Question

identify the muscle. trapezius sternocleidomastoid splenius capitis splenius cervicis scalenes

Explanation:

The sternocleidomastoid muscle is located in the neck. It has two heads - sternal (from the sternum) and clavicular (from the clavicle), and inserts into the mastoid process of the temporal bone. When one side contracts, it rotates the head to the opposite side (as shown by the green arrow in the image indicating rotation), and when both sides contract, it flexes the neck. The trapezius is a large muscle of the upper back. The splenius capitis and cervicis are deep neck muscles more involved in extension and lateral flexion. The scalenes are also neck muscles but are more associated with elevation of the first and second ribs during respiration and lateral flexion/rotation to a lesser extent compared to the prominent role of sternocleidomastoid in the type of rotation shown.

Answer:

Sternocleidomastoid