Depressor Anguli Oris, Lateral View

Description

Shown in left lateral profile, the male facial skeleton and upper cervical spine provide bony context for the depressor anguli oris (triangularis) as it descends from the modiolus and lateral commissure of the mouth to its mandibular attachment along the oblique line near the lower border of the mandible. Superior to its mandibular insertion lie the alveolar process and dentition, while posteriorly the ramus and angle of the mandible align with the masseteric region. Anteriorly, the nasal cavity with conchal contours sits above the oral vestibule, and the occipital bone transitions inferiorly into the atlas and axis with intervertebral discs indicated between cervical vertebrae. Spatial relationships are clear. The muscle fibers course inferolaterally, placing their line of pull toward the mandibular base. For teaching facial expression, a side view like this clarifies how depressor anguli oris lowers the oral commissure and contributes to a downturned mouth angle, opposing elevator anguli oris and zygomaticus major at the modiolus. Clinically, this muscle becomes relevant when assessing marginal mandibular branch (CN VII) injury after submandibular gland surgery or lower face rhytidectomy, where asymmetric depression of the mouth corner can persist even with an intact mental nerve. Injection planning benefits too: over-relaxation with botulinum toxin can exaggerate smile imbalance by unmasking elevator dominance. Facial anatomy and head and neck courses use this plate to anchor origin, insertion, and vector of pull against reliable mandibular landmarks, and it reproduces cleanly in atlases, board-review material, and patient-facing explanations of lower facial weakness. Preoperative counseling documents for facelift, neck dissection, and perioral toxin treatment can also reference the relationships to the mandible and oral commissure. Anatomical accuracy verified by SciePro's Medical Advisory Board.