Ministry of Public Health of Ukraine Ukrainian Medical Stomatological Academy

"Approved" at the meeting of the Department of Human Anatomy «29»08 2020 Minutes № Head of the Department Professor O.O. Sherstjuk ______

METHODICAL GUIDANCE for the lecture

Academic subject Human Anatomy Module No 3 "The heart. Vessels and nerves of the head, the neck, the trunk, extremities" Lecture No 13 The peripheral nervous system. Spinal nerves. Somatic plexus. Cranial nerves. Year of study І Faculty Foreign students' training faculty, specialty «Medicine» Number of 2 academic hours

Poltava – 2020 1. Educational basis of the topic The peripheral nervous system consists of the cranial and spinal nerves and their associated ganglia. There are 31 pairs of spinal nerves that leave the spinal cord and pass through intervertebral foramina in the vertebral column. Inflammatory processes, toxic lesions and injury sequelae are known under common term ‘neuritis’. The state manifests itself as painful sensation in the affected area (mostly in the lumbar and the sacral regions).

2. Learning objectives of the lecture: . to familiarize students with the divisions of the nervous system and structural functional unit of the nervous system; . to specify classification and functional significance of the spinal nerves; . to provide theoretical information on relations of the spinal nerves to the spinal segments; . discuss branches of spinal nerves with featured structural and topographical regularities.

3. Objectives of developing the future specialist’s personality (educational aims and objectives): familiarization with axiological, ethical and deontological principles of medical profession.

4. Interdisciplinary integration The preceding The acquired knowledge subjects Biology What are the main functions of the nervous system. The reflex arc and its variations. Histology Structure of nerve fibers. Neurology Topography of the nervous branches. Physics Describe the mechanism of nerve impulse. Anatomy Structure of the spinal cord, internal and external structures.

5. The plan and organization of lecture structure No The main stages of the lecture Type of lecture. Time and their content Means of motivation. allocation Teaching materials The preparatory stage 5% 1. Determining the relevance of the pp. 1-2 topic, learning objectives and motivation. The main stage Introductory lecture 85% 2. Delivering the lecture material according to the plan: Feedback and questions 1. Name the principal components to students of the peripheral nervous system and give their general PPT presentation with characteristics. diagrams and tables. 2. Describe formation, topography and branches of the spinal nerves. Explain relations of the spinal nerves to the spinal segments. 3. Describe contents, topography and responsibility areas of the posterior branches of spinal nerves. 4. Describe the anterior branches of the cervical plexus including contents, topography and responsibility areas. 5. Describe formation, branches, topography and responsibility areas of the intercostal nerves. 6.Describe formation, topography, parts and classification of branches of the brachial plexus. 7. Describe the femoral nerve. 8. Describe the obturator nerve. 9. Describe the pudendal nerve. 10. Describe the long branches of the sacral plexus. 11. Describe the sciatic nerve. 12. Describe the tibial nerve. 13. Describe the common fibular nerve. 14. Name all pairs of the cranial nerves. 15. Discuss classification of the cranial nerves by fibers contents. 16. Discuss classification of the cranial nerves by origin. 17. Describe origination, formation and topography of the cranial nerves. The final stage Human Anatomy. In 10% 3. General conclusions to the lecture. three volumes. Volume 3: Answers to possible questions. textbook / Edited by Tasks for students’ self-directed V.G. Koveshnikov. - work. Lugansk: LTD «Virtualnaya realnost», 2009. – 384p. 6.The lecture material.

THE CERVICAL PLEXUS, PLEXUS CERVICALIS (Cl - C4) The cervical plexus arises from anterior branches of four upper cervical nerves (Cl — C4). It lies on the deep cervical muscles anterior to the transverse processes of cervical vertebrae, below the sternocleidomastoid. The plexus gives rise to the sensory, the motor and the mixed branches. The cutaneous (sensory) branches from under the posterior margin of the sternocleidomastoid: ■ the lesser occipital nerve, nervus occipitalis minor ascends to the skin of the occipital region; ■ the great auricular nerve, nervus auricularis magnus ascend along the sternocleidomastoid to the auricle and the external acoustic opening; ■ the transverse cervical nerve, nervus transversus colli runs transversely to the anterior and lateral cervical areas; ■ the supraclavicular nerves, nervi supraclaviculares descend to the upper thoracic regions and shoulder along the lateral cervical triangle. On the way to destination point, the nerves cross the clavicle. The ansa cervicalis is a purely motor branch. It is formed of the superior and the inferior roots. The superior root arises from the hypoglossal nerve yet it constitutes the motor fibers from the Cl. The inferior root arises from the cervical plexus (C2 — C3) and joins the superior root thus forming the ansa. It resides anterior to the internal jugular vein below the sternocleidomastoid. The ansa gives off some branches to the infrahyoid muscles (the sternohyoid, the sternothyroid, the thyrohyoid and the omohyoid). The muscular (motor) branches supply the deep cervical muscles like the longus colli, the longus capitis, the scaleni muscles, the rectus capitis anterior and the rectus capitis lateralis and the levator scapulae. The phrenic nerve, nervus phrenicus is the greatest nerve of the cervical plexus and the sole mixed-type nerve of the group. It runs downwards along the anterior scalene, musculuus sca-lenus anterior to reach the thoracic cavity. The right nerve enters the thoracic inlet between the subclavian artery and the subclavian vein and runs further on anterior to the root of lung between the respective pleura and the pericardium. The left nerve enters the thoracic inlet posterior to the subclavian vein along the subclavian artery. The nerve crosses the aortic arch and proceeds anteriorly and leftwards along the pericardium to reach the respective portion of the diaphragm. The motor branches terminate within the diaphragm to provide motor nerve supply to the muscle (C3 — C5). The phrenic nerve also comprises the sensory fibers to the pleura and the pericardium — the pericardial branch, ramus pericardiacus. The sensory phrenico- abdominal branches, rami phrenicoabdominales penetrate the diaphragm to supply the related peritoneum. The sensory branches of the right phrenic nerve traverse the coeliac plexus and reach the liver; they provide sensory nerve supply to the peritoneal investment and the fibrous capsule of liver. Fig. Cervical plexus.

Clinical applications. Some liver diseases may result in painful sensations along the right phrenic nerve. The pain in this case expands onto the cervical region and concentrates between the crura of the sternocleidomastoid (thus providing easily distinguishable ‘phreni- cus-symptom’). The phrenic nerve is a vital nerve that sets the diaphragm to motion. The nuclei of the phrenic nerve reside within the anterior grey columns of the segments C3 through C6. Injury to the nuclei or to the nerves may result in diaphragm paralysis. Fig. Cervical plexus. THE BRACHIAL PLEXUS, PLEXUS BRACHIALIS (C5-C8 and Thl) The brachial plexus arises from anterior branches of four lower cervical nerves (C4 — C8) and greater portion of the anterior branch of the first thoracic nerve (Thl). The brachial plexus features the supraclavicular and the infraclavicular parts. 1) the supraclavicular part, pars supraclavicularis appears as three trunks that pass between the anterior and the middle scaleni muscles. The trunks are the superior trunk, truncus superior, the middle trunk, truncus medius and the inferior trunk, truncus inferior; 2) the infraclavicular part, pars infraclavicularis is the part situated within the axillary fossa where the trunks regroup into the cords, faciculi that surround the brachial artery. The cords are as follows: the lateral cord, fasciculus lateralis runs laterally along the artery; the medial cord, fasciculus medialis runs medially along the artery; the posterior cord, fasciculus posterior runs posteriorly along the artery. The branches of the supraclavicular part This part gives rise to the short branches related to the pectoral girdle; ■ the dorsal scapular nerve, nervus dorsalis scapulae runs to the levator scapulae and the rhomboid muscles; ■ the long thoracic nerve, nervus thoracicus longus supplies the neighboring serratus anterior; ■ the suprascapular nerve, nervus suprascapularis crosses the suprascapular notch and reaches supraspinous and infraspinous fossae. It supplies the respective muscles and the joint capsule of the shoulder joint; ■ the subclavian nerve, nervus subclavius supplies the muscle of the same name; ■ the lateral and medial pectoral nerves, nervi pectorales lateralis et medialis supply the pectoralis major and the pectoralis minor; ■ the subscapular nerve, nervus subscapularis supplies the subscapularis and the teres major, ■ the thoracodorsal nerve, nervus thoracodorsalis runs along the lateral border of scapula; it supplies the latissimus dorsi; • the axillary nerve, nervus axillaris is the greatest of the short branches. It arises from the posterior cord and proceeds to the quadrangular foramen. Upon passing the foramen, the nerve loops around the surgical neck of humerus and reaches the posterior surface of shoulder. There it supplies the deltoid and the teres minor. Apart from this, the nerve gives some fibers to the joint capsule of the shoulder joint and to skin of the posterolateral surface of shoulder.

Fig. Brachial plexus. The infraclavicular part The cords of the infraclavicular part give rise to the long branches that terminate within the various areas of the arm: ■ the musculocutaneous newe, nervus musculocutaneus arises from the lateral cord then traverses the coracobrachialis and appears in between the biceps brachii, musculus biceps brachii and the brachialis, musculus brachialis. It gives the muscular branches, rami musculares to the entire anterior group of brachial muscles (the coracobrachialis, the biceps brachii and the brachialis). The cutaneous branch of the nerve — the lateral cutaneous nerve of forearm, nervus cutaneous antebrachii lateralis arises from under the lateral margin of the biceps brachii and penetrates the fascia to terminate within the skin of antero-lateral area of forearm; ■ the medial cutaneous nerve of arm, nervus cutaneous brachii medialis a thin nerve that arises from the medial cord and terminates within the skin of medial area of arm; ■ the medial cutaneous nerve of forearm, nervus cutaneous antebrachii medialis also arises from the medial cord. The nerve runs to the forearm and terminates within the skin of its anteromedial area. Three other nerves of the group — the median, the ulnar and the radial nerves are the principal nerves of upper limb.

Fig. Brachial plexus. The median nerve, nervus medianus Topography of the median nerve The median nerve arises from two roots given by the medial and the lateral cords (the medial and the lateral roots). In the arm region, the nerve joins the common neurovascular bundle that runs along the medial bicipital groove. In the forearm region, the nerve enters the cubital fossa and quits it via the space between the heads of the pronator teres. Upon escaping from the fossa, the nerve lies in between the flexor digitorum superficial and the flexor digitorum profundus, musculi flexores digi-torum superficialis et profundus. Passing so on, the nerve lies within the median sulcus that leads to the carpal tunnel, canalis carpi. As the nerve appears on the palmar surface of hand, it splits into three common palmar digital nerves, nervi digitales palmares communes that in turn give seven proper palmar digital nerves, nervi digitales palmares proprii. These terminal branches run to both aspects of fingers 1 through 3 and to the radial aspect of the 4th finger.

Fig. Brachial plexus. Responsibility areas of the median nerve The median nerve gives no branches in the arm area (namely from origination point down to the cubital fossa). The first branches to arise are the branches to the joint capsule of the elbow joint. In the forearm area, the nerve supplies both pronators (musculi pronatores teres et quadratus) and all flexors except for the flexor carpi ulnaris and the ulnar half of the flexor digitorum profundus, muscu- lus flexor digitorum profundus. The deep muscles of forearm are under responsibility of the anterior interosseous nerve, nervus interosseus anterior that runs along the anterior interosseous membrane. This nerve terminates at the joint capsule of the joint of wrist. In the palmar area, the motor branches supply two lateral lumbricals and all muscles of thumb except for the abductor pollicis and the deep head of the flexor pollicis brevis. The cutaneous branches supply the skin of the thenar, of the median portion of the palmar surface of hand and of the palmar surface of fingers 1 through 3 including the radial aspect of the 4th finger. Apart from this, the nerve gives small twigs to the dorsal surface of the 2nd and the 3rd fingers together with the radial aspect of the 4th finger. Clinical applications Injury to the median nerve results in inability to pronate the forearm and to oppose the thumb. Flexion of the fingers and the wrist gets affected partially because of the ulnar nerve assistance. Atrophy of the thenar muscles caused by such injury gives a characteristic look to the hand (the ape’s wrist). Motor disorders are usually accompanied by the sensory disorders within the respective areas of responsibility. The ulnar nerve, nervus ulnaris Topography of the ulnar nerve The ulnar nerve arises from the medial cord of the brachial plexus. In the beginning of its route, the nerve runs along the medial bicipital groove within the common neurovascular bundle. In the inferior half of the arm, the nerve detaches from the bundle and proceeds to the ulnar groove situated on the posterior surface of the medial epicondyle, epicondylus medialis of the humerus. There the nerve runs covered by fascia and skin only. Within the forearm region, the nerve runs along the ulnar groove of forearm together with the ulnar artery. On reaching the lower third of the forearm, the nerve splits into the dorsal branch, ramus dorsalis and the palmar branch, ramus palmaris. The branches and responsibility areas of the ulnar nerve Like the median nerve, the ulnar nerve supplies but nothing in the arm area. The first branches given are the branches to the joint capsule of the elbow joint. Within the forearm and the hand, the nerve gives branches as follows: ■ the muscular branches, rami musculares to the flexor carpi ulnaris and the ulnar half of the flexor digitorum profundus; ■ the dorsal branch, ramus dorsalis that arises from the principal trunk within the inferior third of the forearm. The branch runs below the tendon of the flexor carpi ulnaris to reach the dorsal surface of the hand where it splits into the dorsal digital nerves (they arise as three branches that further split into five terminal branches); ■ the dorsal digital nerves, nervi digitales dorsales supply the skin of the medial aspect of the hand and the skin of the dorsal surface of the 4th and the 5th fingers including the ulnar half of the 3rd finger; ■ the palmar branch, ramus palmaris arises at the same level as the dorsal yet it runs on along the ulnar groove with the neighboring ulnar blood vessels. On reaching the pisiform bone, the nerve gives off the superficial and the deep branches; ■ the superficial branch, ramus superficialis supplies the skin of hypothenar and the medial aspect of hand together with underlying palmaris brevis. The branch gives off three proper palmar digital nerves, nervi digitales palmares proprii to the skin of the palmar surface of the 5th finger and of the ulnar aspect of the 4th finger; ■ the deep branch, ramus profundus reaches the deeper palmar layers where it runs along the deep palmar arch. It supplies all hypothenar muscles, all interossei muscles, the third and the fourth lumbricals and two thenar muscles — the adductor pollicis and the deep head of the flexor pollicis brevis. Clinical applications. Injury to the ulnar nerve results in impaired flexion in the joint of wrist and in inability to abduct the fingers (including the thumb). Because of prevailing extensors and paralyzed interossei, the hand acquires a look of the bird’s foot. Sensory disorders within the respective areas are also observed. The radial nerve, nervus radialis Topography and branches of the radial nerve The radial nerve is rather a large nerve that arises from the posterior cord of brachial plexus. In the arm region, the nerve passes within the radial canal, canalis nervi radialis seu canalis humeromuscularis along with the deep artery of arm. Both artery and nerve run spirally down along the radial groove. Here the nerve is covered with the triceps brachii. Fig. Brachual plexus. Fig. Brachial plexus. The nerve quits the canal via its inferior opening (in between the brachialis and the brachioradialis) that leads to the cubital fossa. Here, at the head of radius, the nerve splits into the superficial and the deep branches: ■ the deep branch, ramus profundus runs below the supinator to the posterior surface of forearm where it gives off numerous muscular branches. The longest nerve of this group is the posterior interosseous nerve, nervus interosseus antebrachii posterior that runs along the interosseous membrane to reach the joint of wrist; ■ the superficial branch, ramus superficial runs within the radial groove along with the radial artery. In the lower portion of the forearm, the branch passes in between tbe radius and the brachioradialis to reach the dorsal surface of the hand. There, the branch gives off the dorsal digital branches, nervi digi tales dorsales.

Fig. Brachial plexus. Responsibility areas of the radial nerve The radial nerve is responsible for the posterior surface of the upper limb. In the arm region, it supplies the triceps brachii and the anconeus. Here it also gives rise to the posterior cutaneous nerve of arm, nervus cutaneus brachii posterior that supplies the skin of the arm and to the posterior cutaneous neme of forearm, nervus cutaneus antebrachii posterior. The forearm, the deep branch supplies all extensors, the supinator and the brachioradialis. Within the hand, the nerve supplies the skin only. Its superficial branch is responsible for the dorsal surface of hand where it supplies skin of its lateral aspect and skin of the dorsal surface of the 1st and the 2nd fingers and the radial aspect of the 3rd finger. In the 2nd and the 3rd fingers, the nerve supplies the areas related to the proximal phalanges; the rest is under responsibility of the median nerve. Clinical applications Fractures of humerus may result in damage of the canal-related part of radial nerve. High-point injury to the radial nerve results in paralysis of the extensors with typical wrist stack because of inability of the extensors to counteract the flexors. Skin sensitivity within the respective area gets impaired as well. The anterior branches of the thoracic nerves retain segmental arrangement as opposed to the anterior cervical branches that form plexuses. These branches are related to the intercostal spaces and thus are referred to as the intercostal nerves. The greater portion of the first thoracic nerve joins the brachial plexus and the smaller portion constitutes rather a thin first intercostal nerve. The anterior ramus of the twelfth thoracic nerve is the subcostal nerve, nervus subcostalis found below the twelfth rib; the nerve gives some fibers to the lumbar plexus. The intercostal nerves, nervi intercostales Topography of the intercostal nerves The intercostal nerves occupy the costal grooves of the bodies of ribs. From the origination point and up to the costal angle each nerve is covered with parietal pleura; the portion related to the body of rib passes in between the external and the internal intercostal muscles. The nerves 1 through 6 reach the sternum; the rest quit the intercostal spaces and reach the anterior abdominal wall. There they run in between the internal oblique and the transversus abdominis to enter the rectus sheath and meet the nerves from the opposite side at the anterior median line. Responsibility areas of the thoracic nerves The intercostal nerves are the mixed nerves i.e. they comprise the sensory and the motor branches: ■ the motor branches supply the muscles of chest proper (both external and internal intercostal muscles, musculi intercostales extemi et intemi, the transversus thoracis and the subcostales) and the abdominal muscles (both external and internal oblique, musculi obliquus extemus et intemus, the transversus abdominis, musculus transversus abdominis, the rectus abdominis, musculus rectus abdominis, the pyramidalis, musculus pyramidalis and the quadratus lumborum, musculus quadratus lumborum); ■ the sensory branches supply the skin of the thorax and the abdomen. Each intercostal nerve gives rise to the anterior and the lateral cutaneous branches (pectoral and abdominal), rami cutanei anterior et posterior (pectoralis et abdominales). The anterior branches supply the medial portion of the respective region and the lateral branches — the lateral portions of the same regions. The anterior branches arise along the margins of sternum and the rectus abdominis and the lateral branches arise along the midaxillary line. THE LUMBAR PLEXUS, PLEXUS LUMBALIS (Thl2 — L4) Topography of the lumbar plexus The lumbar plexus arises from the anterior branches of three upper lumbar nerves and partially from the twelfth thoracic nerve and fourth lumbar nerve. It resides within the lumbar region in between the transverse processes of related lumbar vertebrae posterior and in depth of the psoas major. Inferiorly, the lumbar plexus communicates with the sacral plexus. Most of the rami arise from behind the lateral border of the psoas major; one ramus traverses the muscle (the genitofemoral nerve) and one branch arises from behind the medial border of the muscle (the obturator nerve). The branches of the lumbar plexus The greatest branches of the lumbar plexus are the femoral nerve and the obturator nerve. The plexus also gives rise to several smaller branches that terminate within the skin and the muscles of the abdomen, the lower limb and the external genitals: ■ the muscular branches, rami musculares supply both psoas muscles, the quadratus lumborum and the lumbar intertransversarii;

Fig. Lumbar plexus. Sacral plexus. ■ the iliohypogastric nerve, nervus iliohypogastricus arises from behind of the lateral border of the psoas major and runs in between the transversus abdominis and the external oblique. The nerve supplies all abdominal muscles, the skin of hypogastrium and the skin of the gluteal region (its superolateral portion); ■ the ilioinguinal nerve, nervus ilioinguinalis in the beginning of its way runs parallel and below the previous nerve but enters the inguinal canal. Within the canal, the nerve resides anterior to the spermatic cord (the round ligament of uterus); it terminates within the skin of the pubic region and the scrotum (the labia majora) and gives some branches to both oblique muscles and the transversus abdominis; ■ the genitofemoral nerve, nervus genitofemoralis traverses the psoas major and descend along its anterior surface; there it gives the genital branch, ramus genitalis and the femoral branch, ramus femoralis. The genital branch enters the inguinal canal where runs posterior to the spermatic cord (the round ligament of uterus). It supplies the cremaster, the dartos muscle, the skin of scrotum (the labia majora) and the skin of superomedial surface of thigh. The femoral branch passes through the vascular space below the inguinal ligament to a small upper portion of the femoral triangle; ■ the lateral cutaneous nerve of thigh, nervus cutaneus femoris lateralis arises from behind of the lateral border of the psoas major and runs slantwise down to the anterior su-perior iliac spine. On bypassing the spin, the nerve proceeds to the lateral surface of thigh.

Fig. Lumbar plexus. The obturator nerve, nervus obturatorius is quite a large branch of the lumbar plexus. It arises from behind of the medial border of the psoas major and runs along the lesser pelvis wall to enter the obturator canal that leads the nerve to the thigh. Within the thigh, the nerve resides in between the adductors and splits into the anterior and the posterior branches. The nerve supplies the neighboring adductors, the pectineus, the gracilis, the obturator extemus and the joint capsule of the hip joint. Apart from the obturator nerve, the accessory obturator nerve, nervus obturatorius accesorius is also distinguishable. The femoral nerve, nervus femoralis is the greatest branch of the lumbar plexus. Topography of the femoral nerve The nerve arises from behind the lateral border of the psoas major and proceeds to the thigh region via the muscular space. Within the thigh region, the nerve resides in the femoral triangle laterally from the femoral artery. Fig. Sacral plexus. The branches of the femoral nerve In the femoral triangle, the femoral nerve fans out to give numerous branches: ■ the muscular branches, rami musculares supply the quadriceps femoris and the pectineus; ■ the anterior cutaneous branches, rami cutanei anteriores penetrate the fascia and terminate in the skin of anteromedial area of thigh; ■ the saphenous nerve, nervus saphenus is the longest branch of the femoral nerve. It enters the adductor canal together with the femoral artery and the femoral vein. Upon escaping from the canal via its anterior opening (the adductor hiatus) the nerve runs along the medial aspect of shin and foot together with the great saphenous vein and reaches the great toe. In the thigh are, the nerve gives no branches; the first branch to arise is the infrapatellar branch, ramus infrapatellaris. It supplies the skin of the medial surface of knee joint and of the patellar area. Apart from this, the nerve supplies the skin of the medial aspect of shin and foot up to the great toe. Clinical applications. Injury to the femoral nerve leads to paralysis of the quadriceps femo- ris and thus to inability to extend the knee joint. When walking, the victim is unable to withhold extension of leg and the foot strikes against the ground with its entire surface. Injury to the obturator nerve affects abduction of thigh and crossing of legs. THE SACRAL PLEXUS, PLEXUS SACRALIS (L4 — L5\S1 — S4) Topography of the sacral plexus The sacral plexus is the greatest of all nervous plexuses in the human body. It arises from merged upper four sacral nerves, the fifth lumbar nerve and a part of the fourth lumbar nerve, the fourth and the fifth lumbar nerves merge into a single lumbosacral trunk, truncus lumbosacralis that descends to the lesser pelvis cavity and joins the sacral nerves. The lowest portion of the sacral plexus formed of the fifth sacral nerves (S5) and the coccygeal nerve (Col) is the coccygeal plexus, plexus coccygeus. The sacral plexus appears as a thick triangular plate adherent to the pelvic wall (namely to the piriformis). The branches given quit the lesser pelvis via the suprapiriform and the infrapiriform foramina as the short and the long branches. The greatest nerve of the plexus is the sciatic nerve. The short branches These branches stay within the pelvic girdle region to supply the pertaining muscles and skin: ■ the muscular branches, rami musculares supply the piriformis, the obturator internus, both gemelli and the quadratus femoris; ■ the superior gluteal nerve, nervus gluteus superior runs via the suprapiriform foramen to the gluteus medius, the gluteus minimus and the tensor fasciae latae; ■ the inferior gluteal nerve, nervus gluteus inferior runs via the infrapiriform foramen to the gluteus maximus and the joint capsule of the hip joint; . the pudendal nerve, nervus pudendus quits the lesser pelvis via the infrapiriform foramen, loops around the ischial spine and enters the ischio-anal fossa via the lesser sciatic foramen. The nerve supplies the external anal sphincter and other perineal muscles together with related skin. The terminal branch of the nerve called the dorsal nerve of penis (clitoris), nervus dorsalis penis (clitoridis) runs to the dorsal surface of the penis (clitoris). The nerve supplies the corpora cavernosa of the penis (clitoris), the external urethral sphincter, skin of penis (in males) or skin of both labia majora and minora (in females). The long branches The long branches are the posterior cutaneous nerve of thigh and the sciatic nerve. The posterior cutaneous nerve of thigh, nervus cutaneus femoris posterior runs via the infrapiriform foramen to skin of the posterior surface of thigh. The nerve also gives the inferior cluneal nerves, nervi clunium inferiors to skin of gluteal region. Fig. Sacral plexus. The sciatic nerve, nervus ischiadicus Topography of the sciatic nerve The sciatic nerve is the greatest nerve of the human body. It comprises nearly all branches that participate in formation of the sacral plexus. The nerve quits the lesser pelvis cavity via the infrapiriform foramen and runs on below the gluteus maximus. Somewhat below the escape point, the nerve enters in between the ischial tuberosity and the greater trochanter, proceeds onto the quadratus lumborum surface and finally becomes evident within the thigh region, arising from under the lower border of the gluteus maximus. Within the thigh region, the nerve runs deep in between the neighboring muscles. On reaching the upper angle of the popliteal fossa, the nerve splits into the terminal branches — the tibial nerve and the common fibular nerve. High point branching of the sciatic nerve is of common occurrence. In this case, the terminal branches of the nerve arise within the thigh and run together to responsibility areas. The principal trunk of the nerve gives off the muscular branches to the posterior group of muscles of thigh (to the semitendinosus, the semimembranosus and the long head of biceps femoris). Clinical applications Chilling of the area related to the nerve results in neuritis of the sciatic nerve (sciatica). The state features painful sensation within the ischial area and the posterior portion of the thigh. The condition may even feature sensory and motor disorders. The tibial nerve, nervus tibialis Topography of the tibial nerve The tibial nerve arises directly from the sciatic nerve and runs vertically down to the popliteal fossa. Within the fossa, the nerve occupies the most superficial position with respect to neighboring popliteal artery and popliteal vein. From the popliteal fossa, the nerve proceeds to the cruropopliteal canal. On escaping from the canal, the nerve loops around the medial malleolus and gives some branches to the ankle joint. Below the flexor retinaculum, the nerve gives off its terminal branches — the medial and the lateral plantar nerves. The branches of the tibial nerve The tibial nerve gives the branches as follows: ■ the muscular branches, rami musculares supply all posterior muscles of shin (the igastrocnemius, the soleus, the plantaris, the popliteus etc.); ■ the medial sural cutaneous nerve, nervus cutaneus surae medialis arises from the tibial nerve yet within the popliteal fossa. It runs laterally and merges with the lateral sural cutaneous nerve (from the common fibular nerve) to form the sural nerve; ■ the sural nerve, nervus suralis descends midline along the posterior surface of shin together with the small saphenous vein. Upon reaching the ankle joint, the sural nerve loops around the lateral malleolus, gives the lateral calcaneal branches, rami calcanei laterales and becomes continuous with the lateral dorsal cutaneous nerve, nervus cutaneus dorsalis lateralis. The nerve supplies skin of the posterolateral surface of shin and the lateral aspect of foot up to the little toe; The medial plantar nerve, nervus plantaris medialis runs along the groove of the same name. Within the distal portion of foot, the nerve splits into the common plantar digital nerves, nervi digitales plantar- es communes that in turn branch into the proper plantar digital nerves, nervi digitales plantares proprii. They supply the medial aspect of foot, the toes 1 through 3 and a medial half of the fourth toe. The muscular branches of the nerve supply the flexor digitorum brevis, all muscles of great toe (except for the adductor hallucis and the lateral head of flexor hallucis brevis) and two lumbricals (1 and 2). The lateral plantar nerve, nervus plantaris lateralis also occupies the groove of the same name; it splits into the superficial branch, ramus superficialis and the deep branch, ramus profundus. The superficial branch gives off the common plantar digital newes, nervi digitales plantares communes, which become continuous with the proper plantar digital nerves, nervi digitales plantares proprii. They supply the lateral aspect of foot, the fifth toe and a lateral half of the fourth toe. The deep branch supplies all interossei, two lumbricals, the adductor hal-lucis, and the lateral head of flexor hallucis brevis. Fig. Sacral plexus. Clinical applications Injury to the tibial nerve results in paralysis of pertaining flexors. The foot thus becomes permanently extended and the toes may resemble the claws. Fig. Sacral plexus. The common fibular nerve, nervus fibularis communis Topography of the nerve From the arise point, the nerve runs laterally to reach the head of fibula. At that point, the nerve enters between the heads of the fibularis longus and slits into the superficial and the deep fibular nerves. Yet within the popliteal fossa, the nerve gives the lateral sural cutaneous nerve, nervus cutaneus surae lateralis that merges with the medial sural cutaneous nerve to form the sural nerve. Very often, the nerves merge at the lower third of shin or even run separately. The superficial fibular nerve, nervus fibularis superficial runs within the superior musculoperoneal canal (in between the fibilaris longus and the fibula). The nerve quits the canal in the lower half of shin and runs on superficially down to the dorsal surface of foot. There the nerve terminates with the medial dorsal cutaneous nerve, nervus cutaneus dorsalis medialis and the lateral dorsal cutaneous nerve, nervus cutaneus dorsalis lateralis. Both nerves supply the respective areas of the dorsal surface of foot. It also leaves some muscular branches, rami musculares to the fibulares muscles while running within the musculoperoneal canal. The deep fibular nerve, nervus fibularis profundus passes along the interosseous membrane of shin below the anterior group of pertaining muscles. Just like the superficial nerve, it reaches the dorsal surface of foot yet it is responsible for a small area between the first and the second toes. Within the shin, the nerve supplies the anterior group of muscles (the tibialis anterior, the extensor digitorum longus, the extensor hallucis longus) and the joint capsule of ankle joint. Clinical applications. Injury to the fibular nerve leads to inability to extend and to pronate the foot. The foot in this case hangs down and laterally. THE CRANIAL NERVES, NERVI CRANIALES There are twelve pairs of cranial nerves that arise directly from the brain: I. The olfactory nerve, nervus olfactorius; II. The optic nerve, nervus opticus; III. The oculomotor nerve, nervus oculomotorius; IV. The trochlear nerve, nervus trochlearis; V. The trigeminal nerve, nervus trigeminus; VI. The abducent nerve, nervus abducens; VII. The facial nerve, nervus facialis; VIII. The vestibulocochlear nerve, nervus vestibulocochlearis; IX. The glossopharyngeal nerve, nervus glossopharyngeus; X. The vagus nerve, nervus vagus; XI. The accessory nerve, nervus accessories; XII. The hypoglossal nerve, nervus hypoglossus. The cranial nerves develop in tight association with several organs: The pairs I, II and VIII develop in association with the sensory organs; the pairs I and II are plain projections of the brain and have no specific relay nuclei; The pairs III, IV and VI supply the extrinsic muscles of eye and develop in association with the cranial myotomes; The pair V is associated with the 1st (mandibular) visceral arch; The pair VII is associated with the 2nd (hyoid) visceral arch; The pairs IX, X and XI constitute the vagus group and develop in association with the branchial arches; The pair XII develops from fused spinal motor roots. The cranial nerves The olfactory nerve (I) The fibres of the olfactory nerve, unlike other afferent fibres, are unique in being the central processes of the olfactory cells and not the peripheral processes of a central group of ganglion cells. The central processes of the olfactory receptors pass upwards from the olfactory mucosa in the upper part of the superior nasal concha and septum, through the cribriform plate of the ethmoid bone to end by synapsing with the dendrites of mitral cells in the olfactory bulb. The mitral cells in turn send their axons back in the olfactory tract to terminate in the cortex of the uncus, the adjacent inferomedial temporal cortex and the region of the anterior perforated space. The further course of the olfactory pathway is uncertain in man, but it is now clear that the hippocampus – fornix system is not directly concerned with olfaction.

Fig. The base of the brain showing the cranial nerve roots and their relationships to the circle of Willis. Clinical features 1. The sense of smell is not highly developed in man and is easily disturbed by conditions affecting the nasal mucosa generally (e.g. the common cold). However, unilateral anosmia may be an important sign in the diagnosis of frontal lobe tumours. Tumours in the region of the uncus may give rise to the so-called ‘uncinate’ type of fit, characterized by olfactory hallucinations associated with impairment of consciousness and involuntary chewing movements. 2. Bilateral anosmia due to interruption of the 1st nerve is common after head injuries, particularly in association with anterior cranial fossa fractures, when leakage of C.S.F. through the cribriform plate may present as rhinorrhoea.

Fig. Olfactory analyzer.

Fig. Olfactory epithelium. The optic nerve (II) and the visual pathway The optic nerve is the nerve of vision. It is not a true cranial nerve but should be thought of as a brain tract which has become drawn out from the cerebrum. Embryologically, it is developed, together with the retina, as a lateral diverticulum of the forebrain. Devoid of neurilemmal sheaths, its fibres, like other brain tissues, are incapable of regeneration after division. From a functional point of view the retina can be regarded as consisting of three cellular layers: a layer of receptor cells — the rods and cones — an intermediate layer of bipolar cells, and a layer of ganglion cells, whose axons form the optic nerve (Fig. 255). From all parts of the retina these axons converge on the optic disc whence they pierce the sclera to form the optic nerve. The optic nerve passes backwards and medially to the optic foramen through which it reaches the optic groove on the dorsum of the body of the sphenoid. Here, all the fibres from the medial half of the retina (i.e. those concerned with the temporal visual field) cross over in the optic chiasma to the optic tract of the opposite side, while the fibres from the lateral half of the retina (nasal visual field) pass back in the optic tract of the same side.

Fig. The layers of the retina. The great majority of the fibres in the optic tract end in the six-layered lateral geniculate body of the thalamus, but a small proportion, subserving pupillary, ocular and head and neck reflexes, bypass the geniculate body to reach the superior colliculus and pretectal area. From the lateral geniculate body the fibres of the optic radiation sweep laterally, and some forwards into the temporal lobe before passing backwards to the occipital visual cortex (the striate area surrounding the calcarine fissure) where they terminate in such a way that the upper and lower halves of the retina are represented on the upper and lower lips of the fissure respectively. Clinical features 1. Lesions of the retina or optic nerve result in ipsilateral blindness in the affected segment, but lesions of the optic tract and central parts of visual pathway result in contralateral homonymous defects. Similarly, lesions of the optic chiasma (e.g. from an expanding pituitary tumour) will give rise to a bitemporal hemianopia, i.e. there will be a loss of vision in both temporal eye-fields. 2. The lesion responsible for the Argyll Robertson pupil is thought to be in the vicinity of the pretectal area. The pupil is constricted, does not respond to light but responds to accommodation, but there is no satisfactory explanation why the pupillary reaction to light should be abolished while the convergence– accommodation reflex is preserved. It is classically seen in syphilis affecting the CNS.

Fig. Diagram of the optic pathway. The oculomotor nerve (III) In addition to supplying most of the extrinsic eye muscles, the oculomotor nerve conveys the preganglionic parasympathetic fibres for the sphincter of the pupil via the ciliary ganglion. Its nucleus of origin lies in the floor of the cerebral aqueduct at the level of the superior colliculus and consists essentially of two components: the somatic efferent nucleus, which supplies the ocular muscles, and the Edinger– Westphal nucleus from which the preganglionic parasympathetic fibres are derived. From these nuclei, fibres pass vertically through the midbrain tegmentum to emerge just medial to the cerebral peduncle. Passing forwards between the superior cerebellar and posterior cerebral arteries, the nerve pierces the dura mater to run in the lateral wall of the cavernous sinus as far as the superior orbital fissure. Before entering the fissure it divides into a superior and inferior branch; both branches enter the orbit through the tendinous ring from which the recti arise. The superior branch passes lateral to the optic nerve to supply the superior rectus muscle and levator palpebrae superioris; the inferior branch supplies three muscles, the medial rectus, the inferior rectus and the inferior oblique, the nerve to the last conveying the parasympathetic fibres to the ciliary ganglion. The ciliary ganglion This small but important ganglion lies near the apex of the orbit just lateral to the optic nerve. It receives, in addition to the preganglionic parasympathetic fibres from the Edinger–Westphal nucleus, a sympathetic (postganglionic) root ultimately from the plexus on the internal carotid artery, and a sensory root from the nasociliary nerve. Of these fibres, only the parasympathetic synapse in the ganglion, the others pass directly through it. The postganglionic efferent fibres from the ganglion pass to the ciliary muscle and the muscles of the iris by way of about ten short ciliary nerves. Stimulation results in pupillary constriction and in accommodation of the lens. The sympathetic and sensory fibres are, respectively, vasoconstrictor and pupillodilator, and sensory to the globe of the eye. (Note that the majority of sympathetic dilator pupillae nerve fibres are transmitted to the eye in the long ciliary branches of the nasociliary nerve.) Clinical features Complete division of the 3rd nerve results in a characteristic group of signs: • ptosis — due to paralysis of the levator palpebrae superioris; • a divergent squint — due to the unopposed action of the superior oblique and lateral rectus muscles, rotating the eyeball laterally; • dilatation of the pupil—the dilator action of the sympathetic fibres being unopposed; • loss of the accommodation–convergence and light reflexes — due to constrictor pupillae paralysis; • double vision. The trochlear nerve (IV) The trochlear nerve is the most slender of the cranial nerves and supplies only one eye muscle, the superior oblique. Its nucleus of origin lies in a similar position to that of the 3rd nerve at the level of the inferior colliculus, but from here its fibres pass dorsally around the cerebral aqueduct and decussate in the superior medullary vellum. Emerging on the dorsum of the pons (being the only cranial nerve to arise from the dorsal aspect of the brainstem), the nerve winds round the cerebral peduncle and then passes forwards between the superior cerebellar and posterior cerebral arteries to pierce the dura. It then runs forwards in the lateral wall of the cavernous sinus between the oculomotor and ophthalmic nerves to enter the orbit through the superior orbital fissure, lateral to the tendinous ring from which the recti take origin. It then passes medially over the optic nerve to enter the superior oblique muscle. Clinical features A lesion of the trochlear nerve results in paralysis of the superior oblique muscle with the result that diplopia occurs when the patient attempts to look downwards and laterally. This can be remembered as ‘the tramp’s nerve” — it makes the eye go “down and out”! The trigeminal nerve (V) As the name suggests, this nerve consists of three divisions. Together they supply sensory fibres to the greater part of the skin of the head and face, the mucous membranes of the mouth, nose and paranasal air sinuses and, by way of a small motor root, the muscles of mastication. In addition it is associated with four autonomic ganglia, the ciliary, pterygopalatine, otic and submandibular. The trigeminal ganglion This ganglion, which is also termed the semilunar ganglion, is equivalent to the dorsal sensory ganglion of a spinal nerve. It is crescent-shaped and is situated within an invaginated pocket of dura in the middle cranial fossa. It lies near the apex of the petrous temporal bone, which is somewhat hollowed for it. The motor root of the trigeminal nerve and the greater superficial petrosal nerve both pass deep to the ganglion. Above lies the hippocampal gyrus of the temporal lobe of the cerebrum; medially lies the internal carotid artery and the posterior part of the cavernous sinus. The trigeminal ganglion represents the 1st cell station for all sensory fibres of the trigeminal nerve except those subserving proprioception. V1: The ophthalmic division This is the smallest division of the trigeminal nerve; it is wholly sensory and is responsible for the innervation of the skin of the forehead, the upper eyelid, cornea and most of the nose. Passing forwards from the trigeminal ganglion, it immediately enters the lateral wall of the cavernous sinus where it lies beneath the trochlear nerve. Just before entering the orbit it divides into three branches, frontal, lacrimal and nasociliary. The frontal nerve runs forward just beneath the roof of the orbit for a short distance before dividing into its two terminal branches, the supratrochlear and supra-orbital nerves, which supply the upper eyelid and the scalp as far back as the lambdoid suture. The lacrimal nerve supplies the lacrimal gland (with postganglionic parasympathetic fibres from the pterygopalatine ganglion which reach it by way of the maxillary nerve) and the lateral part of the conjunctiva and upper lid. The nasociliary nerve gives branches to the ciliary ganglion, the eyeball, cornea and conjunctiva the medial half of the upper eyelid, the dura of the anterior cranial fossa, and to the mucosa and skin of the nose. V2: The maxillary nerve The maxillary nerve is again purely sensory. Passing forwards from the central part of the trigeminal ganglion, close to the cavernous sinus, it leaves the skull by way of the foramen rotundum and emerges into the upper part of the pterygopalatine fossa. Here it gives off a number of branches before continuing through the inferior orbital fissure and the infra-orbital canal as the infra-orbital nerve which supplies the skin of the cheek and lower eyelid. The maxillary nerve has the following named branches: 1) the zygomatic nerve, whose zygomaticotemporal and zygomaticofacial branches supply the skin of the temple and cheek respectively; 2) superior alveolar (dental) branches to the teeth of the upper jaw; and 3) the branches from the pterygopalatine ganglion, which run a descending course and are distributed as follows: the greater and lesser palatine nerves, which pass through the corresponding palatine foramina to supply the mucous membrane of the hard and soft palates, the uvula and the tonsils, and the mucous membrane of the nose and a pharyngeal branch supplying the mucosa of the nasopharynx. The nasopalatine nerve (long sphenopalatine) supplies the nasal septum then emerges through the incisive canal of the hard palate to supply the gum behind the incisor teeth. The posterior superior lateral nasal nerves (short sphenopalatine) supply the posterosuperior lateral wall of the nose. Fig. Plan of the trigeminal nerve and its nuclei in dorsal view. The pterygopalatine ganglion Associated with the maxillary division of V as it lies in the pterygopalatine fossa is the relatively large pterygopalatine ganglion. This receives its parasympathetic or secretomotor root from the greater superficial petrosal branch of VII, its sensory component from two pterygopalatine branches of the maxillary nerve and its sympathetic root from the internal carotid plexus. Its parasympathetic efferents pass to the lacrimal gland through a communicating branch to the lacrimal nerve. Sensory and sympathetic (vasoconstrictor) fibres are distributed to nose, nasopharynx, palate and orbit. V3: The mandibular nerve This is the largest of the three divisions of the trigeminal nerve and the only one to convey motor fibres. In addition to supplying the skin of the temporal region, part of the auricle and the lower face, the mucous membrane of the anterior two- thirds of the tongue and the floor of the mouth, it also conveys the motor root to the muscles of mastication and secretomotor fibres to the salivary glands. Passing forwards from the trigeminal ganglion, it almost immediately enters the foramen ovale through which it reaches the infratemporal fossa. Here it divides into a small anterior and a larger posterior trunk, but before doing so it gives off the nervus spinosus to supply the dura mater and the nerve to the medial pterygoid muscle from which the otic ganglion is suspended and through which motor fibres are transmitted to tensor palati and tensor tympani. The anterior trunk gives off: 1) a sensory branch, the buccal nerve, which supplies part of the skin of the cheek and the mucous membrane on its inner aspect; and 2) motor branches to the masseter, temporalis and lateral pterygoid muscles. The posterior trunk, which is principally sensory, divides into three branches: 1) the auriculotemporal nerve, which conveys sensory fibres to the skin of the temple and auricle and secretomotor fibres from the otic ganglion to the parotid gland; 2) the lingual nerve, which passes downwards under cover of the ramus of the mandible to the side of the tongue, where it supplies the mucous membrane of the floor of the mouth, the anterior two-thirds of the tongue (including the taste buds by way of fibres which join it from the chorda tympani), and the sublingual and submandibular salivary glands; 3) the inferior alveolar (dental) nerve, which passes down into the mandibular canal and supplies branches to the teeth of the lower jaw. It then emerges from the mental foramen to supply the skin of the chin and lower lip. This branch also conveys the only motor component of the posterior trunk: the nerve to the mylohyoid, supplying the muscle of that name and the anterior belly of the digastric. The otic ganglion The otic ganglion is unique among the four ganglia associated with the trigeminal nerve in having a motor as well as parasympathetic, sympathetic and sensory components. It lies immediately below the foramen ovale as a close medial relationship to the mandibular nerve. Its parasympathetic fibres reach the ganglion by the lesser superficial petrosal branch of the glossopharyngeal nerve; these relay in the ganglion and pass via the auriculotemporal nerve to the parotid gland, and are its secretomotor supply. The sympathetic fibres are derived from the superior cervical ganglion along the plexus which surrounds the middle meningeal artery, while the sensory fibres arrive from the auriculotemporal nerve; they are, respectively, vasoconstrictor and sensory to the parotid gland. Motor fibres pass through the ganglion from the nerve to the medial pterygoid (a branch of the mandibular nerve) and supply the tensor tympani and tensor palati muscles. The submandibular ganglion This is suspended from the lower aspect of the lingual nerve. Its parasympathetic supply is derived from the chorda tympani branch of the facial nerve by which it is conveyed to the lingual nerve; it carries the secretomotor supply to the submandibular and sublingual salivary glands. Sympathetic fibres are transmitted from the superior cervical ganglion via the plexus on the facial artery and supply vasoconstrictor fibres to these same two salivary glands. The sensory component is contributed by the lingual nerve itself, which provides sensory fibres to these salivary glands and also to the mucous membrane of the floor of the mouth. The central connections of the trigeminal nerve The central processes of the trigeminal ganglion cells enter the lateral aspect of the pons and divide into ascending and descending branches which terminate in one or other component of the sensory nucleus of V. This nucleus consists of three parts, each of which appears to subserve different sensory modalities: a chief sensory nucleus in the pontine tegmentum concerned with touch; a descending, or spinal, nucleus subserving pain and temperature; and a mesencephalic nucleus receiving proprioceptive afferents. The motor root of the trigeminal nerve lies just medial to the sensory nucleus in the upper part of the pons; its efferents pass out with the sensory fibres and are distributed by way of the mandibular division of the nerve. Clinical features 1. Section of the whole trigeminal nerve results in unilateral anaesthesia of the face and anterior part of the scalp, the auricle and the mucous membranes of the nose, mouth and anterior two-thirds of the tongue, together with paralysis and wasting of the muscles of mastication on the affected side. Lesions of separate divisions give rise to corresponding sensory and motor deficits in the area of distribution of the affected nerve. Excruciating episodic pain in the area supplied by trigeminal nerve, especially second and third division. There are trigger points are characterized intense pain makes the patient grimace (tic). 2. Trigeminal neuralgia may affect any one or more of the three divisions, giving rise to the characteristic pain over the appropriate area. 3. Pain is frequently referred from one segment to another. Thus, a patient with a carcinoma of the tongue (lingual nerve) frequently complains bitterly of earache (auriculotemporal nerve). The classical description of such a case is an old gentleman sitting in out-patients spitting blood and with a piece of cotton wool in his ear. 4. Herpes Zoster is characterized inflammatory reactions of dorsal root ganglion and as result severe pain on the dermatomes of affected ganglion followed by rashes and vesicle. Fig. Areas of the face and scalp supplied by the three divisions of the trigeminal nerve.

Fig. Zoster ophtahalmicus (ophthalmic division of trigeminal n., V1) Fig. Trigeminal Neuralgia (tic douloureux)

The abducent nerve (VI) Like the trochlear nerve, the abducent nerve supplies only one eye muscle, the lateral rectus. Its nucleus lies in the caudal part of the pons and from there its fibres pass through the pontine tegmentum to emerge on the base of the brain at the junction of the pons and medulla. The nerve then passes forwards to enter the cavernous sinus. Here it lies lateral to the internal carotid artery and medial to the 3rd, 4th and 5th nerves. Passing through the tendinous ring just below the 3rd nerve, it enters the orbit to pierce the deep surface of the lateral rectus. Clinical features On account of its long intracranial course, the 6th nerve is frequently involved in injuries to the base of the skull. When damaged, it gives rise to diplopia and a convergent squint. The patient is unable to deviate the affected eye laterally. The facial nerve (VII) In addition to supplying the muscles of facial expression, the facial nerve conveys secretomotor fibres to the sublingual and submandibular salivary glands and the lacrimal gland as well as the nasal mucosa; it also carries taste fibres from the anterior two-thirds of the tongue. The fibres innervating the facial muscles have their nucleus of origin in the ventral part of the caudal pons; the secretomotor fibres for the salivary glands are derived from the superior salivary nucleus. The sensory fibres associated with the nerve have their cells of origin in the facial (geniculate) ganglion. From the motor nucleus, fibres of the facial nerve run a devious course over the nucleus of the abducent nerve (Fig. 243), where they form an elevation on the floor of the 4th ventricle known as the facial colliculus, then downwards and forwards to emerge from the lateral aspect of the pons together with VIII in the cerebellopontine angle. The sensory and motor fibres pass together into the internal auditory meatus, at the bottom of which they leave the 8th nerve and enter the facial canal. Here they run laterally over the vestibule before bending sharply backwards over the promontory of the middle ear. This bend, or genu of the facial nerve, as it is called, marks the site of the facial ganglion and the point at which the secretomotor fibres for the lacrimal gland leave to form the greater superficial petrosal nerve. The facial nerve then passes downwards, medial to the middle ear, to reach the stylomastoid foramen. Just before entering this foramen it gives off the branch, known as the chorda tympani, which runs back through the middle ear between the incus and malleus, exits via the fissure between the tympanic and petrous parts of the temporal bone to enter the infratemporal fossa where it joins the lingual nerve. Hence its taste fibres reach the anterior two-thirds of the tongue and its secretomotor fibres are conveyed to the submandibular ganglion, thence to the submandibular and sublingual salivary glands. On emerging from the stylomastoid foramen, the nerve supplies the stylohyoid and the posterior belly of digastric muscle. It then enters the parotid gland where it divides into five divisions for the supply of the facial muscles: the temporal, zygomatic, buccal, mandibular, and cervical branches. Fig. The superior orbital fissure and tendinous ring of origin of the extrinsic orbital muscles, showing the relations of the cranial nerves as they enter the orbit.

Fig. Distribution of the facial nerve within the temporal bone.

Fig. Distribution of the facial nerve: T, temporal; Z, zygomatic; B, buccal; M, mandibular; C, cervical; and P, posterior auricular branch. Clinical features 1. It is important to distinguish between ‘nuclear’ and ‘infranuclear’ facial palsies on the one hand and ‘supranuclear’ palsies on the other. Both nuclear and infranuclear palsies result in a facial paralysis which is complete and which affects all the muscles on one side of the face. In supranuclear palsies there is no involvement of the muscles above the palpebral fissure since the portion of the facial nucleus supplying these muscles receives fibres from both cerebral hemispheres. Furthermore, in such cases the patient may involuntarily use the facial muscles but will be unable to do so on request. 2. Supranuclear facial palsies most frequently result from vascular involvement of the corticobulbar pathways, e.g. in cerebral haemorrhage. Nuclear palsies may occur in poliomyelitis or other forms of bulbar paralysis, while infranuclear palsies may result from a variety of causes including compression in the cerebellopontine angle (as by an acoustic neuroma), fractures of the temporal bone and invasion by a malignant parotid tumour. However, by far the commonest cause of infranuclear facial paralysis is Bell’s palsy, which is of unknown aetiology. When the intracranial part of the nerve is affected or when it is involved in fractures of the base of the skull there is usually loss of taste over the anterior two-thirds of the tongue and an associated loss of hearing (8th nerve damage). The auditory (vestibulocochlear) nerve (VIII) The 8th nerve consists of two sets of fibres: cochlear and vestibular. The cochlear fibres (concerned with hearing) represent the central processes of the bipolar spiral ganglion cells of the cochlea which traverse the internal auditory meatus to reach the lateral aspect of the medulla, at the cerebellopontine angle (together with VII), where they terminate in the dorsal and ventral cochlear nuclei. The majority of the projection fibres from these nuclei cross to the opposite side, those from the dorsal nucleus forming the auditory striae in the floor of the 4th ventricle, those from the ventral nucleus forming the trapezoid body in the ventral part of the pons. Most of these efferent fibres terminate in nuclei associated with the trapezoid body, either on the same or the opposite side, and then ascend in the lateral lemniscus to the inferior colliculus and the medial geniculate body; from the former, fibres reach the motor nuclei of the cranial nerves and form the pathway of auditory reflexes; from the latter, fibres sweep laterally in the auditory radiation to the auditory cortex in the superior temporal gyrus. The vestibular fibres (concerned with equilibrium) enter the medulla just medial to the cochlear division and terminate in the vestibular nuclei. Many of the efferent fibres from these nuclei pass to the cerebellum in the inferior cerebellar peduncle together with fibres bypassing the vestibular nuclei and passing directly to the cerebellum. Other vestibular connections are to the nuclei of III, IV, VI and XI and to the upper cervical cord (via the vestibulospinal tract). These connections bring the eye and neck muscles under reflex vestibular control. Clinical features 1. Lesions of the cochlear division result in deafness which may, or may not, be accompanied by tinnitus. The differential diagnosis between middle ear deafness and cochlear (inner ear) or auditory nerve lesions can be made clinically by the use of a tuning fork. Air conduction (the fork being held beside the ear) is normally louder than bone conduction (the fork being held against the mastoid process). If the middle ear is damaged, the reverse will hold true. 2. Apart from injury to the cochlear nerve itself, unilateral lesions of the auditory pathway do not greatly affect auditory acuity because of the bilaterality of the auditory projections. 3. Temporal lobe tumours may give rise to auditory hallucinations if they encroach upon the auditory (superior temporal) gyrus. 4. Lesions of the vestibular division of the labyrinth or of the vestibulocerebellar pathway result in vertigo — a subjective feeling of rotation — nausea, ataxia and nystagmus. The glossopharyngeal nerve (IX) The glossopharyngeal nerve contains sensory fibres for the pharynx and the posterior one-third of the tongue (including the taste buds), motor fibres for the stylopharyngeus muscle and secretomotor fibres for the parotid gland. It is attached to the upper part of the medulla by four or five rootlets along the groove between the olive and the inferior cerebellar peduncle and leaves the skull by way of the jugular foramen in which it gives off its tympanic branch. Below the jugular foramen the nerve courses downwards and forwards between the internal carotid artery and the internal jugular vein to reach the styloid process. From here it passes along the stylopharyngeus muscle to enter the pharnyx between the superior and middle constrictors. Here it breaks up into its terminal branches which supply the posterior one-third of the tongue and the mucous membrane of the pharynx (including the tonsil). Fig. Vestibular Mechanism - Otolithic Membrane The tympanic branch, which is continued as the lesser superficial petrosal nerve, conveys the preganglionic parasympathetic fibres to the otic ganglion (parotid secretomotor fibres). The only other branch of significance is the carotid nerve which arises just below the skull and runs down on the internal carotid artery to supply both the carotid body and carotid sinus. This small twig serves as the afferent limb of the baroreceptor and chemoreceptor reflexes from the carotid sinus and body respectively. Clinical features Complete section of the glossopharyngeal nerve results in sensory loss in the pharynx, loss of taste and common sensation over the posterior one-third of the tongue, some pharyngeal weakness and loss of salivation from the parotid gland. However, such lesions are frequently difficult to detect and rarely occur as isolated phenomena since there is so often associated involvement of the vagus or its nuclei.

Fig. Vestibular Mechanism - Otolithic Membrane

The vagus nerve (X) The vagus has the most extensive distribution of all the cranial nerves, innervating the heart and the major part of the respiratory and alimentary tracts. Central connections The dorsal nucleus of the vagus in the medulla (Fig. 242) is a mixed visceral afferent and efferent nucleus. It receives sensory fibres from the heart, the lower respiratory tract and the alimentary tract down to the transverse colon; in addition it gives rise to preganglionic parasympathetic motor fibres to the heart and the smooth muscles of the bronchi and gut. From the nucleus ambiguus efferent fibres pass to the striped muscles of the pharynx and larynx.

Fig. The central connections of the auditory pathway of VIII. Fig. Innervation of the tongue. Distribution The nerve is connected to the side of the medulla by about ten filaments which lie in series with the glossopharyngeal nerve along the groove between the olive and the inferior cerebellar peduncle. These filaments unite to form a single bundle which passes beneath the cerebellum to the jugular foramen. Two sensory ganglia are associated with this part of the nerve: a superior, within the jugular foramen, and an inferior, immediately beneath the skull. The vagus then passes vertically downwards to the root of the neck, lying in the posterior part of the carotid sheath between the internal jugular vein and the internal and then common carotid arteries. There are a number of important branches in the neck: pharyngeal to the pharyngeal and palatal musculature by way of the pharyngeal plexus; superior laryngeal, supplying the interior of the larynx above the vocal folds and the cricothyroid and inferior constrictor muscles; and the superior and inferior cardiac branches which are inhibitory to the heart. Below the level of the subclavian arteries the course and relations of the nerve on the two sides differ. On the right side the recurrent laryngeal branch is given off as it crosses the subclavian artery; beyond this the nerve descends through the superior mediastinum in close association with the great veins. Behind the root of the lung it takes part in the formation of the pulmonary plexus and then passes on to the oesophagus to form, with its fellow, the oesophageal plexus. The left vagus enters the thorax in close association with the great arteries, lying at first lateral to the common carotid and then crossing the arch of the aorta. The left recurrent laryngeal branch, which is given off as the vagus crosses the aortic arch, passes below the ligamentum arteriosum, behind the arch and then ascends in the groove between the trachea and the oesophagus. The vagus then passes behind the root of the lung, enters into the formation of the pulmonary plexus and passes on to the oesophagus to form a plexus from which emerge two trunks, each comprising fibres from both the left and right vagus. The two vagi then enter the abdomen through the oesophageal opening in the diaphragm, the anterior vagus passing on to the anterior surface and the posterior passing to the posterior aspect of the stomach. Beyond this it is difficult to trace the course of the nerves, but branches are given to the coeliac, hepatic and renal plexuses and, by way of these plexuses, are distributed to the fore- and midgut and to the kidneys. Clinical features 1. Isolated lesions of the vagus nerve are uncommon but it may be involved in injuries or disease of related structures. 2. Asimple test for the integrity of the vagus relies on its innervation of the muscles of the palate. In unilateral paralysis, the uvula deviates to the normal side when the patient says ‘Ah’. The accessory nerve (XI) The accessory nerve is conventionally described as having a cranial and a spinal root. According to standard descriptions, the cranial root is formed by a series of rootlets that emerge from the medulla between the olive and the inferior cerebellar peduncle. These rootlets are considered to join the spinal root, travel with it briefly, then separate within the jugular foramen and are distributed with the vagus nerve to supply the musculature of the palate, pharynx and larynx. A recent, detailed dissection study has demonstrated that all the medullary rootlets that do not join to form the glossopharyngeal nerve (IX) join the vagus nerve at the jugular foramen. All the rootlets that form the accessory nerve arise caudal to the olive and no connections can be demonstrated between the accessory nerve and the vagus in the jugular foramen. The accessory nerve thus has no cranial component and consist only of the structure hitherto referred to as the spinal root of the accessory nerve. This spinal root is formed by the union of fibres from an elongated nucleus in the anterior horn of the upper five cervical segments, which leave the cord mid-way between the anterior and posterior roots, join, then pass upwards through the foramen magnum. The accessory nerve and the converging rootlets of the vagus nerve then enter the jugular foramen in a shared sheath of dura. The glossopharyngeal nerve enters the jugular foramen anterior to the vagus through a separate dural sheath. The nerve passes backwards over the internal jugular vein to the sternocleidomastoid muscle which it pierces (and supplies) and then crosses the posterior triangle of the neck to enter and supply the deep surface of the trapezius. Clinical features Division of the accessory nerve results in paresis of the sternocleidomastoid and trapezius muscles. This follows, for example, most block dissections of the lymph nodes of the neck, the nerve being sacrificed in clearing the posterior triangle. The hypoglossal nerve (XII) The hypoglossal nerve is entirely motor and supplies all the intrinsic and extrinsic muscles of the tongue (with the exception of the palatoglossus). From its nucleus, which lies in the floor of the 4th ventricle, a series of about a dozen rootlets leave the side of the medulla in the groove between the pyramid and the olive. These rootlets unite to leave the skull by way of the anterior condylar, or hypoglossal, canal. Lying at first deep to the internal carotid artery and the jugular vein, the nerve passes downwards between these two vessels to just above the level of the angle of the mandible. Here it passes forwards over the internal and external carotid arteries, and gives off its descending and thyrohyoid branches. It then crosses the hyoglossus and genioglossus muscles to enter the tongue. Its descending branch (descendens hypoglossi) actually derives from a twig of the 1st cervical nerve and therefore transmits C1 fibres. It passes more or less vertically downwards upon the internal carotid artery to join the descending cervical nerve (C2 and 3) to form a loop known as the ansa cervicalis (or ansa hypoglossi) just above the omohyoid muscle. From this loop branches are given to three infrahyoid muscles—sternothyroid, sternohyoid and omohyoid. Clinical features 1. Division of the hypoglossal nerve, or lesions involving its nucleus, result in an ipsilateral paralysis and wasting of the muscles of the tongue. This is detected clinically by deviation of the protruded tongue to the affected side. 2. Supranuclear paralysis (due to an upper motor neurone lesion involving the corticobulbar pathways) leads to paresis but not atrophy of the muscles of the contralateral side. Fig. Lateral view of the tongue, its extrinsic muscles and its nerves. 7. Materials for activating students during the lecture: Models of the spinal cord and spinal nerves. Tables. Theoretical questions 1. Name the principal components of the peripheral nervous system and give their general characteristics. 2. Describe formation, topography and branches of the spinal nerves. Explain relations of the spinal nerves to the spinal segments. 3. Describe contents, topography and responsibility areas of the posterior branches of spinal nerves. 4.Describe formation, branches, topography and responsibility areas of the cervical nerves. 5.Describe formation, branches, topography and responsibility areas of the intercostal nerves. 6.Describe structural features of the nervous plexuses. 7.Describe formation, branches, topography and responsibility areas of the cervical plexus. 8.Describe formation, branches, topography and responsibility areas of the phrenic nerve. 9.Describe formation, topography, parts and classification of branches of the brachial plexus. 10.Describe the lumbar plexus. 11. Describe the sacral and the coccygeal plexuses. 12. Name all pairs of the cranial nerves. 13. Discuss classification of the cranial nerves by fibers contents. 14. Discuss classification of the cranial nerves by origin. Situational problems 1. What nerve is mixed branch of cervical plexus? *A. Phrenic nerve B. Lesser occipital nerve C. Great auricular nerve D. Supraclavicular nerves E. Suboccipital nerves 2. What anatomical structures form a spinal nerve? A. Posterior funiculus of spinal cord B. Lateral funiculus of spinal cord *C. Anterior and posterior roots of spinal cord D. Posterior horn of spinal cord E. Anterior funiculus of spinal cord 3. What anatomical structures form the elementary reflex arch? A. Afferent neuron, intermediate neuron, efferent neuron B. Anterior root of the spinal nerve C. Conductor neuron D. Efferent neuron E. Central nucleus 4. Indicate anatomical structures relating to peripheral nervous system *A. Cranial nerves B. Pons C. Mesencephalon D. Medulla oblongata E. Spinal cord 5. Indicate nervous fibres in spinal nerves. A. Postganglionic parasympathetic B. Sensory, motor, postganglionic sympathetic C. Preganglionic sympathetic D. Cranial nerves E. Anterior root of the spinal cord 6. After a fracture of the upper third of the humerus the paralysis of the posterior group of muscles of the shoulder and forearm developed. Which nerve was damaged? A. Ulnar. *B. Radial. C. Median. D.Musculocutaneous. E. Axillary. 7. Examination of a patient with a knife right hand wound has shown skin sensitivity loss of the lateral part of the hand dorsal surface and proximal phalanxes of the I, II and partially III fingers. Which nerve has been damaged? A. Ulnar. B. Median. *C. Radial. D.Musculocutaneous. E. Lateral cutaneous nerve of forearm. 8. Having hurt the elbow against a table a patient felt burning and pricking on the internal surface of the forearm. Which nerve was traumatized in this case? *A. Ulnar. B. Radial. C. Median. D. Axillary. E. Musculocutaneous. 9. A patient after a trauma has decreased painful and temperature sensitivity in the site of 1.5 fingers on the palmar surface and 2.5 fingers on the dorsal surface from the side of the little finger. Which nerve was injured as a result of the trauma? *A. Ulnar. B. Radial. C. Median. D. Musculocutaneous. E. Medial cutaneous nerve of forearm 10. After an inflammatory process a patient complains of feeling weakness when bending a hand in the site of the I, II, III, and IV fingers, volume reduction of thenar muscles. Examination has shown disorders of pain and temperature sensitivity on palmary surface of the I, II, III fingers and ra¬dial surface of the IV finger. Which nerve has been injured? A. Musculocutaneous. B. Radial. C. Ulnar. *D. Median. E. Medial cutaneous nerve of fore arm. 11. A patient appealed to a doctor with complaints of impossibility to abduce the right hand after a trauma. Examination has shown that passive movements are not limited. Deltoid muscle atrophy has been detected. Which nerve has been injured? A. Suprascapular. B. Radial. C. Ulnar. D. Median. *E. Axillary. 12. After a trauma in the site of a shoulder a patient can not extend a hand. Examination has also shown a decrease of pain and temperature sensitivity in the site of 2.5 fingers of the hand's dorsal surface from the side of the thumb. Which nerve has been injured as a result of the trauma? *A. Radial. B. Median. C. Ulnar. D. Axillary. E. Musculocutaneous. 13. Examining a patient a neuropathologist detected increased pain skin sensitivity on the palmary surface of the I, II, III and the radial surface of the IV fingers, middle part of the palm and thenar. Which nerve was injured? *A. Median B. Medial cutaneous nerve of forearm C. Ulnar. D. Radial. E. Musculocutaneous. 14. To a traumatology center there was taken a teenager who pinched his arm in a door above the elbow joint during a game. Examination has shown the loss of skin sensitivity on the anteromedial shoulder surface. Indicate with what nerve damage the loss of skin sensitivity of the mentioned site is connected? A. Axillary. B. Radial. *C. Musculocutaneous. D. Ulnar. E. Median. 15. A patient lost skin sensitivity of the little finger. Which nerve is damaged? A. Median. *B. Ulnar. C. Radial. D. Musculocutaneous E. Medial cutaneous nerve of forearm 16. A patient was admitted to a traumatology center with the greater psoas muscle damage. The patient lost possibility to straighten his leg in the knee joint. Which nerve is damaged? *A. Femoral. B. Iliohypogastric. C. Ilioinguinal. D. Genitofemoral. E. Obturator. 17. Examining a patient a neuropathologist detected the following symptom complex: cremasteric reflex extinction (reduction of m. cremaster), disorder of skin sensitivity on the anterior and internal surface of the superior third of the thigh and scrotum. Which nerve was injured? A. Ilioinguinal. *B. Genitofemoral. C. Sciatic. D. Femoral. E. Obturator. 18. A patient has characteristic gait changes, so-called waddling gait, observed: during walking the patient sways. Besides, hip reduction is impossible. Which nerve has been injured? A. Femoral. B. Sciatic. *C. Obturator. D. Tibial. E. Superior gluteal. 19. A patient can not extend a knee joint, knee reflex is not observed, skin sensitivity of the anterior surface of the thigh is damaged. Which nerve is damaged? A. Obturator. B. Superior gluteal. C. Common peroneal. *D. Femoral. E. Inferior gluteal nerve. 20. A 30-year-old patient appealed to a neuropathologist complaining of skin sensitivity loss of the middle and inferior third of the posterior region of the leg on the right. Which nerve id damaged? *A. Sural. B. Posterior cutaneous nerve of thigh. C. Genitofemoral. D. Branches of obturator nerve. E. Tibial. 21. Examination of a patient with a cut wound in the inferior third of the right leg anterior area has shown the absence of extension movements in the right ankle joint. Muscles are not injured. Which nerve has been affected? A. Saphenous. B. Common peroneal. C. Superficial fibular. *D. Deep fibular. E. Femoral. 22. Examining a patient the doctor detected the following symptom complex: the paralysis of the digital flexors, the foot thus became permanently extended, the toes resembled the claws. Which nerve was injured? A. Saphenous. B. Common peroneal. C. Superficial fibular. *D. Tibial. E. Femoral. 23. Examining a patient the doctor detected the following symptom complex: the inability to extend and pronate the foot, the foot hangs down and laterally. Which nerve was injured? *A. Fibular. B. Posterior cutaneous nerve of thigh. C. Genitofemoral. D. Branches of obturator nerve. E. Tibial. 24. Carrying out neurologic inspection of the patient, 22 years, the doctor has asked it to open a mouth and to utter a note of "Aaaa", thus estimated, whether the soft palate symmetrically rises. Then the doctor has touched a cotton plug to a soft palate and in the answer there was a vomitive jerk that is accompanied by locomotion of the palate and the pharynx. What cranial nerves were investigated by the doctor? A. 10,11 and 12 B. 5,7 and 9 C. 7,8 and 9 D. 9 and 10 Е. 9 and 12 25. At the patient on a X-ray the enlarged lymph nodes in a field of a root lungs are taped. The patient complains of retardation of a warm rhythm and pain sensation in heart. The doctor considers that symptoms from heart are invoked by pressure upon its nerves of the enlarged knots. What of nerves are compressed by the enlarged lymph nodes? A. N. splanchnicus major B. Rr. cardiaci n. vagus C. Nn. intercostals D. Truncus sympaticus E. N. Phrenicus 9. Materials for the next lecture (key issues) Next lecture topic: «Review of the autonomic nervous system, its central departments. The principles of the autonomic innervation of the organs». Questions: 1. What the autonomic division of CNS is responsible for? 2. What are the evolutional features of the autonomic division of CNS? 3. Name the parts of the autonomic division of CNS. 4. Name the chief function of the parasympathetic part of the autonomic division of CNS. 5. Name the chief function of the sympathetic part of the autonomic division of CNS. 6. Where do the centers of the sympathetic part of autonomic division of CNS reside? What are they represented with? 10. References: The basic literature 1. Human Anatomy. In three volumes. Volume 1 / Edited by V.G. Koveshnikov. - Lugansk: LTD «Virtualnaya realnost», 2009. – 328p. 2. Human Anatomy. In three volumes. Volume 2 / Edited by V.G. Koveshnikov. - Lugansk: LTD «Virtualnaya realnost», 2008. – 248p. 3. Human Anatomy. In three volumes. Volume 3 / Edited by V.G. Koveshnikov. - Lugansk: LTD «Virtualnaya realnost», 2009. - 384p. 4. Gray's anatomy for students / Richard L. Drake, A. Wayne Vogl, and Adam W. M. Mitchell; illustrations by Richard M. Tibbitts and Paul E. Richardson; photographs by Ansell Horn. - 2nd ed. 2012- 1103p. 5. Sobotta Atlas of Human Anatomy / Edited by R. Putz and R. Pabst, 14th ed. - Elsevier GmbH, Munich, 2008 . - 895p. 6. Clay JH, Pounds DM. Basic Clinical Massage Therapy: Integrating Anatomy and Treatment. 2003. 7. Grant's atlas of anatomy/Anne M.R. Agur, Arthur F. Dailey II, 14th ed. - Baltimore: Wolters Kluver, 2017. - 864 p. 8. Martini Frederic H. Martini's atlas of the human body, 8th ed. - Pearson Education, 2009. - 250p. 9. Atlas of Human Anatomy / Frank H. Netter; 7nd ed. // Elsevier Inc, 2019. - 548p. 10.Human Anatomy: textbook / Cherkasov V.G., Herasymiuk I.Ye., Holovatskyi A.S., Kovalchuk O.I. [et al.]. - Vinnytsia Nova Knyha, 2018. - 464 p. The additional literature 1. Beck F. Human embryology: 2 ed / F. Beck, D. Mossat, D. Davies. - Oxford: Blackwell, 1985. - V. 11. - 372p. 2. Moore Keith L. Clinically oriented anatomy: third ed / Keith L. Moore. - 1992. - 917p. 3. Clinical Anatomy. Applied anatomy for clinical students and junior doctors: eleventh edition / Harold Ellis // Oxford, UK: Blackwell publishing. - 2006. - 455p. 4. Pocket atlas of Human Anatomy / Heinz Feneis, Wolfgang Dauber // Thieme, Stuttgart. - 2000. — 5 Юр. Information resources 1. http://www.umsa.edu.ua/kafhome/anatomy/kaf_anatomy_download.html 2. http://anatom.ua/basis/ukr/ 3. http://anatom.ua/basis/rus/ Electronic educational resources 1. Human Anatomy. In three volumes. Volume 1 [educational resources] / edited by V. G. Koveshnikov. - Lugansk: «Шико» TOB «Віртуальна реальність», 2006. - 328 p. https://www.twirpx.com/file/1763162/ 2. Human Anatomy. In three volumes. Volume 2 [educational resources] / edited by V. G. Koveshnikov. - Lugansk: «Шико» TOB «Віртуальна реальність», 2006. - 248 p. https://www.twirpx.eom/file/l 763164/ 3. Human Anatomy. In three volumes. Volume 3 [educational resources] / edited by V. G. Koveshnikov. - Lugansk: «Шико» TOB «Віртуальна реальність», 2006. - 384 p. https://www.twirpx.eom/file/l 763169/ 4. For English-speaking students: a. https://www.umsa.edu.ua/fakultets/stomat/kafedry/anatomiy/resources/navchal ni- materiali-dlya-studentiv-medichnogo-fakultetu b. https://www.umsa.edu.ua/fakultets/stomat/kafedry/anatomiy/resources/uchbovi -materiali-dlya- studentiv-stomatologichnogo-fakultetu-al

The methodical guidance has been compiled by N.L. Svinthythka, Associate Professor at the Department of Human Anatomy, PhD in Medicine, Associate Professor