Anatomical Structure and Location of the Depressor Anguli Oris Under the Skin

Description

Positioned in the superficial lower face, the depressor anguli oris (triangularis) forms a thin, triangular sheet that runs from the anterolateral mandible up to the modiolus at the oral commissure. In profile, its fibers ascend superiorly and slightly medially, lying lateral to depressor labii inferioris and blending with orbicularis oris at the corner of the mouth. Posterior to it, the masseter occupies the ramus of the mandible, while inferiorly the platysma approaches the mandibular border and the anterior neck contours. Key bony landmarks include the body of the mandible and the dentition, with the nasal cavity and cranial base providing deeper skeletal context. Functionally, depressor anguli oris draws the mouth angle inferiorly and laterally, counterbalancing the elevators of the upper lip and commissure during speech, mastication, and facial expression. This is the muscle clinicians target when addressing downturned oral commissures and marionette-line deformity with chemodenervation, and it is also a practical reference when teaching why marginal mandibular branch facial nerve injury produces lower lip asymmetry on smiling. Small anatomy, frequent clinical consequence. Use this profile-based head and neck illustration for dental and maxillofacial anatomy teaching, facial expression modules in gross anatomy, and surgical planning graphics for facelift, submental, or mandibular border approaches where the facial artery, facial vein, and marginal mandibular nerve travel in close neighborhood to the depressor complex. It also suits patient-facing diagrams explaining botulinum toxin placement or postoperative weakness around the oral commissure. Anatomical accuracy verified by SciePro's Medical Advisory Board.