The orbicularis oris is an oral muscle of facial expression. It is the main sphincter muscle of the lips.
- Attachments – Arises from the maxilla and from the other muscles of the cheek. It inserts onto the skin and mucous membrane of the lips.
- Action – Closes the lips to narrow the oral opening.
- Innervation – Buccal branches of the facial nerve.
- Blood supply – Superior and inferior labial branches of the facial artery