A model showing the location of the facial and neck muscles. The top part of the skull has also been removed to reveal the cerebrum, the largest part of the brain, together with the blood vessels which provide its blood supply. The sternocleido- mastoid muscle in the neck has a cylindrical shape and runs obliquely from the posterior lower part of the cranium to the anterior part of the collar bone. The action of this muscle is to rotate and tilt the head. The trapezium, the triangular muscle extending over the back of the neck, controls the position of the shoulder blade during active use of the upper limb. The parotid gland is seen at centre close to the ear.