Orbicularis oris is the sphincter muscle around the mouth, forming much of the tissue of the lips. It has extensive connections to muscles that converge on the mouth. This muscle acts to shape and control the size of the mouth opening and is important for creating the lip positions and movements during speech. Several different strands can be distinguished that allow it to form the lips into versatile shapes. As an expressive muscle, four relatively distinct movements can be produced by orbicularis oris, a pressing together, a tightening and thinning, a rolling inwards between the teeth, and a thrusting outwards.

Orbicularis oris is innervated by the lower zygomatic, buccal, and mandibular branches of the facial nerve (VII) and is supplied with blood by the facial artery.

Actions of the Orbicularis oris

Pressing

Tightening

Thrusting

 

A Human Face