The extensor carpi ulnaris muscle lies on the medial border of the posterior surface of forearm (on the little finger side). It has a long, spindle-shaped belly. It originates from the lateral epicondyle of humerus, the posterior border of ulna, and the capsule of the elbow-joint.
From its points of origin, the extensor carpi ulnaris extends down, slightly obliquely, as it crosses over to the ulnar side of forearm. When it reaches the distal portion of ulna, it becomes a tendon that runs under the extensor retinaculum of wrist. Finally, it is inserted into the base of the dorsal surface of the fifth metacarpal bone by the synovial sheath of the extensor carpi ulnaris tendon.
Action
It abducts the hand to the ulnar side. It also extends it at the wrist-joint.
Innervation
This spindle-shaped muscle is innervated by the radial nerve (C5-C6-C7).
Blood Supply
The extensor carpi ulnaris muscle receives oxygen-rich blood from the posterior interosseous artery.
Image of posterior compartment of forearm, showing the extensor muscles
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