Muscles of the Hand

Question 1

Lumbricals (4)

Answer 1

Origin: Tendon of FDP (radial side)

Insertion: Extensor expansion (2-5 digits proximal phalanges)

Actions: MCP- Flex

PIP/DIP- Extension

Innervation: Median (2-3) C8, T1

Ulnar (4,5) C8, T1

Question 2

Abductor pollicis brevis

Answer 2

Origin: Flexor retinaculum

Tubercle scaphoid/trapezium

Insertion: Proximal phalanx thumb-base, radial side

Actions: CMC: Abductio/flexion thumb

MCP: Flexion

Innervation: Median nerve C8, T1 (recurrent branch)

Question 3

Opponens pollicis

Answer 3

Origin: Flexor retinaculum

Trapezium

Insertion: 1st metacarpal- shaft, radial side

Actions: CMC: Opposition thumb

roll shaft MC to ulnar side

Innervation: Median nerve C8.T1 (recurrent branch)

Question 4

_Flexor pollicis brevis _

Answer 4

Origin: Superior head: flexor retinaculum (trapezium)

Deep head: trapezoid/capitate

Insertion: Proximal phalanx thumb- base, radial side

Radial sesmoid

Actions: CMC- Adduction, flexion, opposition thumb

MCP- Flexion

Innervation: Superior head- Median (recurrent) C8, T1

Deep head- Ulnar (dorsal) C8, T1

Question 5

Adductor pollicis

Answer 5

Origin: Transverse head: 3rd metacarpal

Oblque head: base 1st 3 metacarpals

Distal capitate, trapezoid, trapezium

Ligament floor carpal tunnel

Insertion: Proximal phalanx thumb- base, ulnar side

Ulnar sesmoid

Actions: CMC- Adduction/Flexion thumb

MCP- Flexion

Innervation: Ulnar nerve (dorsal) C8, T1

Question 6

Palmaris brevis

Answer 6

Origin: Palmar aponeurosis (ulnar side)

Insertion: Skin hyothenar eminence

Actions: Stabilize skin palm for gripping

Tightens palmar aponeurosis (protective function)

Innervation: Ulnar nerve C8, T1

Question 7

Abductor digiti minimi

Answer 7

Origin: Pisiform

Insertion: 5th proximal phalanx (base, ulnar side)

Actions: CMC- Flex, Abduct

MCP- Flex, Abduct

PIP/DIP- Extend

Innervation: Ulnar nerve C8, T1

Question 8

Flexor digiti minimi brevis

Answer 8

Origin: Flexor retinaculum

Hook hamate

Insertion: 5th proximal phalanx (base, ulnar side)

Actions: MCP- flex

CMC- flex

Innervation: Ulnar nerve C8, T1

Question 9

Opponens digiti minimi

Answer 9

Origin: Flexor retinaculum

Hook hamate

Insertion: 5th metacarpal (shaft, ulnar side)

Actions: CMC- Opposition little finger to thumb

roll 5th MC to radial side hand

Innervation: Ulnar nerve C8, T1

Question 10

Palmar interossei (3)

Answer 10

Origin: 2nd MC (index)- shaft, ulnar side

4th MC (ring)- shaft, radial side

5th MC (pinky)- shaft, radial side

Insertion: Proximal phalanx (base, same side)

Extensor expansion finger of origin

Actions: MCP- flex

PIP/DIP- Extension/Adduction

Innervation: Ulnar nerve C8, T1

Question 11

Dorsal interossei (4)

Answer 11

Origin: 2 heads on adjacent surface metacarpals

(1/2, 2/3, 3/4, 4/5)

Insertion: 2 (index)- Proximal phalanx (radial side)

3 (middle)- Proximal phalanx (radial/ulnar side)

4 (ring)- Proximal phalanx (ulnar side)

Extensor expansions (2,3,4)

Actions: MCP- Flex

PIP/DIP- Extension/Abduction

Innervation: Ulnar nerve C8, T1