Deep layers of muscles in the posterior compartment of the forearm

Question 1

Supinator

Answer 1

Origin:

• Superficial part - lateral epicondyle of humerus, radial collateral and anular ligaments;
• Deep part - supinator crest of the ulna

Insertion:

• Lateral surface of the radius superior to the anterior oblique line

Innervation:

• Posterior interosseous nerve (C6, C7)

Function:

• Supination

Question 2

Abductor pollicis longus

Answer 2

Origin:

• Posterior surfaces of ulna and radius (distal to the attachments ofsupinator and anconeous)
• Intervening interosseous membrane

Insertion:

• Lateral side of the base of metacarpal I

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Abducts carpometacarpal joint of thumb; accessory extensor of the thumb

Question 3

Extensor pollicis brevis

Answer 3

Origin:

• Posterior surface of ulnar and radius (distal to abductor polices longus) and the adjacent interosseous membrane

Insertion:

• Dorsal surface of base of proximal phalanx of the thumb

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Extends metacarpophalangeal joint of the thumb; can also extend the carpometacarpal joint of the thumb

Question 4

Extensor pollicis longus

Answer 4

Origin:

• Posterior surface of radius (distal to abductor polices longus)
• The adjacent interosseous membrane

Insertion:

• Dorsal surface of base of distal phalanx of the thumb

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Extends interphalangeal joint of the thumb
• Can also extend the carpometacarpal and metacarpophalangeal joint of the thumb

Question 5

Extensor indicis

Answer 5

Origin:

• Posterior surface of ulna (distal to extensor policies longs) and adjacent interosseous membrane

Insertion:

• Extensor hood of index finger

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Extends index finger

Question 6

Origin:

• Superficial part - lateral epicondyle of humerus, radial collateral and anular ligaments;
• Deep part - supinator crest of the ulna

Insertion:

• Lateral surface of the radius superior to the anterior oblique line

Innervation:

• Posterior interosseous nerve (C6, C7)

Function:

• Supination

Answer 6

Supinator

Question 7

Origin:

• Posterior surfaces of ulna and radius (distal to the attachments ofsupinator and anconeous)
• Intervening interosseous membrane

Insertion:

• Lateral side of the base of metacarpal I

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Abducts carpometacarpal joint of thumb; accessory extensor of the thumb

Answer 7

Abductor pollicis longus

Question 8

Origin:

• Posterior surface of ulnar and radius (distal to abductor polices longus) and the adjacent interosseous membrane

Insertion:

• Dorsal surface of base of proximal phalanx of the thumb

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Extends metacarpophalangeal joint of the thumb; can also extend the carpometacarpal joint of the thumb

Answer 8

Extensor pollicis brevis

Question 9

Origin:

• Posterior surface of radius (distal to abductor polices longus)
• The adjacent interosseous membrane

Insertion:

• Dorsal surface of base of distal phalanx of the thumb

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Extends interphalangeal joint of the thumb
• Can also extend the carpometacarpal and metacarpophalangeal joint of the thumb

Answer 9

Extensor pollicis longus

Question 10

Origin:

• Posterior surface of ulna (distal to extensor policies longs) and adjacent interosseous membrane

Insertion:

• Extensor hood of index finger

Innervation:

• Posterior interosseous nerve (C7, C8)

Function:

• Extends index finger

Answer 10

Extensor indicis