Peripheral Nervous System Anatomy

Question 1

What nerves form the Cervical plexus

Answer 1

Ventral rami of C1-C4

Question 2

Describe the supply of the cervical plexus

Answer 2

C1 - geniohyoid and thyrohyoid
Ansa cervicalis (C1-3) - all strap muscles: sternothyroid, sternohyoid, & superior/inferior bellies of omohyoid
Great Auricular (C2&3) - most of the ear skin
Lesser occipital (C2) - skin over back of head to vertex
Transverse cervical (C2 &3) - supplies skin over anterior cervical triangle
Supraclavicular (C3&4) - supply skin over clavicle

Most branches lie in anterior triangle

Question 3

What nerves form the brachial plexus

Answer 3

C5-T1

Question 4

What structures does the roots of the brachial plexus pass through

Answer 4

sclenius anterior and medius muscles in the neck

Question 5

Describe the structure of the brachial plexus (rugby team drinks cold beer)

Answer 5

Roots: C5-T1
Trunks: Upper C5 & C6, Middle C7, Lower C8 & T1
Divisions: Anterior/Posterior Located behind clavicle
Cords: around axillary artery, Posterior - from ALL posterior divisions (C5-T1), Lateral - anterior division s of upper and middle trunk (C5,6,7), Medial - lower trunk of anterior division
Branches

Question 6

Describe the radial nerve and its supply

Answer 6

Radial (C5-T1): All the muscles of the posterior compartment of the arm and forearm BEAST - Brachioradialis, all Extensors of the wrist, Abductors of the thumb and Supinator muscles, Triceps and anconeus

Question 7

Describe the median nerve and it’s supply

Answer 7

Median (C5-T1): supplies all muscles of forearm (except flexor crapi ulnaris and and the ulnar half of FDP) plus LOAF muscles of the thumb (Lumbricals 1&2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis)

The anterior interosseous branch supplies the flexor pollicis breves, pronator quadratus, and radial half of FDP

Question 8

Describe the musculotcutaneous nerve and its supply

Answer 8

C5, 6, 7: (BBC) Biceps, Brachialis, and Coracobrachialis and skin of the lateral forearm

Question 9

Describe the axillary nerve and its supply

Answer 9

C5&6: passes through the quadrangular space and supplies the deltoid and teres minor plus skin over the insertion of the deltoid muscle

Question 10

Describe the branches from roots of the brachial plexus

Answer 10

Dorsal Scapular (C5) - Supplies the levator scapulae, rhomboid major & minor

Long thoracic (C5,6,7) - supplies serratus anterior (damage causes winged scapula)

Question 11

Describe the branches form the trunks of the brachial plexus

Answer 11

Suprscapular (C5&6) - supplies supraspinatus and infraspinatus

Nerve to subclavius (C5-6) supplies subclavius

Question 12

Name the branches from the cords

Answer 12

Posterior cord:
upper and lower subscapular C5&C6 - subscapularis
lower subscapular also supplies the teres minor

Thoracodorsal (C6-8) - subclavius

Medial cord:
Medial pectoral (C8&T1) - pec major and minor
Medial brachial cutaneous - medial arm
medial antebrachial cutaneous - medial forearm

Lateral cord: 
Lateral pectoral (C5,6,7) - Pec major

Question 13

What is erb-duchenne palsy

Answer 13

Damage to C5 and C6 - elbow extended, forearm pronated, and fingers flexed

Question 14

Describe Klumpke’s palsy

Answer 14

damage to C8 and T1 resulting in a claw hand

Question 15

What cord levels make up the lumbar plexus

Answer 15

Ventral rami of L1-L4 formed within the psoas major

Question 16

All of the lumbar plexus nerves leave the lateral aspect of the psoas major EXCEPT

Answer 16

genitofemoral - exits anterioly

obturator - exits medially

Question 17

Branches and their innervations of the lumbar plexus

Answer 17

iliohypogastric L1 - lower abdomen above inguinal region

ilioinguinal L1 - supplies inguinal region

genitofemoral L1,2 - medial upper thigh, anterior scrotum and cremasteric muscle

lateral femoral L2,3 - supplies the anterolateral aspect of the thigh

femoral L2,3,4 posterior divisions - supplies the extensor thigh compartment

obterator L2,3,4 anterior divisions - supplies the adductor thigh compartment

contributaries - to the formation of the lumbosacral trunk L4,5

Question 18

What nerve levels form the lumbosacral plexus

Answer 18

L4,5, S1-4

Sacral nerves exit the anterior sacral foramina and unite in front of the piriformis muscle where they are joined by the lumbosacral trunk

Question 19

Describe the branches of the lumbosacral trunk and their innervations

Answer 19

Superior gluteal (L4, 5, S1) - gluteus medius, minimus and tensor fascia lata and passes through the greater sciatic foramen

inferior gluteal (L5 S1,2) through greater sciatic, supplies gluteus maximus only

pudendal (S2,3,4) - supplies external anal sphincter, deep and superficial perineal, penis (clitoris) and posterior scrotum (labia)

Sciatic,

Question 20

Describe the Sciatic nerve

Answer 20

L4, 5, S1, 2, 3
Largest, passes beneath piriformis through greater sciatic notch
Supplies the muscles of the posterior thigh and all the muscles below the knee
Supplies skin below the knee EXCEPT for a thin strip along the medial aspect of the leg and foot (saphenous branch of the femoral nerve)

Question 21

Describe the tibial portion of the sciatic nerve

Answer 21

Tibial (L4,5,S1,2,3) :
all muscles in posterior compartment of leg
all muscles in the plantar aspect of the foot
Divides into medial and lateral plantar branches after passing behind the medial malleolus
supplies skin over posterior aspect of leg and the planta aspect of foot
Medial plantar - corresponds with median n. in hand, supplies FDB, flexor hallucis brevis, abductor hallicus, and first lumbrical of the foot
Lateral plantar - corresponds with ulnar n. and supplies rest of the muscles in the sole of the foot

Question 22

Describe the common peroneal part of the sciatic nerve

Answer 22

Common peroneal (L4,5 S1,2): anterior and lateral compartment of the leg

Winds around neck of the fibula and then divides into superficial and deep branches

Superficial:
lies in lateral compartment
peroneous longus and brevis
skin of most of the dorsum of the foot EXCEPT the web space between first and second toes

Deep:
passes through peroneus longus (does not supply) enters anterior compartment of leg
tibialis anterior
extensor hallicus longus and brevis
peroneus tertius
skin in web space between first and second toes

Question 23

What structures pass through the greater sciatic foramen

Answer 23

superior gluteal VAN above the piriformis, pudendal n, inferior gluteal VAN, nerve to obterator internus and sciatic nerve below the piriformis

Question 24

What structures pass through the lesser sciatic foramen

Answer 24

Pudendal nerve, internal pudendal artery and vein, nerve to obterator internus, tendon of obterator internus