Posterior compartment of forearm (Superficial layer)

Question 1

What are the muscles in the superficial layer?

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 is the proximal attachment of the brachioradialis?

Answer 2

Proximal two thirds of supra-epicondlyar ridge of humerus

Question 3

What is the distal attachment is the brachioradialis?

Answer 3

Lateral surface of distal end of radius proximal to styloid process

Question 4

What is the innervation of the brachioradialis?

Answer 4

Radial nerve (C5, C6, C7)

Question 5

What is the main action of the brachioradialis?

Answer 5

Relatively weak flexion of forearm; maximal when forearm is in midpronated position

Question 6

What is the proximal attachment of the extensor carpi radialis longus?

Answer 6

Lateral supra-epicondlyar ridge of humerus

Question 7

What is the distal attachment of the extensor carpi radialis longus?

Answer 7

Dorsal aspect of base of 2nd metacarpal

Question 8

What is the innervation of the extensor carpi radialis longus?

Answer 8

Radial nerve (C6, C7)

Question 9

What is the main action of the extensor carpi radialis longus?

Answer 9

Extend and abduct hand at the wrist joint; ECRL active during fist clenching

Question 10

What is the proximal attachment of the extensor carpi radialis brevis?

Answer 10

Lateral epicondyle of humerus (common extensor origin)

Question 11

What is the distal attachment of the extensor carpi radialis brevis?

Answer 11

Dorsal aspect of base of 3rd metacarpal

Question 12

What is the innervation of the extensor carpi radialis brevis?

Answer 12

Deep branch of radial nerve (C7, C8)

Question 13

What is the main function of the extensor carpi radialis brevis?

Answer 13

Extend and abduct hand at the wrist joint; ECRL active during fist clenching

Question 14

What is the proximal attachment of the extensor digitorum?

Answer 14

Lateral epicondyle of humerus (common extensor origin)

Question 15

What is the distal attachment of the extensor digitorum?

Answer 15

Extensor expansions of medial 4 digits

Question 16

What is the innervation of the extensor digitorum?

Answer 16

Deep branch of radial nerve (C7, C8)

Question 17

What is the main action of the extensor digitorum?

Answer 17

Extends medial four digits primarily at metacarpophalangeal joints, secondarily at interphalangeal joints

Question 18

What is the proximal attachment of the extensor digiti minimi?

Answer 18

Lateral epicondyle of humerus (common extensor origin)

Question 19

What is the distal attachment of the extensor digiti minimi?

Answer 19

Extensor expansion of 5th digit

Question 20

What is the innervation of the extensor digiti minimi?

Answer 20

Deep branch of radial nerve (C7, C8)

Question 21

What is the main action of the extensor digiti minimi?

Answer 21

Extends 5th digit primarily at metacapophalangeal joint, at interphalangeal joint

Question 22

What is the proximal attachment of the extensor carpi ulnaris?

Answer 22

Lateral epicondyle of humerus; posterior border of ulna via a shared apeneurosis

Question 23

What is the distal attachment of the extensor carpi ulnaris?

Answer 23

Dorsal aspect of base of 5th metacarpal

Question 24

What is the innervation of the extensor carpi ulnaris?

Answer 24

Deep branch of radial nerve (C7, C8)

Question 25

What is the main action of the extensor carpi ulnaris?

Answer 25

Extends and addducts hand at wrist joint (also active during fist clenching)