Peripheral Nervous System, Part II: Spinal Nerves (2025) PDF

RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves 1 THE SPINAL NERVES Nn. spinales are 31 symmetric and metameric paired nerves. Each spinal nerve is formed by radix anterior and radix posterior and contains both – affe...

RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves 1 THE SPINAL NERVES Nn. spinales are 31 symmetric and metameric paired nerves. Each spinal nerve is formed by radix anterior and radix posterior and contains both – afferent and efferent fibres. Afferent (sensory) fibres convey impulses to the central nervous system – they are peripheral processes of pseudounipolar neurons of the spinal ganglions. There are somatic and visceral afferent fibres. Somatic afferent fibres start from exteroreceptors and proprioreceptors. Visceral afferent fibres also are peripheral processes of pseudounipolar neurons of the spinal ganglions, but they reach the spinal nerve through rr. communicantes albi from interoreceptors of the organs (viscera). Efferent fibres convey impulses from the central nervous system to periphery and are of two groups. Somatic efferent fibres (motor fibres) are axons of nuclei motorii (the anterior column of the grey matter), which run to supply the skeletal muscles. Visceral efferent fibres (vegetative fibres) are axons of two different centers: – from nucleus intermediolateralis start sympathetic (preganglionic) fibres; they run in content of the all thoracic and upper two lumbar spinal nerves and then via rr. communicantes albi join ganglions of the sympathetic trunk, – from nucleus parasympathicus sacralis start parasympathetic (preganglionic) fibres; they run in content of the 2nd, 3rd and 4th sacral spinal nerves, then through the ventral branches of the corresponding sacral nerves to the pelvic parasympathetic ganglions. Each spinal nerve leaves canalis vertebralis through foramen intervertebrale and divides into 4 branches: 1. ramus meningeus contains sensory fibres, returns into the vertebral canal to supply the meninges; 2. ramus communicans albus communicates the spinal nerve with the sympathetic trunk; 3. ramus posterior (dorsalis) usually is smaller than the ventral branch; dorsal branches supply skin and muscles of the back and posterior region of the neck. Some of the dorsal branches are particular: – ramus posterior of the 1st cervical spinal nerve is n. suboccipitalis – it leaves the vertebral canal between the occipital bone and the atlas; usually it has no sensory fibres and supplies deep muscles of the back in the neck region – mm. suboccipitales (m. rectus capitis posterior major et minor, mm. ogliquus capitis superior et inferior), – ramus posterior of the 2nd cervical spinal nerve is n. occipitalis major – it leaves the vertebral canal between the 1st and 2nd cervical vertebra, supplies skin of the occipital region and deep muscles of the back in the neck region (m. semispinalis capitis, m splenius capitis, m. longissimus capitis), – rami posteriores of the 1st, 2nd, and 3rd lumbar spinal nerves form nn. clunium superiores to supply skin of regio glutea upper part; – rami posteriores of the sacral spinal nerves form nn. clunium medii to supply skin of regio glutea middle part; 4. ramus anterior (ventralis) supplies skin and muscles of the lateral and anterior parts of the trunk and the limbs. Metamerity is still present only concerning the thoracic spinal nerves (nn. intercostales). The ventral branches of the other spinal nerves form plexus: – plexus cervicalis is formed by the anterior branches of four upper cervical spinal nerves, – plexus brachialis is formed by the anterior branches of four lower cervical spinal nerves and partly by the 4th cervical and 1st thoracic spinal nerves, – plexus lumbalis is formed by the anterior branches of three upper lumbar spinal nerves, – plexus sacralis is formed by the anterior branches of the 4th and 5th lumbar, all sacral and coccygeal spinal nerves. 2 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves PLEXUS CERVICALIS Plexus cervicalis is formed by rami anteriores of the upper four cervical spinal nerves. It lies on the deep muscles of the neck (in trigonum colli laterale). It is covered by m. sternocleidomastoideus. There are three groups of branches arising from the plexus: motor, sensory and mixed. Motor branches: 1. rr. musculares supply muscles of the lateral, deep and craniothoracal groups of the neck; 2. ansa cervicalis – it is formed by two roots – radix superior et inferior. Radix superior origins from rami anteriores of the 1st and 2nd cervical spinal nerves, passes with n. hypoglossus, then leaves it and joins with radix inferior. Radix inferior arises from rami anteriores of the 2nd and 3rd cervical spinal nerves. Ansa cervicalis lies on the bunch of nerves and blood vessels; it supplies straight muscles of the neck (except m. geniohyoideus). Sensory branches: 1. n. occipitalis minor appears at the middle part of m. sternocleidomastoideus, ascends along its posterior margin and supplies skin of the occipital region and skin of the posterior part of auricula; 2. n. auricularis magnus ascends along the surface of m. sternocleidomastoideus and supplies skin at the region of angulus mandibulae and auricula; 3. n. transversus colli passes horizontally, crosses m. sternocleidomastoideus and supplies skin in trigonum colli mediale; 4. nn. supraclaviculares supply skin of trigonum colli laterale and the shoulder girdle to the level of the 2nd rib. Mixed branch contains motor, sensory and sympathetic postganglionic fibres: 1. n. phrenicus descends along m. scalenus anterior, passes between a. et v. subclavia and through superior thoracic aperture enters the thoracic cavity. It lies in mediastinum superius and in mediastinum medium; then it descends between pleura mediastinalis and pericardium and runs in front of radix pulmonis. The nerve reaches the diaphragm; the sensory fibres supply pericardium, pars mediastinalis et diaphragmatica pleurae parietalis, peritoneum parietale in region around pancreas and liver, and thymus, while the motor fibres supply the diaphragm. PLEXUS BRACHIALIS It is formed by rami anteriores of the lower four cervical spinal nerves and by some fibres of the 4th cervical and 1st thoracic spinal nerves. It lies in space between m. scalenus anterior and m. scalenus medius with a. subclavia, crosses trigonum colli laterale, then through enters the axillary fossa. By clavicula the plexus is divided into two parts: – pars supraclavicularis, – pars infraclavicularis. Pars supraclavicularis 1. Pars supraclavicularis gives n. subclavius (supplies m. subclavius); nn. pectorales (medialis et lateralis) (supply m. pectoralis major et minor); n. thoracicus longus descends over the superficial surface of m. serratus anterior and supplies it; n. subscapularis (supplies m. subscapularis, m. teres major and art. humeri); n. suprascapularis passes posteriorly below m. trapezius to reach fossa supraspinata (through incisura scapulae below ligamentum superius scapulae) and supplies m. supraspinatus et m. infraspinatus; n. thoracodorsalis runs downward over the posterior wall of the axilla to reach m. latissimus dorsi and supplies it; n. dorsalis scapulae pierces m. scalenus medius, runs posteriorly and supplies m. levator scapulae, mm. rhomboidei.  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves 3 Pars infraclavicularis Pars infraclavicularis lies in fossa axillaris and supplies muscles and skin of the upper limb. It surrounds a. axillaris and could be divided into three cords: fasciculus medialis, fasciculus lateralis, fasciculus posterior. Fasciculus medialis has four nerves: – n. cutaneus brachii medialis, – n. cutaneus antebrachii medialis, – n. ulnaris, – radix medialis n. mediani. 1. N. cutaneus brachii medialis runs along sulcus bicipitalis medialis and supplies skin at the anterior and medial region of the brachium. 2. N. cutaneus antebrachii medialis descends along sulcus bicipitalis medialis, continues to the antebrachium and supplies skin at the anterior and medial parts of it. 3. N. ulnaris passes along sulcus bicipitalis medialis together with n. medianus, n. cutaneus brachii medialis, n. cutaneus antebrachii medialis, a. brachialis, vv. brachiales, v. basilica. N. ulnaris in cubital region is covered only by fascia and skin; it lies in sulcus n. ulnaris on epicondylus medialis humeri. Then the nerve pierces m. flexor carpi ulnaris, runs between m. flexor carpi ulnaris and m. flexor digitorum superficialis, goes through canalis ulnaris to the palm and divides into two branches: – ramus superficialis divides into the 3 nn. digitales palmares proprii, which supply skin over the hypothenar eminence, the ulnar side of the ring finger and the little finger; – ramus profundus supplies muscles of the little finger, mm. interossei palmares et dorsales, the 3rd and 4th mm. lumbricales, m. adductor pollicis, m. flexor pollicis brevis (caput profundus). N. ulnaris side branches: a) rr. articulares supply art. cubiti; b) rr. musculares supply m. flexor carpi ulnaris and the ulnar side of m. flexor digitorum profundus; c) r. dorsalis curves around the ulnar side of the hand to the dorsal surface, supplies skin of this region and divides into 5 nn. digitales dorsales to supply skin on the dorsal surface over the little finger, the ulnar side of the ring finger, the radial side of the proximal phalanx of the ring figer, the ulnar side of the proximal phalanx of the middle finger. 4. Radix medialis n. mediani joins with radix lateralis n. mediani from fasciculus lateralis to form n. medianus. Fasciculus lateralis has two nerves: – radix lateralis n. mediani, – n. musculocutaneus. 1. Radix lateralis n. mediani joins with radix medialis n. mediani from fasciculus medialis to form n. medianus. N. medianus is formed in front of a. axillaris by junction of two roots from two cords of plexus brachialis. It descends along sulcus bicipitalis medialis together with n. ulnaris, n. cutaneus brachii medialis, n. cutaneus antebrachii medialis, a. brachialis, vv. brachiales, v. basilica. N. medianus crosses fossa cubitalis, pierces m. pronator teres, runs between m. flexor digitorum superficialis et profundus, then through the carpal tunnel and reaches the palm. In carpal tunnel the nerve lies superficially to the tendons of m. flexor digitorum superficialis. In this place pressure or irritation of n. medianus leads to „carpal tunnel syndrome” in which could occur weakness or paralysis of the thenar muscles and sensory changes in the region supplied by the nerve. N. medianus on the palm lies below aponeurosis palmaris and rests on the tendons of the  4 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves muscles. It gives 3 nn. digitales palmares communes which divides into 7 nn. digitales palmares proprii (the 1st n. digitalis communis divides into 3 nerves, the 2nd and the 3rd – into 2 nerves). Nn. digitales palmares proprii supply skin over the thumb, index finger, middle finger and the radial side of the ring finger. The terminal branches of these nerves wind to the dorsal side and supply skin over the distal and medial phalanges of the same fingers. The 1st n. digitalis palmaris communis supplies the 1st and the 2nd mm. lumbricales, m. abductor pollicis brevis, m. opponens pollicis, m. flexor pollicis brevis (caput superficiale). Nn. digitales palmares communes supply the wrist joint and to the joints of the hand. N. medianus side branches: a) rr. articulares supply art. cubiti, art. radiocarpalis; b) rr. musculares supply the 1st and 2nd layers of the anterior group of musculi antebrachii except muscles supplied by n. ulnaris (m. pronator teres, m. flexor carpi radialis, m. palmaris longus, m. flexor digitorum superficialis); c) n. interosseus antebrachii anterior starts at the upper part of the antebrachium, descends along the ventral surface of membrana interossea antebrachii and supplies the 3rd and 4th layers of the anterior group of musculi antebrachii (m. flexor pollicis longus, the radial side of m. flexor digitorum profundus, m. pronator quadratus). It supplies also art. radiocarpalis; d) ramus palmaris arises above canalis carpi; it supplies skin over eminentia thenaris and over the middle part of the palm. 2. N. musculocutaneus pierces m. coracobrachialis, passes between m. biceps brachii and m. brachialis and supplies the anterior compartment of the arm. Then the nerve lies in sulcus bicipitalis lateralis, a little above the elbow it pierces fascia and continues to the forearm as n. cutaneus antebrachii lateralis to supply skin at the lateral part of the antebrachium. Fasciculus posterior has two nerves: – n. radialis, – n. axillaris. 1. N. radialis lies behind a. axillaris, descends and lies on sulcus n. radialis together with a. profunda brachii, vv. profundae brachii. Then it lies between m. brachioradialis and m. brachialis and in fossa cubitalis divides into two terminal branches: a) ramus superficialis lies between m. brachioradiallis and m. flexor carpi radialis, then under the tendon of m. brachioradialis winds to the dorsal side of the hand to supply skin and divides into 5 nn. digitales dorsales to supply skin of the proximal phalanx of the thumb and the index fingers, the radial side of the proximal phalanx of the middle finger; b) ramus profundus pierces m. supinator, curves around collum radii and reaches the dorsal side of the forearm. It descends between the superficial and deep layers of musculi antebrachii to the wrist joint and supplies all muscles of the posterior compartment of the forearm (also the radial part). The terminal part of ramus profundus is n. interosseus antebrachii posterior. It descends along the posterior side of membrana interossea antebrachii and supplies the deep layer of the posterior compartment of musculi antebrachii; by rr. articulares it also supplies the joints of the hand. N. radialis side branches: a) rr. musculares on the brachium supply the posterior compartment of the arm, b) n. cutaneus brachii posterior supplies skin on the posterior side of the brachium; c) n. cutaneus antebrachii posterior supplies skin on the posterior side of the antebrachium.  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves 5 2. N. axillaris passes backward through the posterior wall of the fossa axillaris together with a. circumflexa humeri posterior, v. circumflexa humeri posterior, curves around the posterior side of collum chirurgicum humeri (could be injured if there are dislocations of the shoulder joint or fractures of the surgical neck). N. axillaris supplies m. deltoideus, m. teres minor, art. humeri. N. axillaris gives off n. cutaneus brachii lateralis, which supplies skin at the lateral part of the brachium. NN. INTERCOSTALES Nn. intercostales are ventral branches of the thoracic spinal nerves; they are twelve pairs, but the lowest – the 12th nerve is called n. subcostalis. The 1st thoracic spinal nerve partly joins to plexus brachialis and the 12th – to plexus lumbalis. Each intercostal nerve enters the intercostal space between pars costalis pleurae parietalis and membrana intercostalis interna and runs forward between intercostal musles and m. transversus thoracis et m. subcostalis; the nerve is not covered by the rib, lies below corresponding intercostal vein and artery (v. et a. intercostalis posterior). The upper six intercostal nerves run along the intercostal spaces to the margin of the sternum. The lower six nerves leave anterior parts of the intercostal spaces by passing deep to the costal cartilages to enter the anterior wall of the abdominal cavity. They run between m. transversus abdominis and m. obliquus internus abdominis to terminte at the margin of m. rectus abdominis. Side branches of nn. intercostales contain only sensory fibres: 1. r. cutaneus lateralis – spread near linea axillaris media to suppy the lateral thoracic and abdominal wall; 2. r. cutaneus anterior – emerge between the lateral margin of sternum and the lateral border of vagina musculi recti abdominis to supply the anterior thoracic and abdominal wall in the upper and middle regions. For female the 2nd, the 3rd and the 4th rr. cutanei anteriores give off rr. mammarii mediales, but the 4th, 5th and 6th rr. cutanei laterales – rr. mammarii laterales to supply skin over glandula mammae. Nn. intercostales are mixed nerves; by motor fibres they supply the deep muscles of thorax (mm. intercostales externi et interni, m. transversus thoracis, mm. subcostales, mm. levatores costarum), the 3rd layer of superficial muscles of back (m. serratus posterior superior et inferior). The lower nerves supply the abdominal muscles (m. obliquus externus abdominis, m. obliquus internus abdominis, m. transversus abdominis, m. rectus abdominis, m. pyramidalis). Nn. intercostales by sensory fibres supply pars costalis pleurae parietalis, fascia endothoracica, fascia endoabdominalis, peritoneum parietale. PLEXUS LUMBALIS Plexus lumbalis is formed by rami anteriores of the upper three lumbar spinal nerves, partly by the 12th thoracic and 4th lumbar spinal nerves. Plexus lumbalis lies in m. psoas major and gives off branches which emerge from the lateral and medial borders of the muscle or appear on its anterior surface. It has two groups of branches – short and long. The short branches supply m. quadratus lumborum, m. psoas major, m. psoas minor. The long branches: 1. n. iliohypogastricus emerges at the lateral border of m. psoas major, crosses m. quadratus lumborum, pierces m. transversus abdominis, runs forward between m. transversus et m. obliquus internus abdominis to m. rectus abdominis. It supplies the lower part of the  6 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves abdominal muscles by motor fibres. It gives off two side branches: a) ramus cutaneus lateralis supplies skin over m. tensor fasciae latae and the lateral part of upper gluteal region, b) ramus cutaneus anterior supplies the skin of abdominal wall in the lower region; 2. n. ilioinguinalis emerges at the lateral border of m. psoas major, passes parallel to n. iliohypogastricus and supplies the lower part of the abdominal muscles. Then the nerve runs along canalis inguinalis. For male in the canal it travels together with funiculus spermaticus, leaves it and terminates as nn. scrotales anteriores to supply skin of radix penis and scrotum. For female it passes in the canal together with lig. teres uteri, then leaves it and terminates as nn. labiales anteriores to supply skin over mons pubis and labia majora pudendi. N. ilioinguinalis also supplies skin at the medial upper part of the thigh; 3. n. cutaneus femoris lateralis appears at the lateral border of m. psoas major, runs over m. iliacus internal surface, then under the lateral part of lig. inguinale to the thigh. It supplies skin over the lateral region of the thigh; 4. n. femoralis emerges at the lateral border of m. psoas major, runs between m. psoas major et m. iliacus. Then the nerve passes through lacuna musculorum to the anterior side of the thigh and gives off rr. articulares to art. coxae; its terminal branches could be divided into two groups: a) rr. musculares supply m. quadratus femoris, m. sartorius, m. pectineus, b) rr. cutanei anteriores supply skin over the anterior surface of the thigh except trigonum femorale region. The longest branch of this group is n. saphenus. N. saphenus passes through canalis adductorius together with a. et v. femoralis. Then the nerve pierces the anterior wall of the canal, curves the knee joint medially and on the lower leg accompanies v. saphena magna to the 1st toe and supplies skin of the medial side of the crus and foot; 5. n. genitofemoralis appears on the surface of m. psoas major and divides into two branches: a) r. genitalis enters canalis inguinalis; for male it supplies funiculus spermaticus, for female – lig. teres uteri, b) r. femoralis descends through lacuna vasorum on the anterior side of the thigh and supplies skin over trigonum femorale; 6. n. obturatorius appears at the medial border of m. psoas major, passes together with a. obturatoria et vv. obturatoriae along canalis obturatorius to the thigh and divides into two branches: a) r. anterior by motor fibres supplies m. pectineus, m. adductor brevis, m. adductor longus, m. gracilis and by sensory fibres – skin at the lower part of the medial side of the thigh, b) r. posterior supplies m. obturator externus, m. adductor magnus and art. coxae. PLEXUS SACRALIS Plexus sacralis is formed by rami anteriores of the 4th and 5th lumbar, all sacral and coccygeal spinal nerves. It lies on m. piriformis and is covered by fascia. It has two groups of branches – short and long. The short branches: 1. n. gluteus superior supplies m. gluteus minimus, m. gluteus medius, m. tensor fascia latae; 2. n. gluteus inferior supplies m. gluteus maximus; 3. rr. musculares supply m. piriformis, m. obturator internus, mm. gemelli, m. quadratus femoris; 4. n. pudendus curves around spina ischiadica and passes through foramen ischiadicum minus to fossa ischioanalis; it runs forward and terminates by n. dorsalis penis (for male) or by n. dorsalis clitoridis (for female) to supply skin of penis or clitoris.  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves 7 N. pudendus side braches: a) nn. rectales inferiores supply m. sphincter ani externus and skin at the region of anus, b) nn. perineales supply all muscles of perineum. They also supply the skin of perineum and terminate as nn. scrotales posteriores (for male) or nn. labiales posteriores (for female) to supply skin of the external genitales, c) n. anococcygeus supplies skin in the region of os coccygis. The long branches: – n. cutaneus femoris posterior, – n. ischiadicus. 1. N. cutaneus femoris posterior exits from pelvic cavity through the greater sciatic foramen (below the piriform muscle), descends under m. gluteus maximus to the posterior surface of the thigh and supplies skin of this region and skin of fossa poplitea. The nerve gives off: a) nn. clunium inferiores to supply skin at the lower part of the gluteal region, b) rr. perineales to supply skin of perineum. 2. N. ischiadicus is the largest nerve of the body (about 2 cm in diameter). It runs through the greater sciatic foramen (below the piriform muscle), lies below m. gluteus maximus, then descends between the muscles of the posterior compartment of the thigh. At the upper part of fossa poplitea it divides into two terminal branches – n. tibialis and n. fibularis communis. N. ischiadicus gives off side branches at the region of the thigh to supply m. obturator internus, mm. gemelli, m. quadratus femoris, m. adductor magnus and muscles of the posterior compartment of the thigh (m. biceps femoris, m. semimembranosus, m. semitendinosus). N. tibialis descends through the middle part of fossa poplitea, lies superficially and laterally to v. poplitea, passes together with a. tibialis posterior and vv. tibiales posteriores between deep flexors of the crus and m. soleus, curves around malleolus medialis, runs below retinaculum musculorum flexorum and on the plantar surface divides into two terminal branches – n. plantaris medialis and n. plantaris lateralis. N. tibialis side brances: a) rr. musculares supply the posterior compartment of the crus (m. popliteus, m. triceps surae, m. tibialis posterior, m. flexor hallucis longus, m. flexor digitorum longus), b) rr. articulares supply art. genus et art. talocruralis, c) rr.calcanei mediales arise above the ankle joint to supply skin of the heel, d) n. cutaneus surae medialis arises from n. tibialis at fossa poplitea region and passes together with v. saphena parva. The nerve supplies skin of the posterior and medial side of the crus. At the lower third of the crus n. cutaneus surae medialis joins with n. cutaneus surae lateralis (n. fibularis communis) and forms n. suralis. N. suralis passes behind malleolus lateralis, then continues along lateral side of the foot as n. cutaneus dorsalis lateralis to supply skin over the lateral margin of the foot and the 5th toe. N. suralis gives off rr. calcanei laterales to supply skin of the heel. N. plantaris medialis supplies by motor fibres m. abductor hallucis, m. flexor hallucis brevis, m. flexor digitorum brevis, the 1st and 2nd mm. lumbricales. The sensory fibres supply medial part of the sole and form 3 nn. digitales plantares communes, which divide into 6 nn. digitales plantares proprii to supply the 1st, 2nd, 3rd and half of the 4th toes. N. plantaris lateralis supplies the lateral part of the sole and divides into two branches: a) r. profundus supplies mm. interossei, the 3rd and the 4th mm. lumbricales, m. quadratus plantae, m. abductor digiti minimi, m. flexor digiti minimi brevis, m. adductor hallucis, 8 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, part II, spinal nerves b) r. superficialis gives off 3 nn. digitales plantares to supply half of the 4th toe and the 5th toe. N. fibularis communis runs obliquelly along the lateral side of fossa poplitea, curves around caput fibulae and in the tissue of m. fibularis (peroneus) longus divides into two terminal branches – n. fibularis superficialis and n. fibularis profundus. N. fibularis communis side branches at the region at fossa poplitea: a) rr. articulares supply art. genus, b) n. cutaneus surae lateralis supplies skin on the lateral surface of the crus. At the lower part of the crus the nerve joins with n. cutaneus surae medialis to form n. suralis. N. fibularis superficialis descends between mm. fibulares and fibula and by rr. musculares supply muscles of the lateral compartment of the crus. Then the nerve emerges at the level of lower third of the crus, supplies skin in this region and below divides into nn. digitales dorsales. They supply skin of the dorsal surface of the foot, except the 1st intermetatarsal space and the lateral side of the 5th toe. N. fibularis profundus descends together with a. tibialis anterior et vv. tibiales anteriores along the anterior side of membrana interossea cruris, goes below retinaculum musculorum extensorum superius et inferius and at the level of distal parts of metatarsal bones divides into 2 nn. digitales dorsales to supply skin of the 1st intermetatarsal space. N. fibularis profundus gives side branches: a) rr. musculares – they supply muscles of the anterior compartment of the crus (m. tibialis anterior, m. extensor hallucis longus, m. extensor digitorum longus) and also dorsal muscles of the foot (m. extensor hallucis brevis, m. extensor digitorum brevis), b) rr. articulares supply art. talocruralis.  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 1 THE CRANIAL NERVES I N. OLFACTORIUS Nn. olfactorii contain sensory fibres and are part of the olfactory pathway. Nn. olfactorii develop in foetus as processes of thelencephalon. The nerves originate by special olfactory cells – cellulae neurosensoriae olfactoriae (the 1st neurons). Dendrites of those cells start with olfactory receptors distributed in the mucous membrane of the nasal cavity – regio olfactoria; axons are collected into 15 – 20 branches – fila olfactoria, which run through lamina cribrosa to bulbus olfactorius. Bulbus olfactorius contains the 2nd neirons of the olfactory pathway; axons of them form tractus olfactorius, which continues into trigonum olfactorium. Bulbus, tractus et trigonum olfactorium lie in sulcus olfactorius (facies inferior thelencephali). From trigonum olfactorium fibres are distributed into bands – striae olfactoriae; they run to subcortical centers of the smell (the 3rd neurons of the pathway): anterior group of thalamic neurons, the mamillary bodies, substantia perforata anterior and the amygdaliod body. The subcortical centers of the smell are connected with the cortical center in uncus. II N. OPTICUS N. opticus is sensory nerve and in foetus it develops as a process of diencephalon. N. opticus participates in formation of the optic (visual) pathway. The optic pathway starts in retina: – the photoreceptors – rods and cones – the 1st neurons, – the bipolar cells – the 2nd neurons, – the ganglionar cells – the 3rd neurons; axons of them leave bulbus oculi and form n. opticus. The nerve passes through canalis opticus together with a. ophthalmica. In fossa cranii media the optic nerve forms chiasma opticum (1), which consists of two sets of fibres – crossed and uncrossed. The crossed fibres start from the medial parts of retina and occupy the central part of chiasma opticum; the uncrossed fibres originate from the lateral parts of retina and occupy the lateral part of chiasma opticum. Chiasma opticum continues into tractus opticus (2), which runs backward and contains fibres from both eyes. Tractus opticus reaches the subcortical visual centers – the 4th neurons of the optic pathway: – nucleus corporis geniculati lateralis, – stratum griseum colliculi superioris. The optic pathway continues from subcortical center nucleus corporis geniculati lateralis. The axons of the 4th neurons form radiatio optica and run through capsula interna to the cortical center in sulcus calcarinus region (cuneus and gyrus occipitotemporalis medialis). There are three reflectoric visual pathways continuing from stratum griseum colliculi superioris. 1. The most part of the axons of the 4th neurons form tractus tectospinalis. At the level of tegmentum mesencephali the tract is crossed – decussatio tegmentalis posterior, then it runs through tegmentum pontis, medulla oblongata, funiculus anterior medullae spinalis to the 5th neurons – nuclei motorii of the spinal cord. Impulses along the axons of the 5th neurons run through the motor root and n. spinalis to supply the skeletal muscles. This reflectoric visual pathway is responsible for reflectory movements according to unexpected visual irritation. 2. Stratum griseum colliculi superioris is connected with fasciculus longitudinalis medialis, which is responsible for coordination of the movements of eyeball, head and neck (fasciculus longitudinalis medialis communicates the motor nuclei of the III, IV, VI and XI cranial nerves with the motor nuclei of the spinal cord). 3. Stratum griseum colliculi superioris is connected with nuclei vegetativi n. oculomotorii. 2 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves Axons of vegetative nuclei are parasympathetic preganglionic fibres and they reach ganglion ciliare. After synapsing in ganglion ciliare parasympathetic postganglionic fibres run to supply smooth muscles of the eyeball – m. sphincter pupillae et m. ciliaris. This reflectoric visual pathway provides light reflex (the narrowing of the pupil) and accomodation. III N. OCULOMOTORIUS N. oculomotorius is mixed nerve. It contains motor and vegetative parasympathetic fibres. It has two nuclei in tegmentum mesencephali at the level of colliculi superiores: – nucleus n. oculomotorii (motor nucleus), – nuclei accessorii n. oculomotorii (parasympathetic vegetative nucleus). The nerve emerges at sulcus oculomotorius mesencephali. Then it extends through the lateral wall of sinus cavernosus, enters the optic cavity via fissura orbitalis superior and divides into two branches: 1. ramus superior contains motor fibres and supplies m. rectus superior, m. levator palpebrae superioris; 2. ramus inferior contains motor and vegetative fibres; motor fibres supply m. rectus inferior, m. rectus medialis, m. obliquus inferior. The vegetative (parasympathetic preganglionic) fibres leave the branch via radix oculomotoria and reach ganglion ciliare; after synapsing the parasympathetic postganglionic fibres run to supply smooth muscles of the eyeball – m. sphincter pupillae et m. ciliaris. IV N. TROCHLEARIS N. trochlearis is motor nerve. It has motor nucleus – nucleus n. trochelaris in tegmentum mesencephali at the level of colliculi inferiores. The nerve emerges on the dorsal side of mesencephalon – on lamina tecti, laterally to frenulum veli medullaris superioris. Then it curves around pedunculi cerebri, passes forward in the lateral wall of sinus cavernosus and enters the orbita through fissura orbitalis superior. N. trochlearis supplies m. obliquus superior. V N. TRIGEMINUS N. trigeminus is mixed nerve – it contains motor and sensory fibres. The nerve has four nuclei in fossa rhomboidea upper part: – nucleus principalis n. trigemini (sensory nucleus), – nucleus mesencephalicus n. trigemini (sensory nucleus), – nucleus spinalis n. trigemini (sensory nucleus), – nucleus motorius n. trigemini (motor nucleus). The nerve appears between pons and pedunculus cerebellaris medius; it has two roots: – radix sensoria, – radix motoria. The sensory root of the nerve forms ganglion trigeminale; the motor root lies inferiorly to the sensory root. The ganglion is surrounded by dura mater cavity – cavum trigeminale in impressio trigeminalis. The nerve splits into three parts: – n. ophthalmicus, – n. maxillaris, – n. mandibularis.  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 3 N. OPHTHALMICUS N. ophthalmicus contains the sensory fibres, passes forward in the lateral wall of sinus cavernosus and gives off ramus meningeus reccurens for tentorium cerebelli. Then n. ophthalmicus enters the optic cavity through fissura orbitalis superior and divides into three nerves: 1. n. lacrimalis – it runs along the lateral wall of the optic cavity together with a. lacrimalis and has a communicating branch with n. zygomaticus. It supplies glandula lacrimalis, conjunctiva and skin at the lateral corner of the eye and the upper eyelid; 2. n. frontalis – it runs along the upper wall of the optic cavity and gives off two branches: a) n. supratrochlearis runs through foramen (incisura) frontalis; it supplies conjunctiva, skin of the forehead, the root of the external nose, the medial corner of the eye and the upper eyelid, b) n. supraorbitalis passes through foramen (incisura) supraorbitalis and supplies skin of the forehead and the upper eyelid; 3. n. nasociliaris passes along the medial wall of the optic cavity and terminates as n. infratrochlearis, which supplies saccus lacrimalis, conjunctiva and skin at the medial corner of the eye. N. nasociliaris along its course gives off side branches: a) n. ethmoidalis posterior – it passes through foramen ethmoidale posterius and supplies the mucous membrane of the nasal cavity, cellulae ethmoidales and sinus sphenoidalis, b) n. ethmoidalis anterior – it passes through foramen ethmoidale anterius to fossa cranii anterior, where it gives off ramus meningeus to supply the meninges. Then n. ethmoidalis anterior descends through foramina cribrosa to the nasal cavity and supplies the mucous membrane of the nasal cavity, cellulae ethmoidales, sinus frontalis. The terminal part of n. ethmoidalis anterior – ramus nasalis externus – pierces the nasal bones and supplies skin of dorsum et apex nasi, c) nn. ciliares longi (2 – 4) – they run between the fibrous and vascular coats of the eye ball and supply sclera and chorioidea, d) sensory root for ganglion ciliare. N. MAXILLARIS N. maxillaris contains the sensory fibres. In fossa cranii media the nerve gives off ramus meningeus for supplying the coverings of this fossa. N. maxillaris leaves the cranial cavity through foramen rotundum and divides into the terminal branches in fossa pterygopalatina: 1. n. infraorbitalis runs through fissura orbitalis inferior to the optic cavity, passes along sulcus et canalis infraorbitalis, then through foramen infraorbitale emerges on the anterior surface of the maxilla. It supplies skin of the face between the eye and mouth openings by small branches: – rr. palpebrales inferiores – skin and conjunctiva of the lower eyelid, – rr. nasales externi – skin of the cheek and lateral surface of the nose, – rr. labiales superiores – skin of the cheek, nasal wing and upper lip. Side branches of n. infraorbitalis: a) nn. alveolares superiores anteriores (1 – 3) – they descend along the anterior wall of sinus maxillaris and supply it; they participate in formation of plexus dentalis superior to supply dentes incisivi et dens caninus, b) nn. alveolares superiores mediae (1 – 2) – they arise from the nerve in sulcus infraorbitalis, take part in formation of plexus dentalis superior and supply dentes premolares, c) nn. alveolares superiores posteriores (1 – 3) – they descend along tuber maxillae, run through foramina alveolaria and canales alveolares to form plexus dentalis superior  4 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves for supplying dentes molares and the mucous of sinus maxillaris. Plexus dentalis superior lies on arcus alveolaris maxillae, supplies the mucous of sinus maxillaris and gives off rr. dentales superiores and rr. gingivales superiores for the upper teeth and gums; 2. n. zygomaticus passes through fissura orbitalis inferior to the optic cavity, runs along its lateral wall and has communicating branch with n. lacrimalis. Then n. zygomaticus leaves the optic cavity through foramen zygomaticoorbitale and divides into two branches: a) ramus zygomaticofacialis – it emerges at the zygomatic region and supplies skin over the cheek, b) ramus zygmaticotemporalis – it supplies skin at the anterior part of the temporal region; 3. sensory root for ganglion pterygopalatinum. N. MANDIBULARIS N. mandibularis is mixed nerve. It leaves the cranial cavity through foramen ovale, enters fossa infratemporalis and divides into the branches. N. mandibularis branches could be divided into three groups – sensory, motor and mixed. Sensory branches of n. mandibularis: 1. ramus meningeus returns into the cranial cavity through foramen spinosum and supplies the meninges of fossa cranii media; 2. n. auriculotemporalis starts by 2 roots surrounding a. meningea media. The nerve runs backward and upward accompaning a. temporalis superficialis. It terminates by rr. temporales superficiales which supply skin of auricula, the posterior part of the temporal region, porus et meatus acusticus externus, membrana tympani, art. temporomandibularis and the parotid gland. N. auriculotemporalis receives vegetative parasympathetic postganglionic fibres from ganglion oticum to supply glandula parotis; 3. n. lingualis passes between m. pterygoideus medialis et lateralis and terminates in the tongue by rr. linguales. The terminal branches supply the mucous membrane of dorsum linguae from apex to sulcus terminalis and papillae filiformes. The beginning part of n. lingualis has communication with chorda tympani (n. intermedius) and receives from it sensory and parasympathetic preganglionic fibres. N. lingualis has side branches: a) n. sublingualis supplies mucous membrane of the mouth cavity and gums, b) sensory root for ganglion submandibulare; 4. n. buccalis runs between m. masseter and m. buccinator; it supplies skin of the cheek and angulus oris and mucous membrane lining the inner surface of the cheek; 5. sensory root for ganglion oticum. Motor branches of n. mandibularis (for muscles – derivates of the 1st visceral arch): 1. n. massetericus – m. masseter; 2. nn. temporales profundi – m. temporalis; 3. n. pterygoideus medialis – m. pterygoideus medialis; 4. n. pterygoideus lateralis – m. pterygoideus lateralis; 5. n. musculi tensoris veli palatini – m. tensor veli palatini; 6. n. musculi tensoris tympani – m. tensor tympani. Mixed branch of n. mandibularis: 1. n. alveolaris inferior descends through foramen mandibulae into canalis mandibulae; it emerges through foramen mentale as n. mentalis to supply skin at the region of the chin and lower lip. In canalis mandibulae the nerve forms plexus dentalis inferior, from which arise rr. dentales inferiores and rr. gingivales inferiores for the lower teeth and gums. N. alveolaris inferior before foramen mandibulae gives off the only muscular branch – n. mylohyoideus – it runs along sulcus mylohyoideus and supplies muscles – derivates of the  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 5 1st visceral arch on the neck – m. mylohyoideus, venter anterior m. digastrici. VI N. ABDUCENS N. abducens is motor nerve. It has nucleus n. abducentis in the upper part of fossa rhomboidea below colliculus facialis. The nerve appears on the ventral surface of medulla oblongata between pons and pyramis. It passes in composition of sinus cavernosus, leaves sinus at processus clinoideus anterior and enters the optic cavity through fissura orbitalis superior. It supplies m. rectus lateralis. VII N. FACIALIS N. facialis contains motor fibres and mixed nerve – n. intermedius. The motor fibres of n. facialis supply mimetic muscles – derivates of the 2nd visceral arch; it has nucleus n. facialis in the upper part of fossa rhomboidea. The nerve emerges between pons and oliva. It runs forward to porus acusticus internus, passes through meatus acusticus internus to canalis nervi facialis and exits from the canal through foramen stylomastoideum. Then the nerve goes to the substance of the parotid gland and forms plexus intraparotideus. From the plexus arise the following branches: 1. rr. temporales supply muscles around auricula (m. auricularis anterior, m. auricularis superior), venter frontalis m. occipitofrontalis, m. orbicularis oculi, m. corrugator supercilii; 2. rr. zygomatici supply m. orbicularis oculi, mm. zygomatici; 3. rr. buccales supply mm. zygomatici, m. levator labii superioris, m. levator anguli oris, m. risorius, m. buccinator, m. orbicularis oris, m. nasalis; 4. r. marginalis mandibulae supplies m. depressor labii inferioris, m. depressor anguli oris, m. mentalis; 5. r. colli supplies platysma. N. facialis side branches: 1. n. stapedius – it arises at the descending part of canalis nervi facialis, runs to the tympanic cavity and supplies m. stapedius; 2. n. auricularis posterior – it starts from n. facialis below foramen stylomastoideum and divides into 2 branches: r. auricularis supplies m. auricularis posterior, r. occipitalis supplies venter occipitalis m. occipitofrontalis; 1. r. digastricus starts from the nerve below foramen stylomastoideum and supplies venter posterior m. digastrici and m. stylohyoideus. N. INTERMEDIUS N. intermedius is part of n. facialis. It has 2 nuclei: – nucleus salivatorius superior (parasympathetic vegetative nucleus) – lies in fossa rhomboidea above striae medullares, – nucleus tractus solitarii (sensory nucleus) – lies in fossa rhomboidea below striae medullares. The nerve appears on the ventral surface of the brain between pons and medulla oblongata laterally from motor fibres of n. facialis. N. intermedius passes through porus et meatus acusticus internus together with n. facialis. At the first curve of canalis nervi facialis the nerve has sensory ganglion – ganglion geniculi. Below it the nerve divides into two branches: 1. n. petrosus major contains parasympathetic preganglionic fibres; it leaves canalis nervi facialis through hiatus canalis n. petrosi majoris, enters fossa cranii media, then it pierces cartilage of foramen lacerum, leaves the cranial cavity and through canalis pterygoideus reaches fossa pterygopalatina. The nerve forms parasympathetic root for ganglion pterygopalatinum;  6 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 2. chorda tympani contains sensory and parasympathetic preganglionic fibres. It leaves canalis nervi facialis through canaliculus chordae tympani, passes through the tympanic cavity, lies between malleus and incus, then through fissura petrotympanica leaves it. Further chorda tympani travels together with n. lingualis; sensory fibres continue to the tongue for supplying papillae fungiformes et papillae foliatae. Parasympathetic preganglionic fibres run to ganglion submandibulare and form the parasympathetic root for it. VIII N. VESTIBULOCOCHLEARIS N. vestibulocochlearis is sensory nerve which consists of two portions: – nervus cochlearis, – nervus vestibularis. N. cochlearis takes part in formation of the auditory pathway. The 1st neurons of the pathway are in ganglion spirale of the internal ear; their dendrits start by the hearing receptors – organon Corti, their axons form n. cochlearis. N. cochlearis passes along meatus et porus acusticus internus to the cranial cavity, joins with n. vestibularis to form n. vestibulocochlearis. The nerve enters the brain between pons and medulla oblongata and runs to nuclei cochleares – the 2nd neurons of the auditory pathway. From nuclei cochleares the most part of the axons go to the opposite side and synapse with nuclei corporis trapezoidei. The other part of axons are not crossed and synapse with nuclei corporis trapezoidei on the same side. The axons of nuclei corporis trapezoidei form lemniscus lateralis, which ascends through tegmentum mesencephali and terminates in subcortical centers of the hearing – colliculus inferior and corpus geniculatum mediale (the 4th neurons of the pathway). The auditory pathway continues from the subcortical centers as radiatio acustica and through capsula interna reaches the cortical center in gyrus temporalis superior. The reflectoric auditory pathway communicates subcortical center in colliculus inferior with stratum griseum colliculi superioris, is crossed in tegmentum mesencephali (decussatio tegmentalis posterior) and descends as tractus tectospinalis. This reflectoric auditory pathway is responsible for reflectory movements according to unexpected hearing irritation. N. vestibularis is part of the balance pathway; it originates by the balance receptors (macula sacculi, macula utriculi, cristae ampullares) in the internal ear. The 1st neurons are in ganglion vestibulare, which lies in meatus acusticus internus; the axons of the 1st neurons form n. vestibularis. It runs along meatus et porus acusticus internus and joins with n. cochlearis to form n. vestibulocochlearis. The nerve enters the brainstem between pons and medulla oblongata and terminates by synapsing with nuclei vestibulares in fossa rhomboidea – the 2nd neurons of the balance pathway. The axons of the 2nd neurons run to nuclei motorii medullae spinalis (tractus vestibulospinalis), to nucleus olivaris (tractus vestibuloolivaris), join with fasciculus longitudinalis medialis, run to cerebellum (tractus vestibulocerebellaris) and to cortex cerebri. Nucleus olivaris is communicated with cerebellum by tractus olivocerebellaris and with nuclei motorii medullae spinalis by tractus olivospinalis. IX N. GLOSSOPHARYNGEUS N. glossopharyngeus is mixed nerve which contains sensory, motor and parasympathetic vegetative fibres. It has three nuclei in fossa rhomboidea: – nucleus ambiguus (motor nucleus), – nucleus tractus solitarii (sensory nucleus), – nucleus salivatorius inferior (parasympathetic vegetative nucleus). The nerve appears at sulcus posterolateralis medullae oblongatae and leaves the cranial cavity  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 7 through foramen jugulare. Above and below the opening there are two sensory ganglions – ganglion superius and ganglion inferius. The nerve descends behind a. carotis interna, then – between the artery and v. jugularis interna. Then it runs to the tongue and distributes into the terminal branches – rr. linguales, which supply the mucous membrane of radix lingue till epiglottis (except vallecula epiglottica) and papillae vallatae. N. glossopharyngeus gives off side branches: 1. n. tympanicus contains sensory and parasympathetic preganglionic fibres; it arises at the level of ganglion inferius, passes into canaliculus tympanicus and forms plexus tympanicus in the tympanic cavity. The plexus is formed also by sympathetic fibres – nn. caroticotympanici from the sympathetic plexus – plexus caroticus internus. Plexus tympanicus supplies cavitas tympani, tuba auditiva, cellulae mastoideae. N. tympanicus terminal part is n. petrosus minor; it contains parasympathetic preganglionic fibres, leaves the tympanic cavity through hiatus canalis n. petrosi minoris, enters fossa cranii media, then goes through foramen lacerum and terminates in ganglion oticum; 2. r. musculi stylopharyngei is motor branch, it supplies m. stylopharyngeus; 3. rr. pharyngei (2 – 3) are sensory branches, they reach the pharynx and together with the branches of n. vagus and sympathetic fibres of truncus sympathicus form plexus pharyngeus. Rr. pharyngei of the IX cranial nerve supply mucous membrane in the upper part of the pharynx; 4. rr. tonsillares (2 – 3) – they are sensory fibres for supplying tonsilla palatina, arcus palatoglossus and arcus palatopharyngeus; 5. r. sinus carotici descends to the hemoreceptors of sinus caroticus and glomus caroticum to participate in regulation of the blood pressure. X N. VAGUS N. vagus is mixed nerve which contains sensory, motor and parasympathetic vegetative fibres. It has three nuclei located in fossa rhomboidea: – nucleus ambiguus (motor nucleus), – nucleus tractus solitarii (sensory nucleus), – nucleus dorsalis n. vagi (parasympathetic vegetative nucleus). N. vagus emerges at sulcus posterolateralis medullae oblongatae. It passes through foramen jugulare and has two sensory ganglions: one is above foramen jugulare – ganglion superius, the other is below foramen jugulare – ganglion inferius. N. vagus descends along the lateral side of the neck. In the upper part of the neck it lies together with a. carotis interna and v. jugularis interna, in the lower part – with a. carotis communis and v. jugularis interna. Then the nerve enters the thoracic cavity through apertura thoracis superior. The course of the nerve differs on the right and left sides of the body. On the righ side n. vagus crosses a. subclavia, descends along the trachea, lies posteriorly to radix pulmonis, approachs the posterior surface of the oesophagus and together with the nerve of opposite side forms plexus oesophageus. On the left side n. vagus passes between a. carotis communis, a. subclavia and v. brachiocephalica. It crosses arcus aortae, then descends behind radix pulmonis, approaches the anterior surface of the oesophagus and together with the nerve of opposite side forms plexus oesophageus. Fibres of plexus oesophageus are arranged into two trunks: – truncus vagalis anterior; – truncus vagalis posterior. The trunks along the anterior and posterior surfaces of the oesophagus pass through the diaphragm (hiatus oesophageus) and distribute to the anterior and posterior walls of the 8 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves stomach – plexus gastricus anterior et posterior, then the fibres of n. vagus run to plexus coeliacus. There are side branches arising from the vagus nerve: 1. ramus meningeus – it contains sensory fibres, starts at the level of ganglion superius, passes through foramen jugulare, returns in the cranial cavity, supplies the meninges of fossa cranii posterior, 2. ramus auricularis – it contains sensory fibres, starts at the level of ganglion superius, supplies skin of the posterior part of auricula and meatus acusticus externus. Between ganglion superius and ganglion inferius to the X cranial nerve joins ramus internus of n. accessorius, which is running to supply muscles of the pharynx, the palatum (except m. tensor veli palatini), the larynx. 3. rr. pharyngei they start at the level of ganglion inferius and contain sensory, motor and parasympathetic vegetative fibres; rr. pharyngei reach the pharynx and together with the branches of n. glossopharyngeus and sympathetic fibres of truncus sympathicus form plexus pharyngeus. Rr. pharyngei of the X nerve supply mucous membrane in the lower part of the pharynx, muscles of the palate (except m. tensor veli palatini), muscles of the pharynx (except m. stylopharyngeus); 4. n. laryngeus superior starts at the level of ganglion inferius and contains sensory, motor and parasympathetic vegetative fibres; it descends along the pharynx and divides into two branches: a) ramus externus – it contains motor fibres and supplies m. cricothyreoideus, b) ramus internus – it contains sensory and parasympathetic fibres; the branch descends along membrana thyreohyoidea, pierces it and supplies the mucous membrane of the larynx from aditus laryngis to plicae vocales, mucous membrane of recessus piriformis and vallecula epiglottica in the tongue. Ramus internus gives small branches to glandula thyroidea and glandula parathyroidea; 5. rr. cardiaci cervicales superiores et inferiores contain sensory and parasympathetic preganglionic fibres; they run along a. carotis communis together with sympathetic fibres of truncus sympathicus to supply the heart; 6. n. laryngeus recurrens contains sensory, motor and parasympathetic fibres; at the right side it originates at the level of a. subclavia, at the left side – below arcus aortae. The nerve ascends between the trachea and the oesophagus and terminates as n. laryngeus inferior, which supplies the mucous membrane of the larynx from plicae vocales to the trachea. It supplies together with n. accessorius muscles of the larynx (except m. cricothyreoideus) and also glandula thyroidea, glandula parathyroidea. It gives off side branches: a) rr. tracheales contain sensory and parasympathetic fibres, they supply mucous membrane, glands and smooth muscular tissue of the trachea, b) rr. oesophagei contain motor, sensory and parasympathetic fibres; they supply the upper third of the esophagus – the mucous membrane, glands and striated muscular tissue. 7. rr. cardiaci thoracici – contain sensory and parasympathetic fibres and supply the heart; 8. rr. bronchiales – they pass along radix pulmonis to the lung and form plexus pulmonalis, which supplies the mucous membrane, glands and smooth muscular tissue of the bronchi and lungs and also pleura visceralis s. pulmonalis; 9. rr. oesophagei start from plexus oesophageus; they supply the mucous membrane, glands and smooth muscular tissue of the oesophagus. In the abdominal cavity the vagus nerve contains sensory and parasympathetic preganglionic fibres and is formed by two trunks – truncus vagalis anterior and truncus vagalis posterior: 1. truncus vagalis anterior passes along anterior surface of the oesophagus and curvatura minor to the anterior surface of the stomach; it gives off two groups of branches: a) rr. gastrici anteriores – they form plexus gastricus anterior to supply the stomach,  RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves 9 b) rr. hepatici – they supply the liver and omentum minus; 2. truncus vagalis posterior passes along posterior surface of the oesophagus to the posterior wall of the stomach. There are four groups of branches arising from it: a) rr. gastrici posteriores – they form plexus gastricus posterior to supply the stomach, b) rr. renales supply the kidneys, c) rr. hepatici supply the liver and the bile pathway, d) rr. coeliaci pass to plexus coeliacus; via plexus coeliacus the parasymphatic preganglionic fibres of truncus vagalis posterior run to the most part of the organs of abdominal cavity. XI N. ACCESSORIUS N. accessorius is motor nerve. It has two motor nuclei: – nucleus spinalis n. accessorii – it lies in the 6 upper segments of the spinal cord between the anterior and posterior horns of the grey matter, – nucleus ambiguus – in fossa rhomboidea. The nerve consists of two parts: 1. From nucleus ambiguus fibres appear on sulcus posterolateralis medulae oblongatae by radices craniales; 2. From nucleus spinalis n. accessorii fibres appear on sulcus posterolateralis medullae spinalis by radices spinales; they ascend along the spinal cord, enter the cranial cavity via foramen magnum and join with radices craniales to form a single trunk of the nerve – truncus nervi accessorii. The nerve leaves the cranial cavity through foramen jugulare and splits into two branches: 1. ramus externus supplies m. sternocleidomastoideus, m. trapezius, 2. ramus internus travels with n. vagus (rr. pharyngei and n. laryngeus reccurens) to supply muscles of the pharynx, the palate (except m. tensor veli palatini) and the larynx. XII N. HYPOGLOSSUS N. hypoglossus is motor nerve. It has nucleus n. hypoglossi (motor nucleus) in fossa rhomboidea. The nerve emerges at sulcus anterolateralis medullae oblongatae. It leaves the cranial cavity through canalis nervi hypoglossi. Then n. hypoglossus runs between a. carotis interna and v. jugularis interna, turns anteriorly, passes through trigonum submandibulare, reaches the tongue and terminates as rr. linguales to supply the muscles of the tongue. To the XII nerve join motor fibres of the ventral branches of the 1st and 2nd cervical spinal nerves. Some of those fibres leave the XII nerve via radix superior to join with radix inferior and form ansa cervicalis (plexus cervicalis). The other part of those fibres travel via n. hypoglossus to supply m. geniohyoideus. PARASYMPATHETIC GANGLIA OF THE HEAD Parasympathetic ganglia of the head belong to the peripheral part of parasympathetic autonomic nervous system.. They supply smooth muscles and glands of the head. Each ganglion is formed by parasympathetic cells; preganglionic fibres from the centers reach the ganglions and synapse to postganglionic fibres. Through the ganglions pass sympathetic postganglionic fibres and sensory fibres: sympathetic fibres are efferent, sensory fibres – afferent. Sensory fibres transmit irritation of interoreceptors from the organs to the centers, they are 10 RSU Institute of Anatomy and Anthropology Peripheral nervous system, part I, cranial nerves branches of n. trigeminus and therefore the ganglions lie close to this cranial nerve. Each ganglion has three roots: radix parasympathica, radix sympathica, radix sensoria. Each ganglion gives off branches containing all three groups of fibres to supply smooth muscles and glands. There are four ganglions: ganglion ciliare, ganglion pterygopalatinum, ganglion submandibulare, ganglion oticum. Ganglion ciliare lies in the optic cavity, laterally to n. opticus. It has three roots: 1. radix parasympathica is formed by radix oculomotoria (n. oculomotorius); 2. radix sympathica is formed by sympathetic postganglionic fibres from the plexus surrounding a. ophthalmica; 3. radix sensoria is formed by sensory fibres of n. nasociliaris. The ganglion gives off branches – nn. ciliares breves; parasympathetic fibres of the nerves supply m. sphincter pupillae and m. ciliaris, sympathetic fibres – m. dilatator pupillae, sensory fibres – external and middle layers of the eyeball. Ganglion pterygopalatinum lies in fossa pterygopalatina. It has three roots: 1. radix parasympathica is formed by n. petrosus major (n. intermedius); 2. radix sympathica is formed by n. petrosus profundus – sympathetic postganglionic fibres are running from plexus caroticus internus surrounding a. carotis interna; 3. radix sensoria is formed by sensory root of n. maxillaris. N. petrosus major and n. petrosus profundus reach the fossa via canalis pterygoideus and both together form n. canalis pterygoidei. The ganglion gives off three groups of nerves: a) nn. palatini descend through canalis palatinus major to the palate and supply the mucosa of the hard and soft palate and glandulae palatinae; b) rr. nasales posteriores run through foramen sphenopalatinum to the nasal cavity and supply the mucosa of cavitas nasi, sinus sphenoidalis and glandulae nasales. One of the branches is longer – n. nasopalatinus; it runs forward along the nasal sept, descends into the oral cavity through foramen incisivum and supplies mucosa of the hard palate; c) some postganglionic parasympathetic fibres join n. zygomaticus and then via communicating branch with n. lacrimalis reach glandula lacrimalis to supply it. Ganglion submandibulare lies below n. lingualis close to the medial surface of glandula sublingualis. It has three roots: 1. radix parasympathica is formed by parasympathetic preganglionic fibres of chorda tympani, which travels to the ganglion with n. lingualis; 2. radix sympathica is formed by sympathetic postganglionic fibres from the plexus surrounding a. facialis; 3. radix sensoria is formed by n. lingualis. The ganglion gives off branches – rr. glandulares to supply glandula submandibularis and glandula sublingualis. Ganglion oticum lies below foramen ovale in fossa infratemporalis. It has three roots: 1. radix parasympathica is formed by n. petrosus minor (n. glossopharyngeus); 2. radix sympathica is formed by sympathetic postganglionic fibres from the plexus surrounding a. meningea media; 3. radix sensoria is formed by sensory fibres of n. mandibularis. The ganglion gives off branches – rr. anastomotici; they travel together with n. auriculotemporalis, then leave it and via rr. parotidei reach the parotid gland to supply it.  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part 1 AUTONOMIC PART OF THE PERIPHERAL NERVOUS SYSTEM The autonomic (vegetative) part of the nervous system regulates the body functions which are not under control of the will – regulation of the respiratory, alimentary and reproductive functions. The autonomic nervous system supplies by nerves in terms of tissues – smooth muscles, cardiac muscle and glandular epithelium; in terms of organs – the heart, blood vessels, iris, ciliary body, hair muscles, internal organs and the glands. The autonomic nervous system has two anatomically separate parts with opposite, antagonistic physiological effects: 1. sympathetic part – pars sympathica; 2. parasympathetic part – pars parasympathica. The sympathetic nervous system determins acceleration of the heart beat and respiratory frequency, narrowing of the diameter of the blood vessels, elevation of the blood pressure, dilatation of the pupilla, increasing of perspiration etc. The parasympathetic nervous system determins slowing of the heart beat and respiratory frequency, dilatation of the diameter of the blood vessels, etc. The sympathetic nervous system helps body in stress and emergency situation, the parasympathetic nervous system serves building up reserves. The sympathetic nervous system has prevalance upon the parasympathetic nervous system during the daytime and also in childhood. Both – sympathetic and parasympathetic nervous systems have centers and peripheral parts. Sympathetic part Parasympathetic part Lower center: Lower centers: 1. nucleus intermediolateralis (from the 1. in mesencephalon: 8th cervical to the 2nd lumbar − nuclei accessorii nervi oculomotorii segments of the spinal cord) 2. in brain stem: – nucleus salivatorius superior – nucleus salivatorius inferior – nucleus dorsalis nervi vagi 3. in medulla spinalis: – nuclei parasympathici sacrales (the 2nd, 3rd, 4th sacral segments of the spinal cord) Peripheral part: Peripheral part: − ganglia paravertebralia – ganglia terminalia/intramuralia − ganglia prevertebralia – parasympathetic fibres of the III, IX, X, XIII − rami communicantes albi cranial nerves − rami communicantes grisei – parasympathetic fibres of the 2nd, 3rd, 4th sacral spinal nerves The autonomic nervous system functions on the reflex arch principle just as the voluntary system does. The autonomic nervous system has some different features to compare with the somatic nervous system: – scattered centers; – numerous ganglia and plexus; – efferent part of the reflex arch consists of 2 neurons; synapse is located in the ganglia, because of what there must be distinguished preganglionic and postganglionic fibres. 2 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part HIGHER CENTERS OF THE AUTONOMIC NERVOUS SYSTEM The sympathetic and parasympathetic parts of the autonomic nervous system are coordinated by the following higher centers. Formatio reticularis is the system to which information converges from all parts of the central nervous system and is projected back to all regions, modulating their activities. The reticular formation influences the activation of the brain (excitatory and inhibitory). Groups of cells regulate respiration, heartbeat and blood pressure. Hypothalamus is the highest integration center for the autonomic nervous system. Tracts extend from it to the lower centers of parasympathetic and sympathetic nervous systems and simultaneously could stimulate or inhibit few or many lower autonomic centers. It regulates the autonomic nervous system via hormone production: regulates blood pressure, heart rate, hunger, thirst, sexual arousal, sleep/wake cycle. Limbic system (emotional brain) receives impulses from the reticular formation of brainstem and by different pathways it influences activity of the cortex and the hypothalamus. It regulates emotions of the person by different expressions and vegetative reactions. The limbic system consists of hippocampus that lies in the temporal lobe and could be seen in the inferior horn of the lateral ventricle (required for the formation of long-term memories), corpus amygdaloideum (performs a primary role in the processing and memory of emotional reactions), gyrus parahippocampalis (plays a role in the formation of spatial memory), gyrus cinguli (regulates the heart rate and blood pressure), fornix (caries signals from hippocampus to the mamillary bodies), nucleus anterior thalami (connections with the cerebral cortex) and hypothalamus. Some additional structures are sometimes also considered to be part of the limbic system: mamillary bodies, pituitary gland, gyrus fornicatus and the olfactory bulb. The limbic system coordinates actions of autonomic nervous system and endocrine system; it regulates emotions of the person by different expressions and vegetative reactions. PARASYMPATHETIC PART The parasympathetic part is characterized by scattered lower centers (the 2nd neurons of reflex arch) in different parts of the central nervous system, preganglionic fibres are rather long, travel as content of the III, VII, IX, X cranial nerves and the 2nd, 3rd, 4th sacral spinal nerves. The parasympathetic ganglia (the 3nd neurons of reflex arch) have different location. Ganglia terminalia (ganglion ciliare, ganglion submandibulare, ganglion pterygopalatinum, ganglion oticum) are ganglia of the head, they are situated near the organs they supply. In the other parts of the body ganglia lie in the walls of organs they supply – ganglia intramuralia. Therefore postganglionic fibres are shorter than preganglionic one. The action of the parasympathetic part of autonomic nervous system is provided by reflex arch, which consists of three neurons – one afferent and two efferent neurons (preganglionic and postganglionic neurons). Pathway of parasympathetic fibres from the centers to the supplying organs. 1. From nuclei accessorii nervi oculomotorii preganglionic fibres in content of n. oculomotorius run to the terminal ganglion – ganglion ciliare, after synapsing postganglionic fibres in content of rr. ciliares breves (15 – 20) reach the eyeball and supply the smooth muscles of it – m. ciliaris et m. sphincter pupillae. 2. From nucleus salivatorius superior preganglionic fibres at first run in content of n. intermedius and then into two directions: a) in content of n. petrosus major to the terminal ganglion – ganglion pterygopalatinum, after synapsing postganglionic fibres pass into three directions:  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part 3 – in content of nn. nasales posteriores to supply the glands of the nasal cavity, – in content of nn. palatini to supply glandulae palatinae, – travel with n. zygomaticus and n. lacrimalis to supply glandula lacrimalis; b) in content of chorda tympani to the terminal ganglion – ganglion submandibulare, after synapsing postganglionic fibres pass as rr. glandulares to supply glandula submandibularis et glandula sublingualis. 3. From nucleus salivatorius inferior preganglionic fibres at first run in content of n. glossopharyngeus, then n. tympanicus to the tympanic cavity to form plexus tympanicus, then as n. petrosus minor to the terminal ganglion – ganglion oticum; after synapsing postganglionic fibres in content of n. auriculotemporalis reach glandula parotis to sypply it. 4. From nucleus dorsalis nervi vagi preganglionic fibres run in content of n. vagus. In the region of the head, neck and thoracic cavity parasympathetic fibres reach the organs by n. vagus branches and synapse with parasympathetic cells of the intramural ganglia directly in the walls of the organs. Postganglionic fibres are very short and supply larynx, cor, pulmo, etc. In the abdominal cavity preganglionic fibres as content of the X cranial nerve run to the intramural ganglia directly for supplying some organs – such as gaster, hepar, vesica fellae, renes. But mostly preganglionic fibres in the abdominal cavity reach the plexus – plexus coeliacus and then via the secundary plexus (together with sympathetic fibres) run to intramural ganglia to supply: – the paired organs of the abdominal cavity (glandula suprarenalis, ren, ureter, testis, ovarium), – the organs of digestive system till the left third of colon transversum, – splen. 5. From nuclei parasympathici laterales preganglionic fibres run in content of motor root and nervus spinalis of the 2nd, 3rd, and 4th sacral spinal nerves, then via rr. ventrales reach the somatic plexus – plexus sacralis. Then preganglionic fibres via pelvic splanchnic nerves travel to plexus hypogastricus inferior and reach (together with sympathetic fibres) the organs to synapse to postganglionic fibres in ganglia pelvica to supply the urinary system and genitalia of the pelvic cavity, and some organs of digestive system: rectum, colon sigmoideum, colon descendens. SYMPATHETIC PART The sympathetic part is characterized by lower center represented in thoracolumbar part of the spinal cord. Sympathetc ganglia are two kinds – paravertebral and prevertebral. Due to location of the ganglia preganglionic fibres are shorter to compare with postganglionic one. Postganglionic fibres are represented like sympathetic nerves and travel along the blood vessels forming plexuses. The reflex arch of sympathetic part of autonomic nervous system is circuit of three neurons – one afferent and two efferent neurons (preganglionic and postganglionic neurons). Pathway of sympathetic fibres from the center for supplying the organs. From the lower center – nucleus intermediolateralis the preganglionic fibres run in content of motor root, nervus spinalis and ramus communicans albus to the ganglia of peripheral part – ganglia paravertebralia et ganglia prevertebralia – containing the sympathetic cells. After synapsing in ganglia postganglionic fibres reach the organs and vessels to supply them. 4 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part Ganglia paravertebralia Ganglia paravertebralia contain sympathetic cells, lie along the vertebral column – ganglia trunci sympathici – and are joined by rami interganglionares into sympathetic trunk – truncus sympathicus dexter et sinister. Every trunk contains aproximately 25 ganglia: superior cervical ganglion, middle cervical ganglion, inferior cervical ganglion, 12 thoracic ganglia, 4 – 5 lumbar ganglia, 4 – 5 sacral ganglia and one impar ganglion (at the place of convergence of both sympathetic trunks). The paravertebral ganglia receive preganglionic fibres from the center – nucleus intermediolateralis through r. ventralis, n. spinalis and ramus communicans albus. Rami communicantes albi are present only in thoracolumbar part of the sympathetic trunk for direct communication with the center. After reaching the paravertebral ganglia the pathway of sympathetic fibres could be different: 1. usually fibres synapse with the parasympathetic cells of the nearest ganglion and transform into postganglionic fibres; 2. some fibres without synapsing in the nearest ganglion via rr. interganglionares could ascend to the cervical ganglia to synapse there; 3. some fibres without synapsing in the nearest ganglia via rr. interganglionares could descend to the lower lumbar, sacral and coccygeal ganglia and synapse in them; 4. some fibres of the thoracic region without synapsing leave the ganglia as nn. splanchnici, run to the paravertebral ganglia and synapse in them. Each ganglion of the sympathetic trunk gives off branches: 1. ramus communicans griseus – via this branch fibres return into content of n. spinalis to reach the skin (for supplying vessels, sweat glands and m. arrector pili) and also skeletal muscles (to maintain trophic and tone); it means that all ventral and dorsal spinal branches receive also sympathetic fibres; 2. ramus vascularis run to form the plexus around blood vessels and supply them; 3. ramus visceralis run to form the plexus around inner organs and supply them. Different features of rami communicantes Ramus communicans albus Ramus communicans griseus 1. is myelinated 1. is non-myelinated 2. contains preganglionic fibres directed 2. contains postganglionic fibres directed from the nerve to the ganglion from the ganglion to the nerve 3. are present only in thoracic and upper 3. are present all along the sympathetic three lumbar segments of the spinal cord trunk Ganglia cervicalia lie on lamina prevertebralis of the neck fascia and are covered by blood vessels and nerves; they receive sympathetic preganglionic fibres via rami interganglionares from the center in upper thoracic segments of the spinal cord. Ganglion cervicale superius lies below basis cranii at the level of the 2nd – 3rd cervical vertebra; it has: 1. rami vasulares – they supply vessels of the head and neck; the main important of them are: a) n. caroticus internus – it forms plexus caroticus internus, which follows all branches of the artery; there are some particular structures of the plexus: – fibres traveling along a. ophthalmica form radix sympathica ganglii ciliaris to supply through the ganglion m. dilatator pupillae, – n. petrosus profundus – it forms radix sympathica ganglii pterygopalatini and through the ganglion supplies glandulae nasales and glandulae palatinae, – nn. caroticotympanici, which run to plexus tympanicus to supply cavitas tympani, tuba auditiva, cellulae mastoideae,  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part 5 b) nn. carotici externi form plexus caroticus externus; the plexus extend along the branches of the artery; some sympathetic fibres of plexus form radix sympathica ganglii otici to supply glandula parotis and radix sympathica ganglii submandibularis to supply glandula submandibularis et sublingualis, c) n. jugularis; 2. rr. viscerales a) rr. laryngopharyngei, b) n. cardiacus cervicalis superior descends to form plexus cardiacus; Ganglion cervicale medium sometimes could be absent; it has: 1. n. cardiacus cervicalis medius – it descends to form plexus cardiacus; Ganglion cervicale inferius usually fuses with the upper thoracic ganglion to form ganglion cervicothoracicum s. ganglion stellatum. Interganglionic fibres between this and the previous ganglion surround a. subclavia to form ansa subclavia. The ganglion has: 1. rami vasulares: a) plexus subclavius, b) n. vertebralis forms plexus vertebralis; 2. rami viscerales: a) n. cardiacus cervicalis inferior; 3. fibres to n. phrenicus; Ganglia thoracica lie in front of caput costae, are covered by fascia endothoracica and pleura mediastinalis. They give off: 1. rr. vasculares for plexus aorticus thoracicus to supply aorta, vasa intercostalia, vena azygos et v. hemiazygos; 2. rr. viscerales form a) rr. cardiaci thoracici; rr. cardiaci thoracici and n. cardiacus cervicalis superior, medius et inferior together with rr. cardiaci cervicales superiores et inferiores of the X cranial nerve form plexus cardiacus; the cardiac plexus could be divided into plexus cardiacus superficialis (in the lower part of arcus aortae) et profundus (in the posterior part of arcus aortae); the cardiac plexus spreads along the coronary arteries as plexus coronarius dexter et sinister to supply all parts and layers of the heart, b) rr. pulmonales – they run to the bronchi and lungs to form plexus pulmonalis; c) rr. oesophageales they run to the esophagus to form plexus oesophageus, to ductus thoracicus – as plexus thoracicus, c) n. splanchnicus major – formed by fibres of the 6th to 9th thoracic ganglions, d) n. splanchnicus minor – formed by fibres of the 10th and 11th thoracic ganglions, e) n. splanchnicus imus – inconstant, formed by fibres of the 12th thoracic ganglion and run to form plexus renalis. N. splanchnicus major et minor are formed by preganglionic fibres, they travel through thoracic ganglions without synapsing and run to abdominal cavity through the diaphragm to reach the prevertebral ganglions for synapsing and take part in formation of plexus coeliacus. Ganglia lumbalia lie in front of the vertebral bodies and are covered by aorta abdominalis on the left side and by v. cava inferior on the right side. They give off: 1. rr. vasculares form plexus aorticus abdominalis; 2. rr. viscerales form nn. splanchnici lumbales for plexus coeliacus et plexus hypogastricus superior. Ganglia sacralia lie medially from foramina sacralia pelvina and both sides are connected by ganglion coccygeum. From them arise: 1. rr. vasculares – they extend along vasa pelvica; 6 RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part 2. rr. viscerales form nn. splanchnici sacrales for plexus hypogastricus inferior. Ganglia prevertebralia Ganglia prevertebralia lie in front of aorta abdominalis at the beginning parts of its branches. To them belong 6 ganglions: 1. ganglion coeliacum – paired, half – moon in shape, surrounds truncus coeliacus; both ganglions could fuse to form one single circular ganglion, 2. ganglion mesentericum superius is unpaired, lies to the right of a. mesenterica superior origin place, 3. ganglion aorticorenale is paired, it lies at the upper part of a. renalis beginning place, 4. ganglion mesentericum inferius – unpaired. PERIPHERAL AUTONOMIC PLEXUSES The peripheral autonomic plexuses usually are a collection of parasympathetic and sympathetic nerve fibres that innervate the corresponding viscera and blood vessels. PLEXUS COELIACUS Plexus coeliacus lies in front of aorta abdominalis between the 12th thoracic and the 2nd lumbar vertebras. It is contains also prevertebral sympathetic ganglia (ganglia coeliaca and ganglia aorticorenalia). It receives also preganglionic sympathetic fibres from the thoracic part of the sympathetic trunk (n. splanchnicus major at minor) and preganglionic sympathetic fibres from the lumbar ganglia of the sympathetic trunk which synapse in the prevertebral sympathetic ganglia. The parasympathetic fibres approach from the n. vagus. From plexus coeliacus arise smaller secondary plexus to the organs, they run along the blood vessels and innervate the corresponding organs (hepatic, splenic, gastric, pancreatic and suprarenal plexuses). The sympathetic fibres and parasympathetic fibres of the vagus nerve continue into the next abdominal plexuses from the coeliac plexus. PLEXUS AORTICUS ABDOMINALIS Plexus lies in front of aorta abdominalis between the 2nd and 4th lumbar vertebras. It receives fibres of coeliac plexus; it descends in front and along the sides of the aorta between the superior and inferior mesenteric plexuses. From coeliac and abdominal aortic plexuses are derived renal, ureteric, ovarian and testicular plexuses and iliac and femoral plexuses. PLEXUS MESENTERICUS SUPERIOR It is continuation of the lower part of the coeliac plexus; it receives preganglionic sympathetic fibres from the sympathetic trunk, it contains the prevertebral sympathetic ganglion (ganglion mesentericum superius) from which the postganglionic fibres start; it contains parasympathetic fibres from the vagus nerve. The plexus surrounds the superior mesenteric artery, accompanies it and divides into a number of secondary plexuses which are distributed to all parts supplied by the artery: small intestine, caecum, colon ascendens and colon transversum. PLEXUS MESENTERICUS INFERIOR It derives from the abdominal aortic plexus; ir receives sympathetic and parasympathetic fibres like the superior mesenteric plexus and contains prevertebral sympathetic ganglion (ganglion mesentericum inferius). The plexus surrounds the inferior mesenteric artery and divides into secondary plexuses, which are distributed to all the parts supplied by the artery:  RSU Institute of Anatomy and Anthropology: Peripheral nervous system, autonomic part 7 colon descendens, colon sigmoideum and upper third of the rectum. The major plexuses of the pelvic cavity are the superior and inferior hypogastric plexus. PLEXUS HYPOGASTRICUS SUPERIOR It is front of the last lumbar vertebra and the promontory of the sacrum, between the two common iliac arteries, and is formed by fibres of the abdominal aortic plexus and lumbar splanchnic nerves; it divides into two lateral portions, which travel inferiorly as the inferior hypogastric plexus. PLEXUS HYPOGASTRICUS INFERIOR S. PELVICUS It is a paired and lies in the pelvic cavity on the side of the rectum. It is formed by sympathetic fibres from the sympathetic trunk (sacral splanchnic nerves) and also receives parasympathetic fibres from nuclei parasympathici sacrales of the spinal cord (pelvic splanchnic nerves). Inferior hypogastric plexus gives off middle and inferior rectal plexus, uterovaginal, prostatic, deferential and vesical plexus, and cavernous nerves of clitoris and penis. From the inferior hypogastric plexus the parasympathetic fibres via blood vessels ascend to supply colon descendens, colon sigmoideum and upper third of the rectum.