Skin

Skin

Your skin consists of several different types of tissue that perform a variety of essential functions for your body. Skin helps regulate your body temperature by sweating in response to heat and decreasing blood flow to the skin in response to cold (thereby keeping the heat deeper inside the body).

The skin’s pigment shields your body from dangerous ultraviolet rays. Nerve endings in the skin pick up and relay information about the surrounding environment to your brain, where it is translated into the sensations of touch, pressure, heat, or cold. Cells known as Langerhans cells are part of the immune system and help the skin fight infection. The skin also makes vitamin D from sunlight, which is essential in making bones strong.

Perhaps most important, your skin forms a physical barrier to injury and infection. The most significant part of this barrier is the top layer of skin, called the epidermis. At the very top of the epidermis, dead cells called keratinocytes (which contain a chemical called keratin) form a soft, protective sheet. The dead cells come from younger, living cells in the lower part of the epidermis, where they are constantly produced.

Apocrine glands are located mainly in the underarm and
genital areas; they may release a smelly liquid in response to
physical or emotional stress.

Below the dermis is the subcutaneous tissue, consisting of
connective tissue and fatty (adipose) tissue. This layer lies
between the dermis and underlying muscles or bones. The
subcutaneous tissue is richly supplied with blood vessels, which
expand or contract to help keep a constant amount of heat inside
the body. This tissue also contains white blood cells, which are
always on patrol to fight off infectious organisms that manage to
break through the top layers of skin. The adipose tissue not only
cushions and insulates the internal tissues, but also helps store
nutrients.

While marvelously effective and efficient, the skin is far from
invincible. Disorders of the skin are common and varied. If the
recommendations in the following section do not work, or if your
condition is severe, consult your doctor, who can care for most
skin conditions. If necessary, he or she will refer you to a
dermatologist, a doctor who specializes in treating skin
disorders.

Copyright 1999 © by President and Fellows of Harvard College
Reprinted with permission from the Harvard Medical School Family Health Guide, Simon & Schuster 1999. Art copyright © Harriet R. Greenfield, Newton, Mass.