Skin Cross-Section

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 is composed of three integrated layers: the epidermis, the dermis and the subcutis.

The thickness of the epidermis and the dermis varies over different parts of the body. It is thickest on the palms of the hands and feet, where friction is...

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Full Skin Cross-Section Description

[Continued from above] . . . 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 and sturdy. It is rich in nerves, blood vessels, and sweat glands. It shields the internal tissues of the body from harm 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 which 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. Although the skin can respond to the most delicate touch, it does harden from use; it also molds into varied shapes. So tough and durable is the skin that when a 2,000-year-old Egyptian mummy was fingerprinted, the ridges were perfectly preserved.