The Skin
The skin is the body’s largest organ.
It protects against heat, sunlight, injury, and infection. It helps regulate body temperature, stores
water and fat, and produces vitamin D.
The skin has two main layers: the outer epidermis
and the inner dermis.
The epidermis is mostly made
up of flat, scalelike 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.
The dermis contains blood vessels,
lymph vessels,
hair follicles, and
glands.
Some of these glands produce sweat, which helps regulate body
temperature. Other 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.
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