Skin is continuous with, but structurally distinct from mucous membranes that line the mouth, anus , urethra , and vagina . The basic cell type of the epidermis is the keratinocyte , which contain keratin , a fibrous protein. Basal cells are the innermost layer of the epidermis.
Melanocytes produce the pigment melanin , and are also in the inner layer of the epidermis.
The dermis is a connective tissue layer under the epidermis, and contains nerve endings, sensory receptors, capillaries , and elastic fibers. The integumentary system has multiple roles in homeostasis, including protection, temperature regulation, sensory reception, biochemical synthesis, and absorption. All body systems work in an interconnected manner to maintain the internal conditions essential to the function of the body. The sweat glands open to the surface through the skin pores. The hair shaft extends above the skin surface, the hair root extends from the surface to the base or hair bulb .