Lecture Notes: The Muscles of the Thumb

Introduction

• Focus on muscles of the thumb
• Importance of understanding thumb anatomy for function and injury assessment

Bones Involved

• Phalanges: Thumb has 2, fingers have 3
• Metacarpal Bone: Base of the thumb
• Carpal Bones: Trapezium, Scaphoid, Trapezoid, Capitate, Lunate
  • Scaphoid is the most commonly fractured bone

Intrinsic vs. Extrinsic Muscles

• Intrinsic Muscles: Located within the hand (thenar eminence)
  • Important for fine movement and dexterity
• Extrinsic Muscles: Located in the forearm
  • Provide greater strength through tendons

Movements of the Thumb

• Flexion and Extension
  • Flexion: Movement towards the palm
  • Extension: Movement away from the palm
• Abduction and Adduction
  • Abduction: Movement away from the hand
  • Adduction: Movement towards the hand
• Opposition and Reposition
  • Opposition: Thumb touches fingers
  • Reposition: Return to natural position
• Retropulsion: Lifting thumb off a flat surface

Muscles of the Thumb

Intrinsic Muscles (Thenar Eminence)

1. Abductor Pollicis Brevis
   • Abduction of the thumb
2. Flexor Pollicis Brevis
   • Flexion of the thumb
3. Opponens Pollicis
   • Assists with opposition by rotating the thumb
4. Adductor Pollicis
   • Adduction of the thumb

• Innervation: Mostly by the median nerve, except adductor pollicis (ulnar nerve)

Extrinsic Muscles

1. Flexor Pollicis Longus
   • Located in the anterior forearm
   • Flexes the thumb
   • Innervation: Median nerve
2. Extensor Pollicis Longus
   • Extends the thumb
   • Located in the posterior forearm
3. Extensor Pollicis Brevis
   • Short extension of the thumb
4. Abductor Pollicis Longus
   • Abducts the thumb

• Innervation: By the radial nerve for posterior muscles

Key Takeaways

• The thumb's movement and function are crucial for grip and dexterity
• Understanding the anatomy and innervation helps assess functional deficits due to nerve injury
• The thumb's unique positioning and movement require a complex muscle structure

Importance

• The thumb is vital for human hand function, and its muscles are essential for various grips and movements.

These notes should provide a comprehensive overview of the lecture on the muscles and movements of the thumb. Understanding these aspects is crucial for anyone studying anatomy, particularly those focused on human motor function and potential injuries.