Depressor anguli oris

Musculus depressor anguli oris

Also known as: triangularis

A triangular muscle from the oblique line of the mandible to the modiolus. It pulls the corner of the mouth down (frowning, sadness).

Show on body map

Overview

Depressor anguli oris arises broadly from the oblique line of the mandible, below the canine, premolar and first molar teeth. Its fibres converge on the modiolus, where it blends with orbicularis oris and risorius. It overlies depressor labii inferioris and is continuous below with platysma. It is supplied mainly by the marginal mandibular branch of CN VII, which runs along the lower border of the mandible and is at risk in submandibular surgery.

Anatomy

Origin: Oblique line of the mandible.
Insertion: Modiolus at the angle of the mouth.
Action: Draws the angle of the mouth inferolaterally.
Innervation: Facial nerve (CN VII), marginal mandibular (and buccal) branches.
Nerve roots: Cranial nerve VII; no spinal roots
Arterial supply: Inferior labial branch of the facial artery; mental artery.

Function

Depresses the angle of the mouth (sadness, frowning)

Clinical significance

Marginal mandibular nerve injury

Damage during submandibular gland excision or neck dissection paralyses the lower-lip depressors, giving an asymmetric smile because the affected side of the lower lip cannot be pulled down.

Congenital hypoplasia

Asymmetric crying facies: in an infant, one corner of the mouth fails to move down when crying. It is sometimes associated with cardiac anomalies.

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.