Muscle
Flexor pollicis longus
Deep flexor of the thumb tip
High-yield
Its nerve supply comes through the anterior interosseous branch of the median nerve. Together with index-finger profundus, it provides the flexion needed for a rounded thumb-index pinch.
Overview
From the front of the radius, a long tendon passes through the carpal tunnel to the thumb's distal phalanx. Its pull bends the thumb at the IP joint and also helps flex the MCP joint.
Reference facts
- Origin
- Anterior radius and its adjacent interosseous membrane
- Insertion
- Palmar base of the thumb's distal phalanx
- Action
- Flexes the thumb IP joint and assists MCP flexion
- Innervation
- Anterior interosseous branch of the median nerve, chiefly C8-T1
- Blood supply
- Anterior interosseous artery; distal tendon portions also receive local thumb arterial branches
Clinical correlation
Anterior interosseous dysfunction can weaken thumb IP flexion and index DIP flexion, producing a flatter pinch. Partial palsies may affect only one muscle, and tendon rupture can cause a similar loss of movement.
Frequently asked questions
What does the flexor pollicis longus do?
The flexor pollicis longus flexes the thumb IP joint and assists MCP flexion.
What nerve innervates the flexor pollicis longus?
Anterior interosseous branch of the median nerve, chiefly C8-T1.
Where does the flexor pollicis longus attach?
Origin: Anterior radius and its adjacent interosseous membrane. Insertion: Palmar base of the thumb's distal phalanx.
What is the blood supply of the flexor pollicis longus?
Anterior interosseous artery; distal tendon portions also receive local thumb arterial branches.