Deep Posterior Forearm

Question 1

Supinator

Answer 1

Origin: Lateral epicondyle of humerus, radial collateral ligament, annular ligament, supinator crest of ulna
Insertion: Lateral, posterior, and anterior surfaces of proximal third of radius
Action: Forearm supination
Innervation: Posterior interosseous nerve

Question 2

Abductor pollicis longus

Answer 2

Origin: Posterior surface of proximal half of radius, ulna and interosseus membrane
Insertion: Base of metacarpal bone 1, (trapezium bone)
Action:
Radiocarpal joint: Hand extension;
Carpometacarpal joint of thumb: Thumb abduction and extension
Innervation: Posterior interosseous nerve

Question 3

Extensor policis longus

Answer 3

Origin: Posterior surface of middle third of ulna and interosseus membrane
Insertion: Posterior aspect of base of distal phalanx of thumb
Action: Thumb extension
Innervation: Posterior interosseous nerve

Question 4

Extensor pollicis brevis

Answer 4

Origin: Posterior surface of distal third of radius and interosseus membrane
Insertion: Posterior aspect of base of proximal phalanx of thumb
Action: Thumb extension
Innervation: Posterior interosseous nerve

Question 5

Extensor indicis

Answer 5

Origin: Posterior surface of distal third of ulna and interosseus membrane
Insertion: Extensor expansion of index finger
Action: index finger extension
Innervation: Posterior interosseous nerve