Which muscle is specifically involved in extending and adducting the wrist?

The extensor carpi ulnaris is the muscle specifically involved in extending and adducting the wrist. It originates from the lateral epicondyle of the humerus and inserts on the base of the fifth metacarpal bone. When it contracts, it works to extend the wrist joint, moving the hand away from the forearm, and simultaneously adducts the wrist by pulling the hand towards the midline of the body. This dual action allows it to perform these specific functions effectively.

In contrast, the flexor carpi ulnaris primarily functions to flex and adduct the wrist, so it does not contribute to extension. The biceps brachii mainly acts on the elbow joint, flexing the forearm and supinating the hand, and does not play a significant role in wrist movement. The extensor carpi radialis, while involved in wrist extension, primarily functions in radial deviation (abduction of the wrist), rather than adduction. Thus, the unique combination of functions performed by the extensor carpi ulnaris solidifies its role in extending and adducting the wrist.