Which muscle serves as the superior boundary of the Carotid Triangle?

The muscle that serves as the superior boundary of the Carotid Triangle is the Sternocleidomastoid. This triangle is an important anatomical region in the neck, bounded laterally by the sternocleidomastoid muscle, which runs from the sternum and clavicle to the mastoid process of the temporal bone.

The Carotid Triangle contains several important structures, including the common carotid artery, internal jugular vein, and various nerves. Being the most prominent muscle in this region, the sternocleidomastoid effectively defines the lateral boundary and helps position the contents of the triangle.

The other muscles listed do have their own significance; for instance, the platysma is a superficial muscle that covers the neck, while the omohyoideus and stylohyoideus serve different roles, but they do not define the superior limit of the Carotid Triangle. Thus, identifying the sternocleidomastoid as the correct boundary helps clarify the anatomy of the neck and the structural relationships within the Carotid Triangle.