Which muscle forms part of the boundary of the anterior triangle in the neck?

Which muscle forms part of the boundary of the anterior triangle in the neck?

• A. Sternocleidomastoid
• B. Platysma
• C. Masseter
• D. Trapezius

Answer: (A)

The boundary of the anterior triangle is defined, in part, by the sternocleidomastoid muscle. Its anterior border forms the posterior limit of the anterior triangle, separating it from the posterior triangle. This makes the sternocleidomastoid the muscle that helps outline the area of interest. The platysma lies superficially over the neck and contributes to the roof of the region, but it does not define the main border. The masseter is a jaw muscle and not involved in the neck triangle borders, and the trapezius marks the posterior boundary of the posterior triangle, not the anterior triangle.

The boundary of the anterior triangle is defined, in part, by the sternocleidomastoid muscle. Its anterior border forms the posterior limit of the anterior triangle, separating it from the posterior triangle. This makes the sternocleidomastoid the muscle that helps outline the area of interest. The platysma lies superficially over the neck and contributes to the roof of the region, but it does not define the main border. The masseter is a jaw muscle and not involved in the neck triangle borders, and the trapezius marks the posterior boundary of the posterior triangle, not the anterior triangle.