Anatomy and Variations of the Lip

The lips are two flaps surrounding the oral orifice. As they are located at the entrance to the digestive tract, the external surface is covered with skin and the internal surface with mucosa. Externally, the appearance of the lip can vary because of syndromes affecting the face. Lip shape is usually defined by the shape of the philtrum. The lateral border of the lip and the nasolabial fold differ among individuals in shape and length. Internally, the labial salivary glands can be affected by disease and aging. The muscles in the lips can also be altered by certain diseases. In this chapter, we describe the anatomy and variations of the lip.