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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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Glossary Terms
dermis (DER-mis)
The inner layer of the two main layers of the skin. The dermis has connective tissue, blood vessels, oil and sweat glands, nerves, hair follicles, and other structures. It is made up of a thin upper layer called the papillary dermis, and a thick lower layer called the reticular dermis.
epidermis (EH-pih-DER-mis)
The outer layer of the two main layers of the skin.
follicle (FOL-i-kul)
A sac or pouch-like cavity.
gland
An organ that makes one or more substances, such as hormones, digestive juices, sweat, tears, saliva, or milk. Endocrine glands release the substances directly into the bloodstream. Exocrine glands release the substances into a duct or opening to the inside or outside of the body.
organ
A part of the body that performs a specific function. For example, the heart is an organ.
sebum (SEE-bum)
An oily substance produced by certain glands in the skin.
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