Zygomaticus major muscle: anatomy and the smile
- Muscle
Quick facts
- Origin
- Lateral surface of the zygomatic bone, in front of the zygomaticotemporal suture.
- Insertion
- Modiolus, at the corner of the mouth, blending with the orbicularis oris and other muscles of the commissure.
- Action
- Draws the mouth corner up and outward: it is the main smile muscle.
- Innervation
- Zygomatic and buccal branches of the facial nerve.
- Relevance in HOF
- Defines the smile; it lies in the path of cheekbone filler and can be reached by toxin placed low in the crow's feet.
- In Harmy
- It lies under the Cheekbone and Nasolabial Fold points.
The zygomaticus major is the main smile muscle. It arises from the zygomatic bone, on the side of the cheekbone, and runs diagonally down to the corner of the mouth. When it contracts, it draws the commissure up and outward. It is the muscle that weighs most in the difference between a spontaneous smile and a restrained one.
Where is it and how is it built?
It is a band-like muscle that crosses the midface diagonally:
| Feature | Description |
|---|---|
| Origin | Lateral surface of the zygomatic bone, in front of the zygomaticotemporal suture |
| Course | Runs diagonally down and inward, across the cheek |
| Insertion | Modiolus, the fibromuscular knot beside the commissure |
| Neighbors | Zygomaticus minor (medial), orbicularis oculi (above), risorius and buccinator (at the modiolus) |
| Innervation | Zygomatic and buccal branches of the facial nerve, which arrive through the deep surface |
The facial vein passes under the muscle, and the buccal fat pad (Bichat's fat pad) lies in a deeper plane. In some people the muscle is bifid, with two bundles at the insertion, a variation associated with a cheek dimple.
Why does it matter in HOF?
The zygomaticus major matters for three reasons:
- Smile and expression: it defines the height and width of the smile. Any intervention that alters its action changes how the whole face reads.
- Toxin in the crow's feet: the lower part of the fan lies close to the origin of the muscle. Spread of botulinum toxin to it can leave the smile asymmetric.
- Midface filler: in cheekbone filler and zygomatic filler, the muscle and the fat pads are in the way. Excess volume in the area can change the shape of the smile, and the cheek usually "rises" when smiling, so the product shows more in motion than at rest.
In the smile, the zygomaticus major works with the levator labii superioris and the zygomaticus minor: the first gives the lateral direction, the others the lift of the lip. The balance among them defines each person's type of smile.
How does it show up in the assessment?
- Spontaneous smile: observe the height and symmetry of the commissures and the cheek.
- Wide smile: see how the cheekbone rises and whether the cheek marks the corner of the eye.
- At rest: assess the midface volume without the influence of the muscle.
- Photo or video record: the smile needs to be documented before any procedure, for later comparison.
For the context of the area, see the cheekbone and zygomatic areas.
Also called: zygomaticus major, major zygomatic muscle.
Frequently asked questions
What is the function of the zygomaticus major muscle?
It pulls the corner of the mouth up and outward, forming the smile. It is the most important muscle of the spontaneous smile.
Can toxin in the crow's feet affect the smile?
It can, when the product spreads to the zygomaticus major, in the lower part of the area. The smile becomes asymmetric or the mouth corner rises less on one side. It is usually temporary.