) Adductor hallucis
47. The relationship between estrogen and the LH "surge" at the midpoint of the menstrual cycle is an example of: a) Positive feedback regulation b) Negative feedback regulation c) Localized stimulation of estrogen secretion by LH d) Localized inhibition of estrogen secretion by LH e) None of the above regulatory mechanisms 48. Unilateral destruction of the motor cortex causes: a) Contralateral paresis and hypotonia b) Contralateral paresis and hypertonia c) Contralateral incoordination and hypertonia d) Contralateral tremor and hypertonia e) Contralateral incoordination and tremor
49. A Graafian follicle immediately before ovulation contains one: a) Oogonium b) Mature ovum c) Primary oocyte d) Primordial germ cell e) Secondary oocyte
50. The final maturation change in spermatozoa occurs in the: a) Seminiferous tubules b) Epididymis c) Vas deferens d) Ejaculatory duct e) Female reproductive tract
51. Blastocyst cavity is the forerunner of the: 154 a) Extraembryonic coelom b) Intraembryonic coelom c) Exocoelomic cavity d) Amniotic cavity e) Peritoneal cavity
52. The two principal components of the mature placenta are: a) Chorion frondosum and decidua capsularis b) Chorion frondosum and decidua parietalis c) Chorion frondosum and decidua basalis d) Chorion laeve and decidua basalis
53. Syncytiotrophoblastic lacunae are the forerunners of the: a) Extraembryonic coelom b) Exocoelomic cavity c) Intervillous spaces d) Decidua basalis e) Chorionic cavity
54. The definitive Notochord: a) Later differentiates into the spinal cord b) Parts of it persist as nucleus pulposus c) Totally obliterates after development of the neurenteric canal d) Is derived from endoderm e) Gives rise to the neural tube
55. Sclerotome cells can differentiate into: a) Osteoblasts b) Angioblasts c) Amnioblasts d) Neuroblasts e) None of the above
56. The first system to reach a functional state is the a) Central nervous system b) Digestive system c) Urinary system d) Cardiovascular system e) Respiratory system
57. The Meiotic stage of the oocyte at the time of fertilization (sperm penetration) is: a) Metaphase I b) Telophase I c) Prophase II d) Metaphase II e) Telophase II
58. The Penicilli arteries are immediately preceded by: a) Trabecular arteries b) Artery of the pulp c) Central arteries d) Sinusoid e) Sheathed arteries
155 59. Turner's Syndrome is characterized by: a) XO b) XXY c) YO d) XX e) XYX 60. The inner plexiform layer of retina contains: a) Axons of the bipolar cells b) Dendrites of the photoreceptor cells c) Axons of photoreceptor cells d) Dendrites of the bipolar cells e) Nuclei of Muller's cells 61. Mitotic activity is characteristic of: a) Stratum basale b) Stratum granulosum c) Stratum lucidum d) Stratum corneum e) 'A' and 'B' only 62. In the vermiform appendix: a) Numerous goblet cells occur in the mucosa b) Villi with crypts of Lieberkuhn are present throughout c) Argentaffin cells are less numerous than elsewhere d) Numerous lymphoid nodules (with very large germinal centres) are found in the lamina propria e) 'A' and 'D' 63. The type II pneumocytes (granular or greater alveolar cells): a) Contain lamellated bodies b) Are the source of surfactant c) Are vacuolated when seen under light microscope d) All of the above e) None of the above
64. Clara cells: a) Contain lamellated bodies b) Secrete mucus c) Are located in the bronchioles d) Are phagocytic cells e) None of the above
65. The Human pineal gland as it ages contains inclusions known as: a) Corpora amylacea b) Corpora arenacea c) Corpora haemorrhagica d) Corpora albicans e) Corpora libera
66. A Corpus luteum on regressing becomes: a) An atretic follicle b) A corpus albicans c) A revascularized structure d) A mass of decidual cells e) None of the above
67. Acidification of the urine takes place in the 156 a) Distal convoluted tubule b) Proximal convoluted tubule c) Thin limb of Henle d) Thick limb of Henle e) Collecting duct 68. During contraction of the skeletal muscle, the _____ band decreases significantly in width: a) A b) I c) M d) N e) Z 69. All have a common characteristic except: a) Temporalis muscle b) Medial pterygoid muscle c) Frontalis muscle d) Masseter muscle e) Lateral pterygoid muscle 70. All have a common characteristic except: a) Optic foramen b) Foramen ovale c) Carotid foramen d) Foramen rotundum e) Stylomastoid foramen
71. Anterior two-thirds of the tongue develops from: a) Lateral lingual swellings b) Tuberculum impar c) Hypobranchial eminence d) 'A' and 'B' e) 'A', 'B' and 'C'
72. The left recurrent laryngeal nerve extends to a lower level because of: a) Persistence of left sixth arch artery b) Presence of the arch of aorta c) Persistence of third arch artery d) Left pulmonary artery e) Unknown reasons
73. The following are the muscles of the second layer of the back of the neck except: a) Levator scapulae b) Splenius c) Trapezius d) The rhomboids e) Serratus posterior
74. Which of the following is not a hyaline cartilage? a) Corniculate b) Thyroid c) Cricoid d) Arytenoid e) Tracheal rings
75. The following are true of nasal conchae except: a) They are curved bony plates 157 b) All these are processes of the ethmoid c) Inferior concha is an independent bone d) Covered with mucoperiosteum e) Interiorly they enclose a space
76. The following are true of the chorda tympani except: a) Branch of the facial b) Supplies submandibular gland c) Supplies sublingual glands d) Joins the glossopharyngeal nerve e) Supplies sensory fibres to anterior two-thirds of the tongue
77. The following are the parasympathetic ganglia in the head except: a) Ciliary b) Sphenoethmoidal c) Otic d) Submandibular e) Pterygopalatine
78. Sympathetic reaction causes the following except: a) Constriction of cutaneous arteries b) Decreases peristaltic movements of the gut c) Relaxation of the sphincters d) Increase in the heart rate e) Liberation of adrenaline
79. The following are true of the structures in the foot of the lung except: a) Upper pulmonary vein in front b) Pulmonary artery in the middle c) Bronchus behind the pulmonary vessels d) Bronchial vessels anterior to the bronchus e) Bronchial vessels posterior to the bronchus
80. The following are true of the right principal bronchus except: a) Wider, shorter and more vertical than the left b) About 2.5cm long c) Enters the lung opposite the fifth thoracic vertebra d) Foreign bodies are more likely to enter it e) Pulmonary artery arches over its superior surface
81. The right border of the heart: a) Extends from right second intercostal space to sixth costal cartilage b) Closely related to the right phrenic nerve c) Right pericardiacophrenic vessels are intimately related to it d) Posterior vagal trunk is not and immediate relation e) All of the above are correct
82. The following are true of coronary sinus except: a) It lies in the posterior part of coronary sulcus b) All cardiac veins drain into it c) Its opening is guarded by a semilunar valve d) It represents the left horn of sinus venosus e) It is about 2-3cm long
83. Superficial cardiac plexus is located: 158 a) Anterior to the right pulmonary artery b) Posterior to the right pulmonary artery c) Below the bifurcation of the trachea d) Above the bifurcation of the trachea e) Above the arch of aorta
84. Pharyngo-tympanic tube develops from: a) First pharyngeal pouch b) Second pharyngeal pouch c) Tubotympanic recess d) Tympanic antrum e) First pharyngeal cleft
85. Superior parathyroid develops from: a) First pharyngeal pouch b) Second pharyngeal pouch c) Third pharyngeal pouch d) Fourth pharyngeal pouch e) Ultimo branchial body
86. The following are the derivatives of the second pharyngeal arch except: a) Stapes b) Stylohyoid ligament c) Styloid process d) Lesser cornu of hyoid bone e) Malleus 87. The following are true of the hypothalamo-hypophyseal system except: a) It is related to neurosecretion b) Involves neurovascular mechanism c) Includes supraoptic hypophyseal tract d) Produces Herring's bodies e) Produces adrenocorticotropic hormone 88. The immediate lateral relation of the lentiform nucleus is: a) Internal capsule b) External capsule c) Claustrum d) Insular cortex e) Cerebral cortex 89. The embryo is called a fetus after: a) Fourth week b) Eight week c) Twelfth week (d) Sixteenth week e) Twenty-eight week 90. Basal vein is formed by the confluence of: a) Anterior cerebral vein b) Deep cerebral vein c) Striated vein d) "A", "B" and "C" e) None of the above
91. The subarachnoid space of the spinal cord extends up to: a) First lumbar vertebra 159 b) Fourth lumbar vertebra c) Fourth sacral vertebra d) Second sacral vertebra e) First coccygeal segment
92. The following are the features of the floor of the fourth ventricle except: a) Tubercle of nucleus gracilis b) Hypoglossal triangle c) Vagal triangle d) Inferior fovea e) Superior fovea
93. The intrinsic muscles of the tongue are supplied by the: a) Facial nerve b) Mandibular nerve c) Glossopharyngeal nerve d) Hypoglossal nerve e) Internal branch of the accessory nerve
94. The articular disc of the temporomandibular joint is attached to the: a) Temporalis muscle b) Medial pterygoid muscle c) Lateral pterygoid muscle d) Posterior belly of the digastric muscle e) Masseter muscle
95. The vocal cords are abducted by the: a) Thyroarytenoid muscle b) Lateral cricoarytenoid muscle c) Posterior cricoarytenoid muscle d) Inter-arytenoid muscle e) Cricothyroid muscle
96. The main sensory nerve to the upper lip is the: a) External nasal nerve b) Buccal nerve c) Facial nerve d) Anterior superior alveolar nerve e) Infraorbital nerve
97. The secretomotor postganglionic fibres supplying the lacrimal gland arise from the: a) Ciliary ganglion b) Pterygopalatine ganglion c) Otic ganglion d) Superior cervical ganglion e) Geniculate ganglion
98. Meckel's cartilage contributes to the formation of: a) Mandible b) Hyoid bone c) Incus d) Stapes e) Malleus
160 99. The placental barrier is composed of: a) Fetal capillary endothelium b) Trophoblast c) Maternal capillary endothelium d) All of the above e) "A" and "B" only
100. The cartilaginous malleus, incus and stapes ossify: a) In the fourth month of intrauterine life b) In the eight month of intrauterine life c) Soon after birth d) Just before birth e) At puberty SECTION B: Which of the following A- J is most closely associated with 1-10? Write your chosen alphabet in front of the appropriate figure. Each choice may be used only once. COLUMN "A" COLUMN "B" 101. GVA fibres in greater A. Nucleus ambiguus palatine nerve. 102. Proprioceptive fibres B. Dorsal sensory nucleus of X 103. GVE fibres in greater C. Inferior salivatory nucleus superficial petrosal nerve 104. SVE fibres in glosso- D. Motor nucleus of VII pharyngeal nerve (IX) 105. GSA fibres in ophthalmic E. Superior salivatory nucleus division of trigeminal nerve (V) 106. GVA fibres in sinu-carotid nerve of F. Abducens nucleus vagus (X) 107. SVE fibres in buccinator branch of G. Mesencephalic nucleus facial nerve 108. GVE (preganglionic parasympathetic) H. Edinger-Westphal nucleus fibres in lesser petrosal nerve 109. GVE(preganglionic parasympathetic I. Nucleus solitarius fibres in oculomotor nerve (III) 110. SE fibres in abduscens nucleus J. Descending (main) nucleus of V
COLUMN "C" COLUMN "D"
111. Is pierced by internal laryngeal A. Piriform recess
112. Is located directly below sella turcica B. Arachnoid granulation
113. Serves as attachment for the C. Lamina terminalis sphenomandibular ligament 114. A cavity of the laryngopharynx. D. Corniculate cartilage 115. Acts as a posterior support for the dens E. Tympanic canaliculus 116. Located in the superior sagittal sinus F. Thyrohyoid membrane
117. Forms part of anterior wall of the third G. Lingula of mandible ventricle 118. Supplies(SE) fibres toinfrahyoid H. Ansa hypoglossi muscles 119. Located in the ary- epiglottic folds I. Cruciform ligament 120. Transmits the tympanic nerve of IX J. Sphenoidal sinus
161 COLUMN "E" COLUMN "F" 121. Somatic cells A. Tropocollagen 122. Cells with multiple of haploid number B. Histamine of chromosomes 123. A cell containing an abnormal number C. Cell associated lymphocytes of chromosomes but not a multiple 124. Nucleolus D. Circulating antibody 125. Genes E. Phagocytosis 126. Fibroblast F. m-RNA 127. Mast cell G. DNA 128. Pericytes (Rouget) H. Aneuploid 129. Lymphocytes I. Diploid 130. Plasma cells J. Polyploid
COLUMN "G" COLUMN "H" 131. Crista terminlis A. Somatopleure 132. Parietal peritoneum B. Heuser’s node 133. Longitudinal muscle of ileum C. Paraxial mesoderm 134. Notochord D. Right venous valve 135. Somites E. Cardiac muscle 136. Heuser’s membrane F. Mesonephric duct 137. Myoepicardial mantle G. Splanchnopleure 138. Pleuroperitoneal membrane H. Foregut 139. Gartner’s duct I. Diaphragm 140. Tracheo-bronchial groove J. Primary yolk sac 162 SECTION C: Indicate whether the following statements are true or false by writing the alphabet "T" or "F" on the left hand side of the question. Each correct answer scores one point. For each wrong answer you lose one mark.
141. After the ingestion of a meal rich in glucose, glucose is first found in Von Kupffer cells. 142. The dust cells are phagocytic. 143. The spleen has extensive lymphatic drainage into the cisterna chyli. 144. The liver is functionally divisible into four "Hepatic segments".
145. The left kidney is entirely retroperitoneal. 146. The urinary bladder has a well-developed muscular internal urethral sphincter at the neck of the bladder in both sexes. 147. The tectum is directly continuous in front with the cerebral peduncles. 148. The vas deferens crosses the ureter superiorly in the pelvis near the bladder. 149. The scrotum is innervated anteriorly by the ilioinguinal nerve.
150. The ovary has a thin capsule of connective tissue, the tunica albuginea. 151. The ovary is connected to the uterus by the round ligament of the uterus. 152. The uterine tubes if ligated (tied off) would prevent further uterine menstrual cycles. 153. The posterior interosseous nerve occasionally presents a pseudoganglion. 154. The vagina has numerous mucous glands which lubricate its wall.
155. The vagina is significantly supported by the pubococcygeus muscle. 156. The clitoris has a root which consists primarily of 2 crura. 157. The deep perineal pouch contains the deep dorsal vein of the penis. 158. The greater omentum forms part of the border of the epiploic foramen of Winslow. 159. The indirect hernia evaginates both peritoneum and transversalis fascia as the "hernial sac".
160. Descending colon receives its parasympathetic supply from the pelvic splanchnic nerves (nervi erigentes) 161. A hysterosalpingogram may demonstrate patency of the uterine tubes. 162. Elastic cartilage is absent in the trachea. 163. The epithelium of the red free margin of the lip contains soft keratin. 164. Ducts directly connected to secretory units are termed intercalated.
165. Aqueous humour is reabsorbed in the posterior eye chamber. 166. Megakaryocyte is the stem-cell of platelets. 167. The clavipectoral fascia is perforated by the lateral pectoral nerve, thoraco-acromial artery and the basilic vein. 168. The floor of acetabulum is primarily articular in function. 169. In Erbs paralysis there is adduction, lateral rotation and pronation.
170. Pampiniform plexus is formed by the testicular veins. 171. The liver can be readily palpated below the costal margin on the right side, in an adult healthy person. 172. The right pulmonary artery is longer than the left. 173. All sternocostal joints are of the synovial variety. 174. A perforated gastric ulcer may bleed into the omental bursa.
175. If the hepatic artery were ligated near the liver, almost the entire blood supply to the liver would be obstructed. 176. If necessary, the spleen may be removed from an adult person with no apparent ill effects. 177. Trochlear nerves are situated in the interpeduncular fossa. 163 178. A gall stone may obstruct both the common bile duct and the main pancreatic duct if the stone becomes lodged in the duodenal ampulla of Vater. 179. Obstruction of the inferior vena cava, superior to the renal veins would probably cause a so- called "caput medusae".
180. At birth the tip of the conus medullaris is at the level of 3rd lumbar vertebra. 181. Inguinal hernias should be common in women, because a spermatic cord is not present within the inguinal canal. 182. The diameters of the pelvic inlet and pelvic outlet can be accurately measured on the person herself, using callipers. 183. The pelvic inlet has a gynaecoid shape in about 42% of women. 184. The tuberosity of the ilium is a palpable landmark for injections into the sacroiliac joint cavity.
185. The medial end of the extensor retinaculum is attached to the triquetral and styloid process of the ulna. 186. Sternoclavicular joint is the only point of articulation of the upper limb with the axial skeleton. 187. The epiphyseal cartilage is more radiopaque than the epiphysis. 188. The facial nerve is a mixed nerve. 189. In the red blood cell the cytoplasm is acidophilic.
190. The most common fixative for light microscopy is formalin. 191. The seventh costal cartilage articulates with the xiphoid process. 192. Cribriform fascia is a modified deep fascia of the thigh. 193. The body of the sternum consists of six fused parts. 194. The lowest part of the costal margin lies at the level of the third lumbar vertebra.
195. Both the superior and inferior apertures of the thorax slope downwards and forwards. 196. Cricothyroid muscle is an abductor of vocal cords. 197. Loss of elasticity of lungs leads to reduction in the tidal volume of air. 198. The intercostal nerves supply all the three intercostal muscles. 199. Muscular branches of the intercostal nerves also supply the limb muscles arising from the thorax.
200. Internal thoracic artery is responsible for the anastomosis between the subclavian and the femoral arteries. 201. Lateral cricoarytenoid muscle is an adductor of the vocal cords. 202. Transverse sinus represents a remnant of an aperture in the dorsal mesentery of the heart between the venous and arterial ends. 203. In the infant, the caecum is conical in shape. 204. Appendix epididymis is the remnant of the cranial portion of the Wolffian duct.
205. Anterior cardiac veins do not enter the coronary sinus. 206. The infundibulum of the right ventricle leads to the pulmonary orifice. 207. The trophoblast contributes to the intraembryonic mesoderm. 208. The conducting system of the heart transmits the impulse through the fibrous skeleton of the heart to the ventricles. 209. The horizontal fissure of the right lung meets the anterior order at the level of fourth costal cartilage.
210. During life the oblique fissure of the right lung begins posteriorly at the level of third thoracic vertebra. 211. Wounds of the scalp bleed profusely but heal rapidly. 212. The mucous lining of the frontal sinus is supplied by both supraorbital and supratrochlear nerves. 213. Emissary veins pierce the skull and open into the venous sinuses inside it. 164 214. Diploic veins are devoid of valves.
215. Meningeal veins drain into the efferent vessels which lie in the outer layer of the dura mater. 216. Facial muscles are invested by the deep fascia of the face. 217. Carotid sheath is formed by the deep fascia of the neck and surrounds the carotid vessels. 218. Supraclavicular nerves supply the skin on the front of the chest. 219. Destruction of the accessory nerve results in wry neck.
220. Both bellies of omohyoid muscle are supplied by the ansa cervicalis. 221. The entire mucoperiosteum on the lateral wall of the nose is olfactory in function. 222. Vocal cords are the same as vocal folds. 223. All intrinsic muscles of the larynx are supplied by the recurrent laryngeal nerve. 224. Hypoglossal nerve supplies all intrinsic and extrinsic muscles of the tongue except the palatoglossus.
225. Fenestra cochlea is closed by the secondary tympanic membrane. 226. Ciliary muscle is an involuntary muscle supplied by post- ganglionic parasympathetic fibres from the ciliary ganglion. 227. The resolving power of the retina is at its maximum at the fovea centralis. 228. The function of the auditory tube is to equalize the pressure in the middle ear with the atmospheric pressure. 229. In majority of cases the septum of the nose is in the median plane.
230. Tegmen tympani separates the tympanic cavity from the middle cranial fossa. 231. Anterior spinocerebellar tract is one of the chief components of the inferior cerebellar peduncle. 232. Ependyma is the epithelium which lines the cavities of the brain. 233. Vibrissae are stout hairs present in the vestibule of the nose. 234. Both preganglionic and postganglionic fibres are myelinated.
235. The olivary nucleus is probably concerned with equilibrium. 236. Superficial perineal space is a closed space. 237. The lateral striate branch of the middle cerebral artery is the artery involved in cerebral haemorrhage. 238. The circulus arteriosus lies in the interpeduncular cistern. 239. Lamina terminalis is a thin layer of white mater.
240. Trochlear nerve is the only nerve attached to the dorsal surface of the brain. 241. The pyramids are bundles of fibres which originate from cells in the cortex of precentral gyrus. 242. Superior belly of omohyoid separates the subclavian triangle from the occipital triangle. 243. The reticular formation controls respiratory and cardiovascular activity. 244. Preganglionic parasympathetic fibres from the superior salivary nucleus pass through the greater petrosal nerve to the pterygopalatine ganglion.
245. The trigone of the bladder is highly distensible and immobile. 246. The menisci are vascular structures. 247. Fissure prima is the first fissure of the cerebellum to appear. 248. The very large size of the cerebellar hemispheres in man is related to the increased size of the cerebral cortex. 249. Inferior medullary velum is related to the median aperture if the fourth ventricle. 250. Stylopharyngeus is an elevator of the larynx. 165 44. APPENDIX I: VERTEBRAL LEVELS
SOME IMPORTANT STRUCTURES AT DIFFERENT VERTEBRAL LEVELS
1ST CERVICAL VERTEBRA (C1) a) The hard palate b) Tip of mastoid process C2: Free margin of the upper teeth DISC BETWEEN C2 AND C3: Superior cervical ganglion C3 a) Hyoid bone b) Symphysis menti c) Beginning of the cervical enlargement of the spinal cord d) Tip of epiglottis C4 a) Bifurcation of the common carotid artery into external and internal carotid arteries. The bifurcation may also be at C3 level. b) Upper border of the thyroid cartilage
C5: Lower border of the thyroid cartilage C6 a) Cricoid cartilage b) Termination of the pharynx and commencement of the oesophagus c) Termination of the larynx and commencement of the trachea d) Middle cervical ganglion e) Superior belly of omohyoid muscle crosses in front of the carotid sheath f) Inferior thyroid artery crosses behind the carotid sheath g) The common carotid artery can be compressed against the carotid tubercle h) The Vertebral artery enters the foramen transversarium i) The inferior and middle thyroid veins enter the thyroid gland
C7: The highest level of the thoracic duct C7/T1: Cervicothoracic (Stellate) ganglion T2: End of the cervical enlargement of the spinal cord T2/T3: Suprasternal (Jugular) notch T3: Base of the spine of the scapula T4/T5 a) The sternal angle of Louis (manubriosternal junction) b) Level of the 2nd costal cartilage c) Termination of the ascending aorta and the commencement of the arch of aorta d) Termination of the arch of the aorta and the beginning of the descending aorta e) Bifurcation of the trachea and the commencement of the bronchi f) The left and right pleurae meet at this level T6: One of the levels of constriction of the oesophagus T7: Inferior angle of the scapula T8 a) The inferior vena cava pierces the diaphragm b) The right phrenic nerve passes through the vena caval opening T9/T10 a) Xiphisternal junction b) The 7th costal cartilage joins the xiphisternal junction c) Beginning of the lumbar enlargement of the spinal cord 166 T10 a) The oesophagus pierces the diaphragm b) The vagal nerves pass through the oesophageal opening c) Oesophageal branches of the left gastric vessels pass through the oesophageal opening d) One of the levels of constrictions of the oesophagus T11: Cardiac orifice of the stomach T12 a) The aorta passes through the diaphragm b) The thoracic duct enters the thorax through the aortic hiatus c) The azygos vein enters the thorax through the aortic hiatus d) The coeliac trunk arises from the aorta at T12 lower border e) End of the lumbar enlargement of the spinal cord. L1 a) The transpyloric plane: level of the pylorus of the stomach b) Fundus of the gall bladder c) Hila of the left and right kidneys d) Neck of the pancreas e) Superior mesenteric vein and the splenic vein unite behind the neck of pancreas to form the portal vein f) Middle suprarenal arteries g) The superior mesenteric artery arises from the aorta h). The renal arteries arise from the aorta 1cm below the SMA at L1 lower border (They may arise between L1 and L2) i) Medial arcuate ligament of the diaphragm j) The spinal cord in the adult terminates at L1 lower border L2 a) Duodenojejunal flexure: attachment of the ligament of Treitz b) Commencement of the thoracic duct c) Commencement of the azygos vein d) The testicular or ovarian arteries arise from the aorta 1cm below the renal arteries L3 a) The subcostal plane: the lowest level of the thoracic cage b) The lower pole of the kidney c) The horizontal part of the duodenum d) The inferior mesenteric artery arises from the aorta e) Termination of the spinal cord at birth L3/L4: Level of the umbilicus L4 a) Transcristal plane: highest point of the iliac crest b) Aorta bifurcates into left and right common iliac arteries c) Junction between the caecum and the ascending colon L5 a) Transtubercular plane: level of the iliac tubercles. b) The left and right common iliac veins unite to form the inferior vena cava c) Ileocaecal valve: junction between the right lateral vertical plane and the transtubercular plane d) Junction between the caecum and the ascending colon. S1 a) Level of the anterior superior iliac spines. b) Level of the arcuate line of the anterior abdominal wall S2 a) Level of the posterior superior iliac spines b) Level of a pair of dimples at lower part of the back c) Termination of the subarachnoid space S3 a) Level of the posterior inferior iliac spines b) Junction between the sigmoid colon and the rectum 167 45. APPENDIX II: DIMENSIONS OF SOME STRUCTURES IN THE BODY
A) CENTRAL NERVOUS SYSTEM
BRAIN Weight: 350g at birth (about 12% of the body weight) 1.0kg at one year 1.4kg in adult male and 1.3kg in adult female (about 2.5% of the body weight)
SPINAL CORD Length: 15cm at birth and 45cm in adults
B) RESPIRATORY SYSTEM
LARYNX Length: 4.5cm in males and 3.5cm in females Transverse diameter: 4.3cm in males and 4.1cm in females Anteroposterior diameter: 3.6cm in males and 2.6cm in females
TRACHEA Length: 10-15cm External diameter: 2cm in males and 1.5cm in females
LEFT BRONCHUS Length: 5cm RIGHT BRONCHUS Length: 2.5cm
LEFT LUNG Weight: 560g RIGHT LUNG Weight: 620g
C) CARDIOVASCULAR SYSTEM HEART Length: 12cm Width: 9cm Depth: 6cm Weight: 20g at birth 280-340g in adult males 230-280g in adult females
D) LYMPHATIC SYSTEM THORACIC DUCT Length: 45cm CISTERNA CHYLI Length: 5-7cm SPLEEN Length: 12cm Width: 7cm Thickness: 3.5cm Weight: 150g (range 50-250g).
E) DIGESTIVE SYSTEM PHARYNX Length: 12-14cm Diameter of the uppermost part: 3.5cm Diameter of the lowermost part: 1.5cm
OESOPHAGUS Length: 25-30cm (the distance from the incisor to cardiac orifice is 45cm)
STOMACH Length: 25cm Capacity: 30-35mls at birth; 1000mls at puberty 1200-1600mls in the adult
SMALL INTESTINE Length: 5m during life 6-7m after death because of loss of muscle tone
168
DUODENUM Length: 25cm Diameter: 4-5cm 1st or superior part: 5.0cm 2nd or descending part: 7.5cm 3rd or horizontal part: 10.Ocm 4th or ascending part: 2.5cm JEJUNUM Length: upper two-fifths of the small intestine Diameter: 3cm
ILEUM Length: lower three-fifths of the small intestine Diameter: 2.5cm
MESENTERY OF THE SMALL INTESTINE Length: 15cm
LARGE INTESTINE Length: 1.5m
CAECUM Length: 6cm Width: 7.5cm APPENDIX Length: 2-20cm (average range 7-12cm)
ASCENDING COLON Length: 15cm TRANSVERSE COLON Length: 45cm or more DESCENDING COLON Length: 25cm SIGMOID COLON Length: 45cm (range 15-80cm) RECTUM Length: 12cm ANAL CANAL Length: 3-4cm
PANCREAS Length: 12-15cm Weight: 90g
LIVER Weight: 1.5kg in males and 1.3kg in females
GALL BLADDER Length: 7-10cm Width: 3cm Capacity: 30-50mls
COMMON BILE DUCT Length: 7-8cm Diameter: 5-6mm
CYSTIC DUCT Length: 3-4cm COMMON HEPATIC DUCT Length: 3-4cm PORTAL VEIN Length: 8cm
F) URINARY SYSTEM KIDNEY Length: 12cm (range 9-15cm) Width: 6cm Thickness: 3cm Weight: 150g in males and 130g in females
LEFT RENAL VEIN Length: 7.5cm RIGHT RENAL VEIN Length: 2.5cm URETER Length: 25cm URINARY BLADDER Capacity: 150mls for desire to micturate 500mls or more when it is fully distended
169 MALE URETHRA Length: 20cm Prostatic urethra 3.0cm Membranous urethra 1-2cm Spongy or penile urethra 15.0cm
FEMALE URETHRA Length: 4cm
G) GENITAL SYSTEM PROSTATE GLAND Vertical diameter: 3cm Transverse diameter: 4cm Anteroposterior diameter: 2cm Weight: 20g
TESTIS Length: 4-5cm Transverse diameter: 2.5cm Anteroposterior diameter: 3cm Weight: 25g
EPIDIDYMIS Length: 5-6cm VAS DEFERENS Length: 45cm EJACULATORY DUCT Length: 2cm SEMINIFEROUS TUBULES Length: 60cm SEMINAL VESICLES Length: 5cm EFFERENT DUCTULES Length: 5cm
UTERUS Length: 8cm (body and fundus: 5cm; cervix: 3cm) Widest diameter: 5cm Thickness: 3cm
UTERINE TUBES Length: 10-12cm
OVARY Length: 3-4cm Width: 1.5-2cm Thickness: 1cm Weight: 4-8g
VAGINA Anterior wall: 7.5cm long Posterior wall: 9cm long
H. DUCTLESS GLANDS SUPRARENAL GLAND Length: 3-5cm Width: 2.5-3cm Thickness: 0.5-1cm Weight: 4-8cm
THYROID GLAND Weight: 25gm Length of each lobe: 5cm Greatest transverse diameter: 3cm Anteroposterior diameter: 2cm
THYMUS GLAND Weight: 10-15g at birth 30-40g at puberty 10g or more in mid adult life (it may remain large in the adult)
170 I. OTHERS
INGUINAL CANAL Length: 4cm FEMORAL SHEATH Length: 3-4cm FEMORAL CANAL Length: 1.25cm FEMORAL RING Widest diameter: 1.25cm FEMUR Length: 45cm
1