The abductor pollicis longus muscle emerges via the associated interosseous membrane and the proximal posterior sides of the radius as well as the ulna. It arises in between the extensor digitorum along with extensor carpi radialis brevis muscles within the distal forearm, in order to create a tendon that enters the thumb and attaches on the lateral side of the base of metacarpal I. The tendon adds to the lateral boundary of the anatomical snuffbox at the wrist.
Interactive Anatomical Interface
Travelling obliquely down and lateralward, it terminates within a tendon, which goes through an indentation on the lateral part of the lower end of the radius, along with the tendon of the extensor pollicis brevis. The abductor pollicis longus is located instantly under the supinator and is often combined with it. The insertion is split within a distal, superficial portion and a proximal, deep portion. The superficial portion is placed with several tendons into the radial part of the base of the first metacarpal bone, and the deep portion is variably placed within the trapezium, the joint capsule and its ligaments, and in the belly of abductor pollicis brevis or opponens pollicis.
- The Radial Nerve
- the posterior interosseus nerve, C7, C8
- The Posterior Interosseus Artery which is a branch of the Ulnar Artery.
- The perforating branches of the Anterior Interosseus artery which is a branch of the Ulnar Artery.
The abductor pollicis longus crosses the first CMC joint anteriorly in order to connect over the metacarpal of the thumb with its fibers going vertically inside the sagittal plane.
Whenever the abductor pollicis longus constricts, it draws the metacarpal of the thumb anteriorly in the sagittal plane, in an instructions that is perpendicular to, and far from the plane of the palm of the hand. This action is called abduction of the thumb.
For that reason the abductor pollicis longus abducts the thumb by abducting the metacarpal of the thumb at the first CMC joint. Due to the rotational development of the thumb embryologically, the called actions of abduction and adduction of the thumb happen within the sagittal plane.