Musculus extensor ossis metacarpi pollicis, also known as the extensor pollicis longus muscle, is a long slender muscle that is located in the forearm. It is one of the primary muscles responsible for extending or straightening the thumb.
The term "musculus" refers to a muscle, while "extensor" denotes its function of extension or elongation. "Ossis" indicates its origin from the bone, and "metacarpi" refers to the metacarpal bones of the hand. Finally, "pollicis" signifies its attachment to the thumb.
The muscle arises from two distinct sites: the posterior surface of the ulna bone (the larger of the two forearm bones) and the interosseous membrane. It then travels through a groove on the dorsal radial aspect of the forearm, passing underneath a fibrous extensor retinaculum.
The musculus extensor ossis metacarpi pollicis extends to the base of the distal phalanx of the thumb, where it inserts via a tendon. Its primary function is to extend the thumb at the carpometacarpal joint, allowing for opposition and extension of the thumb away from the palm.
The musculus extensor ossis metacarpi pollicis is innervated by the posterior interosseous nerve, a branch of the radial nerve. It receives its blood supply from branches of the posterior interosseous artery.
In summary, the musculus extensor ossis metacarpi pollicis is a forearm muscle responsible for extending the thumb. It originates from the ulna bone and interosseous membrane, travels through the forearm, and inserts into the base of the distal phalanx of
