Chapter 5 Peripheral Nervous SystemThe peripheral nervous system consists of thecord, they are divided into the 5 groups: 8 pairs ofcervical nerves,12 pairs of thoracic nerves,5 pairs onervous structures which are located outside the brainlumbar nerves, 5 pairs of sacral nerves and 1 pair ofand spinal cord. The peripheral nervous system iscomposed of nerves and ganglia. According to theircoccygeal nerves.Each spinal nerve is formed by an anterior root-origins, they are usually divided into two portions:and a posterior root which attach to the spinal cord.The cranial nerves which attach to the brain andThe anteriorroot contains motor fibers arising fromemerge out from the skull and the spinal nerves whichthe largemotorneurons inthe anteriorand lateralattach to the spinal cord and emerge out from thehorns of the gray matter.The posterior root containsvertebral canal. According to the distributions, theysensory fibers, which are the central processes of theare usually divided into the somatic nervous systempseudounipolar neurons in the spinal ganglion. Thus,which is distributed to the skin, joints, ligaments andthe spinal nerves are mixed nerves. The spinal gan-skeletal muscles etc,and the visceral nervous systemwhichglionis form an enlargement of the posterior root nearis distributed to the intemal organs.Actually the visceralthe intervertebral foramen.It contains pseudouni-nervous system is formed by visceral sensory and visceralpolar neurons which give off peripheral process-motorcomponents,the latter is called the visceral motores. The peripheral process unites with the ante-nerve, the autonomic nerve or vegetative nerve whichrior root to form the spinal nerve at the intervertebraltravels within certain spinal and cranial nerves to innervateforamen(Fig, VI-5-1),smoothmuscles,cardiacmuscleandglands.There are four types of fibers in the spinal nerves:Section 1SpinalSomatic afferentlsensorNervesfibersSpinal nerves consists of 31 pairs. According tothe regions that the nerves are attached to the spinalThey are the peripheral processes of the pseudoun-PosteriorrootSomatic sensory fiberSpinal ganglionSomaticsensoryfibeVisceral sensory fibersPosteriorbranchof spinal nVisceral motorfibersSomatic motorfibersGray communicutingbranchMuscle spindlWhite communicutingbranchGanglion of sympathetic trunkAnterior branch of spinal n.SkilVisceral organSkeletalmuscleFig. VI-5-1A diagram of the formation of spinal nerve·373-扫描全能王创建
·374·PARTVINERVOUSSYSTEMwith the sympathetic trunk.The posterior branchesipolar neurons in spinal ganglion and distributed toare generally smaller than the anterior,and the distri-the skin, skeletal muscles, tendons and articulationsbutions are segmental. The cutaneous branch from theof the trunk and limbs.They conduct the sensory in-posterior branch of the secondary cervical nerve isformation from those parts to the spinal cord.larger,which is named as the greater occipital nerveand is distributed to the occipital region..Somatic efferent(motor)fibersGenerally most of the anterior branches of thespinal nerves(except the thoracic nerves)form intri-They are axons of the somatic motor neurons incate plexus firstly,before supplying the structures ofthe anterior horn of the gray matter, innervate thethe body.The plexuses include the cervical plexus,skeletal muscles of the trunk and limbs and controlthe brachial plexus, the lumbar plexus and the sacro-the movement of the muscles.coccygeal plexus. Then many nerves arise from themand supply the definite parts of the body.The anterior3.Visceral afferent(sensory)fibbranches of thoracic nerves are separated from eachother and distributed to thethoracic and abdominalwall.They are also the peripheral processes of pseudoun-I.The Anterior Branches ofipolar neurons in spinal ganglia but distributed to thevisceral organs, cardiovascular system and glands,ThoracicNervesand transmit the sensory impulses from them to thecentralnervous system.There are twelve pairs of the thoracic nerve innumber(Fig.VI-5-2).The anterior branches of the4.Visceral efferent (motor)fibersupper eleven pairs lie in the corresponding intercostalspaces and are called the intercostal nerves, but theThesefibers arise from the visceral motor neuronslast pair lies below the twelfth rib, so it is called thein the lateral intermediate nuclei of gray matter, theysubcostal nerve.Theintercostal nerves run forwardare distributed to the smooth muscles of the visceralbetween the pleura and the internal intercostal mem-organs,cardiovascular system andglands,andcontrolbrane medial to the angles of the ribs. They then entertheir activities.the interval between the internal and external inter-All of the spinal nerves emerge out of the ver-costal muscles and traverse along the costal groove,tebral canal via the corresponding intervertebral fo-in company with the intercostal vessels and inferiorramina.However, the first cervical nerve emerges be-to them. The nerves are connected with the adjoiningtween the atlas and the occipital bone, the eighth oneganglion of the sympathetic trunk by gray and whiteemerges between the seventh cervical and the firstcommunicating branches (Fig. VI-5-1).thoracic vertebrae; the first four of the sacral nervesThe upper six intercostal nerves run toward theexitsthroughtheanteriorand posterior sacralforamsternum and terminate as the anterior cutaneousina,the fifth sacral and the coccygeal nerves emergebranches that pierce the intercotal muscles and thefrom the sacral hiatus.pectoralismajor near the sternumto supply the skinAfter leaving the intervertebral foramen, eachof the anterior thoracic wall.The lateral cutaneousspinal nerve is divided into four branches immediate-branches arise from the nerves near the costal angles,ly: @ An anterior branch which is distributed to thethey pierce the external intercostal and serratus ante-limbs and theventrolateral portion of thetrunk;②Ariormuscles,andaredivided intoanteriorandposteposterior branch supplying the structures of the pos-rior branches which are distributed to the skin of theterior region of the body. Above-mentioned branchesscapular region, the ventrolateral thoracic wall andcontain the fibers from the anterior and posteriorthe mammary gland.Their muscular branches supplyroots of the spinal cord;?Asmallmeningeal branchthe intercostal muscles and transverse thoracic mus-running back to the vertebral canal through the inter-cle(Fig. VI-5-3) .vertebral foramen and distribute to the dura mater;The lower five intercostal nerves and the subcostalone or two communicating branches, which connectnerve pass behind the costal arch and proceed forward扫描全能王创建
Chapter 5Peripheral Nervous System ·375 .into the abdominal wall between the obliquus inter-muscles, but also the transversus abdominis, obliquusnus abdominis and transversus abdominis. Then theyinternus abdominis, obliqus externus abdominis andpierce the sheathofrectus abdominis and terminate asrectus abdominis. The cutaneous branches are distrib-anterior cutaneous branches near the linea alba. Theiruted to the skin of abdominal and lower part of themuscular branches not only supply the intercostalthoracic walls(Fig. VI-5-2)T10T12Iliohypogastric n.Ilioinguinal nFig. VI-5-2 The distributions of the anterior branches of thoracic nervescriorbranchIntercostales externiIntercostales interniAnteriorbranchLateral cutaneousbrIntercostales intimiAnteriorcutaneousbrFig. VI-5-3 A diagram of a typical thoracic nerve扫描全能王创建
·376·PARTVINERVOUSSYSTEMThe distribution of the anterior branches of thethoracic nerves are segmental(Fig. VI-5-2) . On theII.The Cervical Plexuschest and anterior-lateral abdominal wall, they pres-ent approximately at thelevels as follows:1.Position and formation ofT,—the level at the sternal angleT,the level at the nipplecervical plexusTthe level at thexiphoid processTthe level between the xiphoid process and theThe cervical plexus is deep to the upper part of theumbilicussternocleidomastoid and ventrolateral to the levatorTro—the level at the umbilicusscapulae and the scalenus medius. It is formed by theTi2—the level at the anterior superior iliac spineanterior branches of the frst four cervical nerves(C,)(Fig. VI-5-4) .lypoglossaln.LeSuperior cervicalganglionoccipital n,ofsympathetictrunkGreater auricular n.Transverse n.of neoAnsacervicalisPhrenicn.Supraclavicular n.Fig. VI-5-4A diagram ofthe formation of cervical plexus and its branchesthe posterior border of the sternocleidomastoid andBranches of cervical plexusdistribute to the skin of the mastoid region.2) Great auricular nerve(C23) It runs upwardover the sternocleidomastoid to the auricle and pa-The branches of the cervical plexus may be divid-rotid gland regions, usually along with the externaled into superficial and deep groups.jugular vein. It supplies much of the external ear andskin around the auricle.(1) Superficial branches3) Transverse nerve of neck(C2.5)It winds aro-und the posterior border of the sternocleidomastoidThey emerge near the midpoint of the posteriorabout its midpoint and runs forward to reach the ante-border of the sternocleidomastoid and are describedriortriangleoftheneck.It isdistributedtothe skinofas follows:(Fig. VI-5-5).the anterior region of the neck.1) Lesser occipital nerve(C) It ascends along扫描全能王创建
Chapter 5 Peripheral Nervous System - 377 .The muscular branches supply the deep muscles4) Supraclavicular nerve(C,-)It emerge be-ofthe neck, such as the levator scapulae, scalenus andlow the transverse nerve of neck and descend in theprevertebral muscles. A part of the nerve fibers fromposterior triangle of the neck where it gives off threethe cervical plexus join together to form the inferiorbranches: the lateral, intermediate and medial supra-root of the ansa cervicalis which unites with the de-clavicular nerves which are distributed to the skin atthe upper portion of the chest, theroot of the neckscending branch of the hypoglossal nerve, to formthe ansa cervicalis. Then the ansa cervicalis gives offand the shoulder.branches to supply the omohyoid, sternohyoid, ster-(2) Deep branchesnothyroid and thyrohyoid muscles.EThe phrenic nerve arises from the third, fourth andThe deep branches of the cervical plexus includefifth cervical nerves of the cervical plexus.It passesthe muscular branches; inferior root of the ansa cervi-downward in front of the scalenus anterior to the rootcalis and the phrenic nerve(Fig. VI-5-6)Greater occipitalStermocleidomastoidLesser occipital n.Cervical br. of facial n.Greater auricular rCommunicating br.PlatismaExtermal br.of accessory nTransveerse n.of neckLateral supraclavicular n.Anterior jugular y.External jugular v.Medial supra-clavicular n.Intermedial supraclavicular n.Fig. VI-5-5 The superficial branches of cervical plexusof the neck, then descends between the subclavianartery and vein to enter the chest. Within the chest itII . Brachial Plexusdescends in front of the root of the lung, between thepericardium and the mediastinal pleura, to the dia-phragm. The phrenic nerve contains motor and sen-Position and formation of thesory fibers. The motor fibers supply the muscle of thediaphragm; the sensory fibers are distributed to thebrachial plexuspericardium, the diaphragmatic pleura and mediasti-nal pleura, and the diaphragmatic peritoneum. The sen-The brachial plexus emerge from the intervalsory fibers of the right phrenic nerve are also distributedbetween the scalenus anterior and scalenus medi-to the liver, the gallbladder and the bile duct system.us which is called the scalene fissure, then extendsoutward and downward behind themedial 2/3 of the扫描全能王创建
·378·PARTVINERVOUSSYSTEMof the trunks is divided into an anterior and a posteriorclavicle in company with the axillary artery to thedivisions. In axilla, the posterior divisions ofall threeaxilla. The brachial plexus is formed by the anteriortrunks to form the posterior cord which is behind thebranches of the four lower cervical nerves(Cs-8) andaxillary artery; the anterior divisions of the superiormost fibers of the anterior branch of the first thoracicand middle trunks uniteto form the lateral cord whichnerve(T,).The plexus may be divided into the roots,is lateral to the axillary artery;the anteriordivision oftrunks, the divisions and the cords. The all of thethe inferior trunk passes downward along the medialanterior branches are the roots, as lie in the scaleneside of the axillary artery and forms the medial cord(-fissure, they are blended into three trunks: a supe-Fig. VI-5-7)rior trunk(Cs-6),a middle trunk(C,) and an inferiortrunk(Cg-T,) . As they pass beneath the clavicle, eachRightcommoncarotidaLeftvagusn.Right vagus nLeftphrenicnAnterior scalene mBrachialplexusAccessory phrenic rLeftsubclaviana.Right recurrent laryngeal nCardiac plexusSuperior vena cavsLeftrecurrentRightphreniclaryngealn.Pericardial bPhrenicoab-dominal br.DiaphragFig. VI-5-6The phrenic nerveroots of the brachial plexus in the neck. Long thoracicnerve descends along the lateral surface of the serra-.Branches of brachial plexustus anterior and supplies it. The damage of the longthoracic nerve results in paralysis of the serratus ante-According to the position, the branches of therior and "winging of the scapula".plexus are divided into two groups, the supraclavicu-2) Suprascapular nerve(Cs, Ce) The nervelar and the infraclavicular groups(Fig. VI-5-7).arises from the superior trunk of the plexus and runsbackward by passing through the scapular notch to(1) Branches of supraclavicular groupscapular region. It supplies the supraspinatus and theinfraspinatus.1) Long thoracic nerve(Cs-7) It arises from the扫描全能王创建
Chapter 5 Peripheral Nervous System · 379 .behind the scalenus medius. The nerve supplies the3) Dorsal scapular nerve(C4, C,)It comes fromthe roots of plexus, runs backward and downwardlevatorscapulaeand rhomboideus.ISuperior trunkMiddle trunkInferiortrunkPosterior divisionsPosteriorcordAnteriordivisionLateral cordIint.-Medial cordAxillary a.Long thoracicn.Radial n.Musculocu-taneous n.Ulnarn.MediannA diagram of the formation and main branches of brachial plexusFig. VI-5-7palmaris longus. It enters the palm by passing throughthe carpal canal finally and is deep to the palmar apo-(2) Branches of infraclavicular groupneurosis.(Fig. VI-5-8)The median nerve has no branches in the arm.In theforearm,itgives off themuscularbranches to1) Median nerve(Ce-g, T,) It is formed by twosupply most of the muscles in front of the forearmroots, one is from the lateral cord and another fromexcept the brachioradialis,the flexor carpi ulnaris andthe medial cord of the brachial plexus, which embracethe medial half of the flexor digitorum profundus.the axillary artery and unite each other in front or onAbove the wrist, the nerve gives rise to a small pal-the lateral side of the artery(Fig. VI-5-7, 8) .Aftermar cutaneous branch that is distributed to the skincombining the median nerve descends along the me-over the lateral part of the palm.In the palm, the me-dial side of the biceps brachii with the brachial artery.dian nerve is divided into a recurrent branch and threeIn the upper part of the arm, the nerve is lateral to thecommon palmar digital nerves(Fig. VI-5-8, 9, 10).artery,crosses the vessel anteriorly or posteriorly atThe recurrent branch innervates the thenar musclesthe middle part, and lies on the medial side of the ar-except the adductor pollicis.Each of common palmartery at the cubital fossa.Then it'enters the forearm bydigital nerves is divided into two proper palmar digpassing between the two heads of the pronator teres,ital nerves which distribute to the skin of the palmarand continues downward between the flexor digito-aspect of the thumb, second, third and the lateralrum superficialis and the flexor digitorum profundus.half of thefourth fingers, as well as the skin on theAt the wrist the median nerve emerges from the later-dorsum of the terminal phalanges. It also gives offal border of the flexor digitorum superficialis and liesmuscular branches to the first and second lumbricalbetween the tendons of the flexor carpiradialis and扫描全能王创建
·380.PARTVINERVOUSSYSTEMthe humerus, here the ulnar nerve is superficial andmuscles.palpable againstthe bone, so that, it is easily injured.In the forearm themedian nervedamage can resultIt enters the in front ofthe forearm between the headsin a loss of pronation of theforearm,flexion oftheof the flexor carpi ulnaris, and then runs downwardsecond, the third fingers and the distal phalanx of thethumb and opposition of thethumb.Wrist flexion isbetween the flexor carpi ulnaris and flexor digitorumprofundus with the ulnar arteryto the wrist.severely affected. The thenar muscles are paralyzed,so that the thumb becomes to lie on the same planeAt the wrist,the ulnar nerve enter the palm of thehand by passing in front of the flexor retinaculumas the other digits, it is so called an “ape-like" hand.and is immediately divided into a superficial and aThere is also a loss or weakness of sensation from thedeep palmar branches, The superficial branch givesskin of the lateral part of thepalm and palmar surfaceoff a proper palmar digital nerve to the ulnar side ofofthe thumb, index,middle and the radial halfof thering finger(Figs. VI-5-9).the little finger and a common palmar digital nerve,2) Ulnar nerve(C,-T) It arises from the medialwhich is divided into two proper palmar digital nervescord of the brachial plexus and descends betweenfor the skin of the hypothenar and opposite sidesthe axillary artery and vein(Fig. VI-5-7, 8).Aboutof fourth and fifth fingers.But the third and fourththe middle of the arm ulnar nerve pierces the mediallumbricals,theadductorpollicis, interosseiand theintermuscular septumand descends alongthegroovemuscles of the hypothenar are all supplied by deepof the ulnar nerve behind the medial epicondyle ofbranch(Fig. VI-5-11) .Short headof biceps brachiiLong head ofbiceps brachiiMusculocutaneousrCoracobrachialisMediann.BrachioradialisUlnarn.Lateral antebrachialBrachialiscutaneous nBiceps brachiiPronator teresMedial epicondyleFlexor carpi ulnarisFlexordigitorumprofundusFlexor pollicis longusFlexordigitorum superficialisTendon of flexorcarpiFlexor carpi ulnarisadialisFlexor retinaculunRecurrentbr.ofmediannMediannDorsal br. of ulnar n.Tendon offlexor digitorumsuperficialisTendon of palmaris longusDeep br.ofuinarn.Superficial br.ofulnarn.operpalmardigitaln.P扫描全能王创建
Chapter 5Peripheral Nervous System·381 :Accessory nMiddle scalene m.Dorsal scapular nAnteriorscalenem.SuprascapularSuprascapularaMusculocCephaliceralpectoralnAxillary n.lateralthoracicnMediannLateral thoracica.CoracobrachialmAxillary a.UlnarMedial antebrachialectoralisminormcutaneous n.Medial brachialcutaneous n.Brachial a.IntercostobrachialnThoracodorsala.LongthoracicnDorsal thoracic n.BFig. VI-5-8A, the musculocutaneous, ulnar and median nerves; B. branches of brachial plexusRadial aPronator quadritusUlnaraUlnarn.MedianrDeep br. of ulnar n.Superficial br.of radial nSuperficialbr.ofulnarnRecurrent br.of median rAbductor digiti minimiAbductor pollicis brevisDeep br. of ulnar n.Flexor pollicis brevisFlexor digiti minimi brevisCommon palmardigital n.Adductor pollicisLumbricalesProper palmardigitalThenervesofpalmarsurfaceofhandFig.VI-5-9扫描全能王创建
·382·PARTVINERVOUSSYSTEM98.5%67.0%4.5%2%67.0%12.5%U-UInar n.R-Radial n. M-Median n.L-Lateral antebrachial cataneous n.Fig.VI-5-10 The nerve distribution of the handThere isn't any ulnar branch in the arm. After-of the hand is know as “clawhand".The sensationit enters the forearm, the nerve gives off muscularfrom the skin of the hypothenar and the lttle finger isbranches to supply the flexor carpi ulnaris and thelost(Fig.VI-5-14).medial half of the flexor digitorum profundus. About3) Musculocutaneous nerve(C,-2) It arises from5 cm above the wrist, it gives off a dorsal branch tothe lateral cord of the brachial plexus and leaves thedistribute to the skin on the ulnar half of the dorsumaxilla by piercing through the coracobrachialis whichand the posterior surface of the ulnar one and a halfit supplies, then descends between the biceps brachiifingers(Fig. VI-5-12, 13) .and brachialis. And then it gives off branches to sup-Sometimes the unlar nerve can be damaged at theply above three muscles. The lateral antebrachial cu-elbow or thewrist.Itmayresult in interfering withtaneous nerve of the Musculocutaneous nerve piercestheflexion of thering finger, littlefingers and meta-the deep fascia between the tendons of the bicepscarpophalangeal joints.The fingers have no abductionand brachioradialis at a lttle above the elbow, whichand adduction fuction.There is also loss of abductionsupplies the skin of the lateral side of the forearm(-of thumb.Owings to atrophy of the hypothenar andFig. VI-5-7, 8).interosseous muscles,this characteristic appearance4) Radial nerve(C,-T,) It is the largest branch扫描全能王创建