Medical Definition of Lip
Lip: One of the two fleshy folds that surround the opening of the mouth. The upper lip is separated from the nose by the philtrum, the area that lies between the base of the nose and the pigmented edge (called the vermillion border or the carmine margin) of the upper lip. The upper and lower lips meet at the corners (angles) of the mouth, which are called the oral commissures. Small blind pits are sometimes seen at the corners of the mouth; they are known as angular lip pits, and are considered normal minor variants. The lips may be abnormally thin or thick. For example, children with fetal alcohol syndrome typically have a thin upper lip and flat philtrum.
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