Lecture Notes on Human Anatomy. Part Two, Fourth Edition. PUB DATE Sep 89 NOTE 105P.; for Related Documents, See SE 051 218-221

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AUTHOR Conrey, Kathleen TITLE Lecture Notes on Human Anatomy. Part Two, Fourth Edition. PUB DATE Sep 89 NOTE 105p.; For related documents, see SE 051 218-221. Black and white illustrations will not reproduce clearly. AVAILABLE FROMAramaki Design and Publications, 12077 Jefferson Blvd., Culver City, CA 90506 ($7.75). PUB TYPE Guides - Classroom Use - Materials (For Learn.,-) (051)

EDRS PRICE MF01 Plus Postage. PC Not Available from EDRS. DESCRIPTORS *Anatomy; *Biological Sciences; *College Science; Higher Education; *Human Body; *Lecture Method; Science Education; Secondary Education; Secondary School Science; Teaching Guides; Teaching Methods

ABSTRACT During the process of studying the specific course content of human anatomy, students are being educated toexpand their vocabulary, deal successfully with complex tasks, and learna specific way of thinking. This is the second volume ina set of notes which are designed to accompany a lecture series in humananatomy. This volume includes discussions of tissues, cells,and histology; development and embryology; epithelial, glandular, connective,blood, and muscular tissues; and the internal viscera includingthe digestive system, the urinary system, the reproductivesystem, the respiratory system, the circulatory system, and the lymphaticsystem. (CW)

X**************************************01*****************************x* * Reproductions supplied by EDRS are the best thatcan be made * 1* from the original document. * *******0.*************************************************************** "PERMISSION TO REPRODUCE THIS U.S. DEPARTMENT OF EDUCATION MATERIAL IN MICROFICHE ONLY Office or Educe:lona Rssearcn and Irsprtnernent H BEEN GRANTED BY EDUCATIONAL. RESOURCES INFORMATION CENTER (ERIC) document hes been reproduced se e1_,..60 )64recetved from the person or orgenuatton orionslono tt. 0 Mtnordueness on have been made to improve reprodouatity TO THE EDUCATIONAL RESOURCES Pointe of view or opinions stated m the doer smolt do not ffeCeate My represent official INFORMATION CENTER (ERIC)." OEM povien or Policy TURE ES

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by KATHLEEN CONREY

11'7' LECTURE NOTES on HUMAN ANATOMY

Part Two Fourth Edition

The author is a Professor of Natural Sciences at FA Camino College. She holdsa master's degree from the Department of Human Anatomy, University of California, SanFrancisco, and has been teaching human anatomy at the community college level since 1967.

by KATHLEEN C3NREY The author is a Professor of Natural Sciences at El Camino College. She holdsa master's degree from the Department of Human Anatomy, University of California, San Francisco, andhas been teaching human anatomy at the community college level since 1967.

Aramaki Design & Publications 12077 Jefferson Boulevard, Culver City, California (213) 822-9800

Fourth Edition, September, 1989 Copyright C4)198?, by Kathleen Conrey

All rights reserved. No part of this publication may be reproduced, stored ina reirkval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recordingor otherwise, without the prior written permission of the copyright owner.

First edition and first printing 1982

Printed in the United States of America TABLE OF CONTENTS HISTOLOGY INTRODUCTION I THE CELL 2 Cell Membranes and Membrane Transport 2 Cell Organelles 3 EMBRYOLOGY 5 Germ Layer Formation 6 Germ Layer Derivatives 7 EPITHELIUM 9 GLANDS 13 CONNECTIVE TISSUE 17 Fiber Types 17 Matrix Types 18 Cell Types 18 Aging Cartilage and Bone 23 BLOOD 24 Hemopoiesis 24 Hemostasis 24 Erythrocytes 26 Hemoglobin and Anemia 26 Leukocytes 27 MUSCLE TISSUE 30 Sarcomere Anatomy 30 Sliding Filament Contraction 31 Types of Muscle Tissue 31 ARCHITECTURAL PLANS OF SIMPLE ORGANS 33 Blood Vessel Walls 33 Skin 33 Mucous Membranes 34 INTERNAL VISCERA PART I DIGESTIVE SYSTEM 36 Peritoneal Membranes 36 Mouth and Pharynx 37 Esophagus and Stomach 38 Intestine 40 ACCESSORY DIGESTIVE GLANDS 43 Liver 43

Le'ture Notes Part I 5 Table of Contents Gallbladder and Pancreas 45 Duct System 45 URINARY SYSTEM 47 GROSS ANATOMY OF THE KIDNEY 47 Kidney Gross Anatomy 47 The Nephron Unit 49 Urine Collection System 51 Summary of Pathways 52 REPRODUCTIVE SYSTEM 53 The Perineum 53 How it Works 55 Reproductive Organ Embryology 56 Male Internal Reproductive Organs 59 Female Internal Reproductive Organs 61 Menstrual Cycle 63 Breast 64 Endocrine Control Mechanisms 64 INTERNAL VISCERA PART II RESPIRATORY SYSTEM 66 Functions 66 Pharynx 67 Larynx 68 Lung 70 Respiratory Tree 71 Pleural Anatomy 73 Pathology 74 HEART 75 Location and Walls of the Heart 75 A Pair of Pumps 76 Major Vessels Attached to the Heart 77 Valves 78 Cardiac Cycle 79 Coronary Vessels 79 Conducting System 82 Fetal Heart 83 BLOOD VESSELS 84 Chest Area Arteries 84 Chest Area Veins 85 Hcad and Neck Arteries 86 Head and Neck Veins 87 Arm Vessels 88 Abdominal Vessels 39

Lecture Notes Part I ii Table of Contents Pelvic Vessels 90 Leg Vessels 91 LYMPHATIC SYSTEM 93 Tissue Fluid Transport 93 Fat Transport 94 Immune Functions 94 Lymphoid Organs 95

ANGIOLOGY 97

Lecture Notes Part I Table of Contents Introduction to Histology

Histology is the microscopic study of tissues and also the microscopic study of organ architecture.

Cells are the building blocks of the tissues.

Tissues are groupings of similaror identical cells. There are four basic tissue types: epithelial tissue, connective tissue, muscle tissue, and nerve tissue.

Tissues are organized into organs. Mostorgans are made of all four tissue types, but the tissuesare put together in different proportions and with a different architectural plan for each organ.

Similar organs are grouped together into units which either obviously function together, or are similar issome other way. Such groupings are called systems. Examples: the digestive system, the endocrine system, the reproductive system, etc.

Lecture Notes Part II 1 Histology 8 The Cell

CELL MEMBRANES ONOSS Osmosis is a special case of diffusior. It The cell membrane (unit membrane) is requires a semipermeable membrane whose trilarred, totaling 75 angstroms in diame- pore size prevents movement of the solute, ter. The core of the triad is phospholipid but permits movement of the solvent. The material The outer layers of the triad are solvent will obey the laws of diffusion; i.e. it globular proteins with which the phosphol- will move down a concentration gradient ipid core is studded. Some of these proteins from an area where there is a greatercon- are purely structural, others are interactive centration of solvent towards an area where enzymes needed for (such things as) mem- there is a lesser concentration of solvent. brane transport functions. In biology the solvent is always water,so a There are pores in the membrane which are good definition of osmosis is: the passage of approximately three angstroms in diameter. water through a semipermeable membrane The presence of these pores is what makes according to the laws of diffusion. the membrane semipermeable. Ions and par- Tonicity ticles smaller than three angstroms diameter The terms hypertonic, hypotonic and iso- are able to pass through the membrane pas- tonic relate to osmosis. sively. Anything larger is prevented passage except by active transport mechanisms. Hypertonic refers to a solution of relatively high solute concentration (low con- MEMBRANE TRANSPORT centration of water). Hypotonic is the opposite of hyper- PASSIVE TRANSPORT tonic. Passive transport through a membrane is a property of the semipermeable nature of the Isotonic refers to a state of equilibrium membrtne. Several types of passive trans- in which the total solute concentrations port are possible: on the two sides of the membrane are equal (even though this state may require DIFFUSION very different volumes of solvent to be Semipermeable membranes permit dif- present on the two sides of the mem- fusion, although a membrane is not neces- brane). sary for diffusion to occur. Diffusion is the -novement of solute parades or ions down a ACTIVE TRANSPORT concentration gradient from an area of Active transport is due to phys;ological higher ,,oncentration toward an area of lower properties of the membrane that make it concentration until er,-ailibtium is estab- selectively permeable. Active transport lished. always requires both: FILTRATION a specific enzyme Fitmipermeable membranes permit filtration. expenditure of energy Filtration is the passive movement of solute Examples: particles or ions through a semipermeable a. Insulin and glucose transport membrane in response to gravity, pressure, b. The Sodium Pump. or suction.

Lecture Notes Part II 2 Histology 9 CELL ORGANELLES plasm. A good example of this is the MITOCHONDRIA lysosome enzymes that are used for cellular Mitochondria are the energy producing digestion of phagocytized particles. factories of the cell. These structuresare VACUOLES responsible for cellular respiration, i.e. the A vacuole is any membrane bound inclusion stepwise degradation of the cellular fuel body found inside the cell. It is producedby glucose Hydrogen ions are released during a pinching off of cellular membranes during this process, and they in turn are combined such processes as phagocytosis and pino- with oxygen in such a way that energy isre- cytosis. Secretion droplets and lysosomes leased. The by products of thisprocess are produced by the Golgi apparatuscan also be carbon dioxide and water. Some of theen- considered as vacuoles. ergy produced is in the form of heat; the rest CB4TROSOPE of the energy is stored in the form of ATP The centrosome contains two pairs of (adenosine triphosphate). centrioles for cell division. ENDOPLASIBC RETICULUM NUCLEAR MEMBRANE: The endoplasmic reticulum is a highly The trilayered endoplasmic reticulum convoluted internal complex of cellular membrane is doubled back on itself around membranes that arise as an invagination of the nucleus in such a way as to forma the outer cellular membrane. The ER double layered nuclear membrane with large is.contiguous with the outer cell membrane pores. and also with the nuclear membrane. CHROMATIN There are two forms of ER, rough and An inclusive name for the DNA material smooth. Rough endoplasmic reticulum is inside the nucleus. rough because it is studded with ribosomes. Smooth endoplasmic reticulum is smooth NUCLEOLUS because of the absence of ribosomes. An area inside the nucleus characterized by a concentration of messenger RNA. The function of rough ER, is protein synthe- MICROVILU sis. RNA copies of the nuclear DNA leave Microvilli are fingerlike evaginations of the the nucleus and travel to the ribosomes of outside cell membrane. Theyserve to in- the ER where they serve as instructional crease the surface area of the cell. Increased templates for the production of protein. surface area is an important consideration The function of smooth ER is mu- for cells whose job is absorption, suchas copolysaccharide synthesis. The production those found in the intestine and in the kidney process is less well understood than that of tubules. the rough ER. CIUA GOLGI APPARATUS (GOLGI BODY) Cilia are special hairlike contractile el- The Golgi body is a special area of the ements of certain epithelial cells. The cilia smooth endoplasmic reticulum where the are rooted inside the cell and extend outward layers of membrane are very tightly convo- through the cell membraneon the lumen luted and packed closely together. side of the cell. Coordinated ciliary beating creates ciliary currents in the fluids bathing The Golgi body is the site where protein the epithelium. This is the chief mechanism precursors are converted into active en- used in the respiratory system for themove- zymes. It also serves as a packaging plant ment of mucous, and in the reproductive for enzymes and secretion products that system.for the transport of eggs from fallo- need to be walled off from the cell cyto- pian wig to uterus. Lecture Notes Part II 3 Histology I 0 A Two Cell Stage B. Four Cell Stage

blastocoel

C. Morula D. Blastula With Inner Cell Mass

chorionic villi

,,!". c. vit dip It. 44 Ala embryonic ectoderm ob15441 embryonic mesoderm VP CM .,,Vor c. amnion embryonic endoderm Opoz,,,,a0.,4D uc..potaio extraembryonic mesoderm E

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E The Embryonic Disk Stage of Development

Fig. 1- Embryonic Germ Layer Formation

Lecture Notes Part 11 4 Histology 1 1 Early Development of the Embryo

FERTILIZATION CLEAVAGE When the egg is released from the ovary it is The first cell division of the zygote produces surrounded by a group of other cells from the 'two cell stage' ; each of these cells then the follicle called the corona radlata. These divides producing the "four cell stage", and cells are held in place around the egg by so on, until a solid balls of cells called a intercellular glue which is mostly hy- morula is produced. Each of the cells ina aluronic acid. Inside the corona radiate, and morula is equipotential, that is, if themass adhering to the outside of the egg is the of cells by chime separates in myway each zona pellucida (vitalise membrane) a thick cell or group of cells can proceed to divide tough capsule of jellylike material which is and will eventually produce an entire new almost pure hyaluronic acid. As the egg is individual. See the discussion belowon swept into the fallopian tube and on toward twins. the uterus, it is met by the sperm cell. Fertil- ization usually takes place in the upper third DIFFERENTIATION of the fallopian tube. A tiny cap on the head The term cleavage is only used for the of the sperm cell, the acrosome, contains divisions up through the morula stage. With hyaluronidau, an enzyme which is capable continued division the solid rnonila becomes of dissolving away the hyaluronic acid a hollow ball of cells called a blastula. Cell protecting the egg. It probably requires division has been so rapid up to this point many sperm cells to provide enough enzyme that the daughter cells have not hadan to allow just one of the sperm cells to pene- opportunity to grow between divisions. Asa trate the egg. Other sperm cells are pre- consequence the cells of each successive vented from entering by changes that take division are about half the size of the previ- place in or on the surface of the egg. The ous cell, and the early blastula is not much nature of these changes is not understood. larger than the original egg. When the head of the sperm cell penrittes Shortly after formation of the blastula the the egg the tail of the sperm is left outside, cells begin to specialize or become and the head of the sperm, containing the different from one another. An inner cell haploid number of chromosomes is now mass appears, perhaps explainable as a pile called the male pronucleus. It fuses with the up of more rapidly dividing cells on one side female pronucleus (also containing the hap- of the blastula. This difference in rate of loid number of chromosomes). This fusion division may be the first sign of specializa- is called fertilization, and the resultant fer- tion among the cells of the early embryo. tilized egg is called a zygote. The zygote Another possible explanation for the appear- with its diploid number of chromosomes ance of a hollow blastula and its inner cell represents the beginning of a new individual mass is that the cells on the surface of the that has received half it's chromosomes manila (the trophoblast or chorion cells) are from the male parent and half from the somehow different than the cells in the in- female parent. If the sperm carried an X terior, and the surface cells begin to secrete chromosome the new individual is a genetic a fluid that collects in the interior of the female. If the sperm carried a Y chromo- morula creating a central cavity and pushing some the new individual is a genetic male. the remaining cells (the inner cell mass) against one wall. Lecture Notes Part 11 S Histology 12 In any case, other signs of differentiation The cells of the inner cell mass which are rapidly appear as the cell. of the inner cell nearest to the trophoblast become the ecto- mass begin to stratify into zones which derm. A fluid filled cavity (the amniotic themselves soon show specialization of cavity) appears in the, center of the ectoderm destiny and function. The body parts of the cells, and this ca ity divides the ectoderm future individual will develop from only a into two parts. The part directly underneath few of the cells of the inner cell mass, the the chorion layer (including a contribution rest of the cells of the blastula are destined from the extra-embryonic mesoderm) is des- to form the life support system for the tined to form the amnion layer, a membrane embryo, namely the extra-embryonic mem- of cells which will eventually completely branes (chorion, and amnion) and the fetal surround the developing embryo. The other contributions to the placenta. part of the ectoderm group of cells become3 one of the layers of the embryonic disc, IMPLANTATION implying that it is destined to form actual The blastula generally arrives in the uterus body parts for the future embryo. about 4 days after fertilization, and it appar- Turning our attention to the remainder of the ently remains free in the uterine cavity for a inner cell mass, a second cavity appears, the few days, because it generally implants on yolk sac cavity. The cells that line this cavity about day 6 or 7. During this time the outer are the endoderm, and the layer of endo- layer of cells of the blastula (the trophoblast) derm closest to the ectooerm layer also divide rapidly, forming a second (inner) becomes part of the embryonic disc, des- layer known as extraembryonic mesoderm, tined to form parts of the future embryo. The and also forming finger like projections of rest of the endoderm forms the yolk sac, the outer surface known as the chorionic which in mammals never actually supplies villi. The cells of the chorionic villi begin to much in the way of nutrient material, and is secrete digestive enzymes which enable the significant only in that it contributes to the blastula to burrow its way into the wall of formation of the umbilical artery and vein, the uterus. This process takes several days, and the future gut tube of the embryo. during which time the chorionic villi and extra-embryonic mesoderm interdigitate with If you imagine cutting the amniotic cavity maternal endometriwn, forming a complex open and looking down on the surface of the vascular organ known as the placenta, two cell layered embryonic disc you would through which exchange of nutrients, blood see that it is flat and oval shaped at this gasses, and metabolic waste products will stage. Its edges will soon start curling under take place for the whole term of the preg- to form a tubular shaped embryo, and simul- nancy. In the placenta the embryo's blood taneously some of the ectoderm cells will circulates within the chorionic villi, and the migrate between the two existing germ mother's blood circulates through the spaces layers to form the third germ layer, the true around the outside of the villi, however the mesoderm of the embryo itself. two blood supplies never come in direct The future head end of the tubular shaped contact with one another. embryo now establishes itself by growing more rapidly than the rest of the embryo, GERM LAYER FORMATION and as a result of this rapid growth the head This is the next stage in the process of end flexes under. differentiation, and it takes place simul- From the three established germ layers, taneously with implantation `i nere will ectoderm, mesoderm, and endoderm, all the eventually be 3 germ layers; two appear first various body parts begin developing. The with the third to follow. Lecture Notes Part II 6 Histology 13 brain and spinal cord, the somites, the gut, and the heart, are among the first to appear. GERM LAYER DERIVATIVES The heart is functional quite early (25 days), TISSUES and it pumps blood to the placenta as well as 1.Epithelial tissue: may be from ectoderm, to the embryo itself. The various organs and endoderm or mesoderm. tissue of the human body can all be traced 2. Connective tissue: from mesoderm back to their germ layer of origin. 3. Muscle tissue: from mesoderm. THE FETUS 4. Nerve tissue: from ectoderm. The embryo is recognizably human at about 8 weeks of development, and at this stage it ORGAN SYSTEMS is called a fetus. At 8 weeks the fetus has ECTODERM DERIVATIVES most of its futureorgans,and many are All outside surfaces cf the embryo and the functional. It seems to exercise its muscles infoldings of the same, including all of the with small movements that are as yet too nervous system. Examples: epidermis, hair, weak to be felt by the mother. This percep- nails, enamel of teeth, epithelium of mouth, tual recognition by the mother of the life nose, and anus, sweat glands, sebaceous within ("quickening") will not occur for glands, mammary glands, brain, spinal cord, several weeks yet. almost all sense organs (inner ear and most of eye), adrenal medulla. TWINNING MESODERM DERIVATIVES IDENTICAL TWINS All strictures needed to move the body around in order to obtain food: bones, If the cells of the morula do not hang to- muscles, all connective tissue, circulatory gether as they should, the separate cells or system. Also most of the urinary system and cell masses may each develop independ- reproductive system. Examples: heart, blood ently, and the resultant offspring will all vessels, bone marrow, lymphatics, spleen, have identical genetics and will of course lymph nodes, tonsils, gonads, uterus, fallop- always be of the same sex. Separation of the ian tubes, ductus deferens, kidney, and morula into two or more parts may be partial connective tissue and visceral muscle of all or complete. If separation is complete the organs. embryos will have separate placentas and chorions; if separation is less complete the ENDODERM DERIVATIVES embryos may share the same placenta, and Epithelium and glands of the digestive perhaps even the same amnion, the same system and respiratory system (excluding nose, mouth, and anus). Examples: Epithe- umbilical cord, or even share body parts. lium of the gut tube and respiratory tubes, FRATERNAL TWINS including that of the: tongue, throat, larynx, If two separate eggs are released at the same trachea, lungs, esophagus, stomach, small time they will be fertilized by separate intestine, large intestine. Examples of sperm cells, and they will of course develop glands: liver, pancreas, salivary glands, independently though simultaneously. They thymus, thyroid gland, parathyroid glands. may however implant so close together in Other examples that may be harder to re- the uterus that the two chorions and pla- member: epithelium of urinary bladder, centas unite. Nevertheless, they do not share urethra, prostate gland, and lower vagina. the same genetics, may or may not be of the same sex, and are no more closely related than any other pair of siblings.

Lecture Notes Part II 7 Histology 14 J Shp le

cuboidal Pseudostratified Epithelial ColumnarI Membranes

Keratinized

Squamous

Norieratinized EPITHELIAL Stratified TISSUE

rdi;togenic Epithell

Fig. 2- Epithelia! Tissue Classification

Lectare Notes Part II S 15 Histology Epithelium

INTRODUCTION faces where we find epithelium include all Epithelial membranes are sheets of cellsone the tubes and passageways leadingto the ex- or more layers in thickness, which line the terior, such as the nose, mouth,anus, vagina, cavities of the body or cover its surfaces. bladder, and urethra. Thesepassages are all Most epithelial membranes include scattered lined with mucous membranes, theouter cells which have a secretory function. layer of which is epithelium. Epithelial derivatives such as hair, nails, Some surfaces of the body do not leadto the teepth and glands develop as either in- outside but instead face internal cavities. growths or outgrowths of the basic epithelial Epithelium in these locations is givena sheet. special name. For example, the epithelial lining of the inside of blood and lymphatic EPITHELIAL MEMBRANES vessels is called endothelium, and theep- In an epithelial membrane the cellsare ithelial surface of the pleura and peritoneum fitted together very closely, there is littleor is called mesothelium. no intercellular material between the cells. SURFACE SPE:IALIZATIONS Epithelial membranes by themselvesare Some epithelial membranespossess surface not mechanically strong. They are always specializations such as microvilli and cilia supported by an underlying layer ofconnec- that relate to the function of the epithelium. tive tissue called the lamina propria. The epithelium is bound to this connective tissue MICROV1111 The free surfaces of cells in the intestine and by a basement membrane. This basement in the kidney possess dense membrane is a very thin layer of protein- groups of microvilli which increases the active surface aceous glue-like material, an extracellular product of the lamina propria. area of these cells. The microvilli give the membranes a fuzzy appearance. In the An epithelial membrane has two surfaces. intestine this appearance is often knownas a One of these, the basal surface restson the striated border. In the kidney tubules the lamina propria. The other surface is free, it same structure is often called a brush bor- has nothing on top of it. This surface is der. called the free or luminal surface. CILIA Epithelial membranes are avascular, i.e. The free surface of epithelial cells in the they do not contain blood vessels. Nutrients respiratory and genito-urinary tracts and are delivered by diffusion from the capillar- parts of the nervous system is ciliated. The ies of the underlying connective tissue. coordinated ciliary beating moves mucus or fluids along the surface of the membrane. All epithelial membranes are subjected to wear and tear; their component cells die and CLASSIFICATION METHOD must be replaced by mitotic cell division if Please refer to Figure 2. the membrane is to remain intact and func- Epithelial membranes are classified accord- tional. ing to two major microscopic features: the number of cell layers EXAMPLES the shape of the cells The outer layers of the skin are an example of an epithelial tissue. Other external sur- Determination of these features requires

Lecture Notes Part II 9 Histology 16 visualization of a tissue sample which has DESCRIPTION OF TYPES been sectioned perpendicular to the membrane surface. SIMPLE EPITHELIA NUMBER OF LAYERS SIMPLE SQUAMOUS EPITHELIUM SliftE One layer of squamous cells. If there is a single layer of cells, all of which Simple squamous epithelial membranes are are in contact with the basement membrane, very delicate and fragile; they present a the epithelium is classed as a simple epithe- barrier of minimum thickness and are found lium. In such a case the nuclei of the cells in regions where diffusion or filtration rather typically line up with one another in an even than protection is the main requirement. row. Examples of their occurrance: STRATIFIED inner surface of blood vessels If maw than one layer of cells is superim- Bowman's capsules of the kidney posed one upon the other, and only the lung alveoli. bottom layer of cells rests on the basement SIMPLE CUBOIDAL EPITHEUUM membrane, the epithelium is said to be One layer of cuboidal cells. stratified.Stratified epithelia are found wherever protection from mechanical Simple cuboidal epithelium is found where abrasion is necessary. The upper cells may the membrane must be somewhat stronger be damaged or scraped off without necessar- than squamous cells or where the cells must ily breaking the integrity of the membrane. work harder and are therefore larger ( each cell contains more organelles). CELL SHAPE Three basic cell shapes are recognized: Simple cuboidal epithelial cells specialize in absorption or secretion. When engaged in SOUNAOUS, CUBOIDAL, COLUMNAR absorption the cells often have microvilli on Squamous cells are flat when viewed from their free surface to increase surface area. the side. A good analogy is that of a fried Kidney tubule cells are an excellent example egg that has been sliced through the middle of simple cuboidal epithelium with a brush of the yolk and viewed from the cut edge. border. All gland cells are also simple The yolk of the egg represents the nucleus of cuboidal type epithelium. The germinal the cell, the white of the egg represents the epithelium covering the outside of the ovary cytoplasm of the cell. and lining the seminiferous tubules of the Cuboidal cells are about as tall as they are testis is also of the simple cuboidal type. wide. SIMPLE COLUMNAR EPITHELIUM Columnar cells are taller than they are wide. One layer of columnar cells. When considering cell shape in a stratified This epithelium also specializes in absorp- epithelium it is only the cells of the surface tion and secretion. It is a stronger epithelium layer that are taken account of since the cells than the simple cuboidal type, and is found in deeper layers are always cuboidal or where mechanical stress is greater. A good irregular in shape. example of this type is the epithelium lining One particular type of columnar cell which the stomach and intestine. stores and secretes mucous is called a goblet PSEUDOSTRATIFIED COLUMNAR cell. When the cell is swollen with stored Apparantly more than one layer of cells, but mucous it becomes goblet shaped. These in actuality only one layer exists. The cells are characteristic of the epithelium of predominant cell shape is columnar. the gastrointestinal and respiratory tracts.

Lecture Notes Part II 10 Histology 17 This epithelium should actually fall in the In stratified squamous keratinized epithelia cart gory of simple, because in fact all of the the cells in the middle strata manufacture the cells touch the basement membrane. How- protein keratin. Keratin is a sticky horn-like ever three unique factors contribute to the protein material made by certain stratified false (pseudo) impression that the epithe- epithelia. Keratin causes the cells in the lium is stratified: upper layers of the epithelium to stick the cells are of different heights, not all together even after they have lost their nu- of them reach the top surface clei. These flake-like layers on the top the nuclei are at different levels rather surface of an epithelium make it imperme- than all lined up in a row able to water, preventing dehydration and the specimen is rarely cut perpendicular absorption of water. to the surface. On a practical level the best way to make the A key point that makes positive identifica- diagnosis between keratinized and nonker- tion easy: all pseudostratified columnar atinized stratified squamous epithelia is to epitheliathat you will see in the lab also look for nuclei in the top layers of cells. If have cilia and goblet cells. nuclei are present the cells are living, and Pseudostratified columnar epithelium with the epithelium is nonkeratinized. If nuclei cilia and goblet cells is restricted to the are absent the cells are nonliving and the upper respiratory tract and is sometimes epithelium is of the keratinized type. called standard reviratory epithelium. The Stratified squamous keratinized epithelium goblet cells secrete mucus which serves to is typical of the epidermis (outer layer of the entrap particulate matter and the cilia move skin) and is found on the dry surfaces of the the stream of mucus toward the oral cavity. body. STRATIFIED EPITHELIA Nonkeratinized stratified squamous epithelia Both stratified cuboidal and stratified columnar are found in areas that are subject to me- epithelia exist in the human body but they are rare chanical abrasion but not to dehydration. and their distribution is erratic, so they will not be Such areas include the lining of the mouth, considered in this discussion. esophagus, anus, and vagina. STRATIFIED SQUAMOUS EPITHELIUM More than one layer of cells, the cells on the TRANSITIONAL EPITHELIUM free surface are squamous in shape. More than one layer of cells. The cells on the free surface are sometimes squamous Many layers of cells, the surface cells are and sometimes not. squamous. (The cells of deeper layers are usually cuboidal or irregular in shape.) 'Transitional epithelium is of the stratified type in that it contains many layers of cells. Stratified squamous epithelia are specialized The top layer of cells sometimes appears for protection. The stratified arrangement is squamous and somtimes appears cuboidal logical since no one cell is very strong, but (with a dome shaped free surface) depending layer piled on top of layer will give a strong on degree of stretch. result. This type of epithelium is found only in the There are two forms: keratinized urinary bladder and is specially adapted for nonkeratinized stretching. Keratonized epithelia are always found on dry surfaces, nonkeratonized epithelia are always found in wet areas.

Lecture Notes Part II 11 Histology QUMMARY OF FUNCTIONS OF EPITHELIA

FUNCTION EPITHELIAL TYPE Protection against Stratified Epithelia mechanical/chemical insult stratified squamous, both keratinized and nonkeratinized (epidermis, mouth, esophagus, vagina, and anus) stretching transitional epithelium of bladder dehydration (weathering) epithelium of the epidermis stratified squamous keratinized

Ciliary Transport of mucus and Ciliated Epithelia particulate matter along membrane ciliated pseudostratified columnar (respira- surfaces: tory tract) and ciliated simple columnar (oviducts & ductus defcrens).

Secretion, both synthesis and release of Simple Cuboidal Epithelia products of glands, both exocrine and endocrine

Diffusion and Filtration of Simple Squamous Epithelia gases, nutrients, and waste products. fining of blood vessels, lung alveoli and renal (Bowman's) capsule of kidney

Abseroption of nutrients and Simple Columnar of gut Reabsorption of renal filtrates Simple Cuboidal of kidney tubules

Lubrication Simple Squamous mesothelium secretion of serous fluid Simple Columnar of gut secretion of mucus lubricant Pseudostratified (goblet Cells) of respiratory tract

Sensory reception Modified Epithelia of taste buds, olfactory epithelia, and inner ear

Reproduction Gametogenic epithelia of ovary/testis

Lecture Notes Part 11 12 Histology 19 GLANDS

INTRODUCTION gland precursor may develop in either of two directions, exocrine or endocrine. SECRETION VS EXCRETION An epithelial cell may synthesize materials EXOCRINE GLANDS which are not used directly by that gam Fig. 3-C showsan exocrine gland. The cell, but instead are expelled from the cell superficial end of the cord of cells has into the blood or onto the body surfaces. hollowed out to form a duct connecting to This process is called glandular activity, or the surface. The deeper end of the cord has secretion. Secretion differs from excretion formed an aggregate of secretory cells each by the nature of the expelled product. If the of which opens on to the duct. This aggre- product is useful to the organism the process gate is called the secretory unit. The secre- is called secretion. Excretion implies re- tion of an exocrine gland is conveyed to the moval of waste products that are potentially surface of the epithelium by way of its duct. toxic to the organism, or removal of ex- ENDOCRINE GLANDS cesses of useful products. Fig. 3-Dshows an endocrine gland. En- UNICELLULAR VS MULTICELLULAR docrine glands are ductless. The developing Glands may be either unicellular or multicel- cord of epithelial cells completely loses its lular. The most familiar unicellular gland is connection with the epithelial membrane the goblet cell, a columnar epithelial cell from which it arose. This leaves the se- specialized for the production of mucus. cretory unit isolated beneath the surface. As Goblet cells are an important part of the a result the cellular secretions are picked up simple columnar epithelium of the intestinal by capillaries and =sported throughout the tract, and also of the pseudostratified colum- body in the blood stream. The secretory nar epithelium of the respiratory tree. Multi- product of an endocrine gland is referred to cellular glands are an aggregation of cells as a hormone. specialized for secretion. Multicellular glands are always derived embryologically from simple cuboidal epithelial membranes. EMBRYOLOGY Figure 3shows the embryologic development of a gland. In Fig. 3-A, a simple cuboidal epithelial membrane is resting upon a layer of connective tissue containing an embryonic blood capillary. From the basal surface of the epithelium a cord of cells is pushing down into till connective tissue. The cells of this cord are produced by the mitotic activity of cells in the epithelium. InFig.3-B continued mitotic division has produced a large number of cells organized into a long cord projecting deeply into the connective tissue. At this time the cord is a solid mass of cells. From this point on the

Lecture Notes Part H 13 Histology 0 A.

C.Exocrine / D. Endocrine

F7g. 3- Embryology of Glands

14 Histology 21 the vacuole fuses with the outer cell mem- CLASSIFICATION brane and the product is discharged to the Glands are basically classified as either outside of the cell with no loss of cytoplasm. exocrine or endocrine. Exocrine glands are then further classified according to the struc- The merocrine method is the mostcommon ture of the duct and the shape of the secre- method of secretion. Almost all glandsare tory unit. Please refer to Figure 4. of the merocrine type. Some examples include: the ordinary sweat glands of the Duct Structure (See Fig. 4-A, B) skin, and all of the glands which produce The duct may be either branched or unbran- digestive enzymes, including the salivary chat If the duct is branched the gland is glands, and the pancreas. classified as compound. If the duct is un- branched the gland is classified as simple. APOCRINE The apocrine method is intermediate be- Secretory Unit Shape (Fig. 4-C, D) tween the other two methods. The secretion The secretory unit may be either tube shaped droplets accumulate in the apex of the cell or it may be rounded into a sac or flask until the membranes in this region pinch the shape. If it is tube shaped the gland is tip off off from the main cell. There isa classed as tubular. If it is sac shaped the moderate amount of cellular debris ac- gland is classed as alveolar (a.k.a. acinar). companying this method. Some compound glands have secretory units The mammary glands and the sweat glands of both shapes in which case it is described of the axilla use this method. Axillary body as a compound tubulo-alveolar gland. (Fig. odor is the result of bacterial actionon the 4-E). resultant cellular debris. In some simple glands the tubular secretory unit may be coiled, in which case it is described as a simple coiled tubular gland.

SECRETION METHODS Glands, whether exocrine or endocrine, are sometimes further described according to the method by which they discharge secretory products from the cells.

HOLOCRINE In the holocrine method secretion products accumulate throughout the whole cell and are not released until the cell dies and disintegrates. This type of secretion is always accompanied by large amounts of cellular debris. The sebaceous (oil secreting) glands are of this type.

MEROCRINE In the merocrine method the secretion droplet is enveloped in membranes which wall it off from the cell cytoplasm. These vacuoles continuously make their way to the surface of the cell where the membrane of

Lecture Notes Part II 15 Histology Z A. Compound Duct B. Simple Duct

C. Tubular Secretory Unit D. Alveolar (Acinar) Secretory Unit

E. Compound Tubulo. alveolar Gland

Fig. 4- Classification of Exocrine Glands

Lecture Notes Part 11 16 Histology 23 CONNECTIVE TISSUE

INTRODUCTION these fibers have a white color. Each fiber Connective tissue serves to connect, support, appears to be quite broad when seen under and bind together the body tissues, whileat the compound light microscope, but when the same time providing flexibility, elastic- examined with the electron microscope each ity, and inn some cases lubrication. All the is seen to be composed of small subunits epithelial tissues are supported from under- called protofibrils. The protofibrilsaggre- neath by a layer of connective tissue (the gate in bundles to form fibrils, and the fibrils lamina pro pia). Every single muscle cell, in turn aggregate into bundles knownas every peripheral nerve cell, and every blood fibers. It is these latter thatwe see with the vessel, is ensheathed with connective tissue. light microscope. The width of the fiber de- pe,nds on the number of fibrils in the fiber. If Embryonic connective tissue is called the fiber appears to branch it is because mesenchyme. It has a mushy consistency, sometimes the fibrils separate from the main and the cells are mtildpatendal (a.k.a. mass of fibers. plaripotential), i.e. capable of developing into many or perhaps all of the more special- Collagen fibers are known for theirgreat ized or differentiated cells of connective tensile strength. When the tension exceeds tissue. fiber strength the fiber breaks and frays, much like the end of a frayedrope. COMPONENT PARTS Collagen is a protein. One third of the The three basic components of connective protein of the body is said to be collagen. tissue are : Collagen can be readily dissolved in dilute cells acid or by boiling in water. Dissolved fibers collagen can reaggregate spontaneously into matrix (ground substance) fibers when the conditions oftemperature Fibers and matrix are extracellular products and pH are suitable, and presumably this is of the living cells. The ratio of cells to what happens in vivo. Dissolved collagen is fibers, and/or the density of the matrix a familiar glue. determines the various connective tissue RETICULAR FIBERS: types. For example, blood has a fluid matrix The protein reticulin is very similar to with many cells and no solid fibers (unless collagen in all ways except aggregation. clotted). Bone has a solid matrix, few cells, Some scientists consider reticular fibersto and many fibers. be immature collagen fibers, and like collagen fibers they are compound fibers, There are three different fiber types, two though much smaller. They branch and basic types of matrix, and eumerous differ- anastomose to form a delicate network ent cell types,. The cells and fibers can be around fat cells, gland cells, and in the easily observed under the light microscope. basement membrane under epithelia. They Matrix on the other hand usually appears to are argyrophilic, but are difficult to stain be amorphous (without form or structure). with any other method, and thus will not be FIBER TYPES: seen in ordinary slide preparations.

COLLAGEN FIBERS: ELASTIC FIBERS: Collagen fibers are also known as "white Elastin is a stringy protein that has the fibers" because in gross anatomy masses of ability to stretch and recoil back into its

Lecture Notes Part U Histology original size and position. Consequently fertilize the egg. Some particularly virulent elastic fibers are found where elasticity is bacteria also possess this enzyme, permitting needed, such as in the skin. They are also them to dissolve away the intercellular glue found in the walls of arteries where their and spread rapidly in the tissue ofan inability to stretch is important since arteries fected animal. dilate or pulse with each heart beat and the elastic recoil of the artery helps to keep the Hyaluronic acid is also found in theaqueous blood moving. Elastic fibers can be And the vitreous humor of the eye and inme stretched to approximately 150% of their synovial fluid of joints. In these places it contributes the properties of lubrication, resting length before breaking. Masses of elastic fibers are yellow in color when seen water retention, and shock absorption. Water in gross anatomy. When seen under the mi- retention is important in the eye in orderto croscope they are not compound. They keep the internal pressures of the eye high, appear as dark, narrow, thread like strands. which in turn maintains the shape of the cornea, and holds the retina smoothly MATRIX TYPES: against the back wall of the eye.

The matrix or "ground substance" of all CHONDROMN SULFATE animal cells can also be thought of as inter- Chondroitin Sulfate is also a polysaccharide- cellular glue. Chemically the matrix is a protein combination but differs from hy- carbohydrate-protein complex that behaves aluronic acid chiefly in that it containsmore physically as a sol-gel. A sol-gel exhibits the sulfur than does hyaluronic acid. Because of properties of both a fluid and a solid. Tem- its high sulfur content, chondroitin sulfate perature, pH, and water content are the main contains numerous disulfide (zul;.ur to determinants of the sol -gel state. For ex- sulfur) bonds. These very strong chemical ample, gelatin mixed with warm water is a bonds produce a firmer gel, providing more sol; when allowed to cool it "sets" or be- shape and form, while still retaining flexibil- comes a gel. There are two basic varieties of ity and elasticity. The most familiar example matrix material: of chondroitin sulfate is cartilage (gristle). HYALUIVNIC ACID The crystalline lens of the eye is also made Hyaluronic acid is a soft jellylike amorphous of this material. viscous substance. Chemically it is a high CELL TYPES: molecular weight polysaccharide combined with protein. While binding cells together it The cells of connective tissue are generally nevertheless permits flexibility. The viscos- divisible into two populations, fixed and ity of hyaluronic acid varies, partly depen- wandering. Cells of the fixed populationare ding on the amount of calcium present. permanent residents of the connective tissue. Those of the wandering population move be- A familiar example of almost pure hy- tween the circulatory system and the con- aluronic acid is the mass of jelly that frog nective tissue. The wandering cells are prob- eggs are imbedded in when you find them in ably relatively inactive while circulating, ponds and quiet streams. Mammalian eggs and become active in the connective tissue. (includir; human eggs) are also surrounded All white blood cells belong to the wander- by a thick coating of this same jelly mate- ing population, and they will be considered rial. Human sperm cells each carry a small in the lecture on blood. Only the fixed packet of the enzyme hyaluronidase, a population of cells will be considered here. multitude of sperm cells being necessary to dissolve away enough of the hyaluronic acid FIBROBLASTS /FIBROCYTES The ending "blast" indicates an active, to permit one sperm cell to penetrate and generative or formative cell. The ending

Lecture Notes Part 11 18 Histology 25 "cyte" indicates an inactive or restingstate which have an affinity for stains witha basic of the same cell. Fibroblasts produce the (alkaline) pH. Thue granulesare known to intercellular (extracellular) substances of contain heparin and histamine. Heparin is connective tissue, namely the fibers andma- an anticoagulant and helps to dissolve small trix material. These productsare formed blood clots and prevent newones from inside the cells and then extruded into the forming in slow moving veins andcap- extracellular space. Fibroblasts/fibrocytes illaries. Basophils and mast cellsare thought are the most numerous cells seen in slides of to secrete heparin continuously. Histamine is loose areolar connective tissue, and theyare involved in tissue inflammation and allergic the only cells seen in tendons and ligaments. reactions, and is only released when the Seen in side view they are long spindle mast cell is damaged. shaped cells with fuseform (cigar shaped) nuclei; seen from a top view the cytoplasm FIXED MACROPHAGES (HSTIOCYTES) You will not be expected to isratify macro- (if it can be seen at all) willappear star phages since to do so wouldk expire special shaped (stellate). However, most often only tissue preparations that are not available. the small dark compact nucleus is visible. These cells belong to a system of cells of FAT CELLS (SIGNET RING CELLS): Some regions of the body are predominantly r.milar function scattered throughout the fat cells in which case this tissue is called body. This system is technically knownas adipose tissue. Young fat cells look much the reticuloendothelial system;you may find the same as fibroblasts, In intermediate it useful to think of the RE systemas the stages the cell cytoplasm contains numerous immune system. small droplets of fat. Lat er these droplets Macrophages exhibit active ameboidmove- coalesce to form a large central vacuole of ment and phagocytic activity. In vivo they liquid fat. The fat vacuole pushes thenu- ingest foreign particles suchas bacteria and cleus and cytoplasm to the periphery of the dust particles, and naturally occurring cell leaving the clear vacuole in the center of particulate matter such as dead cells. In slide the cell; the stained cell thus takeson the ap- preparations they can be positively identi- pearance of a signet ring. The name arose fied only if made to ingest particulatemat- because in the routine technology of slide ter before fixation and staining. preparation the thinly sliced tissue is treated with fat solvents (xylene) before staining, and the solvent effectively empties thestor- age vacuole. Early anatomists did not immediately guess the function of thesestrange empty looking cells. One excellent place to see young healthy looking fat cells under the microscope ison a slide of a cross section of small blood vessels and nerves. Fat cells can always be found serving as packing material around these structures.

MAST CELLS (TISSUE BASOPHILS): Mast cells are widely distributed inconnec- tive tissue and are found in greatly increased numbers in inflamed tissues. Their cytoplasm is heavily laden with large granules

Lecture Notes Part II 19 Histology 4"6 Fig. 5- Classification of Connective Tissue

Lecture Notes Part II 20 Histology 27 ? CLASSIFICATION known as adipose tissue because of the The classification of connective tissue is predominance of fat cells. Adipose tissue is inconsistent from one author to another. The not a typical form of connective tissue scheme of classification used in this course because cells rather than fibers are itspre- is to divide the connective tissues into two dominant feature. Large masses of adipose main groups, ordinary and special. The tissue are found around organs suchas the special connective tissues include bone, kidneys, adrenal glands, and item. A layer cartilage, and blood, each of which will be of adipose tissue beneath the skin isre- considered separately. All connective tissue sponsible for the smooth contours of the body. other than bone, cartilage, and blood is classed as ordinary or fibrous connective RETICULAR tissue. Examples of fibrous connective tissue Reticular connective tissue forms the frame- include: tendons, ligaments, fascia, aponeu- work for all glands, for example the liver, roses, dermis and hypodermis of the skin, spleen, and lymph nodes. It is also found in lamina propria and submucosa of epithelial the bone marrow cavities. Reticular tissue membranes, adipose tissue, etc. consists of a delicate meshwork of fine branching fibers to which are attached fixed Classification of the various fibrous connec- macrophages (cells of the immune system). tive tissues is based on: The open spaces of the network are filled in the density of fibers (loose and dense) with cells of the orp fich it serves as the physical alignment of the fibers a framework. (regular or irregular). the predominant fiber type (collagenous, DENSE FIBROUS TYPES elastic, reticular) In dense connective tissue the fibersare the cell types closely packed together; there is littlespace Classification of the special connective between the fibers, and thus there are few tissues is b ed on: cell types present other than fibrocytes, the density and type of matrix which are responsible for production of the the density and type of fibers. fibers. The density of the fibers gives great mechanical resistance to these types. Dense LOOSE FIBROUS TYPES connective tissue is further divided into two In loose connective tissue the fibers are subcategories, regular and irregular.

loosely and randomly scattered through the REGULAR AND IRREGULAR: matrix, and as a consequence, there are large In this context,regular means thatthe fibers spaces between the fibers, occupied by are arranged parallel to °lie another, and many different kinds of connective tissue irregular means that the fibers cross one cells, capable of performing a wide variety another forming a meshwork type. The of functions. regular types are generally subjected to AREOLAR forces along one axis, so the fibers are Loose connective tissue is best typified by arranged in an orderly parallel manner in the areolarconnective tissue. Areolar connec- direction of the stress. The irregular types tive tissue is the most widespread form of are found in areas where the mechanical connective tissue encountered in the human forces are likely to come from several body. In dissection it appears as a whitish directions. cobwebby material. Tendons and ligaments are examples of ADIPOSE denseregularconnective tissue. The apo- A second type of loose connective tissue is neuroses and the fascia lata of the thigh are

Lecture Notes Part II 21 4 Histology examples of dense irregular connective tissues. coumecon AND ELASTIC: The dense regulrs and irregular connective tissues are further subdivided into collagenous or elastic depending on the predominant fiber type. Tendons ligaments and aponeuroses are dense collagenous connective tissues, because the primary fiber type is collagen. The ligamenta flava (yellow ligaments) of the vertebral column, the vocal cords, and the suspensory ligament of the penis are examples of dense elastic connective tissues. AGING: It now seems apparent that the process of aging is in large part related to changes in the connective tissue cells. All of us are familiar with some of these changes: stiffening of the joints, loss of elasticity of the skin, hardening of the arteries. There is much that we don't know, but we at least know that with aging comes an increase in the amount and thickness of the collagen fibers. We also know that the elastic fibers become thicker and less springy. In fact, all of the extra- mllular substances produced by connective tissue cells, which are so necessary to the organization of living systems, continue to be formed every day of our lives, even after mature growth has been reached. Acquiring multicellularity through the adhesiveness of cells means that aging is simultaneously introduced into the life history of the organism as an inevitable consequence of embryology. Single celled organisms are potentially immortal. Thus, aging can be viewed (in part) as an aspect of development that has gone beyond the optimal needs of the organism for proper functioning.

Lecture Notes Part U 22 Histology 9 Support Tissue

CARTILAGE WHITE FIBROCARTILAGE White fibrocartilage is hyaline cartilage with Active formation of cartilage is done by the addition of many collagenous fibers. It is chondroblasts which secrete matrix material effective as a shock absorber and isstronger around themselves. Once the cell has than hyaline cartilage. It is found in the "painted itself into a corner" it entersa rest- pubic symphysis, in the intervertebral discs, ing phase and is called a chondrocyte. and in the menisci of the knee joint. Clondrocytes reside in small spaces called lacunae that they ,cave lef. for themselves in BONE the matrix. There are no special arrange- Bone differs from cartilage in that it isa ments for delivery of nutrients or removal of highly vascular tissue in whichno bone cell waste products. is more than 0.1 mm away froma blood Cartilage is avascular. No blood vesselscan capillary. The organic matrix of bone tissue penetrate into cartilage due to a chemical is called osteoid tissue, and it is produced by inhibitor in the matrix. Cartilage cellsare osteoblasts. When it is first produced osteoid kept alive by diffusion to and from the blood tissue is rubbery in consistency; later, min- vessels of the petichondrium. As a result the erals are added to convert it to the dense thickness to which a piece of cartilage can rigid material we think of as bone. grow is limited. CANCELLOIS COMPACT BOPE Cartilage is classified as hyalineif it is In cancellous bone the matrix is laid down without visable fibers, or fibrous if the as a meshwork of spicules; the spaces be- fibers are conspicuous. Fibrous cartilage is tween the spicules are occupied by bone subclassified depending on the type of fibers marrow. Cancellous bone is not a weight present. bearing tissue.

HYALINECARTILAGE In compact bone the matrix is laid down in Hyaline cartilage has a glassy smooth tex- concentric lamellae (layers) around small ture that gives it its name. Hyaline cartilage blood vessels or capillaries. The microscopic is found: organizational unit of compact bone is called in embryonic pre-bones thetaversian system. In three dimensions covering the ends of bones at moveable the haversian system has a long cylindrical joints (articular cartilage) shape with an haversian canal) at its center. at the ends of the ribs where they attach The haversian canal is occupied bya small to the sternum blood vessel. The interstices between the in the nasal cartilage, part of the nasal haversian systems are filled in by interstitial septum lamellae.Active osteoblasts become resting in the tracheal rings and plates of osteocytes once they are surrounded on all cartilage in the larger bronchial tubes. sides by matrix material. The space in which an osteocyte resides is called a lacuna. The ELASTIC CARTILAGE Elastic cartilage is hyaline cartilage with the intercellular substance of bone is permeated addition of many elastic fibers. It is found in with canaliculi (tiny canals) thatconnect the pinna of the external ear, in the epiglottis neighboring lacunae. This arrangement of the larynx, and in the Eustachian tube of serves as a transport line between cvillaries the middle ear. and bone cells, for efficient delivery of nutrients and removal of waste products.

Lecture Notes Part II 23 Histology 0 '"

BLOOD

Blood is a modified connective tissue, and HEMOSTASIS as such is composed of matrix, fibers, and cells. The matrix of blood is unique in that it The technical term for the various natural is a liquid. The fibers are unique in that they mechanisms of the body which helpto are usually in the dissolved state. Circulating control bleeding is hemostasis. The most blood volume can be estimated by taking important of the hemostasis mechanisms is 8% of the body weight expressed in kilo- blood clotting. The clotting reactionor grams. Thus a 70 Kg person (150 pounds) cascade reaction is a chain of events that would have about 5.5 Liters of blood. Of can be summarized and simplified into three main steps. this 5.5 L, about 55% or 3L is plasma. Platelet factor a protein contained inside the The liquid matrix of blood is called either thrombocytes, must mix with the plasma in plasma or serum. Plasma is the liquid phase order to initiate the clotting reaction. This of unclotted (whole) blood, and serum is the platelet factor is released from the platelets liquid left over after blood clots. Plasma and when they are bruised, injured or exposedto serum are largely water containing dissolved connective tissue. proteins, and electrolytes. The important proteins include: Prothrombin, Fibrinogen, Lymphocytes] Albumin, Gamma Globulin, other Globu- Lymphoid Tissue lins. The important electrolytes include: [Eryihmertes Na',cr, HCO; Blood ihrombocyles HEMOPOIESIS (Hemopoletic (Platelets) There are two types of he- 'Tissue) Myeloid mopoietic (blood forming) Tissue Monocytes tissue, myeloid and lymphoid. In the fetus the liver and spleen are both Neutrophils 1 Granulocyte actively hemopoietic, but after birth the series Ms most important myeloid tissue is red Eosinoohits bone marrow. In children red bone marrow is found in the cancellous Basophils interior of all bones, but in adults it is found only in the sternum, ribs, rig Embryology & Classification of Blood Cells vertebral bodies, cranial bones, crest of the ilium, and the proximal ends of the humerus and femur. Myeloid tissue pro- Prothrombin and fibrinogen are both liquid duces thrombocytes, erythrocytes, neutro- proteins components of blood plasma. phils, eosinophils, basophils, and mono- Fibrin is a solid protein derived from fi- cytes. brinogen which forms during the clottingre- action. The fibrin precipitates out of solution Lymphoid tissue is found in the thymus, in the form of long sticky strands which lymph nodes, tonsils, Peyer's patches, and form a meshwork that traps all of the cells the spleen. Lymphoid tissue produces the and pulls them out of suspension. This is the white blood cells known as lymphocytes. clot.

Lecture Notes Part II 24 Histology 31 ++ Ca A normal WBC count is in the 1. Platelet Factor Thromboplastin range between 5,000to 8,000 cells per microliter of blood. It will go up during bacterial infections and down if the bone marrow is damaged. 2. Prothrombin Thrombin HEMATOCRITS Determination of the hemato- crite level (packed cell vol- 3. Fthrinogen Fibrin ume), is a quick way to deter- mine the red blood cell content of whole blood without doing Rg. 7- Three Step Clotting Reaction a bluiAl cell count. Whole Calcium ions (Ca") are also very necessary blood is treated with an anticoagulant anda to the clotting reaction, and in fact clotting sample is then centrifuged so that all of the can be prevented by chemicals which bind cells in the sample are packed into the with the calcium ions making them unavail- bottom of the container. Plasma normally able. Chemicals which prevent blood clot- occupies 55% of the total blood volume, and ting are called anticoagulants. Some com- the cells packed into the bottom of the tube mon anticoagulants which act by binding normally occupy 45% of the volume (nor- calcium are Heparin, Sodium Citrate, and mal range 42-47%). The number of white Lithium oxilate. cells is so small compared to the number of red cells that the volume of white cells, seen Platelets (thrombocytes) are not true cells, rather they are fragments of megakaryocyte as a thin buff colored layer on top of the red cells, is virtually non measurable, and is cells found in the bone marrow. There are called the bully coat. about 300,000 per microliter of blood, and their half life is 4 days. DIFFERENTIALS BLOOD CELL COUNTS A differential is not a blood count, rather it is a morphological study of the blood cells, A complete blood count (CBC) includes a red blood cell (RBC) count and a white including a determination of the relativeper- centages of the five or so different types of blood cell (WBC) count. A measured sample of the blood is diluted in a known white blood cells. A stained blood smear is volume of fluid, and the number of His is examined microscopically. As each white blood cell comes into view a decision is counted either by hand or by machine. made as to what kind of white cell it is. A A normal RBC count is in the range of 4.5 tally is kept, and after roughly 100 cells to 5.5 million cells per microliter of blood. have been examined and tallied the results The number will vary depending on such are expressed as percentages. factors as age, gender, pregnancy, aerobic NORMALDIFFERENTIAL: exercise and altitude. Children have a lower Neutrophils:60- 70 % count than adults, women usually have a Lymphocytes: 20- 35 % lower count than men, pregnant women Monocytes: 3- 8% have a lower count than non pregnant Eosinophils: 1- women. Regular aerobic exercise will in- Basophils: 0.3 0.5% crease the number of RBCs, as will living in a high altitude environment.

Lecture Notes Part II 25 Histology White cell morphology and functions will be HEMOGLOBIN discussed below. Hemoglobin is a conjugated protein. It consists of the protein globin and four ERYTHROCYTES molecules of the pigment hone. Each mole- k. MORPHOLOGY & FUNCTION cule of heme contains an iron molecule at its Circulating red blood cells are not true cells center. The iron is responsible for the red since they do not have a nucleus. In recogni- color of the blood. Oxygenated heme is tion of this they are sometimes called red bright scarlet red, deoxygenated heme isa blood corpuscles. Each RBC is a membrane darker maroon red. Some animalsuse bound sac that is loosely filled with hemo- copper instead of iron in their blood pig- globin. ments, and in these animals the color of the blood is green. The average diameter of an RBC is 7.5 ailerons, with a thickness of 2 microns. The Hemoglobin has a reversible affinity for smallest capillaries are nrrower than that. oxygen, depending largely on concentration The loose nature of this sac and the fluid na- of oxygen in the area. Because of this ture of the hemoglobin inside allow the cell property hemoglobin is the perfect agent for to deform in order to squeeze through the transport of oxygen in the body. It takes narrow capillaries and around sharp turns up oxygen in the lungs and transports it to inside the circulatory system. the tissues where it is released. The corpuscle is in the shape of a biconcave When an RBC is phagocytized the hemoglo- disk. The thin center area was probably the bin is disassembled. The iron is removed area occupied by the nucleus during the time and stored and then recycled for making in the cell's life cycle when it had a nucleus. new hemoglobin. The rest of the hemoglobin molecule is converted to bile pigments When the red blood cell is first formed it has which are used for fat emulsification in the a nucleus, but during the maturation phase, digestive system. while the cell is still in the bone manow, it gradually loses its nucleus, and the interior ANEMIA of the cell is then fully occupied by Anemia is any deficiency in hemoglobin, hemoglobin. Erythropoktin, a hormone from whatever cause. The correlation with made by the kidney, stimulates faster pro- RBC number is not absolute. A person with duction of RBCs. Erythropoietin is released anemia might have a decreased number of when hypoJdo (low blood oxygen) occurs, RBCs, but they might also have a normal as it might in a person who lives at high number of RBCs in which each one is of altitude or a person who is doing regular reduced size, or each RBC may be filled heavy physical activity, or in a person who with less than the normal amount of hemo- is anemic or after severe blood loss (hemor- globin. rhage). IRON DEFICIENCY ANEMIA PHAGOCYTOSIS OF RBCs This type of anemia is also called simple Once the RBC enters the peripheral circula- anemia. It is due to lack of adequate iron tion it has a life span of about 120 days, intake in the diet. Iron is required to make after which time the membrane begins to the heme molecule. Good sources of iron in- break down. The worn out RBCs are phago- clude meat and fish, and especially liver, cytized in the spleen, liver, and red bone and also dark green leafy vegetables suchas marrow. spinach. PERNICIOUS ANEMIA: classified into two groups knownas the This type of anemia is due to the inability to "granulocytic series" and the "monocytic make RBCs, usually due to lack of produc- series". These groupings are basedon tion of intrinsic factor by the stomach simple visible morphological differences. epithelium. Intrinsic factor is needed for The term "monocytic series" can be confus- absorption of vitamin B13 which in turn is ing since it includes both themonocyte cell needed to complete the maturation of RBCs. line and the lymphocyte cell line,one of SICKLE CELL ANENA: which conies from myeloid tissue, and the Sickle cell anemia is due to an inequitable other of which comes from lymphoid tissue. abnormal gene for hemoglobin production. The genetic trait is recessive and will not be GRANULOCYTIC SERIES expressed unless the person has inherited Granulocytes all have granules in thecyto- two copies of the abnormal gene, one from plasm of the cell. The color, texture, and the father and one from the mother. This size of the granules is different for the three state is called the homozygous state in con- subcategories of the granulocyte series, and trast to the heterozygous state in which the these differences are ,important to thecorrect person has inherited one abnormal copy and identification of the cell type. The nucleus of one normal copy. all mature granulocyte cells is multilobed, most typically three lobed. A person with the heterozygous condition will be a carrier of the abnormal gene but NEUTROPHILS The Neutrophil is also called a Poly will not usually experience any deleterious or PMN (short for polymorpkonuckar leukocyte). medical effects, except under conditions of Neutrophils have granules which are of . extremely prolonged and strenuous physical a exertion such as one might encounter in the very small size and fine texture. Most of the armed services boot camps. granules are very pale, and a dusty lavender color. If homozygous, the person is subject to Neutrophils are the most numerous and short periodic debilitating sickle cell crises trig- lived (6 hours) of all the white blood cells, gered by activities which demand high and they function as very active phagocytes. oxygen consumption. The abnormal hemo- 100 billion of them are produced globin becomes rigid and distorted, at low every day. Their granules are lysosomes, containing oxygen tensions, and the RBC is stretched enzymes which are used to kill and digest into the so called sickle shape. The cell phagocytized bacteria. They are very mobile membrane of sickled cells is sticky and the and are chemically attracted to the site of cells are fragile. During a sickling crisis an infection. They are the first cells to arrive at small capillaries become clogged due to an infection, and hence are the first line of clumping of cells and inability of cells to defense. An accumulation of these cells at turn corners and squeeze thru narrow chan- the infection site is called pus. nels. In addition many of the fragile cells hemolyze (lyse, burst) spilling the hemoglo- Mature cells typically have three lobed bin into the plasma (where it is non- nuclei. The nucleus stands out very sharply functional). in contrast to the pale dusty looking cytoplasm. LEUKOCYTES White blood cells normally remain in the MORPHOLOGY & FUNCTION bone marrow until they are mature. How- Five types of white blood cells can be distin- ever, if the body is fighting a heavy infec- guished from one another under the light tion the production of neutrophils is stepped microscope. These five are commonly

Lecture Notes Part H 27 Histology r"."...` ^'

up, and immature forms (calledjuveniks MONOCYTES and band or stab cells) may appear in the Monocytes are the largest of all the WBCs, peripheral blood and be tallied in the differ- usually about one and a half to two times the ential. This condition is called a "shift to the diameter of a RBC.The nucleus is large and le". The most visible feature of these loose or foamy looking. It is typically folded immature cells is the nucleus. A juvenile cell into a kidney bean shape. The agranular has a single J shared nucleus that is indented cytoplasm is abundant and has the appear- on one side. A stab or band cell has a nar- ance of frosted glass. rower band shaped nucleus. As soon as lobulation is seen the cell is considered to be Monocytes are active phagocytes that are a matt= neutrophil. mobilized more slowly than neutrophils, and hence act as the so called second line of E00114014113 defense against bacterial infections, however The granules in eosinophils are very large, they are able to ingest larger numbers of refractile, and rusty brown or red-orange in bacteria than are the neutrophils. color. There are so many granules that they obscure the nucleus. The color of the gran- Monocytes probably secrete a factor which ules is due to an affinity for the dye eosin stimulates the release of neutrophils from which is present in the mixture of dyes used the bone marrow. to stain the blood. Monocytes also have an important role to Eosinophils are associated with allergies and play in cellular immunity; in order for a some parasitic infections. Eosnophil levels dedicated T lymphocyte to proliferate, it cre elevated in both conditions. They appar- must first come into physical contact with a ently inactivate some of the chemicals re- macrophage that has ingested a foreign leased from connective tissue mast cells antigen. during allergic reactions, and they are Monocytes remain in the circulating blood known to attack some parasites. for about 24 hours, after which time they BASOPHOS migrate from the blood to the tissues where The granules in basophils are also very they have a half life of about 200 days. All large, but they are nonrefractile, and are tissue macrophages come from circulating dark blue to black looking. The granules are monocytes. clearly visible as separate from the nucleus. The color of the granules is due to an affin- LYMPHOCYTES Lymphocytes are the smallest of all of the ity for the basic hematoxylin dye which is WBCs, their diameter is usually just slightly present in the mixture of dyes used to stain larger than that of a RBC. The nucleus is blood smears. round and very dark and compacted in Basophils are associated with chronic tissue appearance. The cytoplasm is often so and joint inflammations. The granules scanty as to be almost non visible. If cyto- contain histamine and h parin, and it is sug- plasm is visible it is agranular and clear sky gested that this cell plays some role in the blue in color. The so called "large lympho- balance between clotting and nonclotting of cytes" are probably younger versions of the blood. smaller lymphocytes. These larger cells have more abundant cytoplasm, but the nuclear MONOCYTIC SERIES appearance is the same as for the more Both of the cells in the monocytic series mature form. have single nuclei (not lobed). The cytoplasm of each is generally considered to be Lymphocytes are central to the action of the agranular (non granular. immune system. Functionally they are Lecture Notes Part II 28 35 Histology classified into two broad categories, T cells abnormal and rapid proliferation of WBCs. and B cells. These cannot be differentiated Cancer of the blood. from one another visually. Thrombus: a stationary clot Both types arise from multipotentialprecur- sor cells (stem cells) in the bone marrow. Embolus: a moving clot The precursor cells however lack the surface Thrombocytopenia purpura: receptors that allow the B and T cells to insufficient numbers of plateletsare being recognize specific antigens. The surface produced. Large numbers of purple bruises receptors will appear as the daughter cells are one obvious sign of this condition. mature. Each maturing lymphocyte be- Hemophilia: con= programed to recognize only one A genetic condition in which the patient particular antigen by virtue of the fact that it can't form thromboplastin or develops multiple copies of one particular some other type of receptor. necessary component of the clotting reaction. Bleeders. The lymphocyte stem cells are constantly Thrombophlebitis: generating great numbers of new receptor inflammation of a vein which types by an ongoing process of random causes mul- genetic recombination. tiple clots to form. The danger is that the clots will become emboli. B cells are responsible for humeral immunity and T cells are responsible for cellular immunity. B cells produce antibodies against foreign antigens such as bacteria and viruses. T cells (there are four subtypes) produce chemical agents (lymphokines) that cause rejection of foreign cells, as well as defense against tumors, fungi, and viruses. RELATED VOCABULARY Erythrocytosis: increased number of RBCs. Erythrocytosis is a normal response to chronic lowoxygen levels. Leukocytosis: increased number of WBCs (above 10,000 cells per microliter of blood). Leukocytosis is the normal response to bacterial infection. Leukopenia: decreased number of WBCs (below 5000 cell per microliter of blood). Leukopenia is characteristic of typhoid fever, tuberculosis, and radiation sickness. Thrombocytopenia: decreased number of platelets Leukemia:

Lecture Notes Part II 29 Histology MUSCLE TISSUE DEFINITION OF TERMS cause of their diameter the area that they occupy is relatively dense. Each filament of ROOT WORDS myosin has an enlargement or bulge at its myo - Cheek for muscle or meat center. sarco - Greek for flesh (sarcasm means to tear the flesh) Each myosin filament is made up ofmany subunits known as myosin molecules. Each C0101ECTNE TISSUE WRAPPINGS myosin molecule has an enlarged head epimysium - around a muscle which sticks out at the sides of the filament; perimysium around a fascicle these heads form the cross bridges that endomysium - around a cell make contact with adjacent actin filaments BUISCLE CELLS during contraction sarcolemma - cell membrane Z (OR Z BAND) sarcoplasm- cytoplasm This structure is found at each end of the fiber - single muscle cell sarcomere; it marks the boundary between fibrils- subunitsof a fiber adjacent sarcomeres. The actin filaments of filaments the sarcomere are attached to the Z line. myosin and actin subunits of a fibril sarcomere T TUBULES functional sections of a fibril Microtubules that lie parallel to the Z line sarcoplasmic reticulum and reach up to the surface of the cell where endoplasmic reticulum of a muscle cell. they are continuous with the sarcolemma. The sacs of the sarcoplastnic reticulum These tubules bring the neurotransmitter reversibly store and release calcium ions. chemical into the interior of the muscle cell. CROSS STRIATIONS Actin filaments are smaller in diameter than SARCOMERE ANATOMY myosin filaments, hence the end areas of the SWOFILAMENTS sarcomere (where only actin filaments are The myofihunents actin and myosin inter- found) are less dense than the center area of digitate with one another. The myosin the sarcomere where only myosin filaments filaments occupy the center section of the are found. The less dense areas transmit sarcomere, the actin filaments occupy each more light (isotropic bands) than does the end of the sarcomere. denser area (anisotropic band). Actin BANDS Actin filaments are found on the ends of the There are two of these bands for each sarcomere. They are small in diameter and sarcomere, one next to each Z line. Each I therefore the area they occupy is relatively band is an area of the sarcomere where only non dense. Each actin filament is composed actin filaments are found. I stands for iso- of long strands (molecules) of troponin and tropic referring to a relative ability to trans- tropomysin proteins wrapped around one mit light.These bands are areas of low another in a helix formation. density where the actin filaments do not overlap with the myosin filaments. They Myosin appear as light striations relative to the A Myosin filaments are the thicker filaments band in the center of the sarcomere. found in the center of the sarcomere; be-

Lecture Notes Part II 30 Histology A BAND 3. CROSS BRIDGE ROTATION A stands for anisotropic, referring toa At the same time that calcium is flowing relative inability to transmit light. The A into the cell, ATP (adenosine triphosphate, band is the area in the center of eachsar- the energy currency of the cell) is broken comere correspcoding to the actual length of down into ADP + P + freeenergy. This free the group of myosin filaments. The area is energy causes the cross bridges to rotate of high density and therefore anisotropic,so which causes the actin filaments filamentsto it appears as a dark striation relative to the I slide toward the center of thesarcomere bands on either side of it. where they overlap the myosin filamentsto HBAND a greater extent, thus shortening the length The H band is part of the A band. It is the of the sarcomere. Neighboringsarcomeres lighter region in the center of the A band are also shortening, and thus the fibril, the where there is no overlap between actin and fiber, and the whole motor unit also shorten. myosin filaments. It is shaped somewhat 4. CROSS BRIDGE RETURN like a capitol letter H, hence the name "H" ATP expenditure may also be requiredto band. break the connections and return the myosin IA ME heads (cross bridges) to their original posi- M stands for middle. These bulges lineup tions, ready to make contact androtate with one another and create a region of again. Muscle contraction is thusa sequence greater density that looks like a dark line of small ratchet-like connections, rotations, running down the center of the sarcomere. and returns. This line is known as the M line. ANATOMIC CHANGES IN THE SLIDING FILAMENT THEORY CONTRACTING SARCOMERE OF MUSCLE CONTRACTION The myosin filaments do notmove. The actin filaments slide toward thecenter 1. NERVE IMPULSE of the sarcomere. When a nerve impulse arrives at a muscle The Z lines move closer together. cell it causes the release of neurotransmitter (acetylcholine) onto the surface of the thus: muscle cell which spreads into the interior The I bands become narrower. of the sarcomere by way of the T tubules. The H bands become narrower. The neurotransmitter causes calcium ions to The A bands don't change. be released from the sarcoplasmic reticu- The sarcomere shortens. lum. The calcium ions flood into the sarcomere and facilitate contraction by causing them to bind with troponin of the actin TYPES OF MUSCLE TISSUE filament. SMOOTH MUSCLE 2. CALCIUM BONDS The cells are small and delicate and When calcium ions bind with troponin the fuseform (cigar shaped). Each hasa pale troponin molecule physically shifts, ex- centrally located nucleus; the cytoplasm is posing a small socket in the troponin/ tro- not striated. The cells occur in thin sheets, pomysin helix into which a myosin cross- each cell is surrounded by a delicate connec- bridge fits. Thus actin and myosin make tive tissue network, and the whole sheet is physical connection with one another for the separated from other sheets of muscle by first time. areolar connective tissue. When contraction

Lecture Notes Part II 31 n Histology occurs it resembles a slow, smooth, spreading wave. This type of muscle gives the MOTOR UNIT CONCEPT appearance of not fatiguing since it is ca- One motor unit = the total number of skele- pable of continuing to contract for hours (as tal muscle cells supplied by the branches of during childbirth). A whole sheet of muscle a single axon (a single nerve cell). When a cells requires only one nerve since the nerve impulse activates a nerve cell, all impulse spreads readily from one cell to the branches of that nerve will release ACh next. Other names for this type of muscle simultaneously, and the whole motor unit are visceral muscle, Involuntary muscle, will respond. and autonomic nervous system muscle. Some motor units are as small as three Some of the places it is found are: the walls muscle cells, some are as large as 600 or of hollow internal organs (except the heart), more muscle cells. Small motor units allow in the walls of ducts and vessels, and at- for fine motor control and thus delicate tached to the hairs of the skin. movements; large motor units are associated with power. Increased power will also result SKELETAL MUSCLE from activating more nerves, and thus The cells are boldly striated, and each cell is calling into action more motor units (re- enormously long and quite wide. There are cruitment of motor units). many nuclei per single cell; the nuclei are peripheral in position and are small, dark, and condensed looking. The muscle cells are grouped into large fascicles or bundles, and each cell requires individual connection to a branch of an axon; there is no spreading of contraction from one cell to another. The contractions are strong, brief, and powerful, but the muscle fatigues easily. Synonyms for this type of muscle tissue are: striated muscle, voluntary muscle, somatic muscle, and peripheral nervous system muscle.

CARDIAC MUSCLE The cells are small, faintly striated, with central nuclei and blunt ends that anastomose with one another by way of special junctions called intercalated discs. The discs facilitate the spread of contraction from one cell to another. Some cells branch before connecting to another cell, so that the tissue has the appearance of a branched network rather than a group of bundles. Each cell has it's own intrinsic pulsating contractility that appears not to fatigue. The pulsations syn- chronize with one another. There are no synonyms for this type of muscle.

Lecture Notes Part II 32 Histology 39 ARCHITECTURAL PLANS OF SIMPLEORGANS "klIkT,TVA tkA Arteries and veins both have the following s Skin is an organ, not a tissue. It is the three basic layers, but the layersare thicker largest organ by weight. in the human body, in arteries (especially the tunica media), and and serves an important immune system the elastic tissue is lacking in veins. organ, as well as a mechanical and chemical barrier to the outside world. It has three ARCHITECTURAL PLAN basic layers, only one of which is epithelial. 1. TUNICA INTERNA 1. EPIDERMIS This layer is also known as the tunica This is the avascular epithelial surface layer intima. It has three sub parts: of the skin. It has five subsections: A. ENDOTHELIUM A. STRATUM CORNEUM B. BASEMENT MEMBRANE The cells of this zone have lost their This layer is invisible unless a special nuclei and are beginning to dehydrate and stain is used to prepare the slide. flake off of the skin. As longas they are

INTERNAL ELASTIC MEMBRANE present they have a protective function. B. STRATUM LUCIDUM 2. TUNICA MEDIA This zone is translucent. The cells have A. SMOOTH MUSCLE lost their nuclei but the dead cells remain tightly glued in place. They havea B. EXTERNAL ELASTIC ZONE protective function. 3. TUNICA EXTERNA C. STRATUM GRANULOSUM This layer is also known as the tunica The cells of this zone are full of keratin adventitia. It is a layer composed of irregu- granules. Keratin is a protein material lar fibrous connective tissue. that is manufactured by the living cells of the skin. It acts as a type of intercellular PATHOLOGY OF ARTERY WALLS glue which keeps the upper layers of dead

ARTERIOSCLEROSIS cells in place for a considerable length of Arteriosclerosis is a term applied to a num- time. ber of pathologies in which there is thicken- D.STRATUM SPINOSUM ing, hardening, and loss of elasticity of the This zone is also sometimes called the walls of arteries. Changes mayoccur in the Malphigian layer. The cells in the bottom intima, media, or both. part of this zone may contain pigment

ATHEROSCLEROSIS granules which protect the dividing cells Atherosclerosis is a form of arteriosclerosis. in the stratum basale from damage by There is an abnormal growth of cells (tu- sunlight. mor) (atheroma) in the tunica media. These 5. STRATUM BASALE growths are called atheromas. The atheroma Another name for this layer is Stratum disrupts the internal elastic membrane and Germinadrum. This single layer of occludes the lumen of the artery. cuboidalcells clings to the basement membrane of the skin. These are the actively dividing cells whir:h give rise to all of the cells in the higher zones.

Lecture Notes Part II 33 I listology ell 0 2. DERMIS small blood vessels, lymphatics, nerves, and The dermis is a layer of dense irregular sometimes multicellular mucous glands. collagenous connective tissue that is well 3.MUSCULARIS MUCOSA vascularized. It has several interesting The muscularis mucosa is a thin layer of features which are listed below. smooth muscle found beneath the lamina A. DERMA!. PAPILLAE propria. The dermal papillae are raised portions of the dermal layer that help to anchor the RESPIRATORY TUBE WALLS epidermis to the dermis. 1. MUCOSA B. SWEAT GLAWS These glands are also called sudoriferous A. EPITHEUUM Pseudnstratified columnar epithelium glands. They are simple coiled tubular glands which have a long duct that with cilia And goblet cells. reaches to the free surface of the skin. B. BASEMEN' MEMBRANE

C. SEBACEOUS GLANDS C. LAMINA PR1PRIA These oil secreting glands are found only D. MUSCULAR'S MUCOSA in hairy skin. Their ducts always open into the hair follicle. 2. SUBMUCO3A This is a zone of dense fibrous connective 3. HYPODERMIS tissue that may contain pieces of hylaine This section of the skin is also known as the cartilage and multicellular mucous secreting subcutaneous layer. It is a connective tissue glands. zone beneath the dermis, and characterized by the presence of adipose tissue. 3. ADVENTITIA This is a zone of irregular loose fibrous connective tissue surrounding the outside of the trachea and bronchi. Amucous membrane is also known as a mucosa. It has four layers: GUT TUBE WALLS 1. EPITHELIUM 1. MUCOSA The epitheliumof a mucous membrane will vary depending on location and function. A.EPITHEUUM Simple columnar epithelium. For example, in the respiratory system it will be pseudostratified columnar, in the intestine B. BASEMENT MEMBRANE it will be simple columnar, and in the C. LAMINA PROPRIA esophagus it will be strated squamous. D. MUSCULAR'S MUCOSA 2. BASEMENT MEMBRANE 2. SUBMUCOSA The baser, tent membrane is a delicate layer This is a zone of dense fibrous connective of glue-like material secreted by the connec- tissue that may contain large numbers of tive tissue cells of the lamina propria. It is multicellular mucous secreting glands. It usually invisible unless special stains are also contains larger blood vessels and used. It plays an important roll in keeping lymphatics than does the lamina propria. the epithelial sheet intact. 3. MUSCULARIS EXTERNA 3. LAMINA PROPRIA The muscularis externa is also called the The lamina propria is the connective tissue Tunica Muscularis. These layers of smooth layer underlying the basement membrane of muscle are responsible for the churning All mucosae. This layer always includes

Lecture Notes Part II 34 Histology 41 action of the stomach and for peristalsis in the rest of the digestive tube. Only the stomach has all three layers. Otherparts of the digestive tube have two layers.

A. IMERMOST OBLIQUE LAYER This layer is found only in the stomach.

B. OMR CIRCULAR LAYER The muscle cells in this layerare oriented in a circular fashion around the circum- ference of the tube. When these cells contract they constrict the diameter of the tube. In certain locations the inner circular layer is especially thick; suchstruc- tures are known as sphincters.

C. OUTER LOGITUDINAL LAYER The muscle cells in this layerare oriented parallel with the longitudinal axis of the tube. When this layer contracts ina coordinated fashion with the inner circular layer of muscle, a bolus of food is moved forward through the gut tube.

4. SEROSA OR ADVENTITIA A serosa is the same as an adventitiaexcept that it has an additional outer layer of simple squamous epithelium known as mesothelium. This mesothelium secretesserous fluid, which is a thin watery fluid that moistens and lubricates the peritoneum. The esophagus and all retroperitoneal portions of the digestive systemare surrounded by an adventitia rather thana serosa.

Lecture Notes Part 11 35 42 Histology Diestive System hangs from the lower edge (greater There are three types of membranes associ- curvature) of the stomach and doubles under ated with the digestive system: mesentery, to connect the stomach to the transverse omentum, and suspensory ligaments. All of colon. It hangs down loosely over the in- these are derived from peritoneum. testines, and serves as a fat storageorgan and as a reserve storehouse for fixed tissue MESENTERY macrophages.

The term mesentery refers to any double LESSEROMENTUM: fold of parietal peritoneum that connectsan The lesser omentum is a double fold of peri- organ to the posterior abdominal wall. In the toneum stretching between the lesser curva- case of the small intestine, the parietal peri- ture of the stomach and the liver. toneum of the posterior abdominal wall projects forward into the abdominal cavity in us LIGAMENTS OF THE UVER a double fold shaped like a A suspensory ligament is a fold pleated fan. The of peritoneum connecting one organ to another, or connecting outer edge of liver this fan an organ to the body wall. The shaped fold isgallbladder coronary and falcifonn liga- approx- ments are suspensory liga- imately 20 duodenum ments, the ligamentum feet long. The teres is not. posterior transverse CO jejunum CORONARY LIGAMENT border (the The coronary liga- handle of the ascending co ment of the fan) is ap- liver is the proximately 6- descending colonperitoneal 8 inches long. connection It serves as a between the highway for the liver and the mesenteric arteries sigmoid colon diaphragm. The and veins which visceral perito- supply the small intes- rectum neum on the su- tine. It also organizes perior surface of the intestinal tract, pre- the liver leaves the venting it from getting Fig 8- Overview of Digestive System liver and turns tangled. showing theMesenteryof the Intestine upward to become OMENTUM the parietal peri- The greater and lesser omentum are folds of toneum of the bottom surface of the diaphragm. peritoneum connecting the stomach to some other organ. FALCIFORM LIGAMENT The falciform ligament is a double fold of GREATER OMENTUM: peritoneum found between the right and left The greater omentum is the first thing that lobes of the liver. It envelopes the ligamen- one sees upon opening the abdominal cavity. tum teres (see below). It is an apron like double fold of peritoneum Lecture Notes Part II 36 Digestive System 43 LOAMENTUM TERES teeth for only Also known as the round ligament =wary ligament of liver one quadrant of the liver. This structure is of the mouth not a susroory liga- since the lower ment, rather it is a liver jaw pattern is remnant of the um- peritoneum identical to the bilical vein, which lesser omentum upper jaw pat- was the blood vessel tern, and the carrying nutrient stomach pancreas right and left laden blood from the sides are mirror placenta to the fetus. transverse colon images of one (The definition of a mesentery another. The vein is that it carries gmater omentum dental formula blood toward the peritoneum is unique to heat. The umbilical each species. vein carries blood to omental bursa The first set of the fetal heart.). teeth are the 20 Fig. 9- Peritoneal Membranes of the deciduous teeth Al.vioment Midsagittal View. of the child. They begin to erupt at 5-9 months. The second set of teeth are the permanent teeth of the adult. They begin to erupt at 6years and eruption DIGESTIVE FUNCTIONS is completed by the 15th year except for the Chemical digestion processes dependupon wisdom teeth (2nd and 3rd molars) which maximum surface area. Small particles have erupt between 17-25 years of age. more surface area than larger particles. Mastication of food is a mechanical ADULT DENTAL FORMULA process 2:1:2:3 that creates small particles out of larger two incisors, pieces. one canine, Food must be moistened and lubricated to two premolars (bicuspids), aid in swallowing. Saliva contains both three molars water and mucous to serve this end. Food CHILD'S DENTAL FORMULA must also be moistened in order to be tasted. 2 : 1 : 0 : 2 Taste triggers digestive enzyme secretion, two incisors, both in the mouth and in the lower parts of one canine, the digestive system. two molars Saliva contains salivary amylase that begins SALIVARY GLANDS the chemical digestion of starch by breaking PAROTID down the long chain starch molecules into The parotid salivary gland is in front of the simple sugars. ear and behind the ramus of the mandible. Saliva also has antibacterial properties. Mumps is a viral inflammation of thepa- People with compromised saliva secretion rotid gland. have more dental carries. The duct from the parotid glandcrosses over DENTITION the masseter muscle and penetrates the A dental formula indicates the pattern of mucosa to open inside the mouth at the level of the second molar in the upper jaw. Lecture Notes Part 11 37 Digestive System .44 SIHNAANDBULAR frenuhun connecting each lip to the adjacent The submanclibular gland (also knowa as the gum (gingiva), there is also a frenulum submaxillary gland) lies below the body of connecting the tongue to the floor of the the mandible; its duct opens at the base of mouth. If this one is too short (tongue tied) it the frenulum of the tongue. makes speech difficult.

PAPILLAE OF THE TONGUE GINGIVAE The papillae of the tongue are projections of The gingivae are the gums. the epithelium of the upper surface of the SOFT PALATE AND UVULA tongue. Two of the three types contain taste The uvula is part of the soft palate, and the buds. soft palate participates is swallowing by VALLATE (CIRCUMVALLATE) helping to close off the opening to the na- The vallate papillae are the fewest in num- opharynx. ber and the largest of the papillae. There are 7-12 of them on each side, Located at the back of the tongue in a single V shaps4 row. HISTOLOGY Each one is like a castle surrounded by a MUCOSA OF THE ESOPHAGUS moat or trench which is kept clear of debris The epithelium of the esophagus is subject by flooding from glands in the papilla. Each to abrasion from nearly solid food particles, papilla contains several taste buds which and is therefore of the stratified squamous send information to the brain via cranial type. A great deal of mucous is needed to nerve IX. facilitate passage of this food through the tube and into the stomach. There are a large FUNGFOIVA number of mucous glands which extend all The fungiform papillae are located on the tip the way from the lumen down into the and sides of the tongue. These papillae look submucosa. like red spots on the tongue because their epithelium is so thin and transparent that it MUSCULARIS EXTERNA: allows blood to show through. They contain The upper one third of the esophagus con- taste buds which send information to the tains voluntary muscle. The middlz one third brain via cranial nerve VII. contains a mixture of skeletal and smooth muscle. The lower one third contains FIUFORM The filiform papillae are the most numerous smooth muscle. Swallowing begins as a vol- of the papillae. They are evenly distributed untary act but continues as a peristPltic over the whole surface of the tongue. They wave of the smooth muscle. Arrksn,. do not contain taste buds. Each one is shaped like a tiny hooked file. They serve to roughen the surface of the tongue so that it REGIONS CURVATURES: is not so slick, helping to keep food from CARDIAC REGION sliding off of the tongue during chewing. The cardiac region of the stomach is the area They are also sense organs for touch. In immediately surrounding the junction of some animals, like the cat, these papillae ar.: stomach and esophagus. enlarged grid rasp like. FUNDIC REGION MISCELLANEOUS The fundus of the stomach is the bubble like FRENULA OF TONGUE & LIPS area at the top of tree stomach. A frenulum is a thin fold of mucus mem- BODY OF THE STOMACH brane attaching two parts, one of which is The body of the stomach is the main and less movable than the other. Thew !' a largest part of the stomach.

Lecture Notes Part H 38 Digestive System 45 RS

PYLORP REGION active protease) to pep- The pyloric region is lowest part of the sin, the active form. stomach immediately preceding the fundus Perhaps it is the pres- junction between stomach and duode- ence of this acid that num. makes the stomach GREATER CURVATURE ulcer prone (peptic The greater curvature ulcers). Intrinsic factor is the left hand and is needed for ab- inferior border of the sorption of vitamin stomach. which in turn is needed

LESSER CURVATURE for production of red The lesser curvature is the blood cells. right hand border of the stomach. Fig. 10. Stomach filifiCULAMS EXTERNA The smooth muscle of the stom- HISTOLOGY OF THE STOMACH ach is unique in that it has three layers RUGAE rather than the usual two. The extra layer When the stomach is empty the mucosa and of muscle is important to the churning action submucosa are thrown into temporary folds of the stomach. The layers from inside out called rugae which disappear when the are: stomach is distended with food. Innermost Oblique layer Inner Circular layer GASTRIC GLANDS The epithelium of the stomach is the simple Outer Longitudinal layer columnar type with many mucous secreting PYLORIC SPHINCTER goblet cells. The surface of the mucosa is The pyloric sphincter is found at the lower marked by closely set gastric pits which are end of the stomach where it joins with the openings that lead to the subsurface gastric duodenum. It is a thickening of the inner glands. The volume of secretion from these circular layer of the muscularis externa. The gastric glands has been estimated at approxi- sphincter stays tightly constricted until the mately 2500 cc per day. There are three stomach contents are liquified, then it types of secretory cells in the glands. relaxes, allowing the liquified stomach contents (chyme) to enter the duodenum. Mucous Neck Cells The necks of the gastric glands are lined FUNCTIONS OF THE STOMACH with goblet cells called the mucous neck DIGESTION cells. The mucous tends to protect the The churning action of the stomach is an epithelium of the stomach from harm important mechanical part of digestion. In from the HCl produced by other cells of addition the first phase of protein digestion the gastric glands. begins with the pepsin secreted by the stomach. Chief Cells The chief cells secrete pepsinogen, the ABSORPTION inactive form of pepsin, a protease Only a few things are absorbed through the enzyme that begins the process of protein stomach wall, namelysimple sugars such digestion. as fructose, alceaol, & some drugs such as aspirin. Parietal Cells The parietal cells secrete HCl and intrinsic factor. RC/ is a strong acid necessary for conversion of pepsinogen (the in-

Lecture Notes Part U 39 Digestive System Villi are fingerlike folds of the mucosa of the small intestine. They are found in the FUNCTION small intestine only, not in the stomach or The chief function of the small intestine is large intestine. They are just barely visible digestion of food and absorption of nutri- with the naked eye and cause the inside ents. The chief function of the large intestine surface of the small intestine to appear to is absorption of water and electrolytes. have a velvety texture. DIGESTION: The main characteristic of the villi is that the Most of the digestive activity cf the small lamina propria of each contains a blood intestine is due to pancreatic enzymes aided capillary and a lymphatic capillary (lacteal). by bile. Pancreatic enzymes arc made by the It is into these vessels that the products of pancreas, bile is made by the liver cells, both digestion are absorbed. The fat goes mainly are ducted to the duodenum via a system of into the lacteal and the other nutrients are ducts. More will be said about these subjects absorbed into the blood capillaries. below. MICROVILL1 ABIORPTION Microvilli are fingerlike projections of the The term absorption refers to the uptake of membrane of the superior surface of the cell. molecules through the mucosa of the intes- Many microvilli project from the free border tine and into the blood or lymphatic capillar- of each simple columnar epithelial cell. ies. These function requires maximum They are present in both the small and large mucosal surface area. intestine (as well as on the cells in the MUCOSAL SURFACE AREA kidney tubules. Under the light microscope they give a fuzzy appearance to the free bor- There are about 6 different ways in which to ders of the columnar epithelial cells. This increase mucosal surface area in order to mare the absorption process. fuzzy border is sometimes called a "brush border". LENGTH OF INTESTINE A longer tube will have more mucosal INTESTINAL GLANDS The intestinal glands are somewhat similar surface area than a shorter tube. The length to the gastric pits of the stomach in that They of the intestinal tube is related to the diet of are subsurface indentations of the mucosa. the animal in question. Carnivores have The crypts are found between the bases of relatively short intestinal tracts. Herbivores the viii of the small intestine. The only need very long intestinal tracts. Omnivores function they appear to have is that of like the human (and the pig) have intermedi- increasing the surface area. Formerly it was ate length intestinal tracts. thought that the crypts contained a special COILS kind of cell called a Paneth cell, thought to In order to fit a long tube into the abdominal be the source of secretion of special intesti- cavity the tube must be coiled. nal enzymes. Now it is believed that these PLEATS intestinal enzymes are secreted by all parts The inside surface (mucosa and submucosa) of the intestinal mucosa. of the intestine is folded into permanent SMALL INTESTINE pleats. In the small intestine each pleat is The small intestine is approximately 21 feet long and called a plica circulares. In the large intes- is divided into three regions. tine these pleats are called the semilunar folds. DUODENUM The duodenum is the first 10 inches of the V1LU small intestine. It is shaped like a capitol

Lecture Notes Part 11 ao 47 Digestive System letter C. The duodenum is retroperitoneal, especially in the ileum, and especiallynear euept for the first section which is called the ileocecal valve. They alwaysoccur on the cap of the duodenum. See Fig. 10. the side of the intestinal tube opposite to the The ducienum is very ulcer prone (duodenal attachment of the mesentery. ulcers), particularly the second part of the LARGE INTESTINE duodenum which receive the full impact of The large intestine is approximately 3.5 feet the acidic chyme as it squirts out of the long and is divided into six regions. stomach. The submucosa in this area of the duodenum possesses large numbers of CECUM (CAECUM) glands called Bnmixtr's glands which The cecum is the first part of the large produce copious amounts of mucous. intestine to receive the contents of the small intestine when the ileocecal valveopens. It Another feature of the duodenum is the is found in the lower right quadrant of the duodenal ampulla, also known as the abdomen in humans. The size of thececum duodenal papilla, ampulla of Vater and varies among different species; it ispar- papilla of Vater. This papilla is the common ticularly large in herbivores andmay be nonexistent in carnivores. Vermiform appendix The vermiform (worm shaped) appendix is attached to the cecum in the lower right quadrant of the abdomen. It is thought to be a nonfunctional vestigial structure, probably a remnant of what was once a larger cecum. It is not present in all species.

ASCENDING COLON The ascending colon is the direct upward continuation of the cecum on the right side Fig. 11- Duodenal Ampulla of the abdomen. At the level of the liver it makes a right angle turn to the left. This turn opening of the ducts from the gall bladder is called the right colic flexure,or hepatic and the pancreas into the duodenum. flexure. The ascending colon is retro- JEJUNUM peritoneal. The jejunum is approximately 8 feet long. It hepatic has no special features. transverse splenic flexure colon flexure ILEUM The ileum is approximately 12 feet long. At taenia coli its terminal end it enters the haustra 111 cecum at an abrupt right angle. This opening of ileum into cecum is guarded by a sphinc- descending ter called the ileocecal valve. colon

One of the most interesting features of the cecum sigmoid ileum is the presence of Peyer's patches.. colon Peyer's patches are nonencapsulated masses appendix rectum of lymphoid tissue found in the mucosa and submucosa of the wall of the small intestine, Fig. 12- Large Intestine

Lecture Notes Part 11 41 Digestive System TRANSVERSE COLON DISTINGUISHING FEATURES OF LARGE INTESTINE The transverse colon is inferior to the stom- The large intestine can be distinguished ach, and stretches from the right side of the from the small intestine by the following abdomen (near the liver) to the left side of four features: the abdomen where it touches the spleen. In Diameter. The large intestine has a larger pictures of cadavers it is seen as a horizontal diameter than the small intestine. section of the colon. In a living person it usually droops to a variable degree. When it Taenlae coli: The taeniae coli represent reaches the spleen it makes a right angle turn the longitudinal muscle layer of the muscu- downward. This turn is called the left colic laris externa which has been bunched into flexure or spknic flexure. three strips or bands. The anterior taenia

DESCENDING COLON leads to the appendix and is thereforea The descending colon is the section of colon useful landmark. en the left side of the abdomen. The de- Ilaustra The taeniae coli are shorter than scending colon is retroperitoneal. the length of the large intestine itself so they MOD COLON act to gather the large intestine together into The sigmoid colon is the S shaped section of sacculations ( sac-like bulges). colon directly continuous with the descend- Epiploic appendages: The epiploic ap- ing colon. The name refers to the S shape. pendages are fatty bits of visceral perito- RECTUM neum hanging from the outer surface of the The rectum is large intestine. They have no known func- retroperitoneal tion but are unique and are therefore useful and is directly in identifying the large intestine. continuous with the sigmoid colon. It has mucosal folds called rectal valves 7 which help to support the weight of the feces, reducing Fig. 13- Rectal Canal the pressure on the anal sphincter. When taking a rectal temperature it is important not to push against one of the rectal valve since they can tear. There are two rectal (anal) sphincters, the inner one is a thickening of the circular smooth muscle and is involuntary. It opens automatically in response to distention of the rectum. The external anal sphincter is of skeletal muscle and is voluntary. During childhood toilet training the child is taught to recognize the feelings of rectal distersion and to take appropriate action.

Lecture Notes Part II 42 49 Digestive System Accessory Digestive Glands

central vein. Between these cordsare the venous sinusoids of the liver, which are like ANATOMY OF THE LIVER very large capillaries in that the exchange of LOBES nutrients and gasses takes place between the Seen from an anterior view, the liver is blood in the sinusoids and the cells in the divided into right and left lobes by the cords. Here and there along the sinusoidsare falciform ligament. If examined from a the resident macrophages of the liver, called posterior inferior view two additional lobes Kupffer cells. can be seen, the caudate and quadrate lobes. The quadrate lobe is shaped like a At the perimeter of the lobule, in thecorners quadrangle. and is closest to the gall bladder. between neighboring lobules, are groupings The caudate lobe is the most posterior of the called triads, which consist of small F two and partially envelopes the inferior vena branches of the hepatic artery, portal vein, cam and bile duct. Blood arrives in the lobule by way of the PORTA HEPA'TIS portal vein and hepatic artery, and then The term porta hepatis means "gateway to enters the liver sinusoids where it gives up the liver". It lies in the lesser omentum and the food and oxygen it is carrying to the consists of a triad of vessels which supply liver cells. The used blood then drains into blood to and remove bile from the liver. the central vein and from there into the hep- COMMON BILE DUCT atic veins and inferior vena cava. The common bile duct receives bile from the smaller hepatic bile ducts, and carries it to Bile, made by the liver cells, moves in the the duodenum. opposite direction to that of the blood flow. It is initially collected by very fine ducts HEPATIC PORTAL VEIN found between the cells of the liver cords. The hepatic portal vein collects blood from These ducts are called the bile canaliculi the spleen, stomach and intestines. This They drain into the bile duct found in the blood is rich in absorbed dietary nutrient s, triad. These ducts in turn join together to and these nutrients are brought to the liver form the hepatic bile ducts which carry bile for further processing. to the gall bladder for storage. The larger HEPATIC ARTERY bile ducts are readily distinguished from The hepatic artery is a branch of the celiac blood vessels by their cuboidal epithelial lin- trunk, which in turn is a branch of the aorta. ing. This is the route by which oxygen and dietary fat arrive at the liver. FUNCTIONS OF THE LIVER STORAGE LOBULE ARCHITECTURE The liver stores certain items, notably The liver is made up of hexagonal lobules vitamin A, iron, and glycogen. that are just barely visible to the naked eye. At the center of each lobule is a branch of an DETOXIFICATION

hepatic vein called the central vein. The liver removes all kinds of toxic substances from the blood and disposes of them Cords of cuboidal liver cells are arranged in various ways. Notable among these are like spokes in a wheel radiating out from the alcohol and esters of all kinds. Most chem-

Lecture Notes Part 11 Digestive System 43 r0 icals which are volatile and aromatic are Albumin, which is essential for osmotic esters. equilibrium, is 70% of the total plasma protein. Lack of sufficient blood albumin SYNTHESIS OF UREA is often accompanied by ascites, the ede- When amino acids are catabolized they are matous accumulation of fluids in the peri- ckaminated i.e. the nitrogen molecule is toneal cavity. Ascites is a symptom of removed and discarded as a nitrogenous Kwashiorkor (protein starvation). waste product (ammonia). Ammonia is extremely toxic to cells, so the liver immedi- The globulins are used as carrier mole- ately converts the ammonia to urea, which is cules for transport of steroid and thyroid less toxic. The urea is removed from the hormones and cholesterol. Various globu- blood in the kidneys. lins are also blood clotting factors (such as fibrinogen and prothrombin). SYNTHESIS OF BILE Bile is synthesized by liver cells from 2. CATABOLISM OF AMINO ACIDS Amino acids can be burned as fuel if suffi- bilirubin and cholesterol. (Bilirubin is a cient glucose is not available. See number 5 breakdown product of hemoglobin). The bile below. is then ducted to the gall bladder where it is concentrated and stored. Its place of action FAT METABOLISM: is the small intestine, where it acts as an 1. LIPOGENESIS emulsifying agent so that lipase enzymes Production of fat from glucose and/or amino can work efficiently. acids is a function of the liver. When excess GLUCOSE METABOLISM calories are consumed the extra glucose can 1. GLYCOLS be converted into fat which is then trans- The liver removes excess glucose from ported to the adipose cells for storage. blood and converts it into the storage form, 2. UPOLYSIS: glycogen, which is a polymer of glucose. It On the other hand, fatty acids can be used as is a reversible process. a fuel source if glucose is not available. glycogenesis When fats are being burned for fuel by glucose glycogen products known as ketones are produced. A high level of ketones in the blood is called glycogenolysis ketosis. Ketones are acidic; if the levels are very high they cause acidosis which in turn

2. GLYCOGENOLYSIS can produce coma and death. The reverse of glycogenesis is called glycogenolysis. The term implies the measured LIVER PATHOLOGY release of glucose. Hepatitis is any inflammation of the liver.

3. GLUCOGENESIS: Cirrhosis is the destruction of liver cells This term means the production of glucose accompanied by production of scar tissue. from amino acids and or fatty acids. Falling Symptoms of both hepatitis and cirrhosis: blood sugar stimulates glucogenesis. decreased plasma albumin, edema, jaundice, PROTEIN METABOLISM and increase in circulating ammonia. 1. SYNTHESIS OF PLASMA PROTEINS Causes: viral, alcohol abuse, drug abuse, The liver cells have the special job of pro- toxic compounds. Included among the liver ducing plasma proteins, including albumin toxins: alcohol, tranquilizers, anesthetics, all and various globulins (except for immuno- volatile compounds such as carbon tetra- globulin). Lecture Notes Part II 44 Digestive System 51 chloride, gasoline fumes, benzene, xylene, increasing the blood glucose level. acetone, etc. PANCREATIC PATHOLOGY Goat.:Liver produces uric acid rather than DIABETES MELLITUS urea (from cellular nucleic acids). Uric acid Diabetes mellitus (as opposedto diabetes accumulates in the cells and cancause insipidus) is due to insulin insufficiency and/ inflammation. or &creased tissue sensitivity to insulin. Type I Diabetes (juvenileonset diabetes) is The gall bladder concentrates, stores,an the most severe form and has thepoorest releases bile. It's epithelium, like that of the prognosis. It is probably hereditary andis bile ducts, is simple cuboidal intype, spe- usually due to degeneration of the 13 cells. cialized for reabsorption of water. Type II Diabetes (Maturity Onset Diabetes) The release of bile is coordinated with the is due to decreased tissue sensitivityto presence of fat in the duodenum by the insulin (insulin resistance). hormonecholerystokinin. Tissues vary in their sensitivity (or resis- Cholecystokinin,produced by the duodenum, tance) to insulin. Obesity increases insulin causes the gall bladder to contract. resistance and thereforeaggravates diabetes Gallstones:May follow infection of the gall mellitus. Exercise and weight loss raise bladder, or may be due to a hereditary quirk tissue sensitivity to insulin. Orinase raises in cholesterol metabolism. tissue responsiveness and also increases 34'in production.

, .. HYPOGLYCEMIA The pancreas has two kinds of tissue, the Hypoglycemia is thought to be dueto "pancreatic tissue proper" and the "islands overreaction of the pancreas (hypersecretion of Langerhans". of insulin) following ingestion of refined carbohydrates. This results ina too rapid PANCREATIC TISSUE PROPER drop in blood sugar level. Symptoms ofvery This tissue produces digestiveenzymes low blood sugar levels: weakness, fatigue, which are ducted to the duodenum. Theen- depression, and "the shakes". zymes include a variety ofproteases, amylases,andlipases.Proteases are for protein Hypoglycemia is a fad disease, and there is digestion, amylases are for starch digestion, probably much quackery associated with its and lipases are for fat digestion. "diagnosis" and treatment. Be skeptical of any person who says that you or they have ISLANDS OF LANGERHANS hypoglycemia without a thorough physical The islands of Langerhans produce two examination including a three to five hour hormones. insulin and glucagone. glucose tolerance test. IHSUUN: The rate of entry of glucose into all body DUCTSYSTIE cells is chiefly regulated by insulin. A rise in The following is a description of the ducts blood glucose stimulates the secretion of connected to the liver, gall bladder,pancreas insulin from the pancreas and the subsequent and duodenum. leveling off of blood sugar. The bile ducts bringing bile out of the lobes GLUCAGON: of the liver are called the right and left A fall in blood glucose level stimulates the hepatic bile ducts. They join to form the pancreas to secrete glucagon. Glucagon common hepatic bile duct. The bile duct stimulates glycogenolysis by the liver, thus leading to and from the gall bladder is called Lecture Notes Part II 45r2 Digestive System the cystic bile duct. The cystic bile duct and the common hepatic bile duct join to form the common bile duct which goes to the duodenum. Embryologically the pancreas begins in two areas, each with its own duct. Later these combine to become the head of the pancreas and the body of the pancreas. Usually only one of the original ducts remains as the main pancreatic duct or duct of Wirsung. If the second (smaller one) persists it is known as the accessory pancreatic duct.. The ampulla of Vater or duodenal ampulla is formed by the common bile duct joining with the pancreatic duct inside the duodenum. The sphincter of Oddi surrounds the common bile duct only. It is the part of the muscularis externa (of the wall of the intestine) that surrounds the duct as it enters the ampulla of Vater. If the sphincter of Oddi is closed bile backs -up into the gall bladder for storage and removal of water.

Fig. 14- Duct System

Lecture Notes Part II 46 53 Digestive System Urinary System Lecture

GROSS ANATOMY OF KIDNEY has extensions called medullary rays, which extend farther out into the cortex. GENERAL DESCRIPTION The kidney is retroperitoneal and lies MAJOR AND MINOR CALYX against the posterior abdominal wall in the A calyx is a funnel shaped structure that is lumbar region, just below the twelfth rib and part of the urine collection system. Each at the level of the umbilicus. It is held in minor calyx surrounds thepapilla of one place by fat padding. pyramid, and thus receives the urine pro- The hilum of the kidney is the indented duced by that lobe of the kidney. Two or medial surface of the kidney where the renal more minor calyxes may fuse to form a major calyx. The major calyxes in turn artery and renal,tin enter the kidney and the ureter exits. The hilum invaginates the drain into the renal pelvis. kidney to form a nonfunctional pocket called LOBES/LOBULES the renal sinus. The kidney of humans is subdivided into 6- The renal sinus encloses tNe major branches 18 lobes. Each lobe consists of one medul- of the blood vessels,and the renal pelvis, lary pyramid plus the overlying cortex. The which serves as an internal collecting basin lobes in turn are subdivided into lobules. for urine. The renal pelvis can be thought of Each lobule consists of one medullaryray as the expanded upper end of the ureter. plus the overlying cortex. The kidney is surrounded by a fibrous BLOOD SUPPLY capsule of connective tissue which enters The complete circulatory pathway listed in the renal sinus at the hilum and is reflected correct sequence is as follows: back over the calyces and renal pelvis as renal artery their outer coverings. interlobar artery arcuate artery KIDNEY TISSUE interlobular artery A lengthwise section of the kidney shows afferent arteriole two general regions, the medulla or core glomerulus tissue and the cortex or outer layer of tissue. efferent arteriole The medulla is packed with straight tubules peritubular capillary plexus (includes of various sizes running parallel to one an- vasa recta) other. The cortex contains the renal interlobular vein corpuscles, (the filtering units of the kidney) arcuate vein and the convoluted tubules. interlobar vein In some animals, including humans, the renal vein medulla region is broken up into discrete Once the renal artery is inside the renal sinus units called pyramids because of their shape. it branches. These branches extend between The spaces between the pyramids are occu- each pyramid and are therefore called the pied by cortex tissue, and these areas are interlobar arteries. Neighboring interlobar called the renal columns. The base of each arteries anastomose and arch over the base pyramid (the broadest part) points toward of each pyramid as the arcuate arteries. the periphery of the kidney, and the papilla These in turn give off vertical branches into or apex points into a minor calyx. The base the cortex between the medullary rays, of the pyramid is not squared off. but instead Lecture Notes Part II Urinary System 47 54 %,x11-r. tr

Fig. 15- Gross Anatomy of the Kidney

appropriately called the interlobular arter- glomerulus is an efferent arteriole which ies. Each interlobular artery gives off mul- leads to another capillary network theper- tiple side branches (afferent arterioles), one itubular capillary plexus which surrounds to each glomerulus the tubules of the nephron (and also includes some long loops called the vasa recta.) The RENAL PORTAL SYSTEM: peritubular capillary plexus drains into A glomerulus is a capillary bed that looks straight venules which carry the blood into like a small ball of yarn. Exiting from each the interlobular vein, and thee into larger Lecture Notes Part II 48 Urinary System

55g.) veins all of which parallel the branches of NEPHRON EMBRYOLOGY the arteries, and have the samenames: In the embryonic kidney thousands of blind arcuate vein, interlobar vein, renal vein. ended immature nephrons and arterioles Finally the renal vein drains into the inferior grow towards one another. These pairs will vena cava. meet head on, and the arteriole invaginates THE NEPHRON UNIT the blind end of the nephron tubule. This process is analogous to punching your fist The nephron is the functional unit of the into a soft balloon or beach ball. Theresult kidney. Each kidney containsmany thou- is that the tip end of the nephron tubule sands of nephrons. A nephron consists of a (Bowman's capsule) ensheathes thegrow- filtering unit and an attached set of blood ing arteriole, which inturn forms a capillary vessels and urine tubules. bed (glomerulus) inside the Bowman's KIDNEY FUNCTIONS capsule. (Together the glomerulus and The primary function of the kidney is the Bowman's capsule are sometimes called the renal corpuscle.) Eventually removal of nitrogenous wastes from the a blood vessels blood. The secondary function of the kidney works its way out of the glomerulus and be- is to maintain normal composition, volume, comes the efferent arteriole. and pH of the blood and body fluids, i.e. to ADULT NEPHRON ANATOMY maintain normal electrolyte balance. The parts of the nephron tubule listed in The nitrogenous wastes that need to be correct sequence are: removed are the result of protein (specifi- Bowman's capsule (renal capsule) cally amino acid) catabolism, during which proximal convoluted tubule toxic amnia by products are created. loop of Hen le (including ascending and These ammonia by products of metabolism descending limbs) are converted to area in the liver. Urea is distal convoluted tubule also toxic, but less toxic than ammonia, collecting tubule especially if it is kept very dilute. So here is Each collecting tubule drains intoa minor th:, dilemma: urea must be removed from calyx. the blood, but it cannot be selectivelyre- moved since that would bring the selecting NEPHRON FUNCTION cells into direct contact with poisonousurea. FORMATION OF CAPSULAR FILTRATE The begirning stages of urine formatioa The way this problem is solved is to createa occur at the interface between the glomer- very dilute renal filtrate containing urea and ulus and Bowman's capsule. Thesestruc- large amounts of water and salts and glu- tun s are both lined with simple squamous cose, and then to reabsorb most of the water epithelium. The efferent arteriole is halfas and salts and all of the glucose and put these large as the afferent arteriole, thus the blood reclaimed items back into the blood from pressure in the glomerulus is higher than in whence they were taken when the filtrate most capillary beds. This pressure causes the was first formed. filtrate to form. The filtrate is calledcapsu- Exactly how this is done can best be under- lar filtrate. stood by examining the detailed anatomy of Blood cells and most protein moleculesare the nephron. too large to be filtered, but all other ele- ments of the plasma are easily able to leave the capillaries, enter Bowman's capsule, and start down the tubules. Thus, the capsular filtrate contains large amounts of water,and Lecture Notes Part II 49 Urinary System proximal convoluted tubule efferent arteriole distal convoluted afferent arteriole tubule

interlobular Eatery

Bowman's Capsule

arcuate artery

arcuate vein peritubulax capillary plexus hue:lobar artery collecting interlobar tubule vein descending limb of the loop of Hen le ascending limb of the loop of Hen le

loop of Hen le

Fig. 16- The Adult Nephron Unit

Lecture Notes Part II So Urinary System it also contains urea, glucose, and various uredc hormone (ADH) from the posterior dissolved salts (electrolytes). pituitary gland More ADH is released when FILTRATE REABSORPTION the salt concentration of the blood is high. It Most of the water and salts must be re- acts on the distal convoluted tubules and claimed, i.e. reabsorbed back into the blood, collecting tubules of the kidney causing otherwise the person would rapidly die of more water to be reabsorbed back into the dehydration and electrolyte imbalance. blood from these areas. Conversely, when the salt in the blood is too diluted less ADH Almost all parts of the kidney tubulesare is secreted, and more water is excreted in the lined with cuboidal epithelium that have urine. microvilli. These are the cells that reabsorb most of the capsular filtrate. The reabsorbed Salt reabsorption is regulated by the fluids are put back into the blood by way of hormone aldosterone from the adrenil the peritubular capillary plexus which then cortex. Aldosterone causes more Na+ ions to drains into the venous system. Only urea and be reabsorbed, (increased water reabsorption other protein wastes from metabolism are will follow). not reabsorbed. These substances remain in URINE COLLECTION SYSTEM the lumen of the tubules, pass into the The collecting tubules of the medulla all collecting ducts and thence to the minor drain into a cuplike subdivision of the renal calyx, etc. until they are eventually excreted pelvis called the minor calyx. Twoor more as urine. minor calyces verge to form a major calyx, REABSORPTION THRESHOLD and the major calyces merge to form the The reabsorption process involves both renal pelvis. The renal pelvis is drained bya active and passive transport mechanisms. ureter which carries urine to the bladder. Glucose is reabsorbed by active transport The two ureters are connected to the inferior from the proximal convoluted tubule. Active surface of the bladder, which is also where transport requires energy expcndituit and the urethra exits. The three tubes attachedto the presence of highly specific enzymes, the bottom of the bladder create a formation thus there may be a threshold (maximum called the trigone which can be seen from rate limit ) beyond which the substance can't the interior of the bladder. be reabsorbed. This is particularly true of glucose (the glucose threshold). The bladder has two sphincters, an internal

FLUID VOLUMES sphincter of smooth muscle and an external Approximately 180 liters of filtrate is sphincter of voluntary muscle. The internal formed per day (both kidneys). Reabsorption sphincter is the part of the muscle wall of reclaims about 178 liters of fluid for every the bladder which surrounds the beginning 180 liters of original filtrate. This is 99% of of the urethra; the external sphincter is part the filtrate. Only 1.5 to 2 liters is actually of the urogenital diaphragm whichsur- excreted as urine. (180 liters is approxi- rounds the urethra below the bladder. mately equal to 47 gallons, i.e. 9 five gallon The technical term for urination is mictura- carboys lion.. About 20% of the plasma flowing through the kidney at any time is filtered. This means that the kidney takes about 20% of the urea out of the blood with each passage. Water balance is mainly regulated by antidi-

Lecture Notes Part 11 51 Urinary System

,.y Summary of Pathways

CIRCULATORY PATHWAY URINE PATHWAY

1. Renal artery / Inter lobar & vary 3. Arcuate arteries 4. Interlobular arteries 5. Afferent arteriole capsular filtrate 6. Glonterulus 13. Bowman's Capsule 7. Efferent arteriole 14. PCT 8. Peritubular capillary plexus 15. Loop of Henle 9. Interlobular vein 16. DCT 10. Arcuate vein 17. Collecting Tubule 11. Interlobar vein 18. Minor Calyx 12. Renal vein 19. Major Calyx 20. Pelvis of Kidney 21. Ureter 22. Bladder 23. Urethra

Lecture Note; Part 11 52 Urinary System 59 The Reproductive System

There are es of erectile tissue in The perineum is the floor of the pelvic the urogenital triangle of both the male and cavity. Externally it is the region that the lay the female. The physicalappearance of person would vulgarly refer to as the crotch. erectile tissue is best described by the terms Anatomists divide the region into two spongy or cavernous because of the sponge triangular areas, the anal triangle and the like network of large cavernous blood si- urogenital triangle. nuses which are empty most of the time, but fill with blood during sexual excitement. The structures in the anal triangle are identi- Certain parts of the erectile bodiesare cal in both male and female and therefore it covered by thin layers of voluntary muscle will be discussed first The structures in the which contracts during sexual excitement. urogenital triangle of male and female are homologous to one another, but not identi- In the male all three bodies of erectile tissue cal, so the urogenital triangle will be dis- found in the urogenital triangle participate in cussed separately for male and female. the formation of the penis. In the femaletwo of the three bodies of erectile tissue form the ANAL TRIANGLE clitoris and the third body of erectile tissue The three bony points of the anal triangle are surrounds part of the vaginal canal and the two ischial tuberosities and the coccyx. extends into the labia minora. The floor of the pelvic cavity in the anal PARTS OF THE PENIS Wangle is formed by a thin and steeply The male urogenital triangle contains the angled layer of skeletal muscle called the the parts of the penis. The only other structure levator ani. The levator ani muscle layer is present is the scrotum (skin enclosing the penetrated by one opening, the anus. The testicle). The testicle will be discussed in sphincter and extensus is voluntary muscle another lecture. that surrounds the anal opening. 1. CORPUS SPONGIOSUM The anterior boarder of the anal triangle The central body of erectile tissue in the doubles as the posterior border of the uro- male is called the corpus spongiosum (also genital triangle. It consists of a pair of known as the corpus cavernosum urethra narrow transverse musLies, the superficial because it surrounds the part of the urethra transverse perinel muscles, that originate on known as the spongy urethra). In the male the ischial tuberosity and insert on a midline the urethra transmits semen as wellas urine. spot of connective tissue called the perineal body. a. distal end The distal end of the corpus cavernosum UROGENITAL TRIANGLE urethra is called the glans penis. The three bony points of the urogenital b. intermediate section triangle are the two ischial tuberosities and The intermediate section of the corpus the pubic symphysis. The floor of the pelvic cavemosum urethra forms part of the cavity in the urogenital triangle is a thin shaft of the penis. layer of skeletal muscle known as the urogenital diaphragm.The urogenital dia- c. proximal end phragm is penetrated by the urethra in both Tin. proximal end of the corpus caverno- male and female, and by the vagina in the sum urethra is called the bulb of the female. penis because of its bulbous shape. The Lecture Not< a Part II S3 Reproductive System C 0 bulb of the penis is firmly attached to the by compressing the venous drainage from perineal body in the urogenital triangle. the erectile tissue. d. muscle covering 3. PHEPUCE The bulb region is covered by a thin layer The prepuce or foreskin of the penis is a of skeletal muscle known as the bulbo- double fold of skin which is reflected back cavernosus muscle. Voluntary contrac- over the glans penis and connected to the tion of this muscle assists with erection glans penis by a frenulum. Circumcision by compressing the underlying veins, (surgical removal of the prepuce) is custom- thereby trapping blood in the spongy ary in some cultures for religious or hygi- erectile tissue. Reflex pulsations of this enic reasons. A sebaceous secretion known muscle cause ejaculation of the semen as smegma tends to collect under the fore- during the male climax. skin. 2. CORPORA CAVERNOSA (OF THE PENIS) PARTS OF THE VULVA On each side of the corpus cavernosum The two regional terms used in discus zing urethra is a pair of erectile bodies called the the female urogenital triangle are vulva and corpora cavernosa of the penis, or corpora vestibule.Vulva is the more inclusive term; cavernosa for short. Note the pleural end- it refers to all of the female external genita- ings; when this term is used in the singular lia, including the mons veneris, the labia form it becomes corpus cavernosum. majora and all parts of the vestibule. The a. distal end labia majors are homologous to the scrotum The distal ends of the corpora cavernosa of the male except that they do not contain tuck in under the glans penis. the gonad. b. intermediate section PARTS OF THE VESTIBULE The intermediate portions of the two Vestibule refers to the labia minora and corpora cavernosa are the main compo- everything inside of them, namely the nents of the shaft of the penis (in which clitoris, the vagina, and the urethral mea- the cows spongiosum also participates). tus. The labia minora are folds of skin that The shaft of the penis is suspended from contain erectile tissue which is part of the the pubic symphysis by connective tissue bulb of the vestibule. called the suspensory ligaments of the 1. CORPUS SPONGJOSUM Penis. a. proximal end c. proximal end The bulb of the vestibule in the female is The proximal end of each of the corpora homologous to the bulb of the penis in cavernosa diverges (bends) laterally and the male. It is a centrally placed mass of is firmly attached to the ramus of 0-- is- erectile tissue that surrounds the openings chium. Because of this lateral be.. ach of the vagina and urethra and extends of these sections of the corpus caver- superficially into the labia minora. The nosum is called a crus (pleural form be- main difference between the bulb of the comes crura of the corpora cavemosa of vestibule and the bulb of the penis is that the penis). the bulb of the vestibule does not fuse in the midline. d. muscle covering Each crus is covered with a thin layer of b. intermediate section skeletal muscle called the ischiocaver- In the female there is no intermediate sec- nosus muscle. Contraction of these tion to the corpus spongiosum, i.e. the muscles assists with erection of the penis corpus spongiosum does not extend anteriorly to become part of the clitoris. Lecture Notes Part II 54 Reproductive System E1 c. distal end Female "circumcision" is practiced bya few There is no distal portion to the corpus cultures, but the term is misplace since the spongiosum in the female, instead the surgical procedure actually being performed glans of the clitoris migrates during its clitoridectomy. embryology to become part of the lateral corpora cavemosa of the clitoris. d. muscle covering ERECTION Just as in the male, the bulb is covered Sexual excitement (under the influe.ce of with a thin layer of voluntary muscle the parasympathetic nervous system)auses known as the bulbocavernosus muscle. the arteries supplying the erectile tissueto During sexual excitation this muscleas- dilate, and a large quantity of blood under sists with engorgement of the female pressure enters the cavernous spaces. As the erectile tissue in much the same way that blood spaces fill they expand andcompress it does in the male. the deep veins which drain blood out of these spaces, thus holding blood in thecav- 2. CORPORA CAVERNOSA OF CLITORIS ernous spaces. On each side of the bulb of the vestibule is a pair of erectile bodies called the corpora Contraction of the bulbocavernosus and cavernosa of the clitoris. They are almost ischiocavernosus muscles assists with exactly homologous to the corpora caver- erection by compressing superficial veins nosa of the penis. and thereby restricting venous drainage, with the result that more blood enters the a. proximal end erectile tissue than leaves it, p.nd thespongy The proximal end of each of the corpora tissue becomes turgid, firm and erect. cavernosa diverges laterally to become a crus, just at it does in the male. As sexual excitement subsides the arteries contract and muscular tension is reduced, b. intermediate section therefore incoming blood flow is reduced The intermediate portions of the two and venous compression is lessened; blood corpora cavemosa form the main body of is allowed to drain out and erection subsides. the clitoris, which is approximately an inch in length. In the female the clitoris and the bulb of the vestibule both become erect; swelling of the c. distal end vestibule serves to increase the frictionon The distal ends of the corpora cavernosa the penis during coitus. of the clitoris are attached to the glans clitoris. ORGASM d. muscle covering The clitoris and penis are supplied with Just as in the male, each crus is covered abundant sensory nerve fibers leading to the with a thin layer of skeletal muscle called sacral and lumbar regions of the spinal cord the ischiocavernosus muscle. This stimulation of which can lead to a general voluntary muscle assists with erection of buildup of sexual tension that culminates in a series of spinal reflexes (including sympa- the clitoris during sexual excitation just as it does in the male. thetic nervous system reflexes), accompanied by a sense of abrupt physiological and 3. PREPUCE psychological release. The prepuce of the female is more commonly known as the hood of the clitoris. Its In the male these spinal reflexes includes frenulum is continuous with the labia mi- ejaculation, the sudden propulsion of the nora. semen out of the urethra. This is due to pul-

Lecture Notes Part II 55 Reproductive System 62 sating contractions of the bulbocavernosus a. an abnormal individual with only a muscle, and sequential contractions of the single x but no y chromosome (Turner's bulbourethral glands, then the prostate syndrome.) will develop as a female; gland, ejaculatory ducts, and finally the sterile in humans, normal in themouse. seminal vesicles. b. an abnormal xxy individual In the female orgasm is accompanied by (Kleinfelter's syndrome) will developas rhythmic contraction of the perinea' a male but with some female secondary muscles, vagina, uterus, and fallopian tubes. characteristics, and often (but not always) These contractions probably aid in the with severe mental retardation. transport of sperm cells. c. an abnormal xyy will develop as an Following orgasm, still under the direction apparently normal male. There aresome of the sympathetic nervous system, blood arguable studies indicating that such an flow to the erectile tissues is decreased and individual may have "superaggressive" the erection subsides. Also, the muscles of behavioral characteristics. the perineum relax, further aiding de- d. an abnormal embryo with only a single tumescence. y chromosome is nonviable. Scientists have long puzzled over how to explain the rare existence of xx males and xy females. Very recently (Dec. 23 1987, The development of the sex of an embryo is Cell) this has been shown to be the result of determined primarily by genetic inheritance. genetic cross over during production of the In the body cells (somatic cells) of humans sperm cells. Cross over is a process wherein there are 23 different kinds of chromosomes, part of a chromosome winds around its each of which can be recognized on sight by partner during chromosome pairing (meta- a skilled person, and each of which has been phase of meiosis), and then breaks away named, or rather numbered, from 1 to 23, from the original chromosome and re- with the last of the 23 different types being attaches to the partner. In this way short called the sex chromosomes, either x or y. sections of a chromosome are sometimesex- changed between pairs of chromosomes. If Our somatic cells all contain 2 copies of cross over happens between the xy pair, the each of these 23 different types of chromo- gene(s) on the y chromosome which deter- somes. Thus each body cell has 46 chromo- mine maleness may cross over and becomea somes in total. This doubled number is part of the x chromosome. Subsequently, called the diploid number. With regard to when this particular x carrying sperm cell chromosome number 23, the sex chromo- fertilizes an egg the xx embryo will develop some pair, females have an xx and males into a male because of the abnormal pres- have an xy. ence of the gene determining maleness on GENETIC DETERMINANT the x sperm cell. Likewise when the ab- The physical development of the sex organs normal y sperm cell (lacking the male of an embryo is determined primarily by the determining section) fertilizes an egg that presence or absence of the y chromosome, particular xy embryo will develop into a or to be more exact, by the presence or female. absence of a specific small section of the y HORMONAL DETERMINANT chromosome. It has been known for some Every vertebrate embryo of whatever ;en- time that: der, contains the primordia (immature

Lecture Notes Part II S6 63 Reproductive System structures) for formation of both male and female reproductive systems. The development of one or the other system is largely controlled by testosterone concentrations during a specific window of time during embryonic development, and also by different sensitivities of the target organ tissues to the hormone. These factorsare presumably regulated by the crucial section of they chromosome discussed above. The reproductive prinxrdia consist ofa double set of internal "plumbing" attached to the gonad, one male set and one female set. Only one of the double set of tubes and ducts develops into the mature reproductive tract, the other set degenerates and disappears. In the adult female the set that remains becomes the fallopian tubes and uterus. In the adult male the set that remains becomes the tubes and ducts thatcarry the sperm cells from the testicle to the urethra. If the gonads are removed froman early animal embryo both sets of plumbing remain in the undeveloped form. In addition to the double "plumbing" each- early embryo has a single set ofstructures in ar. iLdifferent stage of development, i.e. they could develop into either maleor female structures. These structures become the ovary, the labia majors, the bulb of the vestibule, and the clitoris in the female. In the male these same structures become the testes, scrotum, and penis. Each structure has a homologue in the oppositesex. HOMOLOGUES testes/ ovary scrotum/ labia majora bulb of penis/ bulb of vestibule crura of penis/ crura of clitoris glans of penis/ glans of clitoris gubernaculumiguternaculum

Lecture Notes Part II 64 Reproductive System MITOSIS MEIOSIS

spennatogonium primary spermatocyte (diPlold) WO)

one replication one replication

onedivision first of two divisions

primary spermatocytes secondary spermatocytes

(diploid) (haploid)

second division fsecond division

spermatids (haploid)

spermatozoans (haploid)

Fig. 17- Spermatogenesis

Lecture Notes Part II $8 6 5 Reproductive I.,stem called a spermatozoan. Spermatogenesis is temperature dependent; THE TESTICLE it requires a temperature considerablylower The testicle has two functions, namely than that of the interior of the body. When gametogenesis (spermatogenesis) and male the testes are in the scrotum theyare kept hormone production (testosterone). cool enough for spermatogenesisto proceed normally. SPERMA'TOGENEMS The sperm cells are produced from the HORMONE PRODUCTION inside epithelial lining of the seminiferous In the interstices between seminiferous tubules in the testicles. Thereare many tubules there are cells knownas the intersti- miles of these highly coiled tubules packed tial cells of the testes. These interstitialcells inside each testicle. The tubule epithelium in produce the male hormone testosterone an immature male is of the simple cuboidal which is responsible for the male secondary type; at puberty the epithelium starts divid- sexual characteristics and for male libido. ing and becomes stratified cuboidal With each subsequent division the daughter cells MALE "PLUMBING" are pushed into the next layer of cell (toward The mature sperm cells migrate from the the lumen of the tubules). seminiferous tubules into the straighttu- bules, into the rete testes, into the efferent The basal layer of the germinal epitheliums ductuks and on into the epididymis for consists of cells called spennatogonia that temporary storage. The epididymis is a very have the usual diploid number of chrom- highly coiled tubular structure that is osomes (46). They duplicate by ordinary wrapped with a heavy layer of connective mitosis so that their daughter cells (layer 2, tissue. From a surface view the coiled tube primary spermatocytes)- also have 46 chro- cannot be seen, and it looks somewhat likea mosomes. From the time of puberty on into tadpole in that it has a head, body, and tail. old age primary spermatocytesare continu- The tail is directly continuous with the ally being produced by mitosis,so that no ductus deferens (old name= vas deferens). sperm cell is ever around for very long. As the ductus deferens leaves thescrotum it The primary spermatocytes undergo meio- passes through the body wall via the ingui- sis, a process that includes one replication of nal canal Inside the abdominal cavity it chromosomes followed by two divisions, (in hooks around the ureter, descends into the contrast to mitosis which consists of one replication pelvic cavity, and enters theprostate gland followed by one division) so that the chromo- where its name changes. The short section of some number is reduced from diploid to duct inside the prostate gland is called the haploid.Thus the daughter cells in layer 3, ejaculatory duct. From the ejaculatory duct (secondary spermatocytes) and layer 4, the sperm cells next pass into the prostatic (spermatids), have 23 chromosomes. urethra, membranous urethra, andspongy (penile) urethra. Each spermatid undergoesa maturation phase during which it develops a flagellum ACCESSORY GLANDS AND SEMEN and becomes ready for its journey. During The fluid that is ejaculated at the time of leis time they bury their heads in and derive male orgasm is called the semen. It contains nourishment from the supportive Sertoli sperm cells and the alkaline secretions of Sertoli cells are large glycogen con- three accessory glands. taining cells that extend from the basement BULSOURETHRAL GLANDS membrane toward the lumen of the sem- The bulbourethral glandsare a pair of very iniferous tubule. A mature sper'natid is small glands embedded in the urogenital

Lecture Notes Part II 59 Reproductive System 66 diaphragm layer of muscle. They also go by clocked at 3 mm per min. That speed is the older name of "Cowper's glands". The insufficient to account for the fact that secretion they produce is a crystal clear sperm cells appear in the upper ends of the mucoid material that has an alkaline pH. A female fallopian tubes 45 minutes after ejac- drop of this mucoid secretion usually ap- ulation. The distance involved is greater pears at the tip of the glans penis during than can be accounted for by the fiagelkz sexual arousal. It acts as a lubricant to aid in movements of the sperm. This emphasizes intromission (penetration of the female) and the important contribution to sperm trans- its alkalinity helps to neutralize the natural port made by contractions of the female acidity of the the male urethra preceding vagina and oviducts.

ejaculation. SEMINAL VOLUME PROSTATE The volume of seminal fluid produced will The prostate gland is a single walnut sized vary depending on such factors as age and structure located immediately below the frequency of ejaculations, but on the average urinary bladder, and surrounding the urethra. we can speak of volumes in the approximate It produces a thin, milky, alkaline secretion range of 2.3 to 3.5 cc per ejaculation.

that accounts for most of the volume of the SPERM NUMBERS semen. The alkalinity of the secretion helps Sperm cells are present in very high num- to neutralize the normal acidity of the ber3, but they do no account for much of the female reproductive tract. volume of the semen. The average sperm SEMINAL VESICLES cell count is 100 million per cc of semen. The seminal vesicles are a pair of elongated An individual is considered "sterile" if his saclike glands located behind the bladder sperm cell count drops to 20 million per cc, and connected to the ductus deferens. They because his chances of fathering a child are produce a clear thick mucoid, alkaline se- practically zero in such a case. The idea that cretion that is rich in the sugar fructose. The it only takes one sperm cell to fertilize an fructose probably serves as an energy source egg is misleading. Each sperm cell carries a for the sperm cells as they make their jour- small amount of the enzyme hyaluronidase ney through the female uterus and up into in the acrosome region, and it takes millions the fallopian tubes. of sperm cells, to contribute sufficient hyaluronidase to dissolve the hyaluronic SPERM CELL MOTIUTY The alkalinity of semen is important in that acid (jelly coat) protecting the egg. it helps protect the sperm from acid present LIFE SPAN OF GAMETES in the male urethra and in the female vagina. Sperm cells generally live for two to three Acid depresses sperm motility. Motility is days inside the female reproductive tract. greatest in a neutral or slightly alkaline en- Egg cells generally live for one to two days vironment. after ovulation. One consequence of these The seminal fluids also contain figures is that conception can result from prostaglandins, chemicals that are found in sexual intercourse occurring both before and many tissues and have a wide variety of after the actual moment of ovulation. functions, but in the reproductive tracts they apparently aid in the transport of sperm cells toward the egg by causing peristaltic waves in the female reproductive tract. The speed at which sperm cells can travel by virtue of flagellar action alone has been

Lecture Notes Part II 60 Reproductive System 67 ztzt of the corpus luteum is dependentupon the tk t fate of the ovum. If the egg is fertilized the THE OVARY corpus luteum will expand and persist for The ovary has two functions, namelygame- the first 3 to 4 months of thepregnancy. If togenesis (odgenesis) and female hormone pregnancy does not occur the corpus luteum production (estrogen and progesterone). lasts for about two weeks and then it invo- OW lutes, leaving a large white COGENESIS scar called the During the third month of fetal life the corpus albicans. germinal epithelium, which is the epithe- Several hundred thousand primary follicles lium covering the outside of the ovary, are produced in the embryonic female; fewer produces groups of cells called primary than 500 of them will ever develop fully. follicles that leave the surface of the ovary The main point however is that all of the and descend into the connective tissue future eggs are sitting there waiting for the stroma of the interior of the ovary. Each chance to develop, and while theyare follicle consists of one primary olkyte (egg) waiting they are subject to a variety of surrounded by a group of supporting cells environmental insults, many of which (like called follicular cells or granulosa cells. X-Rays) are cumulative overa life time. For The primary follicles remain in a quiescent this reason, eggs released late in the life of state until puberty. From puberty on several the female are less likely to be viable than follicles each month begin to grow and those released early in the childbearing develop; one of them will continue to de- years. velop; the others atrophy, leaving tiny white HORMONE PRODUCTION scars called atretk follicles. The cells of the ovarian stroma whichare in immediate contact with the follicle (theca Inside the developing follicle the oocyte intern cells) produce the female hormone matures, and the granulosa cells increase in estrogen. More and more estrogen is pro- number and produce follicular fluid which duced day after day as the follicle enlarges, collects in the antrum of the follicle. As the ruptures, and becomes a corpus luteum. follicle enlarges and the pressure inside the Estrogen is responsible for the femalesec- antrum rises, the ovarian tissue covering the ondary sexual characteristics and for female follicle becomes compressed, then ischemic, libido; it also acts on the uterus and breast and finally necrotic. This fully ripe stage is preparing them for a possible pregnancy. known as the Gratifian follicle; when it ruptures (about day 14 of the cycle) the After ovulation the corpus luteum produces event is known as ovulation; The egg is the hormone progesterone. Progesterone is released into the peritoneal cavity but is secreted by the cells inside the corpus usually swept up by the fallopian tubes luteum which were formerly calledgran- ulosa cells, but which are now called lutein Ovulation is usually somewhat painful due cells. In addition the corpus luteum contin- to the trauma suffered by the ovary, and also ues to produce estrogen, but the cells which due to some minor irritation of the perito- make the estrogen are now called paralutein neum (peritonitis) caused by the blood and cells (formerly theca interim cells). Proges- follicular fluid entering the peritoneal cavity. terone acts on the uterus and breast to con- After ovulation the ruptured follicle heals tinue their preparation for a possible preg- and the metabolism of the granulosa cells nancy. changes so that they begin to accumulate lipids. The resultant structure is known as the corpus luteum. The length of existence

Lecture Notes Part 11 61 Reproductive System 68 MITOSIS MEIOSIS

atgonium primary acyte (0101d) 01:1101d)

one repication

aiedw'adon

(iP 1st polar body primary ***tea (diploid) secondary osicyte ihardoid) rcvision two\\), lor (<4:s/ontwo o y V 0 2nd polar body

aid(egg) (haploid)

Fig 18- agenesis

Lecture Notes Part II 62 Reproductive System 69 FALLOPIAN TUBES & VAGINA the uterus to the body wall. Running through One end of each of the fallopian tubes (or the broad ligament and extending frombody uterine tubes) is ditectly continuous with the wall to uterus to ovary, isa round cord that uterus. The other end is expanded into a is a vestige of the gubernaculum. Thepart funnel shaped infundibulum, the margin of that is between body wall anduterus is which is fimbriated (fringed). The, rmbria called the round ligament of the uterus. The and the inside surface of the fallopian tubes part that extends from uterus toovary is is lined with cilia, all of which beat toward called the ovarian ligament. Thesuspensory the uterus, creating a ciliary current which ligament of the ovary is actually just the transport the egg to theuterus. Fertilization ovarian artery and vein.

usually occurs in the upper one third of the UTERINE WALL fallopian tubes. The egg usually lives for The smooth muscle in the well of theuterus one to two days after ovulation. is called the myometrium. The stratified The vagina is an expandable soft tissue tube squamous epithelium lining the interior of leading from the cervix of the utenn iI the the uterus is called the endometrium. vestibule. The fact that it attaches high The uterine wall is responsiveto the the sides of the cervix creates a pocket hormones produced by theovary. The between the cervix and the vaginal wall, myometrium is kept relaxed and quiet by the called the fornlx or fornkes. The hymen is hormone progesterone. The endometetim a vestigial remnant of mucosal membrane responds to both estrogen andprogesterone. that early in embryonic life covered the Estrogen causes the epitheliumto proliferate vaginal orifice. (become thick and spongy), progesterone UTERUS causes the epithelium to become secretory, and causes the unique spiral arteries The uterus has three regions, body, fundus to develop. and cervix. The body of the uterus is the

main part of the uterus. The fundus of the ti uterus is the bubble like region at the top, The purpose of the menstrual cycle is above the level of au -;hment of the fallo- to prepare the uterus freshly for each possible pian tubes. The cervix is the neck of the pregnancy. The average length of a men- uterus. which projects downward into the strual cycle is 28 days. Dayone is the first vagina. The opening in the center of the day when blood is seen externally. All of the cervix, leading to the interior of the uterus is changes in the uterus are correlat:d with called the os cervix. ovarian follicle growth and with changes in The normal position of the uterus is anti- blood hormone levels. flexed, i.e. bent forward over the bladder. A Abrupt withdrawal of estrogen andproges- retroflexed uterus is one that is tipped intoa terone (when the corpus luteum involutes), straight lie with the cervix or bent back- causes cramplike waves of contraction in the ward. It was once believed thata tipped myometrium, and causes the spiral arteries uterus caused infertility. of the endometrium to undergo alternate The vesicouterine pouch is a peritoneal constriction, dilation, and then constriction pocket locatedbetween the bladder andthe again. The initial constriction of the spiral uterus. Similarly, the rectouterine pouch is arteries causes ischernia and then necrosis in between the rectum and the uterus. the endometrium. When the arteries subse-

LIGAMENTS OF THE UTERUS quently dilate the necrotic tips of the arteries The broad ligament of the uterus isa will not hold the surge of blood under double fold of peritoneum which connects pressure, and the endometrium sloughs off Lecture Notes Part II 63 70 Reproductive System

44;,..1 la a phenomenon known as menstruation. Bleeding only occurs for a short time; it tkt stops when the spiralarteries constrict for INTRODUCTION the second time. In the male, hypothalamic hormones control

7=:;:s.Ms*A the anterior pituitary, and pituitary hormones in turn control the testicle. The male is non- Breast tissue is mostly fat, but it also cyclic, i.e. thehormones and sperm cells are contains lobules that with extensive hormo- secreted on a steady state basis. nal preparation and support will secrete milk. Each lobule is connected to the nipple In the female hypothalamic hormones by a duct. Each duct has a dilated portion control the anterior pituitary, pituitary called an ampulla imirediately beneath the hormones control the ovary, and ovarian nipple The amok: is the deeply pigmented hormones control the uterus and also shut external skin of the breast surrounding the off the hypothalamic hormones. Thus the female is cyclic; one egg is produced each nipple. Each areola contains numerous sebaceous glands, the purpose of which iss to month, and a fresh uterine lining is prepared keep the skin from drying and cracking dur- for each new egg. ing suckling. The suspensory ligaments of HYPOTHALAMIC HORMONES the breast are short tough strands of connec- The hormones of the hypothalamus which tive tissue that extend inward into the breast control the anterior pituitary are called from the skin and underlying fascia. releasing factors or releasing hormones. In order to manufacture milk the breast There are two important ones: FSH-RH tissue must be exposed to massive amounts (follicle stimulating hormone releasing of estrogen, progesterone, and prolactin factor) and LH-RF (luteinizing hormone (LTH) over a period of many months. The releasing factor). action of these hormones on the breast is In both male and female FSH-RH causes the called the priming action. pituitary to secrete FSH, and LH-RH causes When a child suckles the milk letdown the pituitary to secrete LH (LH is called reflex is initiated. Suckling causes the ICSH in males). hormone oxytocin to be released from the ANTERIOR PITUITARY HORMONES posterior pituitary, and oxytocin causes the The hormones of the anterior pituitary gland lobules and ducts of the breast to contract, which stimulate the gonads are called by the ejecting milk into the mouth of the child. group name gonadotropic hormones. There are three of them; they were first discovered in female animals and were named according to their functions in the female.

FSH Follicle stimulating hormone in the female stimulates follicle growth with the result that an egg is prepared for ovulation and estrogen is secreted, which in turn prepares the uterus. Follicle stimulating hormone in the male stimulates the sperrnatogenic epithelium of the seminiferous tubules to produce sperm cells.

Lecture Notes Part U 64 Reproductive System 71 LH QM) Luteinizing hormone in the femalecauses ovulation and subsequentcorpus luteum formation, with the result thatprogesterone is secreted, which in turn augments the preparation of the uterus. Interstitial cell stimulating hormone in the male.stimulates the interstitial cellsto produce testosterone.

LTH Luteotropic hormone, also knownas prolacdn,stimulates breast development and milk secretion, and keeps thecorpus luteum healthy. NEGATIVE FEEDBACK LOOPS Negative feedback loops occur only in the female; they are responsible for the cyclic nature of the female reproductive system. A rising estrogen titerwill shut off FSH-RH so that no new follicles are allowed to develop until the fate of the firstegg is determined. (Rising progesterone titermay perhaps also stimulate the secretion of LTH (prolactin) by the pituitary) Arising progesterone titerwill shut off LH- RH so that no further ovulationsare allowed until the fate of the first egg is determined. Rising progesterone may perhaps also stimulate the secretion of LTH (prolactin) by the pituitary). If a pregnancy occurs the placentasecretes estrogen, progesterone, and alsoHCG (human chorionic gonadotropin. HCG stimulates the further development of the corpus luteum, and therefore reinforces the high levels of estrogen and progesterone, ensuring that the placenta remains in place in the uterus. If pregnancy does not occur,no HCG is made, and therefore the corpus luteum involutes and progesterone and estrogen levels fall. This decrease causes menstruation, and also allows FSH-RH and LH-RF1 to be secreted so that the cycle begins all over again.

Lecture Notes Part II 65 Reproductive System Res iratoS stem of cilia and mucous. Small particulate matter falls out of the airstream by gravity as air The respiratory system has two main functions: gas exchange and air conditioning. speed decreases in the depths of the respiratory tree. The particles stick to the mucous GAS EXCHANGE on the surface of the epithelium. Ciliary EPITHELIUM OF ALVEOLI beating then clears the mucous by creating Diffusion of gasses is maximized by pre- currents that stream toward the throat where sentiiig the thinnest possible barrier between small quantities are swallowed and larger the air in the alveoli and the blood cap- quantities are coughed up. illaries. Thus the epithelium of the alveoli is of the simple squamous type.

PROXIMITY OF CAPILLARIES NASAL CONCHAE The capillary network of the lungs is very The superior, middle and inferior conchae or rich and extensive, and the capillaries are turbinate bones of the nasal cavity create very closely applied to the outside surface of currents and eddies that slow the passage of the alveoli. The epithelium of the capillaries the air stream and divert some of it into the is also simple squamous. paranasal sinuses. This slowing of the air stream, along with the increased surface ELASTIC CONNECTIVE TISSUE The connective tissue between alveoli and area, aids the air conditioning functions of capillaries is kept to a minimum, but what the epithelium. little there is, is elastic connective tissue. PARANASAL SINUSES The elastic recoil of this connective tissue is The paranasal sinuses lighten the weight of a very important factor in flushing dead air the skull, provide expanded surface area for out of the lungs during expiration. the nasal mucosa, and act as resonance AIR CONDITIONING chambers for the voice. The paranasal Standard respiratory epithelium is respon- sinuses drair. into the nasal cavity. sible for the air conditioning functions of the NASAL MEATUSES respiratory system. By definition, standard The word meatus is used slightly out of con- respiratory epithelium is pseudostratified co- text in this instance. Usually the word mea- lumnar with cilia and goblet cells. tus means opening, but by definition a nasal WARMING meatus is the space beneath a nasal conchae. When air passes over the mucous mem- Thus, the superior meatus is the area be- branes of the nasal passages, sinuses, and neath the superior concha, the middle conduit system, the air is warmed by picking meatus is the area beneath the middle up heat from the underlying blood vessels. concha, and the inferior meatus is the area beneath the inferior concha. In addition, the MOISTENING Moisture is added to the air from the serous area above the superior concha is called the and mucous secirtions produced by the sphenoethmoidal recess. Each meatus is mucous membrane. the receiving area for a small canal connecting one or more of the paranasal sinuses to FILTERING the nasal cavity. In addition, the nasolacri- Filtering is accomplished first by the hairs in mal duct (tear duct) drains into one of the the nose which screen out the larger dust meatuses, into the inferior meatus to be particles, and second by the combined action Lecture Notes Part It 66 Respiratory System precise. All of this drainage pattern informa- tubes..This tonsil, (along with the less important tion is summarized in the chart that follows: tubal tonsils sometimes seen as a slight swelling mound the opening of the eustachian tube), guards Fig. 19- Sinus Drainage Pattern the entrance to the eustachian tubes. The

NAME OF CAVITY DRAINAGE SiTE purpose of these tonsils is to help prevent throat infections from spreadingto the Sphenoid Sinus Sphencsethmoidal Recess middle ear and mastoid sinuses.

Ethinoidal Air US 44, Superior Meatus OROPHARYNX \.0 The oropharynx is the part of the throat directly to the rear of the cal cavity. The Frontal Sinuses Mdde Meatus epithelium of this region is oral epithelium because it normally comes in contact with MaxMary Sinuses food and drink as well as air. Oral epithelium is stratified squamous epithelium. The

structures found in the oropharynx are the . Nasolacemal Duct Inferior Meatus following:

UVULA This structure is simply part of the soft There are duce parts to the pharynx (throat): palate that hangs down from the palate into nasopharynx, oropharynx, and laryngophar- the oropharynx. During coughing and ynx. Each will be discussed in the following swallowing,the soft palate contracts against paragraphs. the posterior wall of the throat, closing off the nasopharynx so that food and drink do NASOPHARYNX not travel upwards into the nasopharynx. The Nasopharynx is the part of the throat The uvula participates in this action, but that is abovo the soft palate. The epithelium otherwise has no special function. of this region is standard respiratoryep- ithelium because it normally comes incon- PALATINE ARCHES tact with air only, not food or water. The The palatine arches are the soft tissue walls structures found in the nasopharynx are the of the lateral throat at the posterior end of following: the soft palate. PALATINE TONSILS EUSTACHIAN TUBE OPENINGS The eustachian tubes are soft tissue tubes The palatine tonsils are two discrete oval that lead from the throat to the chamber of encapsulated nodes of lymphoid tissue the middle ear. The purpose of the tube is to found nestled in the palatine archeson each allow ambient air to enter the middle ear side of the throat at the lower entrance to the chamber so that the air pressure on the nasopharynx.. Two thirds of their bulk is inside of the tympanic membrane (ear drum) hidden beneath the epithelium, one third is equal to the air pressure on the outside of projects freely upward. A good analogy isan the tympanic membrane. The openings of iceberg, only the tip of which shows above these tubes look like narrow slits in the roof the surface of the water. These tonsils try to of the nasopharynx. prevent nasopharynx infections from spreading into th,!, oro- and laryngopharynx. PHARYNGEAL TONSIL (ADENOIDS) The pharyngeal tonsil is a single patch of LARYNGOPHARYNX friable nonencapsulated lymphoid tissueon The laryngopharynx is the region of the the roof of the nasopharynx in the midline throat right around the epiglottis, which is between the openings of the two eustachiar. the most superior part of the larynx. When

Lecture Notes Part II 67 Respiratory System 7 4 relaxed, the epiglottis projects upward into during breathing. It is closed completely in the laryngopharynx. The epithelium of this preparation for sneezing and coughing, then region is mostly of the oral type because it opened suddenly so that air explosively comes in contact with food and water during exits, the purpose being to dislodge an ir- swallowing. The one exception is the in- ritant from the respiratory passages. ferior surface of theepiglottis,which closes down over the glottis during swallowing, EPIGLOTTIS and hence does not come in contact with The epiglottis is the most superior cartilage food 'This surf- = is normally covered with of the larynx. It projects upwards and standard respil &oozy epithelium. In smokers slightly posteriorly into the cavity of the the epithelium is transformed to stratified larynx. During swallowing the epiglottis squamous due to the abrasive nature of remains relatively stationary and the rest of smoke particles. the larynx is raised up to it so that the epiglottis effectively covers the glottis (opening leading to the larynx and trachea). The larynx (voice box) lies below the phar- THYROID CARTILAGE ynx, below the hyoid bone, and above the The common name for this cartilage is trachea in the anterior neck (see "Adam's apple". The cartilage is an incom- Ng. 20A). It has a skeleton EPiglonis plete ring (horseshoe shaped) with the constructed of nine "open" part of the horseshoe facing pos- separate pieces of teriorly. The anterior side of the cartilage, is lined with standard respi- Throhrid membrane ratory Ipithelium, and houses the vocal COIllialiate cartilage cords. It also serves as Arytenoid cartilage the entryway to the trachea and lungs. Vocal cord Abrasion or vibration Cricothyroid membrane cause the standard respiratory epithelium of the Cricothyroid larynx to convert to stratified membrane squamous epithelium. There- fore the vocal cords because of their vibration, are covered with stratified B. Lateral View of Larynx A. Lateral View of Larynx squamous epithelium, and with thyroid cartilage removed in smokers the epithelium of Fig. 20- Cartilage Skeleton of the Larynx the larynx may be transformed to stratified squamous due to the abrasive action of smoke particles. ring is formed by two large flat plates joined in the midline at an angle to one another to The opening (space) between the vocal form the laryngeal prominence. The angle at cords is called theglottis.Only air passes which these plates join, and the overall size through the glottis. Muscles attached to the of the thyroid cartilage is affected by the arytenoid cartilages adjust the size of the mai: hormone testosterone which begins to glottis and also adjust the amount of tension be secn.::!cl in large quantities at the time of on the vocal cords. The glottis is wide open puberty. This accounts for the voice changes Lecture Notes Part II 68 75 Respiratory System in males at puberty. See below under "vocal cords" for more detailed information. VOCAL CORDS Each vocal cord or vocal fold iscomposed CRICOID CARTILAGE of multiple strands of tough collagenous The cricoid cartilage is below the thyroid connective tissue fibers. The cordsare cartilage. It is a completering of cartilage covered with stratifiedsr,,aamous epithe- shaped like a class ring. The anterior side of lium. Each is attachedto a corner of an ary- the cartilage ring is narrow and the posterior tenoid cartilage posteriorly, andto the inte- side is enlarged, analogousto the palmar and rior surface of the laryngeal prominence dorsal surfaces of a class ring. anteriorly (see Fig. 21). Connecting the cricoid and thyroid carti- The false vocal cordsor ventricular folds lages anteriorly is a thin connective tissue are simply slack portions of the mucous mmbrane called the cricothyroid memb- membrane in the interior of the larynx.They rane. This is the membrane that is punctured can be made to disappear if stretched andare during emergency tracheostomy procedures. of no functional importance. Theyare given It is safely below the vocal cords and isnot their name due to the fact that theyare easily crossed by any important muscle,artery or mistaken for the actual vocal cords. Theylie nerve. above the true cords and are the first folds ARYTENOID CARTILAGES seen when examining a patient's throat. The two arytenoid cartilages siton Laryngeal prominence top of the cricoid cartilage on its Thyroid cartilage posterior side. They are small and somewhat triangular in shape. Vocal Cord Muscles attached to theary- (fold) tenoid cartilages cause them Glottis to rotate, which in turn changes the tension on the vocal cords and adjusts the size of the glottis.

CORNICULATE Arytenoideus Arytentoid cartilage muscle CARTILAGES The two corniculate Fig. 21. Vocal Cords and Glottis, Superior View cartilages are very small and shaped like pieces of candy corn. The siton the top of each arytenoid cartilage. VOICE CHANGES Testosterone causes the thyroid cartilageto CUNEIFORM CARTILAGES enlarge overall; it also causes the angleat The two cuneiform cartilagesare extremely which the flat plates of the thyroid cartilage small and elongated. Theyare anterior to the meet to become more acute. The effect that arytenoid and corniculate cartilages in the this has on the vocal cords is tocause them edge of the aryepiglottic membrane,a to lengthen. As with any stringed musical mucous membrane which connects the ary- instrument, longer strings vibratemore tenoid cartilage to the epiglottis. slowly and thus produce a lower pitch. These physical chl,nges thereforecause the male's voice to deepen.

1, ore Notes Fart II 69 Respiratory System The lung itself is very light spongy, and highly Vox example of elastic. The hilum or root 3 lobules of the lung is the area where the bronchi and upper lobe pulmonary vessels are at- oblique tached and where the fissure pleural layers reflect back upon one another. The lower base of the lung refers to lobe the surface which is next cardiac notch to the diaphragm. The lingula of upper lobe apex ci the lung is the rounded top portion of the RIGHT LUNG upper lobe. It rises above LEFT LUNG the clavicle so that sur- lig. 22- Lobes and Lobules of the Lung prisingly part of the lung actually extends into the neck. The left lung has 2 lobes, the right lung has 3 lobes. Fron le lobes on down the subdivisions are the same for both lungs. Bronchonulmonary segments have clinical lobes significance in that they are the smallest bronchopulmonary segments subsection of the lung that can be removed lobules surgically; ru-moval of anything smaller respiratory units creates air leaks that cannot be sealed. alveolar sacs alveoli

medial

medial basal

RIGHT LUNG LEFT LUNG Fig. 23- Bronchopulmonary Segments as seen from seen from the Mum of the lung

Lecture Notes Part II 70 Respiratory System 77 141t. 1.,:y.04 a PRIMARY BRONCHI The branches of the respiratory tree are The right primary bronchus leads to the right intimnely connected with the subdivisions lung, ane the left primary bronchus leadsto of the lung itself, and each branching of the the left lung. The right primary bronchus is respiratory tubes is accompanied by similar shorter, wider, and more vertical than the branchings of the pulmonary arteries and left primary bronchus. For thisreason veins. aspirated objects usually lodge in the right side of the respiratory tree (see Figs. 24 & 25). As the respiratory tree branches the walls of the tubules become thinner and thinner until The epithelium of the primary bronchi is finally at the bottom of the lung there is a standard respiratory epithelium. The mucosa minimum barrier to gas exchange between contains smooth muscle and the submucosa the alveoli and the capillaries. contains cartilage. The cartilage in the submucosa of these bronchi is in the form of First the amount of cartilage is decreased complete rings. until it disappears, then the epithelium is gradually simplified, and finally smooth SECONDARY (LOBAR) BRONCHI muscle disappears. At the bottom of the The secondary bronchi are the lung, the alveoli are lined with simple branches of the primary bron- squamous epithelium accompanied by a chi. Each secondary bron- few macrophage cells (dust cells) and primary bronchi chus leads to one of the reinforced by a small amount of elastic lobes of the lung. There connective tissue. Watch for are three secondary these changes in the descrip- bronchi on the right tions that follow. side and two on the left, corresponding TRACHEA to the fact that The trachea or secondary the right bronchi windpipe lies latiarY lung has below the larynx and (segmental) bronchi three anterior to the esophagus lobes and in the anterior neck. It the left begins at vertebral level C. lung has and ends by bifurcating two lobes. (forming the two primary The epithelium bronchi) at level T.. Fig. 24- Major Divisions of the Brronchi, of the secon- The trachea is kept patent primary. secondary, tertiary dary bronchi is (open) by the cartilages in its standard respi- wall. These horseshoe shaped rings of carti- ratory epithelium. The mucosa contains lage are filled in at the back by the trachealis smooth muscle and the submucosa contains muscle (membrane), which embryologically overlapping plates of cartilage rather than was part of the wall of the esophagus. complete rings.

The interior epithelium of the trachea is TERTIARY (SEGMENTAL) BRONCHI standard respiratory epithelium. The mucosa Each secondary bronchus divides into two or contains smooth muscle (muscularis mu- sometimes three tertiary bronchi. Each ter- cosa), and the submucosa contains cartilage. tiary bronchus supplies a subunit of a lobe known as a bronchopuhnonary segment. (see Fig. 23). Lecture Notes Part U 71 Respiratory System 78 The right lung has 10 broncho- trachea pulmonary segments, the left lung has 8 or 10 segments. Fig. 26- Respirator), Tree Diagram The epithelium of the tertiary bronchi is standard right primary respiratory ep- left primary bronchus ithelium. The bronchus mucosa contains smooth muscle and the submucosa contains cartilage plates that An not overlap. BRONCHIOLES Each tertiary bronchus secondary (lobar) bronchi divides into numerous bronchioles which by definition are 1 mm tertiary (segmental) in diameter (see Fig. 25). Each bronchiole bronchi supplies a subunit of a bronchopulmonary segment known as a lobule (see Fip. 22 & 25). ors ampl broncho- The epithelium of the bronchiole is stan- bronchiole pulmonary dard respiratory epithelium. The mucosa segment contains smooth muscle but the submucosa lacks cartilage. There is no cartilage in terminal bronchioles the wall of a bronchiole or in any of respiratory bronchioles the smaller tubes respiratory unit which follow. alveolar duct TERMINAL BRONCHIOLES Bronchioles divide into smaller tubes called terminal bronchioles. alveolus alveolar sac Each terminal bronchiole supplies a subunit of a lobule known as a respiratory unit.. (See Fig. 25) some small amount of gas exchange is taking place at this level. (See Fig. 25). The epithelium of the terminal bronchiole lacks goblet cells and is therefore simple Each respiratory bronchiole leads to a columnar rather that pseudostratified subsection of a respiratory unit known as an columnar. Smooth muscle is still present in alveolar sac. (A useful analogy for the the mucosa. alveolar sac is "a bunch of grapes", whereas each individual grape would be analogous to RESPIRATORY BRONCHIOLES one alveolus. Terminal bronchioles divide to form respira- The epithelium of the respiratory bronchiole tory bronchioles, so called because each has lacks cilia as well as goblet cells and is a few alveoli attached to its wall, so that Lecture Notes Part II 72 Respiratory System 79 more cuboidal than columnar.Notice that the Mediastinal Surface cilia persist deeper into the respiratory tree The surface facing the mediastinum. than do the mucous secreting cells. This is an appropriate arrangement, since if the cilia PLEURAL REFLECTIONS ended before the glands did there would be The parietal and visceral layers of the pleura no way to move the secretions out of the are actually one continuous sheet of mem- alveolar area. brane which turns back upon itself at the hilum of the lung. This turning back is ALVEOLAR DUCTS termed a reflection. Each respiratory bronchiole branches to form several alveolar ducts, each of which PLEURAL CAVITY leads to a subsection of the alveolar sac. (An The pleural cavity is thespace between the analogy would be one subsection of a very parietal and visceral layers of the pleura. large bunch of grapes. (See Fig. 25) There is a negative air pressure (i.e.vac- uum) in this cavity. It is necessary for there The wall of the alveolar duct lacks smooth to be a negative pressure in this cavity in muscle and the epithelium is the cells are a order for the lung to inflate. very low cuboidal in shape (perhaps actually more squamous than cuboidal). PLEURAL RECESSES The pleural recesses are potentialspaces or pockets in the pleural cavity (See Fig. 26) where fluids collect following injuryor in- PLEURAL MEMBRANES fection of the thorax. Drainsmay be put into (See Fig. 26). The pleural membranes are thin these areas following thoracicsurgery in layers of connective tissue lined with meso- order to draw off fluids. thelium (simple squamous epithelium). A thin watery lubrication fluid called RIGHT COSTODIAFHRAGMATIO RECESS serous fluid is secreted by the pleura. This recess is a pocket found on the right This lubrication is very side of the chest between the costal and diaphragmatic surfaces of the parietal pleura. important in order to pleural cavity prevent friction and eteA00 LEFT COSTODIAPHRAGMATIC RECESS /0,000/0 1,01,010/ pain with respiration. 00/00.0"00 This recess is similar to theone 00 OOOOO II, %%%%%%. teeteeoeeeeo %%%. eetvooteette %%%%% %%% above except that it VISCERAL LAYER 0,00,000/000, % % % % % % % % % % % 00.00,00/00,0.01 0 teteeeeeeeet Pleural eeeetooeteeett vb. voo. is found on the left The visceral pleura eeo eeeeeeee to e Aeoeeoetwoottet refleclions 0/0/00,1/00/100 side of the chest. clings to the outside 00000010/00.00/0.0 OOOOOOO 00000/0, //tow/ern/toe eeeeeeteeeeee of the lungs. eeeteeteetto 4006%%%%%%%%%%%%% chest wallCOSTOMEDIASTINAL eeeoeeete RECESS PARIETAL LAYER lb This recess is asso- The parietal pleura parietal ciated with the is the interior lining pleura cardiac notch of of the chest wall. It's the left lung. It is surfaces have names. visceral pleura found agaii 1t the diaphragm Costal Surface anterior chest wall The inside surface of right left between the costal costodiaphragmatic the rib cage. costodiaphragmatic and mediastinal recess recess Diaphragmatic surfaces of the parietal pleura. Surface Fig. 26- Pleural Cavity, Pleural Reflections The top surface of and Pleural Recesses the diaphragm.

Lecture Notes Part II 73 Respiratory System 0 In the case of black lung disease, the dusty air is also toxic as a result of coal tars, and as a result emphysema will also eventually PNEUMOTHORAX Pneumothorax means air in the pleural develop. cavity.The usual cause is puncture of the BROWN LUNG DISEASE chest wall or tearing of the lung. The lung Textile workers disease. Textiles, especially on that side of the thorax will collapse, but if cotton, produce a lot of dust. Breathing the the opening is sealed the air will be reab- dusty air leads to pulmonary fibrosis and sated gradually over a period of a few chronic bronchitis. weeks. A pneumothorax is sometimes ASBESTOSIS artificially induced in order to collapse the Asbestos is a fibrous mineral, the fibers of lung to let it rest. which are exceedingly light and prone to PLEURISY traveling long distances in the air. Breathing Inflammation of the lung and pleural mem- this mineral leads to the usual pulmonary branes with consequent friction and pain fibrosis and chronic bronchitis. In addition upon respiration. asbestos fibers are carcinogenic. The type of

EMPHYSEMA cancer that results is usually a mesothe- Emphysema is due to loss of elasticity of the lioma. lung alveoli, thus preventing normal passive ASTHMA expiration. The patient has difficulty getting Asthma has many different causes and is rid of inspired air and this of course makes accompanied by many different degrees of gas- exchange very difficult. debilitation of the respiratory system, but the symptoms always include constriction of the Emphysema is mostly due to the toxic effect bronchioles due to overactive smooth of smoke. Cells die and release enzymes muscle, and excess secretion of mucous which self digest the walls of the alveoli. from the respiratory epithelium. The elastic tissue breaks into short strands, and the septal walls between the alveoli break down so that the alveoli coalesce into large blebs with much less surface area for gas exchange. Cigarette smoke also contains other toxins such as nicotine, hydrocarbons, tars, and carbon monoxide. Nicotine constricts the arterioles and CO competitively binds with hemoglobin, both of which contributes to anncxia and cell death. The hydrocarbons and tars are cancer inducing agents.

BLACK LUNG DISEASE Coal miners disease. As is the case with all lung disease due to breathing of dusty air, there is pulmonary fibrosis and chronic bronchitis. The fibrosis is a collagen scar- ring and thickening of the septal walls; it yields poor lung expansion and poor gas exchange.

Lecture Notes Part II " 61 Respiratory System nFr

The Heart

The heart lies obliquely in the mediastinum The heart wall has 3 parts, pericardium, of the chest with the apex of the heart ml Jcardium, and endocardium. pointing down. The apex of the heart lies in the left fifth intercostal space approximately PERICARDIUM the width of two fingers to the left of the The pericardium hastwo subparts, the sternum. This knowledge is useful clinically fibrous pericardium and theserous pericar because the apex is part of the left ventricle dium, and the serous pericardium inturn has of the heart, which is the main pumping two subparts. chamber, and it is occasionallynecessary to FIBROUS PERICARDIUM inject directly into the left ventricle. The The fibrous pericardium is likea connective most reliable bony landmark used to locate tissue box or envelope in thecenter of the the apex is the sternal angle which is level with the second rib. The great aortic arch vessels of the heart pulnumary left atrium attach to ti the up- right ventricle permost left ventricle part of the heart at the level of the third A. Anterior Silhoutte B. Lateral Silhoutte rib.

Fig. 27- Position of the Heart in the Chest Cavity

mediastinum. It houses the heart. The The heart as seen from the front view has bottom surface of the fibrous pericardium is been rotated or twisted toward the left,so fused with the central tendon of the diaph- that the right half of the heart liesmore or ragm. The top of the fibrous pericardium ex- less in front of the left half of the heart. tends upward to surround the beginnings of From t' t front therefore youcan see the the great vessels. right atrium, the right ventricle,a good part SEROUS PERICARDIUM of the left ventricle (because it isso large) The serous pericardium consists oftwo and only a very small part of the left atrium. layers, parietal pericardium and visceral Almost none of the left atrium can be seen pericardium from the front since it occupiesmost of the posterior surface of the heart. The visceral pericardium (also knownas epicardium) clings directly to the outside

Lecture Notes Part 11 75 82 Cardiovascular System surface of the heart muscle. The parietal 1,V pericardium is attached tightly to the inside Think of the heart as a pair of muscular surface of the fibrous pericardium. pumps fused together, side by side. The serous pericardium is a smooth transparent membrane resembling a balloon CHAMBERS OF THE HEART blown up inside the boxlike fibrous pericar- Each cardiac pump is composed of an dium. It is invaginated or indented by the abium and a ventricle.The atria are upper- fist sized heart. Both layers of serous peri- most and the ventricles are below them. The cardium secrete a thin film of watery lubri- atrium is the receiving chamber of each cating fluid to reduce friction as the heart pump. The ventricle is the propelling cham- beats. The parietal and %:sceral layers are ber of each pump. separated by the pericardial cavity. Attached to each atrium is a nonfunctional The pericardial cavity is the space between ear shaped appendage called an auricle. The the parietal and visceral layers of the serous inside surface of each auricle is marked by pericarditmx It is normally empty. If fluid coarse sasnds of muscle that look like the of any kind collects in the pericardial cavity teeth of a comb, the pectinate muscles. it will put pressure on the heart and inhibit The interior surface of each atrium is very its function. This condition is called cardiac smooth as compared to the ventricles which lemonade. have an interior surface marked by numer- MYOCARDIUM ous strands called trabectskte comae. In addition the atria have very thin walls com- The myocardtm is the ampsl muscle of the pared to the walls of the ventricles. This is heart. It is thickest in theells of the left because the atria are required to propel ventricle, thinner in the walls of the right blood only as far as the nearest ventricle ventricle, and thinnest of all in the walls of w}..Leas the ventricle must pump blood to the atria. some part of the body. ENDOCARDIUM SEPTAE The endocardium is the The right and left heart are separated simple squamous epithe- from one another by a wall lium which lines the in- fibrous pericardium called the median septum. side cavity of the In the adult heart there is heart. It is continu- no com- ous with the endo- parietal layer of serous pericardium municat- thelium of the ion be- blood vessels. tween visceral layer of serous pericardium the pericardial cavity right myocardium and left halves of the heart. The part of the median septum which is between the atria is called the

diapltrap, interatrial septum. The part of the septum which is between the ventricles is called the interventricular septum. Fig. 28- Layers of the Pericardium

Lecture Notes Part II 76 Cardiovascular System S3 Between the atria and the ventricles is the col 'pared to the pulmonary circulation the abioventricular septum (A-V septum). The muscular wall of the left ventricle is about part of this septum in the right heart is called three times thicker than that of the rightven- the rig V septum; the part in the left tricle.. heart is -the left AV septum. AN, '$4? *At Y. V fe, BLOOD FLOW 'THROUGH THE HEART The right heart is the pump for the pulmonary circulation. It receives venous blood A vein is a vessel that carries blood toward from the body mass and propels it to the the heart. An artery is a vessel that carries lungs for removal of carbon dioxide and blood away from the heart. enrichment with oxygen. RIGHT HEART VEINS The left heart is the pump for the systemic circulation. It receives oxygenated blood Three veins bring blood to the right atrium: superior vena cava, inferior vena from the lungs and propels it out to the rest cava, and coronary sinus. of the system. Because of the proportionately greater mass The superior vena cava brings blood from the head, neck, upper limbs, and chest wall. and resistance of the systemic circulation as left common carotid a. brachiocephalic artery left subclavian a.

superior vena cava

right pulmonary artery left pulmonary aa.

Alli°11".+left pulmonary vv right pulmonary vv Alks'

cusps of mitral valve right atrium cusps of sonic valve cusps of tricuspid valve pulmonary valve

opening of coronary sinus left ventricle

silt ventricle inferior vena cava

descending aorta

Fig. 29- Blood Flow Through The Heart

Lecture Notes Part II 77 Cardiovascular System The inferior vena cava brings blood from The right atriowntricular valve (Right A-V the abdomen, pelvis, and lower limbs. The valve) has three cusps or flaps and is called coronary sinus brings blood from the the tricuspid valve. muscle of the heart wall. The left atrioventricular valve (Left A-V RIGHT HEART ARTERIES valve) has two cusps and is called the bicus- The artery carrying blood away from the pid or mitral valve. right ventricle to the lungs is the pulmonary SEMILUNAR VALVES trunk. It splits into two branches, the right These valves are found in the aorta and and left pulmonary arteries. pulmonary trunk exactly at the point where LEFT HEART VEINS the vessel rises out of the top of its respec- There are four pulmonary veins returning tive ventricle. They are designed to prevent from the lungs to the heart. These four bring blood from fallir g back into the ventricle oxygenated blood to the left atrium. during the period of time following contraction, when the ventricle is relaxed and the LEFT HEART ARTERIES blood pressure in the ventricles is low. The artery carrying blood away from the left The aortic and pulmonary semilunar valves ventricle to the systemic circulation is the are identical to one another. Each valve has aorta. It assends a short distance, then thee halfmoon cup shaped cusps. The cups arches to ti e left and descends through the diaphragm and into the posterior surface face upward right left so that abdomen. atrioventricular atrioventricularwhen they valve valve fill with The heart has four .'a!s, blood they two atrioventricular valves bulge into the lumen and two semilunar aortic valves semilunar of the artery valve left and close it Valves are one way coronaryoff. The full artery flow devices designed to right cups are self keep blood moving in onecoronary bracing shapes direction by ineventing artery pulmonary with no pro- backflow. They open or semilunarlapse problems. valve close as a simple response to anterior surface blood pressure changes inside the heart chamber Fig. 30- heart Valves, Superior View during contraction or relaxation of that chamber. PROLAPSE PREVENTION During ventricular contraction the pressure ATRIOVENTRICULAR VALVES increases enormously on the underside of Each atrium communicates with its own the A-V valve cusps, therefore these valves ventricle through an atrioventricular orifice. require special structures to prevent them The orifices are guarded by valves designed from prolapsing,i.e. overdosing or behav- to allow blood to flow from the atrium to the ing like a swinging door. The structures ventricle when the ventricle is relaxed, but which prevent prolapse are known as the not in the reverse direction when the ven- papillary muscles and cliordae tendinae. tricle contracts. They are visible from inside the ventricle only. Lecture Notes Part U 78 Cardiovascular System 65 4 4 : 1 :

1 Ira 1a I 1: a 4 1 11 1 : 0! : 1 1

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ionic semilunar valve left auricle superior vena cava left coronary artery

right auricle circumflex artery

pulmonary trunk anterior interventricular right atrium artery

anastomoses right coronary artery

inferior venacave marginal artery

Fig 32- Transparent View of Coronary Arteries

Cardiovascular System $o S 7 right coronary artery

middle caidiac vein

Fig. Ws Posterior View of Heart

aortic semilunar valve superior vena left auricle cava

great coronary cardiac sinus vein

coronary sinus middle opening cardiac into right atrium vein

small-- cardiac vein inferior vena cava

Fig. 34- Transparent View of Cardiac Veins

81 Cardiovascular System 88 The tributary veins draining into the coro- contractility. The individual muscle cell nary sinus correspond in position to the contractions are synchronized into a rhyth- branches of the coronary arteries. mic beat by a dominant group of specialized muscle cells which sets the pace for the The great cardiac vein corresponds to the contractions. This specialized group of anterior interventricular and circumflex muscle cells is called the pacemaker, or branches of the left coronary artery. more technically, the sinoatrial node. The middle cardiac vein corresponds to the The SA node is located in the ceiling of the posterior interventricular portion of the right right atrium next to the superior vena cava. coronri artery. A wave of contraction spreads downward The small cardiac vein corresponds to the from the SA node, engulfing both atria and marginal branch of the right coronary artery. pushing the blood from the atria into the ventricles. The SA node normally fires CORONARY ARTERY PATHOLOGY about 72 times per minute. The rate and If any part of the subendocardial plexus strength of contractility is adjusted by the becomes starved for blood the muscle in that autonomic nervous system; the sympathetic area is described as being ischemic. Is- nervous system increases and the para- chemia is usually accompanied by a charac- sympathetic decreases the frequency and teristic kind of chest pain called angina strength of the contractions. pectoris. AV NODE Angina pectoris is a severe cramp like pain As the wave reaches the bottom of the right in the chest region. It is a referred pain that atrium it is diminished in strength until it chacteristically radiates down the medial triggers contraction in a second node of spe- surface of the left arm The pain is due to cialized heart muscle cells called the atrio- spastic contraction of the coronary vessels ventricular node. The AV node acts like an that occurs when blood flow is reduced. amplifier which will start a wave of contrac- Ischemia is usually.temporary, however, if tion in the ventricles. However, the ven- the corollary arteries are significantly nar- tricles cannot be allowed to contract from rowed or occluded, the ischemia may be- the top down because the arteries of the come prolonged causing muscle cells necro- heart are attached to the upper side of the sis. Death of heart muscle cells is called a ventricles; there is no exit for blood from the myocardial infarct. The common term for a bottom of the heart. If the ventricles were to myocardial infarct is "heart attack", or contract from the top down the blood would sometimes "coronary". The severity of a blow a hole out of the bottom of the heart. heart attack will depend on what part of the heart is damaged, and on how large an area AV BUNDLE is damaged. The solution for this situation is a bundle of

...... '. specialized heart muscle cells called the atrioventricular bundle (bundle of His). The AV bundle is located in the interatrial wall, extending from the AV node to the The heart is synchronized by specialized interventricular septum. It conducts the tissue derived from muscle. contraction impulse from the AV node to the SA NODE right and left bundle braines which ran down the interventricular s 3 urn to the, The heart de-...s not need a separate nervous bottom of the ventricles where they spread supply in order to beat. The muscle cells of out into the musculature of the ventricle the heart have their own inherent rhythmic

Lecture Notes Part H 82 Cardiovascular System 9 walls. Thus the wave of actual muscle CHANGES AT BIRTH contraction starts at the bottom of theven- tricles and spreads toward the top, propel- FOSSA OVALIS ling blood upwards into the aorta and pul- At birth, when the child starts breathing, the monary trunk. pressure in the left atrium rises and equal- izes with the pressure in the right atrium, The terminal fibers of the bundle branches holding the curtain of tissue in the midline were discovered before the existence of the between the two atria. This closes the conduction system was known, and these foramen ovale functionally, and withina fibers were called the Puridyde fibers.The short time the edges of the flap fuse closing name now applies to the specialized tissue the foramen anatomically. of the AV bundle as seen microscopically. When the foramen ovale closes it leaves behind a depression in the interatrialseptum The fetus does not use its lungs, and there- where the wall is thin. This thin depression fore blood is diverted away from the the is called the fossa If for whatever pulmonary circulation vessels. reason the foramen remains open the defect is referred to as patent foramen ovale. There are two short circuit devices in the fetal heart which effectively route blood LIGAMENTUM ARTERIOSUM away from the pulmonary arteries. The first At birth blood flow thru the ductusceases of these is the foramen ovale, the second is due to pressure changes in the thorax and the ductus arteriosis. heart, and shortly thereafter the ductus constricts and begins to fill in withconnec- FORAMEN MALE tive tissue. The foramen ovale is an oval hole in the interatrial septum near the junction of the The filled in duct resembles a ligament and superior vena cave and right auricle. A thin is therefore called the ligamentum arteries loose flap of tissue hangs down from the top sum. If for some reason it remains open the of the foramen like a curtain. This flap is defect is referred to as patent ductus pushed out of the way by the pressure of arteriosis. blood flowing through the foramen (in the fetus only) from the right atrium directly into the left atrium, bypassing the right ventricle and pulmonary vessels.

DUCTUS ARTERIOSIS The ductus arteriosis is a short open vessel leading from the top of the pulmonary trunk to the bottom of the aortic arch. Whatever amount of blood does fall from right atrium into right ventricle will be propelled upward from the ventricle and into the pulmonary trunk. When it hits the top of the pulmonary trunk it will keep on going straight into the aortic arch, bypassing the right and leftpul- monaryarteries.

Lecture Notes Part II 83 Cardiovascular System 80 Blood Vessels: Chest AreaArteries with the posterior intercostals (whichare direct branch :a of the descending thoracic aorta). The arch of the aorta in hairns has three branches: brachiocephalic, leftcommon 2. Thyrocervlad (and Costocetvleal )aa. carotid, and left subclavian. In the cat there The branches of these arteries supply the are only two branches off the arch: brachio- neck and shoulder muscles. cephalic and left subclavian. + LEFT COMMON CAROTID A. BRACHIOCEPHAUC A. The anatomy of the leftcommon carotid is An older name for this artery is "Innominate identical to that of the rightcommon carotid Artery". In humans it has two branches,one described above. heading for the brachium andone heading 4 LEFT SUBCLAVIAN A. for the cephalic region. In cats the left The anatomy of the left subclavian is identi- common carotid is also attached to the cal to that of the right subclavian described brachiocephalic artery. above. 1. RIGHT COWIN CAROTID A. The word common in the name ofa vessel indicates that it will soon split into two other vessels. The common carotid travels up the 1. Posterior Intercostal aa. neck to the level of the thyroid cartilage The descending aorta in the thorax gives (Adam's apple) where it splits into internal off many small branches to the intercostal and external carotids. It comes closest to the areas. These anas:omose with the anterior skin just below its bifurcation point (a pulse/ intercostals which are branches of the pressure point used when taking a patients internal thoracic artery (see above). heart rate). 2. Esophageal,Bronchial, and Dlaphtagm at 2. RIGHT SUBCLAVIAN A. The veins of the chest that empty into the The word subclavian means under the clavi- heart include the pulmonary veins, the cle. This vessel passes under the clavicleon coronary sinus, inferior vena cave, and its way to the arm where it will become the axillary artery of the arm. Along theway it gives off three branches which distributeto the brain, chest, and shoulder. a. Vertebral a. This artery is one of the main sources of blood for the brain. It will be discussed with the head and neck arteries. b. Internal Thoracic A. (Internal Mammary) This artery clings to the internal surface of the chest wall, giving off branches to the rib cage as it descends. These branches supply the breast as well as the ribs. 1. MOM Intercostal aa. The anterior intercostals will anastomose

Lecture Notes Part II 84 Cardiovascular System Blood Vessels: Chest AreaVeins the superior vena cava. Of these the a. Poslatlor Intercostal veins pulmonary veins and the coronary sinus were covered in the heart lecture. The b veins from : Esolfiumus,Ott, Diaphragm inferior vena cava does not receiveany c. Homier/9os veht significant tributaries in the chest, there- This vein may or may not be present. If it fore it will be discussed under the head- is present it receives the posterior inter- ing of Abdominal Veins. This leaves the costals from the left side of the chest. If it superior vena cava for present discussion. is not present those same intercostals simply cross the midline and empty ;i directly into the azygos vein. The superior vena can brings blood to the + INTERNAL THORACIC VEIN heart from the upper part of the body (head, The two internal mammary (internal tho- gams, shoulders). It is formed by the joining racic) veins are companions to the arteries of together of the the right and left brachio- the same name; they receive the anterior cephalic veins, and it also receives two other intercostal veins. The two internalmanimRry small tributaries, the azygos vein and the veins fuse just before draining into thesu- joined internal mammary veins. perior vena cava. BRACHIOCEPHAIJC VEINS There are two brachiocephalic (innominate) veins. Each is formed by the junction of a subclavian vein from the arm and an internal jugular vein from the head and neck region. The tributaries of the brachiocephalic veins on the right and left sides of the chest are mirror images of one another, so the words "right" and "left" are not used in the list below.

1. SUBCLAVIAN VEIN The subclavian vein is the directcon- tinuation of the axillary vein of the arm. Close to the junction where it empties into the brachiocephalic vein it receives the external jugular vein, which is a major tributary from the heat' rid neck.

2. INTERNAL JUGULAR VEIN This vein will be discussed with the "Head and Neck Veins".

AZYGOS VEIN The Lzygos vein collects blood from the chest wall. It rec.;ives blood f In the following tributaries. Lecture Notes Part II 85 92 Cardiovascular System Blood Vessels: Head and Neck Arteries

arteries to one another. Most of the brays of the external carotid Opthalmic Artery stay outside of the skull. The exception is Supplies blood to the orbit. Anastomoses the meningeal branch of the maxillary with the facial branch of the external carotid. artery. MIDDLE CEREBRAL ARTERY + FACIAL ARTERY The middle cerebral artery is a large branch The facial artery wanders around over the of the internal carotid artery that follows the face and finally ends up in the orbit where it lateral fissure and supplies the parietal and anastomoses with the opthalmic branch of temvoral lobe areas of the brain. the internal carotid artery Posterior Communicating Artery OCCIPITAL ARTERY The posterior communicating artery is a This branch supplies the scalp in the occipi- small branch that joins the middle cerebral tal region. artery to the posterior cerebral artery. SUPERFICIAL TEMPORAL A. This is the direct upward continuation of the These arteries a= also an important source external carotid artery. It supplies the scalp of blood for the Circle of Willis of the brain. in the temporal and parietal regions. On their way up the neck toward the head, each vertebral artery threads its way through MAXILLARY ARTERY the transverse foramena of the cervical This supplies blood to the teeth in the upper vertebrae. They enter the skull through the jaw, and also to the nose. One interesting foramen magnum. branch enters the skull to supply the meninges. BASILAR ARTERY As soon as the two vertebral arteries enter MIDDLE MENINGEAL ARTERY This artery is the exception to the rule in that the skull they join together to form the sin- it goes inside the skull, but even this branch gle basilar artery which is located on the stays external to the brain. It supplies the base of the brain stem. The basilar artery meninges. soon splits again to form the two posterior

" e < r i :;" : cerebral arteries, which are part of the Circle of Willis.

The internal carotid enters the skull through POSTERIOR CEREBRAL ARTERIES the carotid foramen and carotid canal. The The posterior cerebral arteries supply the two carotid arteries are the most important occipital pole of the brain. source of blood for the brain. Each internal Posterior Communicating Artery carotid has two branches, both of which See the description above under "middle part of the Circle of Willis of the brain. cerebral artery. ANTERIOR CEREBRAL ARTERY The anterior cerebral artery is a small branch CEREBELLAR ARTERIES of the internal carotid that turns toward the The cerebellar arteries branch off of the frontal pole of the brain. basilar artery and head for the cerebellum. nterior Communicating Artery This artery joins the two anterior cerebral

Lecture Notes Part II 86 Cardiovascular System S3 'T

Blood Vessels: Head andNeck Veins .MIIMINIM11111 aat located next to the sella turcica in thecenter This vein drains blood from the exterior of of the skull. They receive blood from neigh- the skull. Its branches are identidal to those boring brain areas and drain that blood into of its companion, the external carotid artery. the transverse sinuses. Of clinical importance is the fact that they receive some ) blood from the facial veins via the orbital This vein is the companion to the internal veins. This constitutes a potential entry carotid artery in the neck. It is a direct route for bacteria from facial and orbital in- continuation of the venous sinuses of the fections. skull whose tributaries drain blood from the + STRAIGHT SINUS brain. The straight sinus is a continuation of the These venous sinuses were first discussed in inferior sagittal sinus.

the unit on bones where you were asked to INFERIOR SAGITTAL SINUS observe the grooves made by these veins on The inferior sagittal sinus is located in the the interior of the skull. The venous sinuses inferior border of the falx cerebri. It receives were discussed a second time in the nervous blood from adjacent cerebral veins. system unit under the topic "cerebral spinal fluid circulation". The points to emphasize here is a clinical one. There are two possible routes by which infections may spread into the cranial cavity and cause meningitis. These potential entry routes involve the cavernous sinus and the sigmo:1 sinus.

SUPERIOR SAGITTAL SINUS The superior sagittal sinus receives blood from adjacent cerebral veins.

Remember that it also receives cerebral , spinal fluid which is reabsorbed by way of the arachnoid +TRANSVERSE & SIGMOID SINUSES These sinuses drain blood from adjacent areas of the brain. Note the following points of clinical interest :

AURICULARVEINS These small tributaries from the middle and inner ear drain into the transverse and sigmoid sinuses. This constitutes a potential entry route for bacteria from ear infections.

CAVERNOUSFINIS There are t -emous sinuses, each is

Lecture Notes4drt II 87 Cardiovascular System 34 0

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1 Blood Vessels: Abdominal Arteries and Veins

mesentery of the intestine, and supplies the These single branches of the abdominal descending and sigmoid colons, and also aorta supply all the viscera that are part of gives off the superior rectal artery (superior htmorrhoidal) to the rectum. the digestive system. 4* CELIAC TRUNK ARTERY The celiac trunk in humans is only about a These branches supply the organs that are quarter of an inch long. It divides into three not part of the digestive system. arteries. + RENAL ARTERIES SPLB4C ARTERY These are the very large arteries that supply The splenic artery runs along the upper edge blood to the two kidneys. of the pancreas. It supplies the spleen, with multiple small branches to the pancreas and +GONADAL ARTERIES a gastroepiploic branch which follows the The gonadal arteries are also known as greater curvature of the stomach and anas- ovarian or testicular or spermatic arteries, tomoses with a similar branch from the depending on gender. hepatic artery. + COMMON ILIAC ARTERIES Pomade brandtes Left gastroeplploic artery The abdominal aorta ends by bifurcating into the two common iliac arteries which COMMON HEPATIC ARTERY supply the pelvis and lower limbs with The common hepatic artery carries oxygen- blood. lted blood to the liver, with important secondary branches to the stomach, pancreas, upper half of the duodenum, and gall bladder. The veins that drain directly into the inferior Right GashIc artery vena cave are the counterparts of the paired Gastroduadenal artery abdominal arteries. The exception to the rule Cholecystle artery is the blood draining into the inferior vena LEFT GASTRIC ARTERY cava from the multiple hepatic veins. The left gastric artery follows the lesser curvature of the stomach and ends by anas- leoRENAL VEINS tomosing with the right gastric artery (a These are the veins that drain blood from the branch of the common hepatic artery) kidneys into the inferior vena cava. + SUPERIOR MESENTERIC A. + GONADAL VEINS The superior mesenteric artery travels in the The left gonadal vein often drains into the mesentery of the intestine, and supplies all left renal rather than directly into the inferior of the small intestine, including the lower vena cava. half of the duodenum. It also supplies the COMMON ILIAC VEINS upper parts of the large intestine, namely the These veins return blood from the lower cecum, ascending colon, and transverse limbs and pelvis. colon. + HEPATIC VEINS + INFERIOR MESENTERIC A. The hepatic veins are the veins that are The inferior mesenteric artery travels in the exiting from the liver. They collect blood Lecture Notes Part II 89 Cardiovascular System 96 from the hepatic sinusoids (capillaries) of 46SPLENIC VEIN the liver lobules. The blood in these veins is This vein receives blood from the spleen and blood that the liver has already finished also from the stomach and pancreas. It is the processing. The raw nutrients received from companion vein to the splenic artery. the digestive tract have been metabolized or stored by the liver, and the usable nutrients SUPERIOR MESENTERIC VEIN are now ready to be sent on to the heart for The superior mesenteric vein receives blood distribution. fmm the small intestine and from the upper parts of the large intestine. It is the companion vein to the superior mesenteric artery.

itTe VeMS t COnStitlite the INFERIOR MESENTERIC VEIN hepatic portal system. All of these veins drain into the hepatic portal vein, which col- The inferior mesenteric vein drains into either the splenic vein or equally often into lects blood from the digestive tract and carries it to the liver for processing. These the superior mesenteric vein. It receives blood from the lower half of the large veins are the counterparts to the single intestine. It is the companion vein to the branches of the abdominal aorta. (There is inferior mesenteric artery no veins corresponding to the celiac trunk per se, but rather the veins correspond to the + LEFT GASTRIC VEIN branches that the celiac trunk gives rise to. This vessel is a minor contributor to the portal vein. It is the companion vein to the left gastric artery.

Blood Vessels: Pelvic Arteries & Veins

The arteries and veins of the pelvis are iden- The middle sacral artery is attached to the tical to one another, and the vessels on the center of the inverted Y of the bifurcation_ if right side are identical to those on the left aorta. It supplies the tail. ide. INTERNAL RAC ARTERY AND VEIN The descending aorta and its companion The internal iliac vessels distribute to the vein the inferior vena cave, end at approx- pelvic and perinea' organs and the buttocks. imately the level of the pelvic brim, just The organs supplied include the: rectum, slightly below the level of the umbilicus. bladder, prostate, seminal vesicle, penis, They end by bifurcating into two common scrotum, uterus, vagina, and vulva, (but not iliac vessels which distribute to the pelvis the ovary and testicle which are supplies by and legs. the gonadal artery, a branch of the aorta). it is more important to remember the structures COMMON ILIAC ARTERY & VEIN supplied than to remember the names of the branches.

Use of the term "common" indicates that EXTERNAL ILIAC ARTERY AND VEIN these vessels will branch into two other iliac The external iliac vessels become the femo- vessels, one for the pelvis and one for the ral vessels of the thigh. The name change leg. occurs as the artery passes under the ingui- Cats have a common iliac vein, just as do nal ligament. humans, however cats do not have a common iliac artery. In cats the internal iliac artery comes off of the middle sacral artery

Lecture Notes Part II 90 Cardiovascular System Blood Vessels: Arteries and Veins of the Leg

The deep veins of the leg are identical to the ately heads for the front of the lower leg. It companion arteries, and the vessels on the passes between the fibula and tibia and right side are identical to those on the left descends with the tibialis anterior muscle. side. At its lower end its name changes to dorsis pedis artery or vein. Donis Pedis artery and vein The main femoral artery and vein are direct As its name indicates, the dorsis pedis vessel continuations of the external iliac vessels; is on the top of the foot. they distribute to the thigh and are the equivalent of the brachial artery and vein in Arcuate Artery the arm. The main femoral has many small This vessel is the direct continuation of branches, but only two large ones: the deep the dorsis pedis. The term "arcuate" femoral and the popliteal. One of these (the refers to the arch that this vessel forms on popliteal) is really just a name change for the top of the foot. It distributes to the the continuation of the femoral vessel into toes by way of the digital branches. the popliteal fossa. POSTERIOR TIBIAL ARTERY AND VEIN The posterior tibial vessel is the main branch + DEEP FEMORAL ARTERY & VEIN of the popliteal vessel. It heads in the direc- These vessels are also known as the pro- tion of the big toe, gives off one main funda femoris artery and vein. They run branch up high on the calf (the peroneal parallel to the main femoral vessel and artery and vein), passes behind the medial distribute to the muscles of the thigh. They malleolus, and ends by bifurcating into the are the most important collateral circulation medial and lateral plantar vessels on the vessel of the leg, i.e. if the main femoral bottom of the foot It is the source of distri- vessel is occluded the Jeep femoral vessel bution to the calf muscles. can often take over the job of supplying blood to the rest of the limb. The posterior tibial artery is equivalent to the radial artery of the lower arm; a pulse LATERAL FEMORAL CIRCUMFLEX A. & V. This is the largest branch of the profunda and pressure point are available behind the femoris. it winds around the thigh laterally medial malleolus. and distributes to the hip joint. One long de- Peroneal artery and vein scending branch winds around the knee and This branch of the posterior tibial vessel anastomoses with branches of the popliteal distributes to the lateral calf (peroneal vessel. muscles). POPUTEAL ARTERY & VEIN Medial and Lateral Plantar a & v The popliteal vessels are the direct con- These two vessels are the direct continuation tinuation of the main femoral vessels. The of the posterior tibial vessel. They anasto- name comes from the popliteal fossa at the mose to form an arch on the bottom of the back of the knee. They have small branches foot. to the knee and end below the knee by bifur- a. Plantar arch cating into the anterior and posterior tibial The plantar arch distributes to the toes by vessels. way of the digital branches. ANTERIOR TIBIAL ARTERY AND VEIN This branch of the popliteal vesel immedi-

Lecture Notes Part II 91 Cardiovascular System t

x9Zti:Ozi..` These veins are prone to becoming varicose because of the fact that being under the skin they do not benefit from the massaging action of the muscles. 4 LESSER SAPHENOUS VEIN This vein is found under the skin in the area of the calf (posterior surface of lower leg). It drains blood into the deep veins by joining the popliteal vein behind the knee. GREATER SAPHENOUS This vein drains all of the skin of the leg except for the area covered by the lesser saphenous vein. It drains into the femoral vein at the groin.

Lecture Notes Part II 92 Cardiovascular System Lymphatic System

The lymphatic system of vessels and lym- added. phoid organs have three main functions: 1. transport of tissue fluid VALVES 2. transport of dietary fats All lymphatic vessels that drain in the 3. immune system functions upward direction have valves to prevent the

e ,z.; 4:;;;; fluid from falling back down from whence it Cr 04, Af came. These vessels usually have a beaded Ma appearance due to dilation of the vessel WHAT IS TISSUE FLUID above the valve. Tissue fluid (also known as lymph or intercellular fluid or interstitial fluid) is derived METASTASIS from blood plasma by capillary diffusion Cancer spreads by way of the lymphatic and filtration. Two systems of vessels vessels. Cancers are a type of tumtor thatare collect this fluid from the intercellular not recognized as foreign, so the body does spaces and return it to the circulatory sys- not throw up a protective encapsulation tem. These two systems are: around the tumor. As the tumor grows larger 1. the venous system cells break off from the edges of the mass 2. the lymphatic system and travel by way of the lymphatic vessels. The lymph fluid percolates through the FLUID VOLUMES lymph nodes and other lymphoid organs on It is important that the amount of tissue fluid its way toward the collecting ducts. Often being returned to the circulatory system cancer cells get hung up in these filtering exactly equal the amount being created. The stations and secondary tumors start growing. amount of fluid leaving the arterial ends of This spreading process is called metastasis. the capillaries is large because of the arterial pressures. There are four times as many COLLECTION DUCTS veins as there are arteries in order to equal- THORACIC DUCT ize the pickup and delivery aspects of tissue The thoracic duct is the major collecting fluid flow, but even these are not sufficient duct of the lymphatic system. It is found on to keep the fluids balanced. The deficit is the left side of the thorax hugging the handled by the lymphatic capillaries. anterior surface of the vertebral bodies. Most of the lymphatic capillaries of the LYMPHATIC VESSELS body drain toward the thoracic duct; it col- There are thousands of miles of lymphatic lects all the lymph from blow the waist, vessels in the body. They begin as transpar- from the left side of the head neck and chest, ent microscopic blind ended capillaries in all and from the left arm. the tissues of the body except for the central nervous system. If these capillaries are The thoracic duct drains into the subclavian blocked by pathological processes (such as vein just lateral to the point where the filariasis (elephantiasis)) or disrupted by internal jugular vein joins with the sub- surgery, that part of the body will swell due clavian. Thus the tissue fluid, which came to the accumulation of intercellular fluids. from the circulatory system is returned to This situation is called edema, or in the case the circulatory system. of fluid accumulation in the peritoneal Cisterna Chyli cavity, ascites. Usually the swelling is The cisterna chyli is the expanded lower temporary because new capillaries are easily end of the thoracic duct. It is found at the T Lecture Notes Part II 93 Cardiovascular System 00

1 level close to the diaphragm. This cistern or pool is the main collecting depot for lymph AUNkt The main job of the immune system is to fluid collected from the lower half of the recognize the difference between "self' and body. "non-self', and to destroy that which is FUGHT LYMPHATIC DUCT "non-self'. i.e. foreign. The right lymphatic duct is a small version of the thoracic duct. It collects lymph fluid Any molecule recognized as foreign to the from the right upper quadrant of the body body is called an antigen. Recognition of (head, neck, arm, chest) and returns it the antigens is accomplished by matching the circulation in the same way, by draining into shape of an antigen molecule with a minor the right subclavian vein next to the internal image receptor site on the surface of an jugular vein. immune system cell. Immune system stem cells continuously generate new receptors by a process of random genetic recombination. The digestion of carbohydrates, proteins and The immune system has two basic families fats in the small intestine produces smaller of cells that react to antigens. molecules called glucose, amino acids, and These are: fatty acids respectively. By comparison with glucose and amino acids, the fatty acids are 1. the macrophage fatally of cells (the still fairly large molecules. Perhaps it is this reticuloendothelial system), and size difference that causes them to travel a 2. the lymphocyte family of cells. different route than the other two molecules. Whereas glucose and amino acids are picked Macrophages are produced by mitotic up by the venous capillaries in the walls of activity in the red bone manow. They then the intestine, 60% of the absorbed fatty acids are distributed to all parts of the body where are picked up by the lymphatic capillaries. they protect against infection by attacking and eating (phagocytizing) antigens. LACTEALS Lymphocytes are produced by mitotic Each intestinal villus contains a lymphatic activity in the germinal centers of the capillary called a lacteal. Lymphatic vessels lymphoid organs. Most of these cells enter are normally transparent, but these vessels the circulating bloodwhere they do surveil- of the intestine look white after a meal due lance work, looking for particular antigens. to the presence of emulsified microdroplets of fat dispersed in the lymph fluid. Because The lymphocyte family of cellsconsists of of the superficial resemblance to milk, these two functional groups, the B lymphocytes, vessels are called lacteals and the T lymphocytes, both of which have circulating stem cells on surveillance duty. CHYLE The white fluid inside of a lacteal is called Recognition of an antigen by a lymphocyte chyle. After leaving the intestinal wall this stem cell causes that lymphocyte to rapidly fluid travels in the mesentery of the gut divide, so that a clone of identical lympho- toward the cisterna chili, the main collection cytes dedicated to that one particular antigen point for the abdomen, pelvis, and lower is produced. The members of the clone then limbs. have the further capacity to differentiate into two specialized subfamilies. B stem cells may differentiate into plasma cells or into memory cells: Plasma cells produce antibodies, molecules Lecture Notes Part II 94 Cardiovascular System 101 which attach to the surface of an antigen and physically mask its disease causing sites. tol Plasma cells are present only so long asan Macrophage cells and lymphocyte cellsare antigen is present. found in all parts of the body; theyare Memory cells persist after the antigen is especially concentrated in the lymphoid organs. defeated, and give the body the capacity to respond very rapidly if it is exposed to that THYMUS same antigen again at some future time. The thymus is the primary lymphoidorgan. T stem cells differentiate into two sub- It has a cortex and a medulla, and it is groups called Ts and Ts. known to produce a number of different hormones. The T4 and Ts subgroup mums refer to surface markers found on the cell membrane EARLY SEEDING ACTION of the cell. Each subgroup contains cells that Before the age of 12 the thymus produces act directly (electors) or by influencing many thousands of committed T lymphocytes that then migrate to and take up resi- other immune system cells (regulators). dence in all of the secondary lymphatic Ts effectors activate other white blood organs.

INVOLUTION T, regulators are called helper cells; they After the age of 12 the thymus involutes facilitate both B and T cell functions. (gets smaller and turns fatty) as its seeding function is completed. Ts effector cells are called cytotoxic cells; they attach to an antigen and attack it by THYMIC HORMONE secreting a toxin that is lethal to the Thymic hormones stimulate the function of antigen. the outlying lymphatic organs in some way. The thymus continues to produce these hor- T8 regulators are suppressors of other T mones, but the quantity of hormone pro- ors cells. duced declines with age. This may be one of the reasons for increased susceptibility to viral infections and cancer with advancing age. + LYMPH NODES The lymph nodes are small nodules that vary in size from that of a pin head to an olive. They are surrounded by a capsule of connective tissue, and they often become swollen and tender during infectious diseases. The lymph stream enters the node via the afferent vessels around the periphery, filters through the lymph sinuses of the nodule, and exits at the hillan via the efferent vessel. Fixed macrophages are found in the medulla in the center of the node. B cells occupy the germinal centers and T cells occupy the cortex areas.

Lecture Notes Part II 9S Cardiovascular System 102 Lymph nodes are generally found in small pharyngeal tonsil, so callea because of its groups near veins. Especially large concen- location in the roof of the nasopharynx. This trations of them are found in the cervical, is a single patch of lymphoid tissue located =Mary and final regions. in the midline of the nasopharynx between the openings of the two eustachian tubes. It PEYER'S PATCHES is not encapsulated by connective tissue and Peyer's patches are nonencapsulated patches is very friable. of lymphoid tissue found in the submucosa of the intestinal wall. They play a vital role The last pair of tonsils. the "tubal tonsils" in defending the body against mass invasion are found as a ring of lymphoid tissue by bacteria from the gut around the mouth of each eustachian tube. These tonsils are difficult to see unless SPLEEN swollen, and are not included in the usual "T The spleen differs from other lymphatic & A" operation. tissue in that it filters blood; worn out RBCs are phagocytized here. It is also interesting to note that the spleen has the highest concentration of B cells and plasma cells. + TONSILS A tonsil is a mass of lymphatic tissue located in the oro or nasopharynx (throat). There are three tonsils by name, two of them occurring as paired organs. They act as guard stations which help to prevent the spread of bacteria to other parts of the respiratory system. They often swell when they are actively fighting an infection, sometimes they themselves become infected and become part of the problem rather than part of the solution. When this happens they may be surgically removed. They are known to regrow if any portion of the tonsil is left behind during the "T & A" (tonsillectomy and adenoidectomy). The most widely known pair of tonsils, the palatine tonsils (often known simply as "the tonsils"), are located on each side of the throat, nestled between the glossopalatine and pharyngopalatine arch. These tonsils are encapsulated with connective tissue. Most of the tonsil is out of sight beneath the epithelium of the throat, only the tip of the tonsil projects above the surface and can be seen from inside the throat. The second most well known tonsil is commonly known as the adenoids, but more accurately described by its technical name,

Lecture Notes Part II 96 Cardiovascular System .163

1:171'. Angiology

to:I A-A OR VA/ SHUNTS Arteries are smaller in diameter than veins. An anastomosis between a main vessel anda Arteries have thicker walls than veins. secondary vessel provides collateral circu- There are usually three- four veins for lation, i.e. an alternate mute to and from every artery. each area of the body. These shunts between vessels may be especially important if nor- These differences between the vessels can mal mutes are interrupted by trauma,sur- be accounted for by the fact that the arterial gery, etc. system is a high pressure system in comparison to the low pressure venous system, and sr' ,$ A yet both systems must move equal volumes Blood in veins is not pushed by a pump as it of blood per unit time. is in the arteries. How is blood flow main- tained in the venous system?

A shunt is an anastomosis, i.e. a direct Development of sufficient pressure inside communication between two vessels larger the veins to maintain flow can be accounted than a capillary. for by the following mechanisms. A-V SHUNTS OSMOSIS (Arterio-Venous Anastomosis) Osmotic pressure is created by the fact that An A-V shunt is a direct communication blood proteins do not leave the capillaries. between an artery and its companion vein. Their presence inside the venous end of the When the precapillary sphincters are tight- capillary bed is the chief reason why tissue ened arterial blood will bypass the capillary fluids move from the intercellular spaces bed and flow directly into the vein via the into the veins. shunt, thus blood is returned to the heart MUSCULAR MASSAGE much more quickly than it would be if it had Veins are generally surrounded by muscle to go through the capillary bed. This is the masses. During muscular activity the venous arrangement used by the autonomic nervous blood is moved forward through the veins system to reroute blood flow to the parts of by the massaging action of the surrounding the body that have the most need of it at any muscle:.. given time. VENOUS VALVES Sympathetic Veins that carry blood upward against the The sympathetic nervous system dilates force of gravity have simple valves that act the precapillary sphincters leading to the as one way flow devices. These valves are skin, lungs, and muscle. It constricts inward folds of the tunica intima of the vein. those leading to the digestive system. The pulmonary veins, the portal system Parasympathetic veins and the vena cavae do not have valves. The parasympathetic nervous system dilates the precapillary sphincters leading SUCTION (THORACIC PUMP) to the digestive system. It constricts those The negative thoracic pressure and the leading to the muscles and skin. bellows like action of breathing creates a suction in the thoracic cavity known as the thoracic pump. In addition blood moving

Lecture Notes Part it c4 Cardiovascular System rapidly through the larger diameter veins creates venturi type forces that suck blooa from smaller veins into the larger vein at their junction points.

HYDROSTATIC PRESSURE Hydrostatic pressure is simply the pressure created by the weight of a column of fluid. Hydrostatic pressure increases as the volume of fluid accumulates inside a vessel.

Lecture Notes Part II 98 1G5 Cardiovascular System