Posterior Compartment of the Forearm

Question 1

Brachioradialis

Answer 1

PA:
+ proximal 2/3 of lateral supra-epicondylar ridge of humerus

DA:
+ lateral surface of distal end of radius proximal to styloid process

N:
+ radial n. (C5, C6*, C7)

A:
+ weak flexion of the elbow; maximal when forearm is in mid pronates position

Question 2

Extensor Carpi Radialis Longus

Answer 2

PA:
+ lateral supra-epicondylar ridge of the humerus

DA:
+ dorsal aspect of base of 2nd metacarpal

N:
+ radial nerve (C6, C7)

A:
+ extends wrist joint
+ abducts wrist joint
+ extends carpometacarpal joints

Question 3

Extensor Carpi Radialis Brevis

Answer 3

PA:
+ lateral epicondyle of humerus

DA:
+ dorsal aspect of 3rd metacarpal

N:
+ deep branch of radial nerve (C7*, C8)

A:
\+ extends wrist joint
\+ abducts wrist joint
\+ extends carpometacarpal joints
*active during fist clenching*

Question 4

Extensor Digitorum

Answer 4

PA:
+ lateral epicondyle of humerus

DA:
+ extensor expansions of medial four fingers

N:
+ posterior interosseous nerve (C7*,C8) [cont’n of deep branch of radial nerve]

A:
\+ extends wrist joint, carpometacarpal joints
\+ extends medial four fingers
     1º at metacarpophalangeal joints
     2º at interphalangeal joints

Question 5

Extensor Digiti Minimi

Answer 5

PA:
+ lateral epicondyle of humerus

DA:
+ extensor expansion of 5th finger

N:
+ posterior interosseous nerve (C7*,C8) [cont’n of deep branch of radial nerve]

A:
\+ extends wrist joint, carpometacarpal joints
\+ extends 5th finger primarily
     1º at metacarpophalangeal joint
     2º at interphalangeal joint

Question 6

Extensor Carpi Ulnaris

Answer 6

PA:
+ lateral epicondyle of humerus
+ posterior border of ulna via shared aponeurosis

DA:
+ dorsal aspect of base of 5th metacarpal

N:
+ posterior interosseous nerve (C7*,C8) [cont’n of deep branch of radial nerve]

A:
+ extends wrist joint
+ adducts wrist joint, carpometacarpal joints
active during fist clenching

Question 7

Abductor Pollicis Longus

Answer 7

PA:
+ posterior surface of proximal halves of ulna, radius, and interosseous membrane

DA:
+ base of 1st metacarpal

N:
+ posterior interosseous nerve (C7,C8*) [cont’n of deep branch of radial nerve]

A:
+ extends wrist joint, carpometacarpal joints
+ abducts thumb
+ extends thumb at carpometacarpal joint

Question 8

Extensor Pollicis Longus

Answer 8

PA:
+ posterior surface of middle third of ulna and interosseous membrane

DA:
+ dorsal aspect of base of distal phalanx of thumb

N:
+ posterior interosseous nerve (C7,C8*) [cont’n of deep branch of radial nerve]

A:
+ extends wrist joint, carpometacarpal joints
+ extends distal phalanx of thumb at interphalangeal joint
+ extends metacarpophalangeal and carpometacarpal joints

Question 9

Extensor Pollicis Brevis

Answer 9

PA:
+ posterior surface of distal third of radius and interosseous membrane

DA:
+ dorsal aspect of base of proximal phalanx of thumb

N:
+ posterior interosseous nerve (C7, C8*), cont’n of deep branch of radial nerve

A:
+ extends wrist joint, carpometacarpal joints
+ extends proximal phalanx of thumb at metacarpophalangeal joint
+ extends carpometacarpal joint

Question 10

Extensor Indicis

Answer 10

PA:
+ posterior surface of distal third of ulna and interosseous membrane

DA:
+ extensor expeansion of 2nd finger

N:
+ posterior interosseous nerve (C7, C8*), cont’n of deep branch of radial nerve

A:
+ extends wrist joint, carpometacarpal joints
+ extends 2nd finger; independent extension
+ extends hand at wrist

Question 11

Supinator

Answer 11

PA:
\+ lateral epicondyle of the humerus
\+ radial collateral and anular ligaments
\+ supinator fossa
\+ crest of ulna

DA:
+ lateral, posterior, and anterior surfaces of proximal third of the radius

N:
+ deep branch of the radial nerve (C7, C8*)

A:
+ supinates forearm
+ rotates the radius to turn palm anteriorly or superiorly