Anatomy, Shoulder and Upper Limb, Hand Flexor Pollicis Longus Muscle

Excerpt

The flexor pollicis longus (FPL) muscle is one of the three deep flexors of the volar compartment of the forearm. Originating on the volar surface of the proximal aspect of the radius, FPL courses along the radial aspect of the volar forearm before transitioning into a long tendinous slip that traverses deep to the transverse carpal ligament as a constituent of the carpal tunnel, and inserting distally on the base of the distal phalanx of the thumb.