Abductor pollicis longus muscle Abductor pollicis longus muscle In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand. As the name implies, its major function is to abduct the thumb at the wrist. Its tendon forms the anterior border of the anatomical snuffbox. The abductor pollicis longus lies immediately below the supinator and is sometimes united with it. It arises from the lateral part of the dorsal surface of the body of the ulna below the insertion of the anconeus, from the interosseous membrane, and from the middle third of the dorsal surface of the body of
Anatomical terms of location the x, y, and z axes familiar from three-dimensional geometry. The terms "intermediate", "ipsilateral", "contralateral", "superficial", and "deep", while indicating directions, are relative terms and thus do not properly define fixed anatomical axes. Also, while the "rostrocaudal" and anteroposterior directionality are equivalent in a significant portion of the human body, they are different directions in other parts of the body. In anatomical terminology superior () is used to refer to what is above something, and inferior () to what is below it. For example, in the anatomical position the most superior part of the human body is the head, and