Anatomy of the posterior forearm

Question 1

What is the general function of the posterior forearm muscles and what are they innervated by?

Answer 1

Extensor

Radial nerve

Question 2

What are the 7 superficial posterior forearm muscles?

Answer 2

Brachioradialis
Ext. carpi radialis longus + brevis
Ext. digitorum
Ext. digiti minimi
Ext. carpi ulnaris
Anconeus

(all ext. except radialis longus have common origin = lateral epicondyle/common extensor origin)

Question 3

What is the action of ECRL + ECRB? What is ECRL origin and where do they both insert?

Answer 3

Abduct + extend wrist
ECRL = lateral supracondylar ridge humerus to dorsal (post.) 2nd metacarpal
ECRB = same insertion but 3rd

Question 4

Describe extensor digitorum

Answer 4

Splits to 4 tendons on extensor hood of 4 fingers
Linked by fibrous bands (juncturae tendinum) = prevents full ext. of middle/ring if others flexed
ACTION = extend 4 @ MCPJ + IPJ
NERVE = post. interosseous branch of radial

Question 5

Describe ext. digiti minimi

Answer 5

Inserts ulnar side ext. dig. tendon of little finger
Ext. little finger + wrist
Post. interos. radial

Question 6

Describe ext. carpi ulnaris

Answer 6

Humeral head = common ext. origin
Ulnar head = olecranon, post. prox. ulna + deep fascia
Onto base 5th metacarpal
Adduction + wrist ext.
Post. interos. radial

Question 7

What are the 5 deep muscles of the post. forearm?

Answer 7

Supinator
Abductor pollicis longus
Ext. pollicis longus + brevis
Ext. indicis
(all act on thumb, except supinator)

Question 8

Describe abductor pollicis longus

Answer 8

From inteross. mem. to radial base of 1st metacarpal
Abducts thumb + ext. carpometacarpal joint
Post. inteross. radial

Question 9

Describe ext. pollicis longus

Answer 9

From middle 1/3rd post. ulna + inteross. to distal phalanx thumb
Ext. all 3 thumb joints
Post. inteross. radial

Question 10

Describe ext. pollicis brevis

Answer 10

From post. radius + inteross. to base proximal phalanx thumb
Ext. metacarpophalangeal + carpometacarpal joints of thumb
Post. inteross. radial

Question 11

Describe extensor indicis

Answer 11

Post. ulna + inteross. to extensor hook of index finger
Ext. index finger indep.
Post. inteross. radial

Question 12

What does the deep branch of the radial nerve innervate? What does the superficial branch innervate?

Answer 12

Muscles of post. forearm (becomes post. inteross. nerve after supinator)
Dorsal surface of lateral 3 1/2 digits