It is a subcutaneous muscle present under the chin that overlies the sternocleidomastoid. It belongs to the group of cross-striated musculature.
It usually occurs as a pair of broad sheet of muscles on either side of the anterior neck.
It arises from the fascia overlapping the pectoral muscle at the chest and deltoid muscles of the shoulders. It further rises over the collarbone/clavicle and proceeds upward in a slanting manner along the sides of the neck.
Behind and below the symphysis menti, which is the external surface of the mandible, the fibers of the anterior and posterior regions of the muscle sheet interconnects, and crosses the jawbone. It inserts into the inferior border of mandible and skin over the lower region of the face. Some of the fibers merge with the muscles at the angle and lower part of the mouth. The lip muscle of the oral cavity called zygomaticus as well as the margin of the orbicularis oris are also distributed with the fibers of the muscle sheet. The external jugular vein descends from the angle of the mandible to the clavicle underneath the broad muscle.
The distribution of the muscle over the face, clavicle and shoulder often undergoes variations. It may either be absent or interlocked with the muscle of the opposite side in the anterior region of the neck. In some cases, the fibers are anchored to the clavicle, mastoid process or occipital bone. A slender bundle of fibers of the occipitalis minor may extend from the fascia over the trapezius to the fibrous tissue overlying the sternocleidomastoideus. It is normally innervated by the cervical branch of the facial nerve.
While in action, the broad muscle pulls the lower lip and corner of the mouth sideways and down to change the facial expression when an individual is in an emotional state. It also depresses and wrinkles the skin of the neck, a common sign of aging, and helps in the lowering of the mandible. The muscle increases the diameter of the neck during the intensive breathing when all the fibers work in coordination.
The flap of the muscle is often used to correct defects on the lower face, buccal mucosa, and floor of mouth.
The muscle at the front of the neck can be tightened and toned down to prevent drooping chin, sagging jaw line and loose skin under the chin. Range of motion workouts for the neck keeps the muscle sheets flexible and strong. Hanging head exercises as well as chin firm performed during the normal aging process firm the regions around the jaw and neck.