Overview of PNS Spinal Nerves

Guo Ling, MD, PhD Department of Anatomy

Peripheral Nervous System(PNS)

spinal cord

brain

cranial nervesspinal nervesvisceral nerves

CNS

PNS

NS

Overview of Nervous SystemCentral nervous System(CNS)

Spinal nerves

Nerve ： It is a long & solid macrostructure into which numerous nerve fibers only in PNS are bundled.

Nerve fibers:They are long microstructures formed by neuronal processes which are enveloped by both thick/ thin myelin sheath and neurilemma; or are only covered by neurilemma. The fibers distribute in CNS or PNS.

Classification of PNS 1. Based on distributions of component: somatic nerve & viseral nerve

2.Based on functions of component: afferent(sensory) & efferent (motor) nerves 3. Based on combination of the above two items:

(1) somatic nerve : sensory and motor nerves (2) viseral nerve: 1) sensory nerve 2) motor nerve

(vegetative nerve / autonomic nerve) a. sympathetic nerve b. parasympathetic nerve4. Based on relay stops of nervous informatiom

(1) cranial ganglia as well as spinal ganlia (g) (2) sensary ganglia(8):spinal g, genulate g of CN7,

cochlear g & vestibular g of CN8 ,super g & infer g of CN9, super g & infer g of CN10)

(3) ganglia of vegetative nerve:1)ganglia of sympathetic nerve: paravetebral g (19~24) & prevertebral g (4):celiac g,aorticorenal g,

super mesenteric g & infer mesenteric g) 2)ganglia of parasympathetic nerve:a.paraorganic ganglia

in head (4): ciliary g of CN3, otic g of CN9, pterygopalatine g & submandibular g of CN7

b.paraorganic ganglia in body except those in head & intraorganic ganglia in body including those in head

Spinal Nerve (SN)Focus on the following items:

1.Buildup o f Spinal Nerve 2. Functional Features of

Each Primary branch of SN 3.Composition and Position

of Each Plexus of SN 4.Typical Nerves in Each Plexus

(1)Innervation of skin areas (2)Innervation of muscular groups

(3)Vulnerable places of nerve injury(4)Subsequent symptoms

resulting from the Injury

Spinal Nerves

1.Formation: Each nerve consists of the

ant.root and pos.root,which are conjoined

together at an intervertebral foramen.

2.Division:31 pairs in total,8C(C 1- 8),12T(T1-12),

5L( L1-5), 5S( S1-5) & Co1. 61 separate nerves.

3. Branches of Each Spinal Nerves ： 4 pairs(1) meningeal branches (containiung sensory &sympathetic fibers-mixed nerves) (2) communicating branches(white & gray )→ sympathetic trunks (containing visceral motor fibers) (3)dorsal branches (mixed nerves) (4) anterior branches(mixed nerves,C,L,S&Co first form plexes ,and then send concrete nerves;while only T immediatedly gives off its own nerves.)

Focusing on the following items of anterior branch forming plexuses:

1.Compsition of each plexus 2.Position of each plexus

3.Representive nerves of each plexus (1) Invervation of specific skin areas

(2) Invervation of concrete skeletal muscles (3) Places vulnerable to injury (4) Relative symptoms & signs

(1) Formation It is made up of the anterior branches from C1-4. (2) Location It lies in the upper part of the neck.

4.Cervical Plexus

(3) Main Branches

　 1) Superficial branches(sensory)

a. Greater auricular N

b. Lesser occipital N

c. Transverse N of neck

d. Supraclavicular N

The four are all sensory Ns and

emerge from the middle point

of the post border of the

sternocleidomastoid,which is

a fixed mark for

anaesthenia pucture.

2) Deep branches(mixed N)

e. phrenic nerve

Phrenic nerve

1) Greater auricular N

2) Lesser occipital N

3) Transverse N of neck

4) Supraclavicular N →

5) Phrenic nerve →

(4) Distributions of Cervical Spinal Nerves

The skin of neck

The skin of sup. part of thoracic wall

DiaphragmDiaphragmatic and mediastinal pleuraePericardium ,liver, gallbladder, biliary system

5.Brachial Plexus (1) Formation: the ant. branches of C5~8

and most part of the ant. branch of T1

(2)Branch Transition:ant branches→sup,mid,inf trnuks →3 cordsLateral cord ：a.musculocutaneous N →lat Antebrachial cutaneous N b.median N lat rootMedial cord ：c. median N. med.root d.ulnar N.Posterior cord ：e.radial nervef.axillary N.g.long thoracic N.→serratus ant.h.thoracodorsal N.→latissimus dorsi

long thoracic N.

thoracodorsal N.

(3). Location: lying in scalene fissure ， supraclavicular fossa & axillary fossa

Axillary N

innervates deltoid& the skin of shoulder

Lateral antebrachial cutaneous N

Skin of lat.side of forearm

Radial N→Triceps brachilBrachioradialisExtensor of the forearm ,the skin on radial side of dorsum of the hand,proximal digits of the lateral two & half fingers

Rad

ial N &

its d

istribu

tion

Ulnar N→

Flexor carpi ulnarMedial half of the flexor digitorum profoundusUlnar half of the dorsum of the handPost. Surface of the ulnar one and half fingersThe muscles of hypothenarInterosseous muscles3th, 4th lumbricalesAdductor pollicis

Distributions of Median NPronator Most of the flexor muscles except the brachoradialis the flexor carpi ulnarisMedial half of the flexor digitorum profoundus Thenar muscle except for adductor pollicis1st,2nd lumbricales,the skin of thenar & central part of the palm, the skin of palmar aspect of the thumb, 2nd,3rd lateral half of 4th fingers & the dorsum of the middle & terminal phalanges

Humerus Fracture and Relaitve Injuries

a. Fracture of surgical neck →axillary N

→“winging of the scapula”

b.Fracture of middle part of humerus →radial N

→“wristdrop”

c.Fracture of med epicondyle of humerus→ulnar N

→“claw-like hand ”

d.Fracture of lower end of humerus→median N

→“ape-like hand ”

Innervation of Skin of Hand by Median,Ulnar &Radial Ns

Flexing elbow joint ： biceps brachii brachialis musculocutaneous N. brachioradialisExtending elbow joint ： triceps brachii radial N.

Innervation of Flexor and Extensor Muscles Acting on the Elbow Joint

Nerve Supply of Forearm Muscles

a. brachioradialis ----radial N. b. ulnar half of flexor digitorum superficialis, flexor carpi ulnaris------------ulnar N. c. the remaining muscles of anterior muscular group of forearm----median N. d. all muscles of posterior muscular group of forearm ---radial N.

Composition: 12 pairs 11 pairs of intercostal Ns.

1 pair of subcostal N Location:lying along the relative costal groove & going between the int ext intercostal Ms﹠ Segmental arrangements ： T2—-the sternal angle T4----the nipple T6----the xiphoid process T8----the costal arch T10----the umbilicus T12----the ant.superior iliac spine

Anterior Branches of Thoracic Nerves(Intercostal Nerves ）

② Obturator N ③ iliohypogastric N

④ilioinguinal N⑤Lat. femoral cutaneous N⑥Genitofemoral N

Lumbar PlexusComposition ：ant.branches of L1—3 & parts of the subcostal N and L4Location ：going within the psoas major

Main branches:①Femoral N →

→ Saphenous N ①

⑥②

③④

⑤

Obturator N.

Femoral N.

Saphenous N.

Distributions of the Branches of Lumbar Plexus

Femoral N---→muscles of anterior muscular group in the thigh

(quadriceps femoris, sartorius, pectineus)

Saphenous N →the skin of the medial side of the leg and foot

Obturator N→muscles of medial muscular group in the thigh

iliohypogastric N →the muscles of the lower part of the

abdominal wall,

the skin of hypogastric region & inguinal region

ilioinguinal N → muscles of lower partof abdominal wall

Lat. femoral cutaneous N →skin on ant.& lat.parts of the thigh

Genitofemoral N →cremaster, scrotum(greater lip of pudendum)

Composition ：the ant. branches of L5~8 ， the ant.branches of all the sacral Ns and coccygeal N.

Location ： in the pelvis ，going on ant.surface of the piriformis,looking like a triangle shape.

Sacral Plexus

1. sup.gluteal N.

2. inf.gluteal N.

3. post.femoral

cutaneous N.

4. pudendal N.

Main Branches

5. sciatic N.

sup.gluteal N.

pudendal N.

pos.femoral cutaneous N.

inf.gluteal N.

sciatic N.

Pudendal N. →infrapiriformis foramina →the lesser sciatic foramen→the ischiorectal fossa,innervating the muscles and the skin of the perineum

Sciatic N

Tib

ial N

Com

mon

Peron

eal N

Med

ial plan

tar N lateral p

lantar

N Su

ral N Su

perf.p

eroneal

N deep

peron

eal N

Sciatic nerve →muscles of post muscular group & skin in thigh

Tibial N →muscles of post muscular group & skin of leg

Med.& lat. Plantar N→plantar muscles & skin over the sole

of the foot

Sup.peroneal N→muscles of lat muscular group & skin of leg

Deep peroneal N→muscles of ant muscular group & skin of leg

Sup.gluteal N→gluteal medius & minimus ,tensor faciae latae

Inf.gluteal N→gluteal maxium & lower part of gluteal region

Post.femoral cutaneous N→skin of the post part of the thigh

Perineal N→the muscles of perineum & the skin of sacrum

Distributions of the Branches of Sacral Plexus ：

Sural N→the skin of post.& lat. surfaces on the leg

Innervation of Muscles in Lower Limbs

muscles of ant. group in thigh ---femoral N

muscles of med. group in thigh ---obturator N

muscles of post. group in thigh ----- sciatic N

muscles of post. group in leg

plantar muscles in foot-- -------------------tibial N

muscles of lat. group in leg----- superficial peroneal N

muscles of ant. group in leg------ deep peroneal N

Innervation of Muscles Acting on Knee Joint

flexing knee joint（ leg ）

Extending knee joint （ leg ）

muscles nerves

gastrocnemius tibial N.

Quadriceps femoris femoral N.

Ms of post. group in thigh

sciatic N.

Movements

Innervation of Skin of Foot

saphenous N. →skin on medial side of footdeep peroneal N. →dorsal skin between 1st &2nd toessup. peroneal N. →most part of dorsum skin of foot tibial N. →sole skin of footsural N. →dorsal skin on post.& lat.borders of foot