Forearm Extensor muscles

Question 1

Brachioradialis

Answer 1

O: Lateral supracondylar
ridge of humerus,
Lateral intermuscular
septum of arm
I: (Proximal to) Styloid process of radius
N: Radial Nerve (C5- C8)
F: Elbow joint: Forearm flexion (when semi pronated)

Question 2

Extensor carpi radialis longus

Answer 2

O: Lateral supracondylar ridge of humerus, Lateral intermuscular septum of arm

I: Posterior aspect of base of metacarpal bone 2

N: Radial Nerve (C5- C8)

F: Wrist joints: Hand extension, Hand abduction (radial deviation)

Question 3

Extensor carpi radialis brevis

Answer 3

O: Lateral epicondyle of humerus (common extensor tendon)

I: Posterior aspect of base of metacarpal bone 3

N: Radial Nerve (C5- C8)

F: Wrist joints: Hand extension, Hand abduction (radial deviation)

Question 4

Extensor digitorum

Answer 4

O: Lateral epicondyle of humerus (common extensor tendon)

I: Extensor expansions of digits 2-5

N: Posterior interosseous nerve (C7, C8)

F: Finger extension 2-5

Question 5

Extensor digiti minimi

Answer 5

O: Lateral epicondyle of humerus (common extensor tendon)

I: Extensor expansions of digit5

N: Posterior interosseous nerve (C7, C8)

F: joint 5: Finger extension

Question 6

Extensor carpi ulnaris

Answer 6

O: Lateral epicondyle of humerus, Posterior border of the ulna

I: Base of metacarpal bone 5

N: Posterior interosseous nerve (C7, C8)

F: Wrist joint: Hand extension and adduction

Question 7

Supinator

Answer 7

O: Lateral epicondyle of humerus, Radial collateral ligament, Anular ligament, Supinator crest of ulna

I: Lateral/posterior/anterior surfaces of proximal third of radius

N: Posterior interosseous nerve (C7, C8)

F: Forearm supination

Question 8

Abductor pollicis longus

Answer 8

O: Posterior surface of proximal half of radius, ulna and interosseus membrane

I: Base of metacarpal bone 1, (Trapezium Bone)

N: Posterior interosseous nerve (C7, C8)

F: Radiocarpal joint: Hand abduction (radial deviation); Carpometacarpal joint of thumb: Thumb abduction and extension

Question 9

Extensor pollicis longus

Answer 9

O: Posterior surface of middle third of ulna and interosseus membrane

I: Posterior aspect of base of distal phalanx of thumb

N: Posterior interosseous nerve (C7, C8)

F: Wrist joints: Weak hand extension Metacarpophalangeal and interphalangeal joint of thumb: Thumb extension

Question 10

Extensor pollicis brevis

Answer 10

O: Posterior surface of distal third of radius and interosseus membrane

I: Posterior aspect of base of proximal phalanx of thumb

N: Posterior interosseous nerve (C7, C8)

F: Carpometacarpal and Metacarpophalangeal joint 1: Thumb extension

Question 11

Extensor indicis

Answer 11

O: Posterior surface of distal third of ulna and interosseus membrane

I: Extensor expansion of index finger

N: Posterior interosseous nerve (C7, C8)

F: Wrist joints: Weak hand extension Metacarpophalangeal and interphalangeal joints of index finger: Finger extension