What is the action of the common digital extensor?

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

Answer: (C)

The common digital extensor is primarily responsible for extending the carpus and the digits II to V in the forelimb. This muscle plays a crucial role in facilitating movements that involve lifting and straightening the fingers, as well as supporting the carpus during various activities.

When considering the action of the common digital extensor, it is important to note its anatomical position and attachments. This muscle originates from the lateral epicondyle of the humerus and radiates down to insert on the extensor processes of the distal phalanges of the digits. Therefore, its extension function is directly aligned with extending both the wrist (carpus) and the fingers (digits II-V).

Understanding the specific loci of muscle actions is essential for comprehending how they contribute to overall limb movement and function, which reinforces why choice C accurately describes the action of the common digital extensor.