extensor pollicis longus muscle

ex·ten·sor pol·li·cis lon·gus mus·cle

(eks-ten'sŏr pol'i-sis long'gus mŭs'ĕl)

Muscle of posterior (extensor) compartment of forearm; origin, posterior surface of middle of shaft of ulna; insertion, dorsal aspect of base of distal phalanx of thumb; action, extends distal phalanx of thumb; nerve supply, radial (posterior interosseous).
Synonym(s): long extensor muscle of thumb, musculus extensor pollicis longus.