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.