Part of the next and throat, the sternocleidomastoid includes the sternum and the medial third of the clavicle. It is located at the mastoid process on the skull. The sternocleidomastoid is responsible for bending the head laterally to the same side, bringing the ear toward the shoulder. It is also responsible for rotating the head – allowing the face to turn away. The head rolls toward the back from both of its sides working together.