Posterior Compartment of Forearm (superficial, deep) extensors

Question 1

Brachioradialis (s)

Answer 1

relatively weak flexion of elbow joint, maximal when forearm is in midpronated position
nerve supply - radial nerve
proximal two thirds of lateral supra-epicondylar ridge of humerus -> lateral surface of distal end of radius proximal to styloid process

Question 2

Extensor carpi radialis longus (s)

Answer 2

extends and abduct wrist joint; extends carpometacarpal joints (extensor carpi radialis brevis active during first clenching)
nerve supply - radial nerve
lateral supra-epicondylar ridge of humerus -> dorsal aspect of base of 2nd metacarpal

Question 3

Extensor carpi radialis brevis (s)

Answer 3

extends and abduct wrist joint; extends carpometacarpal joints (extensor carpi radialis brevis active during first clenching)
nerve supply - deep branch of radial nerve
lateral epicondyle of humerus -> dorsal aspect of base of 3rd metacarpal

Question 4

Extensor digitorum (s)

Answer 4

extends wrist joint, carpometacarpal joints; extends medial four fingers primarily at metacarpophalangeal joints, secondarily at interphalangeal joints
nerve supply - posterior interossesous nerve
lateral condyle of humerus -> extensor expansions of medial four fingers

Question 5

Extensor digiti minimi (s)

Answer 5

extends wrist joint, carpometacarpal joints; extends 5th finger primarily at metacarpophalangeal joints, secondarily at interphalangeal joints
nerve supply - posterior interosseous nerve
lateral epicondyle of humerus -> extensor expansion of 5th finger

Question 6

Extensor carpi ulnaris (s)

Answer 6

extends and adducts wrist joint, carpometacarpal joints (also active during first clenching)
nerve supply - deep branch of radial nerve
lateral epicondyle of humerus; posterior border of ulna via a shared aponeurosis -> dorsal aspect of base of 5th metacarpal

Question 7

Supinator (deep)

Answer 7

supinates forearm; rotates radius to turn palm anteriorly and superiorly (if elbow is flexed)
nerve supply - deep branch of radial nerve
lateral epicondyle of humerus, radial collateral and anular ligaments, supinator fossa, crest of ulna -> lateral, posterior and anterior surfaces of proximal third of radius

Question 8

Abductor pollicis longus

Answer 8

extends wrist joint, carpometacarpal joints; abducts thumb and extends it at carpometacarpal joint
nerve supply - posterior interosseous nerve
posterior surface of proximal halves of ulna, radius and interosseous membrane -> base of 1st metacarpal

Question 9

Extensor pollicis longus

Answer 9

extends wrist joint, carpometacarpal joints; extends distal phalanx of thumb at interphalangeal joint; extends metacarpophalangeal and carpometacarpal joints
nerve supply - posterior interousseous nerve
posterior surface of middle third of ulna and interossesous membrane -> dorsal aspect of base of distal phalanx of thumb

Question 10

Extensor pollicis brevis

Answer 10

extends wrist joint, carpometacarpal joints; extends proximal phalanx of thumb at metacarpalphlangeal joint; extends carpometacarpal joint
nerve supply - posterior interoussesous nerve
posterior surface of distal third of radius and interosseous membrane -> dorsal aspect of base of proximal phalanx of thumb

Question 11

Extensor indicis

Answer 11

extends wrist joint, carpometacarpal joints; extends 2nd finger (enabling its independent extension); helps extend hand at wrist
nerve supply - posterior interossesous membrane
posterior surface of distal third of ulna and interssoeous membrane -> extensor expansion of 2nd finger