Intrinsic Muscles Acting on the Hand

Question 1

Abductor Digiti Minimi

Answer 1

Act: Abduction of the 5th finger and assists in opposition
O: Tendon of flexor carpi ulnaris and pisiform
I: By two slips into the 5th finger: Ulnar side of the base of the proximal phalanx and ulnar border of the extensor expansion
Innervation: Ulnar

Question 2

Abductor Pollicis Brevis

Answer 2

Act: 1st CMC joint abduction, 1st MCP joint adduction, and assists in opposition
O: Flexor retinaculum, trapezium, and scaphoid
I: Radial surface of the base of the proximal phalanx of the thumb and via a slip into the extensor expansion
Innervation: Deep Palmar Branch

Question 3

Adductor Pollicis

Answer 3

Act: 1st CMC joint adduction, 1st MCP joint adduction, 1st MCP joint flexion, and assists in opposition
O: Capitate bone, bases of 2nd and 3rd metacarpals, palmar surface of 3rd metacarpal
I: Ulnar surface of the base of the proximal phalanx of the thumb and via a slip into the extensor expansion
Innervation: Deep Palmar Branch

Question 4

Dorsal Interossei

Answer 4

Act: Abduction of the 3rd-5th fingers, assists in MCP flexion, assists in extension of the IP joints
O: Thumb: ulnar border of 1st metacarpal and radial border of 2nd metacarpal
2-4th fingers: adjacent sides of metacarpals
I: Thumb: radial border of the 2nd finger and radial side of the 3rd finger
3rd Finger: ulnar side of 3rd finger
4th Finger: ulnar side of 4th finger
Innervation: Deep Palmar Branch

Question 5

Flexor Digiti Minimi

Answer 5

Act: 5th MCP joint flexion, assists in opposition
O: Hook of the hamate bone and flexor retinaculum
I: Ulnar border of the proximal phalanx of the 5th finger
Innervation: Ulnar

Question 6

Flexor Pollicis Brevis

Answer 6

Act: 1st MCP joint flexion, 1st CMC joint flexion, assists in opposition
O: Flexor retinaculum, trapezoid, and capitate
I: Radial surface of the base of the proximal phalanx and via a slip into the extensor expansion
Innervation: Median and Deep Palmar Branch

Question 7

Lumbricals

Answer 7

Act: Flexion of the 2nd-5th MCP joints and extension of the PIP and DIP joints
O: 1st and 2nd: radial surface of flexor profundus tendon
3rd: adjacent sides of flexor profundus tendons of 3rd and 4th fingers
4th: adjacent sides of flexor profundus tendons of the 4th and 5th fingers
I: Radial border of the extensor tendons of the respective digits
Innervation: 1st and 2nd: Median
3rd and 4th: Deep Palmar Branch

Question 8

Opponens Digiti Minimi

Answer 8

Act: Opposition of the 5th finger
O: Hook of the hamate and flexor retinaculum
I: Ulnar border of the length of the 5th metacarpal
Innervation: Ulnar

Question 9

Opponens Pollicis

Answer 9

Act: Thumb opposition
O: Flexor retinaculum and trapezium
I: Length of 1st metacarpal
Innervation: Median

Question 10

Palmar Interossei

Answer 10

Act: Adducts 1st, 2nd, 4th, and 5th fingers and assists in flexion of the MCP joints
O: Thumb: ulnar border of the 1st metacarpal
2nd: ulnar border of the 2nd metacarpal
3rd: radial border of the 4th metacarpal
4th: radial border of the 5th metacarpal
I: Thumb: ulnar border of thumb
2nd: ulnar side of 2nd finger
3rd: radial side of ring finger and radial side of little finger
Innervation: Deep Palmar Branch