Zygomaticus major
Musculus zygomaticus major
Also known as: smiling muscle, zygomaticus
The principal smiling muscle. It runs from the zygomatic bone to the modiolus and draws the angle of the mouth upward and laterally.
Overview
Zygomaticus major runs obliquely from the lateral surface of the zygomatic bone to the modiolus at the angle of the mouth, where it blends with orbicularis oris and levator anguli oris. Contraction pulls the corner of the mouth superolaterally, producing a smile. A genuine "Duchenne smile" also contracts the orbital part of orbicularis oculi, which crinkles the skin at the corners of the eyes. A bifid zygomaticus major is thought to account for cheek dimples. Zygomaticus minor lies medial to it and lifts the upper lip.
Anatomy
- Origin
Lateral surface of the zygomatic bone, in front of the zygomaticotemporal suture.
- Insertion
Modiolus at the angle of the mouth (skin and orbicularis oris).
- Action
Elevates and draws back the angle of the mouth.
- Innervation
Facial nerve (CN VII), zygomatic and buccal branches.
- Nerve roots
Cranial nerve VII; no spinal roots
- Arterial supply
Superior labial branch of the facial artery; transverse facial artery.
Function
- Draws the angle of the mouth up and laterally (smiling, laughing)
Clinical significance
Asymmetric smile
A drooping corner of the mouth when smiling is often the first sign of facial palsy noticed by patients. Marginal mandibular branch injury instead affects the lower-lip depressors.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.