Skin

The skin is the outside covering of body tissue, which protects inner cells and organs from the outside environment. The skin is the largest organ of the body, and its cells are continuously replaced, as they are lost to normal wear and tear. The skin totals somewhere between twelve and twenty square feet in area and accounts for 12% of a human's body weight. It is composed of three integrated layers: the epidermis, the dermis and the subcutis. The thickness of the epidermis and the dermis...

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    Full Skin Description

    [Continued from above] . . . varies over different parts of the body. It is thickest on the palms of the hands and feet, where friction is needed for gripping, and it is thinnest on the eyelids, which must be light and flexible. The epidermis also grows into fingernails, toenails and hair. The dermis, or true skin, is thick, sturdy, and rich in nerves and blood vessels and in sweat glands. It shields and repairs injured tissue. This layer consists mostly of collagen, which originates from cells called fibroblasts and is one of the strongest proteins found in nature. It gives skin durability and resilience. The subcutis, joined to the bottom of the dermis, is the deepest layer of the skin. It contains lipocytes, which produce lipids for the subcutaneous tissue to make a fatty layer that cushions muscles, bones and inner organs against shocks, and acts as an insulator and source of energy during lean times. The skin registers sensation constantly and supports a teeming, unseen population of tiny organisms. Not only does the skin harden from use, but also it molds into varied shapes, and it responds to the most delicate touch, becoming an organ of communication.