The outermost covering of body tissue, which protects internal organs from the environment. Skin has 2 layers: the outer epidermis, and the inner dermis. The outermost epidermis is composed of dead cells and the protein keratin. As these dead cells are worn away, they are replaced by new ones from the inner epidermis. Some epidermal cells produce the pigment melanin, which protects the body from ultraviolet light in sunlight. The dermis is composed of connective tissue interspersed with hair follicles, sweat glands, sebaceous glands, blood and lymph vessels, and sensory receptors for pressure, temperature, and pain.


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