Skin Anatomy

The skin is the body's largest organ. It protects us against heat, sunlight, injury, and infection. It helps regulate body temperature, stores water and fat, and produces vitamin D.  The skin has 2 main layers: the outer epidermis and the inner dermis.  The epidermis is mostly made up of flat, scale-like cells called squamous cells. Round cells, called basal cells, lie under the squamous cells in the epidermis. The lower part of the epidermis also contains melanocytes.

Melanocytes are pigment cells that are found in the lower part of the epidermis. They produce melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

The dermis contains blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands produce sweat, which helps regulate body temperature. Other dermis glands produce sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin's surface through tiny openings called pores.