The lips (labium, from Latin labia; singular: lip) are a visible body part at the mouth of humans and many animals. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. The upper and lower lips are referred to as the "Labium superius oris" and "Labium inferius oris", respectively. The juncture where the lips meet the surrounding skin of the mouth area is the vermilion border, which is known for its prominent display in humans as well as a wide variety of mammals.[1] The vermilion zone of the upper lip is known as the cupid's bow. The skin of the lip, with three to five cellular layers, is very thin compared to typical face skin, which has up to 16 layers.[2] With light skin color, the lip skin contains fewer melanocytes (cells which produce melanin pigment). Because of this, the blood vessels appear through the skin of the lips, which leads to their notable red coloring. With darker skin color this effect is less prominent.[3] The skin of the lip forms the border between the external environment and all internal organs. The lip surface has a high density of

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