Flexor pollicis longus (Musculus flexor pollicis longus)
Educational content only — not medical advice.
Anatomy
The lone deep radial-sided forearm muscle, solely flexing the thumb’s distal phalanx; the median nerve passes between it and flexor digitorum profundus into the hand.
Origin & insertion
Anterior radius below the oblique line and the interosseous membrane.
Action
Flexes the thumb at its distal phalanx and the joints above — the key to precision pinch and opposition.
Innervation
Median nerve — anterior interosseous branch (C8–T1).
Clinical notes
Palsy with FDP and pronator quadratus is anterior interosseous syndrome (Kiloh-Nevin): motor-only, an "incomplete prayer sign" with intact grip; open injuries over the scaphoid commonly cut its tendon.
Related structures
Educational references
FAQ
What is the role of the Flexor pollicis longus?
The lone deep radial-sided forearm muscle, solely flexing the thumb’s distal phalanx; the median nerve passes between it and flexor digitorum profundus into the hand.
Why is the Flexor pollicis longus clinically important?
Palsy with FDP and pronator quadratus is anterior interosseous syndrome (Kiloh-Nevin): motor-only, an "incomplete prayer sign" with intact grip; open injuries over the scaphoid commonly cut its tendon.
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details