Lips

The lips (fig. 14) consist of three structures. The outer skin is covered by epidermis, a stratified squamous keratinized epithelium. The vermillion zone, or red area of the lip, is covered by a stratified squamous keratinized epithelium but has no sweat glands or oil glands, which is why we often need to moisten our lips. The junction between the outer skin and the vermillion zone is known as the vermillion border (fig. 14). The internal side of the lip is covered by stratified, non-squamous and non-keratinized epithelium overlying a dense collagenous connective tissue (fig. 14). The lips, which are designed to have maximum flexibility, are tied to the alveolar mucosa via a thin labial frenum that consists of sickle shaped folds of connective tissue. (fig. 15-16)