Week 28 Get a Grip LO
What is the innervation of the muscles of the forearm and hand?
FOREARM MUSCLES
Anterior forearm: FLEXORS/PRONATORS
Superficial:
Pronator teres
Intermediate:
Flexor carpi ulnaris (U n.)
Flexor digitorum superficialis
Flexor carpi radialis
Palmaris longus
Deep:
Flexor digitorum profundus
(U n. & M n.)
Flexor pollicus longus
Pronator quadratus
The anterior forearm compartment muscles are supplied by the median nerve. Except for flexor carpi
ulnaris and ulnar half of flexor digitorum profundus which have ulnar nerve innervation.
Median nerve origin:
 Lateral root of median nerve is a terminal branch of lateral cord (C6, C7)
 Medial root of median nerve us a terminal branch of medial cord (C8, T1)
Median nerve course:
Lateral and medial roots merge to form median nerve lateral to axillary artery, descends through arm adjacent
to brachial artery, with nerve gradually crossing anterior to artery to lie medial to artery in cubital fossa.
Posterior forearm: EXTENSORS/SUPINATORS
Superficial layer:
Extensor digitorum
Extensor carpi radialis longus
Extensor carpi radialis brevis
Brachioradialis
Extensor digiti minimi
Common extensor tendon on lateral epicondyle
Deep layer:
Extensor pollicus longus
Extensor pollicus brevis
Abductor pollicus longus
Extensor indicis
Supinator
The posterior forearm muscles are all supplied by the radial nerve.
Radial nerve origin:
Larger terminal branch of posterior cord (largest branch of plexus), receiving fibres from C5-T1.
Radial nerve course:
Exits axillary fossa; passes posterior to humerus in radial groove with deep brachial artery, enters cubital fossa
dividing into superficial (cutaneous) and deep (motor) radial nerves.
HAND MUSCLES
Lumbricals
Interossei
Thenar muscles (muscles of the thumb)
Hypothenar muscles (muscles of the 5th digit)
Intrinsic muscles of the hand are innervated by the ulnar nerve. Except for the thenar eminence and 1st
and 2nd lumbricals which are supplied by the median nerve.
Ulnar nerve originates from medial cord, receiving fibres from C8, T1 and often C7.
Course: descends medial arm; passes posterior to medial epicondyle of humerus; then descends ulnar aspect of
forearm to hand.