ABSTRACT
Anatomic delineation of the lower face for our purpose encompasses the perioral region and chin, which is the area that includes the remainder of the superficial muscles of facial expression. The orbicularis oris provides motor function to the upper and lower lips, and the corners of the mouth. The remaining facial muscles consist mostly of the upper lip levators and the depressors of the lower lip, which are not necessarily antagonistic to each other, but act more synergistically with one another, opening and closing the mouth and performing essential buccal functions in unison with the orbicularis oris, such as maintaining sphincter control and lip competence with or without a mouth filled with solid material, liquid, or air. Other vital functions of the orbicularis oris together with its levators and depressors include the ability to make sounds and articulate them into speech, chew, and swallow solids and liquids. This is in direct contrast with the upper face where levators and depressors take on an antagonistic role and are in direct opposition to each another. In addition, by contracting the orbicularis oris along with its levators and depressors in a particularly idiosyncratic manner, a person consciously or unconsciously can express various and sundry emotions.
