Forearm/Hand/Wrist: Posterior Compartment (Deep Layer)

Question 1

Supinator

Answer 1

PA: Lat epicondyle of humerus, radial collateral ligament, annular ligament, supinator crest of ulna

DA: Proximal 1/3 of radius along post and lat surfaces

Inn: Deep branch of radial n C6,7

Actions: Supinates the FA

Question 2

Abductor Pollicis Longus

Answer 2

PA: Middle post shaft of ulna, interosseus membrane, middle 1/3 of post surface of radius

DA: Base of 1st MC on radial side & trapezium

Inn: Posterior Interosseus n C7,8

Actions: Abducts the thumb @ 1st CMC joint

Question 3

Extensor Pollicis Longus

Answer 3

PA: Middle 1/3 of post surface of ulna, adjacent interosseus membrane

DA: Distal phalanx of thumb on dorsal surface

Inn: Posterior Interosseous nerve C7,8

Actions: Extends the IP, MCP & CMC jts of thumb

Question 4

Extensor Pollicis Brevis

Answer 4

PA: Posterior surface of radius, adjoining interosseus membrane

DA: Base of proximal phalanx of 1st digit along dorsolateral surface

Inn: Posterior Interosseous nerve C7,8

Actions: Extends the 1st MCP & CMC joint

Question 5

Extensor Indices

Answer 5

PA: Post distal surface of ulna, adjacent interosseus membrane

DA: Extensor digitorum tendon to 2nd digit along its medial side

Inn: Posterior interosseous nerve C7,8

Actions: Assists in extending the 2nd digit & wrist