Forearm Extensors and Compartments

Question 0

What is the second compartment of the dorsal hand?

Answer 0

Extensor carpi radialis longus and extensor carpi radialis brevis

Question 1

What is the first compartment of the dorsal hand?

Answer 1

Extensor pollicis brevis and abductor pollicis longus

Question 2

What is the third compartment of the dorsal hand?

Answer 2

Extensor pollicis longus

Question 3

What is the fourth part of the dorsal hand?

Answer 3

Extensor digitorum

Question 4

What is the fifth compartment of the dorsal hand?

Answer 4

Extensor digiti minimi

Question 5

What is the sixth compartment of the dorsal hand?

Answer 5

Extensor carpi ulnaris

Question 6

Brachioradialis

Answer 6

Origin: proximal two thirds of the lateral supra-epicondyle of the humerus

Insertion: lateral surface of the distal end of the radius proximal to the styloid process

Innervation: radial nerve (C5,C6,C7)

Action: weak flexor of forearm; maximal when forearm is in midpronated position

Question 7

Extensor carpi radialis longus

Answer 7

Origin: lateral supra-epicondylar ridge of the humerus

Insertion: dorsal aspect of the base of the 2nd metacarpal

Innervation: radial nerve (C6,C7)

Action: extend and ABD hand at the wrist joint

Question 8

Extensor carpi radialis brevis

Answer 8

Origin: lateral epicondyle of the humerus

Insertion: dorsal aspect of the base of the 3rd metacarpal

Innervation: deep branch of the radial nerve (C7,C8)

Action: extend and ABD hand at wrist joint; active during fist clenching

Question 9

Extensor digitorum

Answer 9

Origin: lateral epicondyle of the humerus

Insertion: extensor expansion of the medial four fingers

Innervation: posterior interosseous nerve (C7,C8)

Action: extends medial four fingers at the MCP joint and secondarily at IP joint

Question 10

Extensor digiti minimi

Answer 10

Origin: lateral epicondyle of the humerus

Insertion: extensor expansion of the 5th finger

Innervation: posterior interosseous nerve (C7,C8)

Action: extend 5th finger at MCP joint and secondarily at IP joint

Question 11

Extensor carpi ulnaris

Answer 11

Origin: lateral epicondyle of the humerus and posterior border of ulna via a shared aponeurosis

Insertion: dorsal aspect of the base of the 5th metacarpal

Innervation: posterior interosseous nerve (C7,C8)

Action: extend and ADD at wrist joint; active during fist clenching

Question 12

Supinator

Answer 12

Origin: lateral epicondyle of the humerus, radial collateral ligament, annular ligament, supinator fossa, and crest of the ulna

Insertion: lateral, anterior, and posterior surfaces of the proximal third of the radius

Innervation: deep branch of the radial nerve (C7,C8)

Action: supinates the forearm

Question 13

Abductor pollicis longus

Answer 13

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

Insertion: base of the 1st metacarpal

Innervation: posterior interosseous nerve (C7,C8)

Action: abduct the thumb and extend at the CMC joint

Question 14

Extensor pollicis longus

Answer 14

Origin: posterior surface of the middle third of the ulna and the interosseous membrane

Insertion: dorsal aspect of the base of the distal phalanx of the thumb

Innervation: posterior interosseous nerve (C7,C8)

Action: extend distal phalanx at IP, MCP, and CMC joints

Question 15

Extensor pollicis brevis

Answer 15

Origin: posterior surface of the distal third of the radius and interosseous membrane

Insertion: dorsal aspect of the base of the proximal phalanx of the thumb

Innervation: posterior interosseous nerve (C7,C8)

Action: extend proximal phalanx at IP, MCP, and CMC joints

Question 16

Extensor indicis

Answer 16

Origin: posterior surface of distal third of the ulna and interosseous membrane

Insertion: extensor expansion of the 2nd finger

Innervation: posterior interosseous nerve (C7,C8)

Action: extends 2nd finger and helps extend hand at the wrist joint