The levator anguli oris (also known as the caninus muscle) is a small facial muscle of the oral group that contributes to the elevation of the mouth angle, which enables smiling and other facial expressions used in nonverbal communication and speech. It lies deep to the levator labii superioris, near the oral opening. The infraorbital nerve and vessels pass between these muscles at their origin sites.

Origin and insertion of levator anguli oris

The levator anguli oris originates from the canine fossa and extends anteroinferiorly to insert into the modiolus, which is a fibromuscular structure at the corner of the mouth. Other muscles inserting into the modiolus include the zygomaticus major, buccinator, risorius, depressor anguli oris, and orbicularis oris. All these muscles contribute to diverse facial expressions by pulling the angle of the mouth in different directions.

Origin: canine fossa on the anterior surface of the maxilla, approximately 0.4 inches (1 centimeter) below the infraorbital foramen.

Insertion: modiolus at the angle of the mouth, blending with the fibers of the zygomaticus major, depressor anguli oris, and orbicularis oris muscles.

Action: pulls the angle of the mouth up, curving the mouth line upward at its end (as in smiling). It also contributes to lateralization of the oral commissure and lip stretching.

Innervation: buccal branches of the facial nerve (CN VII); may also receive input from the zygomatic branches.

Arterial blood supply: superior labial artery (branch of the facial artery), infraorbital artery (branch of the maxillary artery), transverse facial artery (branch of the superficial temporal artery).

Venous drainage: tributaries of the facial vein and infraorbital vein, which drains into the pterygoid venous plexus.

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Levator anguli oris