Three general groups of muscles are found in the head and neck: those that move the head or neck, the muscles of facial expression, and the muscles for chewing. The muscles that turn or bend the head, such as the sternocleidomastoids (flexion) and the pair of splenius capitis muscles (extension), are anchored to the skull and to the clavicle and sternum anteriorly or the vertebrae posteriorly. The muscles for smiling or frowning or raising our eyebrows in disbelief are anchored to the bones of the head or to the undersurface of the skin of the face. The masseter is an important chewing muscle in that it raises the mandible (closes the jaw).See table 1 for details of muscles of head and neck.
