Theis a broad muscle that originates in the tissue overlying the clavicle. It is a thin broad sheet of superficial muscle that inserts into the mandible from the midline to the angle and has some fibers that insert into the corner of the lip. It acts somewhat to pull down the corners of the mouth and lower lip plus can help depress the mandible. However, it is not a major player in either of those actions but is usually contracted when the mandible is clenched which protrudes the overlying skin of the neck. This action is usually interpreted as fear or exasperation depending on the other muscles of the face that are activated simultaneously.