Zygomaticus major muscle

The zygomaticus major muscle is a muscle of the face. It arises from either zygomatic arch (cheekbone); it inserts at the corner of the mouth. It is innervated by branches of the facial nerve (cranial nerve VII).

It is a muscle of facial expression, which draws the angle of the mouth superiorly and posteriorly to allow one to smile. Bifid zygomaticus major muscle is a notable variant, and may cause cheek dimples.

Origin
The zygomaticus major muscle originates from the superior margin of the lateral surface of the temporal process of zygomatic bone, just anterior to the zygomaticotemporal suture.

Insertion
It inserts at the corner of the mouth by blending with the levator anguli oris muscle, the orbicularis oris muscle, and the deeper muscular structures.

Nerve supply
The muscle receives motor innervation from the buccal branch and zygomatic branch of the facial nerve (CN VII).

Vasculature
The muscle receives arterial supply from the superior labial artery.

Variation
The zygomaticus major muscle may occur in a bifid form, with two fascicles that are partially or completely separate from each other but adjacent. It is thought that cheek dimples are caused by bifid zygomaticus major muscle.

Function
The zygomaticus major muscle raises the upper lip to bare the upper teeth. It additionally deepens and raises the nasolabial furrow. Acting in conjunction with other muslces of facial expression that elevate the lip, it curls the upper lip to produce facial expressions such as smiling, disdain, contempt, or smugness.

Physiology
The average muscle can contract with a force of 200 g.

Clinical significance
The zygomaticus major muscle may be used in reconstructive surgery to replace lost tissue, such as with injuries to the lips.