Lecture Notes: Muscles of the Hand and Thumb Function

IP Flexor of the Thumb

• Prime Mover: Flexor pollicis longus
  • Ends at the distal part
  • Bends the IP joint of the thumb
  • Roles on MCP and CMC joints

Thumb Extension and Radial Abduction

• Prime Movers: Extensor pollicis brevis and longus
• Abductor pollicis longus: Supports radial abduction

Thumb Palmar Abduction

• Prime Mover: Abductor pollicis longus (APL)
  • Better mechanical advantage in supination

Intrinsic Muscles of the Thumb and Little Finger

• Thumb (Thenar Muscles)
  • Abductor pollicis brevis (outside)
  • Flexor pollicis brevis (inside)
  • Opponens pollicis (deeper layer)
• Little Finger (Hypothenar Muscles)
  • Abductor digiti minimi (outside)
  • Flexor digiti minimi (inside)
  • Opponens digiti minimi (deeper layer)

Adductor Pollicis

• Function: Works with flexor pollicis brevis for pinch movement
• Positioning for Pinch: Thumb and CMC joint perform adduction and MCP joint may perform flexion

Types of Pinch

• Tripod Pinch (Palmar Pinch)
  • Involves adductor pollicis, flexor pollicis brevis, and flexor pollicis longus
• Lateral Pinch (Key Pinch)
  • Involves adductor pollicis, flexor pollicis brevis, and flexor pollicis longus

First Dorsal Interossei

• Location: On the outside
• Function: Abducts the index finger
• Role in Key Pinch: Coordinates with thumb muscles

Coordination for Pinch Movements

• Palmar and Tip Pinch
  • Requires coordination between index and middle fingers
  • Involves both finger extensors and flexors, extrinsic and intrinsic muscles

Summary

• Basic hand muscles and their functions
• Mechanism and pathology of recent hand functions to be discussed further