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Origins, insertions, innervation and function of the extensor indicis muscle.
Well, hello, everyone! It’s Matt from Kenhub, and in this tutorial, we will be discussing the extensor indicis muscle. The deep extensors of the forearm consist of five muscles located at the posterior side of the forearm. Their muscle bellies and tendons form the surface of the distal forearm and the wrist where they can be easily palpated. The focus of this video will be one of these muscles called the extensor indicis. This muscle runs parallel to the extensor pollicis longus on its medial side.
The extensor indicis muscle originates at the posterior side of the ulna and the interosseus membrane near the wrist. The extensor indicis inserts at the dorsal aponeurosis of the index finger. Like all extensors of the forearm, these five muscles are innervated by the radial nerve which is seen here highlighted in green in this image. The radial nerve divides into a superficial branch and deep branch at the height of the radial head. The deep branch penetrates the supinator muscle and branches off as the posterior interosseus nerve which supplies the extensor indicis.
The main function of the deep extensors is to move the joints of the hand and fingers. The extensor indicis pulls the index finger by performing extension at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints. This leads to an extension of the wrist joint as well.
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