Depressor Anguli Oris Muscle, Lateral View

Description

Running from the oblique line of the mandible to the modiolus at the oral commissure, the depressor anguli oris (DAO) appears as a triangular sheet on the anterolateral chin, with a broad inferior attachment and a narrow superior convergence at the corner of the mouth. Superior and slightly lateral to it, fibers of the zygomaticus major and the risorius approach the commissure, while the depressor labii inferioris lies more medial, nearer the lower lip. Posterior to the perioral complex, the auricle and adjacent facial musculature sit lateral to the parotid region, and inferiorly the superficial cervical contour suggests continuity toward the platysma and sternocleidomastoid. Clinically, the lateral view clarifies how the DAO counterbalances the elevators of the mouth and how small changes in its tone alter resting commissure position. Overactivity or age related descent can contribute to downturned mouth corners and marionette lines, a common target for botulinum toxin injection, but the DAO must be distinguished from the depressor labii inferioris to avoid unwanted lower lip depression or asymmetry. Surgical planning around the mandibular border also benefits from appreciating the DAO’s proximity to the marginal mandibular branch of the facial nerve as it courses forward toward the lower lip. Facial anatomy instructors can pair this plate with lessons on muscles of facial expression and the modiolus, where multiple muscles interdigitate in clinically visible patterns. A clean reference for dermatology and aesthetic medicine texts discussing perioral rejuvenation, and for maxillofacial or plastic surgery materials that need accurate orientation at the mandibular border. Anatomical accuracy verified by SciePro's Medical Advisory Board.