[TA] muscle of deep layer of anterior (flexor) compartment of forearm; origin, anterior surface of middle third of radius; insertion, palmar aspect of distal phalanx of thumb; action, flexes thumb at interphalangeal joint; nerve supply, median (anterior interosseous). SYN: musculus flexor pollicis longus [TA], long flexor muscle of thumb, musculus flexor longus pollicis.
