This relatively thick muscle passes obliquely across the side of the neck and is used to measure the widest part of the neck. What is it called?

The sternocleidomastoid muscle is the correct answer in this context. This muscle is located on either side of the neck, running from the sternum and clavicle to the mastoid process of the temporal bone behind the ear. Its oblique orientation across the neck is distinctive, making it a prominent landmark for both anatomical studies and practical applications, including measuring the widest part of the neck.

In practical terms, the sternocleidomastoid muscle can be palpated easily, and its size and position help in various medical and cosmetic assessments. This muscle also plays a significant role in movements of the head and neck, including rotation and flexion, which can be especially important in the fields of anatomy and mortuary science, where an understanding of the human body is crucial.

The other options, while relevant to neck anatomy, do not fulfill the specific criteria of being the muscle that measures the widest part of the neck. The trapezius is a large muscle that covers much of the upper back and neck but does not measure the neck's width. The platysma is a thin muscle that covers the front of the neck and is not used for this measurement. The scalenes are deeper neck muscles involved in respiration and also do not