Posterior compartment of forearm (Deep layer)

Question 1

What are the muscles in the deep layer?

Answer 1

Supinator

Extensor indicis

Question 2

What is the proximal attachment of the supinator?

Answer 2

Lateral epicondyle of humerus; radial collateral and anular ligaments; supinator fossa; crest of ulna

Question 3

What is the distal attachment of the supinator?

Answer 3

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

Question 4

What is the innervation of the supinator?

Answer 4

Deep branch of radial nerve (C7, C8)

Question 5

What is the the main the action of the supinator?

Answer 5

Supinates forearm; rotates radius to turn palm anteriorly or superiorly (if elbow is flexed)

Question 6

What is the proximal attachment of the extensor indicis?

Answer 6

Posterior surface of distal third of ulna and interosseous membran

Question 7

What is the distal attachment of the extensor indicis?

Answer 7

Extensor expansion of 2nd digit

Question 8

What is the innervation of the extensor indicis?

Answer 8

Posterior interosseous nerve (C7, C8), continuation of deep branch of radial nerve

Question 9

What is main action of the extensor indicis?

Answer 9

Extends 2nd digit (enabling its independent extension); helps extend hand at wrist