Orbicularis oris muscle

Last revised by Dr Daniel J Bell on 22 Sep 2021

The orbicularis oris muscle, also known as the orbicular muscle of the mouth, (TA: musculus orbicularis oris) is one of the facial muscles and its primary action is as the sphincter of the mouth

Orbicularis oris muscle comprises both of its own fibers and those lent from the dilator muscles of the mouth, mainly the buccinator muscle. Orbicularis oris is subdivided into four quadrants (upper, lower, right and left). Each quadrant consists of a major peripheral portion and a smaller marginal portion in the vermillion of the upper and lower lips. 

  • as the sphincter of the mouth and lips, contraction of orbicularis oris decreases the size of the mouth, with pursing of the lips, i.e. whistling action

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