Which muscle forms the lateral boundary for the common carotid artery in the cervical triangle?

The sternocleidomastoid (SCM) muscle forms the lateral boundary for the common carotid artery within the cervical triangle. This muscle is a prominent feature of the neck, dividing it into anterior and posterior triangles. The SCM is responsible for various movements of the head and neck, including rotation and flexion.

In the context of the common carotid artery, the SCM is important as it provides a landmark for anatomical orientation. The artery typically runs deep to this muscle, and understanding its location in relation to the SCM is crucial for medical professionals, particularly for procedures involving the neck or vascular access to the artery.

The other muscles listed do not have the same anatomical relevance in this context. The deltoid is primarily involved in shoulder movements and located laterally over the shoulder, while the sartorius and adductor longus are both situated in the thigh and are not involved in the cervical triangle. Thus, recognizing the SCM's role helps clarify its significance in both anatomy and clinical practice related to the common carotid artery.