Origin: Oblique line of the mandible, between the symphysis and the mental foramen
Insertion: Integument of the lower lip, Orbicularis oris fibers, its fellow of the opposite side
Nerve: Facial nerve
Action: Depressthe lower lip
Depressor labii inferioris is a small quadrilateral muscle. It arises from the oblique line of the mandible, between the symphysis and the mental foramen, and passes upward and medialward, to be inserted into the integument of the lower lip, its fibers blending with the Orbicularis oris, and with those of its fellow of the opposite side. At its origin it is continuous with the fibers of the Platysma. Much yellow fat is intermingled with the fibers of this muscle.