Depressor Anguli Oris Muscle Under the Skin, Anterior View

Description

Positioned in the superficial lower face, the depressor anguli oris forms a paired, triangular sheet that runs from the anterolateral mandible (near the oblique line) superiorly to the modiolus at the corner of the mouth, where it interlaces with orbicularis oris, zygomaticus major, and risorius. From an anterior perspective under the skin, its fibers sit lateral to depressor labii inferioris and inferior to the oral commissure, framing the lower lip as they descend toward the mandibular body. Bilateral symmetry is apparent, allowing side-to-side comparison of fiber direction and muscle bulk. Skin removed. Expression muscles exposed. Clinically, this is the muscle you track when explaining why lower facial paralysis produces drooping of the mouth corner, while forehead sparing points toward an upper motor neuron pattern. The depressor anguli oris also matters in aesthetic and reconstructive planning, since botulinum toxin injection for downturned commissures targets this muscle, and imprecise placement can weaken depressor labii inferioris and cause an asymmetric lower lip during speech and smiling. Its relationship to the modiolus is the landmark, not the muscle belly alone. Facial anatomy and head and neck courses use this view to teach the layered organization of perioral mimetic muscles and the mechanics of frowning, pouting, and oral competence. Medical publishers often pair it with diagrams of facial nerve (CN VII) marginal mandibular branch injury after submandibular surgery or facelift, and with procedural atlases for cosmetic toxin mapping around the lower lip. Anatomical accuracy verified by SciePro's Medical Advisory Board.