Unit 2 - Upper Limb: Thenar Muscles (Ex. II)

Question 1

abductor pollicis brevis

Answer 1

O: scaphoid and trapezium; flexor retinaculum
I: base of proximal phalanx of thumb via radial sesamoid
Inn: median N (C8, T1)
A: abduction @ CMC joint of thumb

Question 2

flexor pollicis brevis

Answer 2

O: superficial head - flexor retinaculum; deep head - capitate and trapezium
I: base of proximal phalanx of thumb via radial sesamoid
Inn: superficial head - median N (C8, T1); deep head - ulnar N (C8, T1)
A: flexion @ CMC joint of thumb

Question 3

opponens pollicis

Answer 3

O: trapezium
I: radial border of 1st metacarpal
Inn: median N (C8, T1)
A: opposition @ CMC joint of thumb

Question 4

adductor pollicis

Answer 4

O: transverse head - palmar surface of 3rd metacarpal; oblique head - capitate and bases of 2nd and 3rd metacarpals
I: base of proximal phalanx of thumb via ulnar sesamoid
Inn: ulnar N (C8, T1)
A: adduction @ CMC joint of thumb; flexion @ MCP joint of thumb