| Skin Forms a remarkable protective
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| | "prickle" cells, which move upward to
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| barrier against the outside world,
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| | replace them as they are shed (around 90
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| helping to regulate temperature and fluid
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| | percent of household dust is dead skin
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| balance, keeping out harmful germs and
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| | cells). The epidermis also contains
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| chemicals, and offering natural
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| | melanocytes, cells that secrete melanin,
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| protection against sunlight. It grows
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| | the pigment responsible for varying skin
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| hair, sweats, produces oil for
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| | color. Melanin production is stimulated
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| self-lubrication, and gives an accurate
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| | by sunlight: in white races this creates
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| perception of touch, heat, cold, and
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| | a tan, which offers some protection
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| pain, as well as the more complex
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| | against further exposure to the sun's
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| sensations such as tickle, itch, and
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| | ultraviolet rays.
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| pressure.
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| | Under the epidermis is the middle layer,
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| Skin caliber varies in different body
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| | or dermis, a bulky fibrous and protein
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| sites, from the thin, delicate tissue of
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| | layer containing hair follicles, sweat,
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| the eyelid, to the thick, hard padding of
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| | and sebaceous (oil-producing) glands, and
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| the heel. Some sites have particular
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| | specialized sensory receptors for
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| characteristics - luxuriant hair growth
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| | conveying information about touch,
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| on the scalp, sweating in the armpits,
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| | temperature, and pain. Mast cells in the
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| highly-tuned touch discrimination in the
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| | dermis respond to physical or chemical
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| fingertips - yet the basic structure of
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| | damage by releasing histamine, a
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| the skin is the same everywhere, although
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| | substance leading to allergic responses.
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| its actual thickness varies between
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| | Finally there is a layer of subcutaneous
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| different physical types. Redheads, for
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| | fatty tissue that gives the skin its
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| example, have considerably thinner skin
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| | feeling of softness and plumpness and
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| than brunettes, and, consequently, their
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| | acts as insulation against the cold. The
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| skin often reacts with more sensitivity.
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| | blood vessels supplying nourishment to
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| The outer of the three skin layers, the
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| | the outer skin layers are carried in this
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| epidermis, comprises the skin surface of
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| | layer.
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| dead "horny" cells, and underlying
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