Extensor Region of Forearm and Hand

Question 1

Aconeus

Answer 1

O: Lateral Epicondyle of Humerus
I: 1. Lateral surface of olecranon
2. Superior part of posterior surface of ulna
N: Radial Nerve
A: 1. Assists triceps in extending forearm
2. Stabilizies elbow joint
3. May abduct ulna during pronation

Question 2

Brachioradialis

Answer 2

O: Proximal 2/3 of supracondylar ridge of humerus
I: Lateral surface of distal end of radius proximal to styloid process
N: Radial Nerve C5, C6
A: Relatively weak flexor of forearm; maximal when forearm is mid- pronation position

Question 3

Extensor Carpi Radialis Longus

Answer 3

O: Lateral Supracondylar ridge of Humerus
I: Dorsal aspect of base of 2nd metacarpal
N: Radial Nerve C5, C6
A: 1. Extend and abduct hand at wrist
2. Active during hand clenching

Question 4

Extensor Carpi Radialis Brevis

Answer 4

O: Lateral epicondyle of humerus
I: Dorsal aspect of base of 3rd metacarpal
N: Radial Nerve C7, C8
A: Extend and abduct hand at wrist

Question 5

Extensor Digitorum

Answer 5

O: Lateral Epicondyle of Humerus
I: Extensor expansion of medial 4 digits
N: Radial Nerve C7, C8
A: Extends medial 4 digits primarily at MCP joints, secondarily at IP joints

Question 6

Extensor Digiti Minimi

Answer 6

O: Lateral Epicondyle of Humerus
I: Extensor expansion of 5th digit
N: Radial Nerve
A: Extends 5th digit primarily at MCP joint, secondarily at IP joint

Question 7

Extensor Carpi Ulnaris

Answer 7

O: 1. Lateral epicondyle of humerus
2. Posterior border of ulna via shared aponeurosis
I: Dorsal aspect of base of 5th metatarsal
N: Radial Nerve
A: 1. Extends and adducts hand at wrist joint
2. Also active during fist clenching

Question 8

Supinator

Answer 8

O: 1. Lateral epicondyle of humerus
2. Radial Collateral and Annular Ligaments
3. Supinator fossa
4. Crest of Ulna
I: Lateral, posterior, and anterior surfaces of proximal 1/3 of radius
N: Radial Nerve C6, C7
A: 1. Supinates forearm
2. Rotates radius to turn palm anteriorly and superiorly (if elbow is flexed)

Question 9

Abductor Pollicis Longus

Answer 9

O:  Posterior surface of proximal halves of ulna, radius, and interosseous membrane
I:  Base of 1st metacarpal
N:  Radial Nerve
A:  1.  Abducts thumb
     2.  Extends it at CMC joint

Question 10

Extensor Pollicis Brevis

Answer 10

O: 1. Posterior Surface of distal 1/3 of radius
2. Interosseous Membrane
I: Dorsal aspect of base of proximal phalanx of thumb
N: Radial Nerve
A: 1. Extends proximal phalanx of thumb at MCP joint
2. Extends CMC joint

Question 11

Extensor Pollicis Longus

Answer 11

O: 1. 1/3 of ulna
     2.  Interosseous Membrane
I:  Dorsal Aspect of Base of Thumb
N:  Radial Nerve
A: 1.  Extends distal phalanx of thumb at IP joint
    2.  Extends MCP and CMC joints

Question 12

Extensor Indicis

Answer 12

O: 1. Posterior surface of distal 1/3 of ulna
2. Interosseous Membrane
I: Extensor expansion of 2nd digit
N: Radial Nerve
A: 1. Extends 2nd digits (enabling its independent extension)
2. Helps extend hand at wrist