Orbicularis oris muscle

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

Gross anatomy

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.

Arterial supply

Venous drainage



  • 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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