What is one of the primary muscles involved in left trunk rotation?

• A. Right External Oblique
• B. Left Internal Oblique
• C. Right Internal Oblique
• D. Left External Oblique

Answer: (D)

The primary muscle involved in left trunk rotation is the left external oblique. This muscle is situated on the lateral side of the abdomen and plays a crucial role in trunk rotation and lateral flexion. When contracting, the left external oblique assists in rotating the trunk toward the left by working in conjunction with the right internal oblique muscle. This coordinated action creates a rotational force that effectively facilitates leftward trunk movement.

The left external oblique's fibers run diagonally from the lower ribs to the midline of the abdomen, which positions it ideally for this function. When examining the role of trunk rotation, it is essential to recognize the contribution of both external and internal oblique muscles; however, in the context of left trunk rotation, the left external oblique has the primary responsibility.

Understanding the anatomy and function of these muscles helps clarify how movements such as trunk rotation are facilitated in the human body.