Depressor Anguli Oris
Facial Expression · Head & Neck
The depressor anguli oris is a triangular muscle of facial expression that pulls the corner of the mouth downward in frowning. It arises from the oblique line of the mandible, below the canine, premolar, and first molar teeth, and its fibres converge upward to insert into the modiolus at the angle of the mouth. When it contracts it depresses the angle of the mouth, producing an expression of sadness or displeasure, acting as the direct antagonist of the levator anguli oris. It is supplied by the facial nerve (CN VII) through its buccal and marginal mandibular branches. The marginal mandibular branch runs a superficial course near the lower border of the mandible, where it is vulnerable during surgery in the region.
Origin, Insertion, Action & Nerve
Origin
Oblique line of the mandible (below the canine, premolar, and first molar)
Insertion
Modiolus at the angle of the mouth
Action
Depresses the angle of the mouth (frowning)
Nerve
Buccal and marginal mandibular branches of facial nerve (CN VII)
Attachments explained
The Depressor Anguli Oris is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Oblique line of the mandible (below the canine, premolar, and first molar)
Insertion
Modiolus at the angle of the mouth
Action & function
When the Depressor Anguli Oris contracts, it produces the following movement: Depresses the angle of the mouth (frowning).
As part of the Facial Expression group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Depressor Anguli Oris receives its nerve supply from the Buccal and marginal mandibular branches of facial nerve (CN VII).
Because a muscle can only contract when its nerve is intact, injury to the Buccal and marginal mandibular branches of facial nerve can weaken or paralyse the Depressor Anguli Oris, impairing the movements it normally produces (depresses the angle of the mouth (frowning)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Depressor Anguli Oris (the OIANS method)
Study the depressor anguli oris as the mirror image of the levator anguli oris: one lowers and the other raises the same corner of the mouth, and both attach to the modiolus. Fix its broad origin along the oblique line of the mandible, from which the fibres taper upward, so its downward pull on the modiolus and the resulting frown follow naturally from its shape and position.
Emphasise the clinically important nerve: the depressor anguli oris is supplied partly by the marginal mandibular branch of the facial nerve (CN VII), which travels superficially near the lower jaw and is easily injured in operations there, producing an asymmetric smile. Pairing this muscle with the depressor labii inferioris, which shares the same marginal mandibular supply, reinforces both muscles at once.
Frequently asked questions
Where is the Depressor Anguli Oris located?
The Depressor Anguli Oris is a muscle of the Facial Expression group, located in the Head & Neck.
What is the origin of the Depressor Anguli Oris?
Oblique line of the mandible (below the canine, premolar, and first molar)
What is the insertion of the Depressor Anguli Oris?
Modiolus at the angle of the mouth
What movements does the Depressor Anguli Oris produce?
Depresses the angle of the mouth (frowning)
What nerve supplies the Depressor Anguli Oris?
Buccal and marginal mandibular branches of facial nerve (CN VII)
Is the Depressor Anguli Oris free to study in OIANS?
The Depressor Anguli Oris is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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