Orbicularis oris

Musculus orbicularis oris

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What it is

Sphincter of the mouth made of fibres encircling the lips; many are continuations of buccinator and the other lip muscles converging at the modioli, with small incisive slips to the maxilla and mandible.

Function

Closes, purses and protrudes the lips (whistling, kissing) and keeps food in the mouth while chewing.

Size

Ring about 6 cm wide and 3.5 cm tall around the oral fissure.

Clinical note

Its fibres must be re-joined precisely in cleft-lip repair for normal lip movement and speech.