The Probert Encyclopaedia of Medicine

ORBICULARIS ORIS

The orbicularis oris (sphincter oris) muscle lies between the skin and the mucous membrane of the lips. It consists of a bundle of muscle fibres that surround the mouth and extends upward to the septum of the nose and downward to the region between the lower lip and chin. These muscular fibres are partially derived from other facial muscle that are inserted into the lips. It is innervated by the facial nerve (VII cranial nerve) and supplied by the facial artery. The orbicularis oris pulls the lips against the teeth and causes lips to close and pucker, as when kissing.
Research Orbicularis Oris