lips/شفاه/嘴唇(Zuǐchún)

What Are Lips?

Lips by definition

lip \'lip\ n :  either of the two fleshy folds which surround the opening of the mouth in humans and many other vertebrates and in humans are organs of speech essential to certain articulations; also : the pinkish or reddish margin of a human lip composed of nonglandular mucous membrane and usually exposed when the mouth takes on its natural set.

Lip "skin" is different

Why do millions suffer from dry chapped lips each winter? The reason can be found in the structure of the lips themselves. The lips' exposed mucous membrane structure is actually different than other skin. As shown in the diagram to the left, lips do not have the same protective outer layer, or stratum corneum, found in other skin; nor do lips have the same complement of oil and sweat glands. Sweat glands add moisture to skin, but the lips' only source of moisture is saliva inside the mouth. Thus, harsh winter wind, cold, sun and dryness--indoors and outdoors--make lips a vulnerable target for chapping.