Zygomaticus minor muscle: anatomy and the upper lip
- Muscle
Quick facts
- Origin
- Anterior surface of the zygomatic bone, just behind the zygomaticomaxillary suture and medial to the origin of the zygomaticus major.
- Insertion
- Skin and muscle of the upper lip, between the levator labii superioris and the zygomaticus major.
- Action
- Raises the upper lip and exposes the upper teeth; deepens the lateral part of the nasolabial fold.
- Innervation
- Zygomatic and buccal branches of the facial nerve.
- Relevance in HOF
- One of the three lip elevator muscles cited in the gummy smile; it can be weakened by toxin spreading in the cheekbone area.
The zygomaticus minor is a thin muscle of facial expression that arises from the zygomatic bone and inserts into the upper lip. Its main action is to raise the upper lip, exposing the upper teeth and deepening the lateral portion of the nasolabial fold. It belongs to the group of lip elevators, alongside the levator labii superioris and the levator labii superioris alaeque nasi.
Where is the zygomaticus minor?
It arises from the anterior surface of the zygomatic bone, just behind the suture with the maxilla, slightly medial and above the origin of the zygomaticus major. It runs medially and downward and inserts into the skin and fibers of the orbicularis of the upper lip, between the levator labii superioris (more medial) and the zygomaticus major (more lateral). It lies in a superficial plane of the facial muscles, covered by cheek fat, and part of its origin sits under the lower fibers of the orbicularis oculi.
It is a muscle with considerable variation: it can be thin, fused with the levator labii superioris or underdeveloped on one side. That is why the same stimulus can produce different smiles in different people.
Zygomaticus minor and major: what is the difference?
| Feature | Zygomaticus minor | Zygomaticus major |
|---|---|---|
| Origin | Zygomatic bone, more medial | Zygomatic bone, more lateral |
| Insertion | Upper lip | Modiolus, at the corner of the mouth |
| Action | Raises the upper lip | Draws the mouth corner up and outward |
| Role in the smile | Exposes the upper teeth and gum | Defines the width and lift of the smile |
| Innervation | Zygomatic and buccal branches of the facial nerve | Zygomatic and buccal branches of the facial nerve |
Why does it matter in HOF?
- Gummy smile: when the lip elevators are very active, the lip rises more than expected and exposes the gum. The topic is covered in botulinum toxin for the gummy smile. Weakening this group too much can lengthen the lip and flatten the smile.
- Crow's feet and cheekbone area: botulinum toxin placed low at the corner of the eye or in the cheekbone area can spread to the zygomatic muscles and alter the smile. See asymmetric smile after toxin and drooping lip after toxin.
- Nasolabial fold: contraction of the zygomaticus minor and the levators deepens the upper part of the fold. This helps explain why part of the fold is dynamic and is not solved with volume alone.
How does it show up in the assessment?
- Spontaneous and forced smile: observe how much the upper lip rises and how much gum shows on each side.
- Comparison between sides: uneven lip elevation can be a pre-existing muscle asymmetry, and must be recorded before any procedure.
- Photos and a short video: the smile in motion shows the contribution of the elevators better than a still photo.
- History of toxin: previous applications in the crow's feet, cheekbone area or gummy smile change the balance of the lip.
Also called: musculus zygomaticus minor, minor zygomatic muscle.
Frequently asked questions
What is the difference between the zygomaticus minor and the zygomaticus major?
Both arise from the zygomatic bone, but the major is more lateral and runs to the corner of the mouth (modiolus), pulling the commissure up and outward in the smile. The minor is more medial and attaches to the upper lip, raising it and exposing the teeth.
Does the zygomaticus minor take part in the gummy smile?
Yes. It is cited, with the levator labii superioris and the levator labii superioris alaeque nasi, among the muscles that raise the lip and expose the gum. The contribution of each varies between people.