Extensor muscles of forearm

muscles may be organized into three functional groups:

1. Muscles that extend and abduct or adduct the hand at the wrist joint: extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), and extensor carpi ulnaris (ECU) 2. Muscles that extend the medial four digits: extensor digitorum, extensor indicis, and extensor digiti minimi (EDM) 3. Muscles that extend or abduct the thumb: abductor policis longus (APL), extensor pollicis brevis (EPB), and extensor pollicis longus (EPL).

dorsal interossei

DAB = dorsal ABduct

posterior interosseous nerve, continuation of deep branch of RADIAL NERVE

EXTENSOR DIGITI MINIMI

Action - Extensor carpi radialis longus

Extend and abduct wrist joint; extensor carpi radialis brevis active during fist clenching

Action - extensor carpi radialis brevis

Extend and abduct wrist joint; extensor carpi radialis brevis active during fist clenching

Action -extensor digitorum

Extend wrist joint Extend medial four fingers primarily at metacarpophalangeal joints, secondarily at interphalangeal joint

Action - carpi ulnaris

Extends and adducts wrist joint (also active during fist clenching)

Abductor pollicis longus -Action

Extends wrist joint Abducts thumb and extends it at carpometacarpal joint

action -extensor indicis

Extends wrist joint Extends 2nd finger (enabling its independent extension); helps extend hand at wrist

Action - extensor digiti minimi

Extends wrist joint Extends 5th finger primarily at meta- carpophalangeal joint, secondarily at interphalangeal joint

Action - extensor pollicis longus

Extends wrist joint Extends distal phalanx of thumb at interphalangeal joint; extends meta- carpophalangeal and carpometa- carpal joints

Action -extensor pollicis brevis

Extends wrist joint Extends proximal phalanx of thumb at metacarpophalangeal joint; extends carpometacarpal joint

common extensor tendon to the lateral epicondyle

Four superficial extensors (ECRB, extensor digitorum, EDM, and ECU) are attached proximally by a common extensor tendon to the lateral epicondyle

palmar interossei

PAD = palmar aduct

Action - Brachioradialis

Relatively weak flexion of elbow joint, maximal when forearm is in midpronated positio

Action - supinator

Supinates forearm; rotates radius to turn palm anteriorly or superiorly (if elbow is flexed

Radial nerve

brachioradialis, Extensor carpi radialis longus, ECRB, E. digitorum, E. carpi Ulnaris, supinator

extensor retinaculum

prevents bowstringing of the tendons when the hand is extended at the wrist joint. As the tendons pass over the dorsum of the wrist, they are covered with synovial tendon sheaths, which reduce friction for the extensor tendons as they traverse the osseo- fibrous tunnels formed by the attachment of the extensor retinaculum to the distal radius and ulna

lateral supra epicondylar ridge of humerus + intermuscular septum

superficial extensors (brachioradialis and ECRL) i