Levator anguli oris

At a glance

English

Levator anguli oris

Latin (TA2)

Levator anguli oris

System

Muscle

Region

Head

Side

Paired, left and right

About the levator anguli oris

The levator anguli oris, formerly called the caninus, is a muscle of facial expression in the upper lip region. It lies deep to the levator labii superioris and the zygomaticus minor, close against the front of the maxilla, so most of it is hidden from the surface. Its job is to lift the corner of the mouth, and it shares that task with the zygomaticus major, which pulls the corner more outwards.

It arises from the canine fossa, the shallow depression on the front of the maxilla just below the infraorbital foramen and above the root of the canine tooth. Between its origin and the levator labii superioris lies a narrow plane through which the infraorbital nerve and vessels fan out after leaving their foramen, so the muscle separates these structures from the bone below. From the fossa it runs down and slightly lateral to the modiolus at the angle of the mouth. There its fibres interweave with those of zygomaticus major, depressor anguli oris and orbicularis oris, and some continue into the lower lip.

Contraction raises the angle of the mouth and draws it a little towards the midline, deepening the nasolabial fold. It helps to produce a smile and, with the levator labii superioris, an expression of contempt or sneering that shows the canine tooth, which is why it was once named after that tooth. Acting with the depressor anguli oris, which pulls the corner the other way, it helps to steady the modiolus during speech and chewing.

Its nerve supply is from facial nerve buccal branches, which reach its superficial surface, and its blood comes from the superior labial branch of the facial artery and the infraorbital artery. In facial palsy its loss contributes to the drooping corner of the mouth on the weak side, and in reanimation surgery a muscle or tendon transfer is often aimed at this corner to restore a symmetrical smile.

Attachments, action and supply

Origin

Canine fossa of the maxilla, below the infraorbital foramen.

Insertion

Modiolus at the angle of the mouth, blending with zygomaticus major, depressor anguli oris and orbicularis oris.

Action

Raises the corner of the mouth and draws it slightly medially, deepening the nasolabial fold.

Nerve supply

Facial nerve (VII), buccal branches.

Blood supply

Superior labial branch of the facial artery and the infraorbital artery.