Depressor Anguli Oris

Description

Shown in a lateral view of the male face and upper neck, the depressor anguli oris (triangularis) is highlighted as a superficial muscle of the lower lip that runs from the oblique line of the mandible superiorly to the modiolus at the oral commissure. Its fibers lie lateral to depressor labii inferioris and blend with orbicularis oris at the corner of the mouth, while the platysma sits more inferiorly and posteriorly as a thin sheet over the submandibular region. Posterior to the perioral muscles, the masseter occupies the lateral mandibular ramus, and temporalis is seen superiorly in the temporal fossa. Fiber direction is explicit. Functionally, depressor anguli oris provides an inferior pull on the angle of the mouth, opposing the elevators of the commissure such as zygomaticus major and levator anguli oris, and its relationship to the modiolus helps explain coordinated facial expression rather than isolated muscle action. This view matters in facial nerve teaching because the muscle is supplied by buccal and marginal mandibular branches of the facial nerve, which are at risk during submandibular incision, parotid surgery, and lower face rejuvenation procedures; weakness produces an asymmetric smile with drooping of the oral commissure. The close proximity to the facial artery near the mandibular border also makes it a practical landmark in injection planning and surgical dissection. Use this artwork in head and neck anatomy coursework, dental and maxillofacial training materials, and facial nerve examination guides where students must connect a visible movement (frown, commissure depression) to a specific muscular vector. It also fits operative atlases and patient education handouts discussing marginal mandibular nerve palsy, lower lip asymmetry, or perioral botulinum toxin technique. Anatomical accuracy verified by SciePro's Medical Advisory Board.