The extensor indicis is a deep muscle of human forearm, which lies on its posterior side, underneath the extensor digitorum. It has a narrow, elongated, and spindle-shaped belly.
The extensor indicis muscle arises from the lower third of dorsal (posterior) surface of the ulna. Stretching downwards and slightly obliquely, the it ends up as a long tendon that runs under the extensor retinaculum. Together with the extensor digitorum tendon, it passes through the synovial sheath. Finally, it is inserted in the tendinous expansion of dorsal surface of index finger.
Action
This long spindle-shaped muscle extends straight the index finger, as when we point at something or to give a sign.
Innervation
The extensor indicis muscle is innervated by a branch of the radial nerve (C6-C7-C8).
Blood Supply
It receives oxygenated blood from the posterior and anterior interosseous artery.
Below, schematic image that shows the extensor indicis and other extensor muscles of forearm
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