Posterior Forearm

Question 1

What muscles are in the superficial layer of the posterior compartment of the forearm? (6)

Answer 1

Brachioradialis
Extensor carpi radialis longus (ECRL)
Extensor carpi radialis brevis (ECRB)
Extensor digitorum
Extensor digiti minimi (EDM)
Extensor carpi ulnaris (ECU)

Question 2

What muscles are in the deep extensor layer of the posterior compartment of the forearm? (2)

Answer 2

Supinator

Extensor indicis

Question 3

Which muscles are in the deep “outcropping thumb muscles” layer of the posterior compartment of the forearm?

Answer 3

Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus

Question 4

Abductor pollicis longus AAI

Answer 4

Attachments: proximal posterior radius, ulna, interosseous membrane to the base of the 1st metacarpal and trapezium

Actions: abducts and extends thumb at carpometacarpal joint and abducts hand at wrist (radial deviation)

Innervation: Radial nerve (C6-8)

Question 5

Brachioradialis AAI

Answer 5

Attachments: lateral supracondylar ridge of the humerus to the distal radius lateral to the styloid process

Actions: flexes the elbow

Innervation: Radial nerve (C5-6)

Question 6

Extensor carpi radialis brevis AAI

Answer 6

Attachments: lateral epicondyle of the humerus to base of the 3rd metacarpal

Actions: extends and abducts hand at wrist (radial deviation)

Innervation: Radial nerve (C6-8)

Question 7

Extensor carpi radialis longus AAI

Answer 7

Attachments: lateral supracondylar ridge of the humerus to the base of the 2nd metacarpals

Actions: extends and abducts hand at wrist (radial deviation) and assists in flexion of the elbow

Innervation: Radial nerve (C6-8)

Question 8

Extensor carpi ulnaris AAI

Answer 8

Attachments: lateral epicondyle of the humerus to base of the 5th metacarpal

Actions: extends and abducts hand at wrist (ulnar deviation)

Innervation: Radial nerve (C6-8)

Question 9

Extensor digitorum AAI

Answer 9

Attachments: lateral epicondyle of the humerus to the extensor expansions of digits 2-5

Actions: extends phalanges (primarily at metacarpophalangeal, secondarily at interphalangeal) and hand at wrist

Innervation: Radial nerve (C6-8)

Question 10

Extensor digiti minimi AAI

Answer 10

Attachments: lateral epicondyle of the humerus to digital expansion of the 5th digit

Actions: extends 5th digits (metacarpophalangeal and interphalangeal)

Innervation: Radial nerve (C7-8)

Question 11

Extensor indicis AAI

Answer 11

Attachments: posterior surface of the ulna and interosseous membrane to the digital expansion of the 2nd digit

Actions: extends 2nd digit (metacarpophalangeal and interphalangeal)

Innervation: Radial nerve (C7-8)

Question 12

Extensor pollicis brevis AAI

Answer 12

Attachments: posterior radial surface and interosseous membrane to the base of the 1st proximal phalanx

Actions: extends thumb (metacarpophalangeal) and extends and abducts CMC joint

Innervation: Radial nerve (C6-8)

Question 13

Extensor pollicis longus AAI

Answer 13

Attachments: middle 1/3rd of the posterior surface of the ulna and interosseous membrane to the base of the 1st distal phalanx

Actions: extends thumb (CMC and metacarpophalangeal and interphalangeal)

Innervation: Radial nerve (C6-8)

Question 14

Supinator AAI

Answer 14

Attachments: lateral epicondyle of humerus, radial collateral ligament and supinator crest of the ulna to the lateral surface of the proximal radius

Actions: supinates forearm

Innervation: Radial nerve (C5-6)