The superior part originates from the alveolar process of maxilla, opposite the three maxillary molar teeth.It is composed of three parts superior, inferior and posterior. The buccinator muscle forms the muscular basis of the cheek, filling the interval between the maxilla and mandible. Through these actions, the orbicularis oris facilitates speech and helps produce various facial expressions. An isolated contraction of certain parts of the muscle can produce different movements of the mouth, such as lip pouting, puckering, twisting and others. A bilateral contraction of the entire muscle brings the lips together and closes the mouth. The function of the orbicularis oris is to produce movements of the lips. Its blood supply mainly stems from the superior and inferior labial branches of facial artery, with contributions from the mental and infraorbital branches of maxillary artery and the transverse facial branch of superficial temporal artery. The orbicularis oris is innervated by the buccal and marginal mandibular branches of the facial nerve (CN VII). Some of the fibers curl upon themselves, forming the vermilion border, which is the demarcation between the lips and the adjacent skin.
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