Thumb Flexor Muscles Anatomy Quiz

Muscle Functions and Anatomy

• The Flexor Pollicis Longus muscle assists in flexion of the thumb metacarpophalangeal and carpometacarpal joints.
• The Flexor Pollicis Longus muscle is supplied by the anterior interosseous nerve.
• The main action of the Flexor Pollicis Longus muscle is to flex the interphalangeal joint of the thumb.

Muscle Origins

• The primary origin of the Flexor Pollicis Longus muscle is the middle half of the anterior surface of the radius and the adjacent interosseous membrane.
• The primary origin of the Deep Head of the Flexor Pollicis Brevis muscle is the ulna and the adjacent interosseous membrane.
• The origin of the Superficial Head of the Flexor Pollicis Brevis muscle is the flexor retinaculum, the trapezium, and the adjacent part of the first metacarpal bone.

Joint Mobility

• The range of motion for thumb-metacarpophalangeal joint flexion is 50-60 degrees.
• The range of motion for interphalangeal joint flexion of the thumb is 80-90 degrees.

Muscle Weakness and Actions

• Weakness of the Flexor Pollicis Longus muscle can lead to weakness in opposition of the thumb toward the little finger.
• The Flexor Pollicis Brevis muscle is responsible for flexing the interphalangeal joint of the thumb and may assist in opposition of the thumb toward the little finger.
• The Flexor Pollicis Longus muscle assists in flexion of the wrist.
• The action that is NOT primarily associated with the Flexor Pollicis Brevis muscle is extension of the thumb.