What action does the extensor carpi radialis perform?

• A. Abduct manus, flex carpus
• B. Extend carpus, extend digits II-V
• C. Flex elbow
• D. Abduct digit I, extend carpus

Answer: (A)

The extensor carpi radialis primarily functions to extend the wrist (carpus) and assist in abducting the hand (manus) at the wrist joint. It is responsible for actions where the wrist is extended while also moving the hand laterally away from the body's midline. Therefore, the correct choice involves extending the carpus alongside the action of abduction.

The other options do not accurately describe the primary functions of the extensor carpi radialis. The second choice involves extending the digits, which is not the primary action of this muscle. The third choice, stating flexion of the elbow, does not relate to the extensor carpi radialis, as it specifically acts on the wrist. The fourth choice inaccurately combines actions related to the abduction of digit I (the thumb) with extension of the carpus, which does not represent the primary function of this muscle. Hence, the identification of the extensor carpi radialis is centered on its role in extending the wrist and assisting with abduction, marking it distinct from these other functions.