Lab 4 - Module 1 - Extensor Compartments of the Arm and Forearm: Page 4 of 9
Extensor Muscles of the Forearm
| The eleven muscles in the posterior aspect of the forearm are classified as extensors. They can be organized into functional groups as follows: muscles that extend the hand at the wrist (extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris); muscles that extend the fingers (extensor digitorum, extensor indicis, and extensor digiti minimi); and muscles that extend or abduct the thumb (abductor pollicis longus, extensor pollicis longus, and extensor pollicis brevis). They can also be organized into superficial and deep groups. |
Deep Extensor Muscles
| Remove the Brachioradialis and add the Supinator muscle. |
|
Origin - Lateral epicondyle of the humerus, radial/lateral collateral ligament, annular ligament, and supinator crest of the ulna
Insertion - Lateral, posterior, and anterior surfaces of the proximal 1/3 of the radius Innervation - Deep Branch Radial Nerve Action - Supination of the forearm Blood supply - Radial and posterior interosseous arteries. |
| Add the Extensor Indicis muscle. |
|
Origin - Posterior surface of the ulna and the interosseous membrane
Insertion - Extensor hood of the index finger (2nd digit) Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve Action - Extends index finger and may aid in hand extension Blood supply - Radial and posterior interosseous arteries. |
| Add the Abductor Pollicis Longus muscle. |
|
Origin - osterior surfaces of both the radius and ulna and interosseous membrane
Insertion - radial side of base of the first metacarpal and on trapezoid bone Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve Action - abducts the thumb and assists in wrist flexion; extends thumb at the carpometacarpal joint Blood supply - Radial and posterior interosseous arteries. |
| Add the Extensor Pollicis Brevis muscle. |
|
Origin - Posterior surface of the radius and interosseous membrane
Insertion - Base of the proximal phalanx of the thumb Innervation - Posterior Interosseous Nerve from deep branch of radial nerve Action - Extends thumb, may aid in wrist extension Blood supply - Radial and posterior interosseous arteries. |
| Add the Extensor Pollicis Longus muscle. |
|
Origin - Posterior shaft (middle 1/3) of the ulna and interosseous membrane
Insertion - Base of the distal phalanx of the thumb Innervation - Posterior Interosseous Nerve from deep branch of radial nerve Action - Extends thumb, may aid in wrist extension Blood supply - Radial and posterior interosseous arteries. |
| This completes the deep extensor muscles. |