What is the primary action of the cutaneous truncii muscle?

• A. Twitch skin
• B. Draw scapula dorsally
• C. Advance limb
• D. Support trunk

Answer: (A)

The cutaneous truncii muscle primarily functions to twitch the skin. This muscle is a thin layer of muscle located in the subcutaneous tissue, and its contraction helps in the movement of the skin, allowing for a variety of actions such as flicking away insects or other irritants. This twitching action is particularly useful in animals with fur or hair, as it enables them to respond quickly to stimuli on their skin without requiring a significant movement of the underlying body or limbs.

In different contexts, the other choices refer to muscles with different roles: drawing the scapula dorsally relates to the function of muscles that control scapular movement; advancing the limb is linked to muscles that facilitate limb movement; and supporting the trunk pertains to muscles involved in maintaining posture and stability. However, these actions do not describe the primary function of the cutaneous truncii muscle.