Deep Layer of Posterior Forearm Muscles

Question 0

Abductor Pollicus Longus

Answer 0

Origin: Posterior surface of proximal half of ulna, radius, and interosseous membrane

Insertion: Base of 1st metacarpal

Innervation: Posterior Interosseous Nerve (C7, C8), deep branch of radial nerve

Question 1

Supinator

Answer 1

Origin: 1) Lateral epicondyle of humerus, 2) radial collateral and anular ligaments, 3) supinator fossa, 4) crest of ulna

Insertion: Lateral, posterior, and anterior surfaces of proximal third of radius

Innervation: Deep branch of radial nerve (C7, C8)

Question 2

Extensor Pollicus Longus

Answer 2

Origin: Posterior surface of middle third of ulna and interosseous membrane

Insertion: Dorsal aspect of base of distal phalanx of thumb

Innervation: Posterior Interosseous Nerve (C7, C8), deep branch of radial nerve

Question 3

Extensor Pollicus Brevis

Answer 3

Origin: Posterior surface of distal third of radius and interosseous membrane

Insertion: Dorsal aspect of base of proximal phalanx of thumb

Innervation: Posterior Interosseous Nerve (C7, C8), deep branch of radial nerve

Question 4

Extensor Indicis

Answer 4

Origin: Posterior surface of distal third of ulna and interosseous membrane

Insertion: Extensor expansion of 2nd finger

Innervation: Posterior Interosseous Nerve (C7, C8), deep branch of radial nerve