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.
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.
- muscular branches of the facial artery
- muscular tributaries of the facial vein
- buccal and marginal mandibular branches of the facial nerve (VII)
- 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