Muscles of Post Compartment of Forearm

Question 0

extensor carpi radialis longus

Answer 0

O: lateral supra-epicondylar ridge of humerus
I: dorsal aspect of base of 2nd metacarpal
N: radial nerve (C6, C7)
A: extend and abduct hand at wrist joint,
extensor carpi radialis brevis active during fist clenching

Question 1

brachioradialis

Answer 1

O: prox 2/3 of lateral supra-epicondylar ridge of humerus
I: lateral surface of distal end of radius prox to styloid process
N: radial nerve (C5, C6, C7)
A: relatively weak flexion of forearm, max when forearm is in
midpronated position

Question 2

extensor carpi radialis brevis

Answer 2

O: lateral epicondyle of humerus
I: dorsal aspect of base of 3rd metacarpal
N: deep branch of radial nerve (C7, C8)
A: extend and abduct hand at wrist joint,
active during fist clenching

Question 3

extensor digitorum

Answer 3

O: lateral epicondyle of humerus
I: extensor expansions of medial 4 fingers
N: post interosseous nerve (C7, C8) continuation of deep branch
of radial nerve
A: extends medial 4 fingers primarily at metacarpophalangeal
joints, secondarily at interphalangeal joints

Question 4

extensor digiti minimi

Answer 4

O: lateral epicondyle of humerus
I: extensor expansion of 5th finger
N: post interosseous nerve (C7, C8), continuation of deep branch
of radial nerve
A: extends 5th finger primarily at metacarpophalangeal joint,
secondarily and interphalangeal joint

Question 5

extensor carpi ulnaris

Answer 5

O: lateral epicondyle of humerus, post border of ulna via a shared
aponeurosis
I: dorsal aspect of base of 5th metacarpal
N: post interosseous nerve (C7, C8), continuation of deep branch
of radial artery
A: extends and adducts hand at wrist joint
also active during fist clenching

Question 6

supinator

Answer 6

O: lateral epicondyle of humerus, radial collateral and anular ligs,
supinator fossa, crest of ulna
I: lateral, post, and ant surfaces of prox 1/3 of radius
N: deep branch of radial nerve (C7, C8)
A: supinates forearm, rotates radius to turn palm ant or sup (if
elbow is flexed)

Question 7

abductor pollicis longus

Answer 7

O: post surface of prox halves of ulna, radius, and interosseous
membrane
I: base of 1st metacarpal
N: post interosseous nerve (C7,C8), continuation of deep branch
of radial nerve
A: abducts thumb and extends it at carpometacarpal joint

Question 8

extensor pollicis longus

Answer 8

O: post surface of middle 1/3 of ulna and interosseous membrane
I: dorsal aspect of base of distal phalanx of thumb
N: post interosseous nerve (C7,C8), continuation of deep branch
of radial nerve
A: extends distal phalanx of thumb and interphalangeal joint,
extends metacarpophalangeal and carpometacarpal joints

Question 9

extensor pollicis brevis

Answer 9

O: post surface of distal 1/3 of radius and interosseous
membrane
I: dorsal aspect of base of prox phalanx of thumb
N: post interosseous nerve (C7,C8),continuation of deep branch
of radial nerve
A: extends prox phalanx of thumb at metacarpophalangeal joint,
extends carpometacarpal joint

Question 10

extensor indicis

Answer 10

O: post surface of distal 1/3 of ulna and interosseous membrane
I: extensor expansion of 2nd finger
N: post interosseous nerve (C7,C8) continuation of deep branch
of radial nerve
A: extends 2nd finger (enabling its independent extension)
helps extend hand at wrist