Layers of the Skin

The top layer of skin is the epidermis. Its outer portion (called the stratum corneum, or horny layer) consists of dead, flattened cells. The stratum corneum resembles a sheet of plastic wrap. It acts as a barrier, separating the body from the environment, and helps control how much water evaporates from the skin. As the dead cells on the surface wear away, cells below them are pushed up to take their place. The epidermis is where vitamin D is formed. It contains many cells and substances that help defend against infection. Melanocytes, the cells that provide color to the skin, are in this layer. These cells produce a pigment called melanin, which reduces damage due to ultraviolet radiation from sunlight.

Under the epidermis is the dermis. This layer gives the skin strength and elasticity. It is composed mostly of connective tissue fibers (collagen fibers). Blood vessels, lymph channels, and nerves pass through these fibers.

The deepest layer is the subcutaneous fat layer. It varies enormously in thickness, depending on what part of the body it covers and how the person is built. The fat layer is important because it insulates the body from heat and cold and helps protect bones and deeper organs from injury. It also helps regulate the activity of certain hormones.

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