Posterior Forearm Muscles

Question 1

Brachioradialis

Answer 1

O: proximal 2/3rds of lateral supracondylar ridge of humerus
I: lateral surface of distal end of radius
I: radial nerve (c5-c6)
A: flexes forearm at elbow, especially in midpronation

Question 2

Extensor carpi radialis longus

Answer 2

O: lateral supracondylar ridge of humerus
I: base of 2nd metacarpal bone
I: radial nerve (c6-c7)
A: extends and abducts hand at wrist

Question 3

Extensor carpi radialis brevis

Answer 3

O: lateral epicondyle of humerus
I: base of 3rd metacarpal bone
I: radial nerve (deep branch) (c7-c8)
A: extends and abducts hand at wrist

Question 4

Extensor digitorum

Answer 4

O: lateral epicondyle of humerus
I: extensor expansions of medial four digits
I: radial nerve (posterior interosseous) (c7-c8)
A: extends medial four digits at metacarpophalangeal joints; extends hand at wrist joint

Question 5

Extensor digit minimi

Answer 5

O: lateral epicondyle of humerus
I: extensor expansion of 5th digit
I: radial nerve (posterior interosseous) (c7-c8)
A: extends 5th digit at metacarpophalangeal and interphalangeal joints

Question 6

Extensor carpi ulnaris

Answer 6

O: lateral epicondyle of humerus and posterior boarder of ulna
I: base of 5th metacarpal bone
I: radial nerve (posterior interosseous) (c7-c8)
A: extends and adducts hand at the wrist

Question 7

Supinator

Answer 7

O: lateral epicondyle of humerus; radial collateral and anular ligament; superior fossa; and crest of ulna
I: lateral, posterior, and anterior surfaces of proximal 3rd of radius
I: radial nerve (deep branch) ( c6-c7)
A: supinates forearm

Question 8

Abductor pollicis longus

Answer 8

O: posterior surfaces of ulna, radius, and interosseous membrane
I: base of 1st metacarpal bone on the lateral aspect
I: radial nerve (posterior interosseous) (c7-c8)
A: abducts thumb and extends it at carpometacarpal joint

Question 9

Extensor pollicis brevis

Answer 9

O: posterior surfaces of radius and interosseous membrane
I: base of proximal phalanx of thumb on the dorsal aspect
I: radial nerve (posterior interosseous) (c7-c8)
A: extends proximal phalanx of thumb at carpometacarpal joint

Question 10

Extensor pollicis longus

Answer 10

O: posterior surface of middle third of ulna and interosseous membrane
I: base of distal phalanx of thumb on the dorsal aspect
I: radial nerve (posterior interosseous) (c7-c8)
A: extends distal phalanx of thumb at metacarpophalangeal and interphalangeal joints

Question 11

Extensor indicis

Answer 11

O: posterior surface of ulna and interosseous membrane
I: extensor expansion of 2nd digit
I: radial nerve (posterior interosseous) (c7-c8)
A: extends 2nd digit and helps extend hand at wrist