The skin is the body's largest organ. It protects against heat, light, injury, and infection. It helps control body temperature. It stores water and fat. The skin also makes vitamin D.

The skin has two main layers:

• Epidermis: The epidermis is the top layer of the skin. It is mostly made of flat cells. These are squamous cells. Under the squamous cells in the deepest part of the epidermis are round cells called basal cells. Cells called melanocytes make the pigment (color) found in skin and are located in the lower part of the epidermis.
• Dermis: The dermis is under the epidermis. It contains blood vessels, lymph vessels, and glands. Some of these glands make sweat, which helps cool the body. Other glands make sebum. Sebum is an oily substance that helps keep the skin from drying out. Sweat and sebum reach the surface of the skin through tiny openings called pores.

This picture shows the layers of the skin.

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