What is sternocleidomastoidus?

The sternocleidomastoidus, commonly known as the sternocleidomastoid muscle, is a prominent muscle located in the neck. It originates from the sternum and clavicle and inserts into the mastoid process of the temporal bone of the skull. This muscle plays a crucial role in rotating and flexing the head, as well as assisting with neck movements. Its distinct structure allows for significant mobility and support of the head.