1. The forearm

Question 1

describe the arrangement of muscles in the anterior compartment of the arm

Answer 1

4 superficial muscles with common flexor tendon at medial epicondyle of humerus:

1. pronator teres
2. flexor carpi radialis
3. palmaris longus
4. flexor carpi ulnaris

1 intermediate muscle:
5. flexor digitorum superficialis

3 deep muscles:

6. flexor digitorum profundus
7. flexor pollicis longus
8. pronator quadratus

Question 2

what is the difference between FDS and FDP

Answer 2

FDS splits into 4 tendons at wrist and inserts into MIDDLE PHALANGES of 4 fingers. Functions:

i. wrist flexion
ii. MCP joint flexion
iii. proximal IP joint flexion

FDP splits into 4 tendons at wrist (passes through carpal tunnel) and inserts into DISTAL PHALANGES of 4 fingers. Functions:

i. wrist flexion
ii. MCP joint flexion
iii. distal IP joint flexion

Question 3

which anterior forearm muscles mediate pronation

Answer 3

i. pronator teres

ii. pronator quadratus

Question 4

which nerves innervate the anterior compartment muscles

Answer 4

• mostly median n. (C6-T1)

- except flexor carpi ulnaris and medial 1/2 FDP: ulnar n. (C8-T1)

Question 5

which structure supports the flexor muscle tendons at the wrist

Answer 5

flexor retinaculum and palmar carpal ligament

Question 6

name the 7 muscles of the superficial layer of posterior compartment and their function

Answer 6

i. brachioradialis (elbow flexion)
ii. extensor carpi radialis longus (wrist extension and abduction)
iii. extensor carpi radialis brevis (wrist extension and abduction)
iv. extensor digitorum (MCP and IP joint extension of 4 fingers)
v. extensor digiti minimi (little finger MCP and IP joint extension)
vi. extensor carpi ulnaris (wrist extension and adduction)
vii. anconeus (elbow extension)

Question 7

name the 5 muscles of the deep layer of posterior compartment and their function

Answer 7

i. supinator (supination)
ii. abductor pollicis longus (thumb abduction and MCP joint extension)
iii. extensor pollicis brevis (thumb MCP and carpometacarpal joint extension)
iv. extensor pollicis longus (carpometacarpal, MCP and IP joint extension)
v. extensor indicis (index extension)

Question 8

which nerve innervates the posterior forearm compartment and what is the consequence of lesion to this nerve

Answer 8

radial n. (C5-T1)

WRIST DROP: paralysis of all extensor muscles so unopposed flexion of wrist joint