[TA] facial muscle of mouth; origin, anterior portion of base of mandible; insertion, interdigitates with fibers of orbicularis oris musculus to reach skin of lower lip; action, depresses lower lip; nerve supply, facial. SYN: musculus depressor labii inferioris [TA], depressor muscle of lower lip, musculus quadratus labii inferioris, musculus quadratus menti.
