Sternocleidomastoid muscle
The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the accessory nerve.
The sternocleidomastoid (right muscle shown) can be clearly observed when rotating the head.
The scalene muscles are a group of three muscles on each side of the neck, identified as the anterior, the middle, and the posterior. They are innervated by the third to the eighth cervical spinal nerves (C3-C8).
Scalene muscles. Muscles of the neck. Lateral view.
Scalene muscles. Muscles of the neck. Lateral view.