What Are Lips
What are the Lips Exactly?
The anatomists and physiologists who have investigated the mucosa of the oral cavity have classified the lips as the external part of this mucosa: the lips do not exist as isolated structures, they have to be considered as the transition between the mucosa and the skin.
The lips have an epidermal tissue with a very thin corneal layer, and have therefor no effective barrier to restrict moisture loss. Neither do they have sweat glands or sebaceous glands. The thin epidermis makes it possible to see the underlying dermis, which is intensely vascularized, and gives the lips their colour.