T
he sun burns it. T e wind chaps it. You
scratch, scrape, and bruise it. Your skin sure takes a lot of abuse, but that’s all part of its job. Look at your hands and arms. Touch your
face and neck. What you see and feel is your very own suit of armor, your skin. It isn’t hard and shiny like the knights wore.
Yet skin does a lot more to keep you safe than any clunky metal suit ever could. Skin protects your body. It keeps you at just
the right temperature. It gives you your sense of touch. People aren’t the only ones with skin. Animals have it, too. Let’s explore skin from the outside in.
A Tough Outer Layer Skin may seem like just a covering for your body. Well, it’s much more than that. Your skin is an organ made of diff erent layers. Each layer plays certain roles in protecting you. T e layers also keep you healthy. You see only the outside of the top layer.
T is top layer is the epidermis. Your outer skin is made of dry, flat cells. A cell is the smallest and the most basic part of a plant or animal. If you look at these skin cells under a
microscope, you’ll see that they look like f lattened corn flakes. T ey overlap, or lie on top of one another. T ese overlapping cells are thickest on the
palms of your hands and the soles of your feet. T at makes sense. Just think about all the running, walking, standing, grabbing, and holding these body parts do. T ey need a tough outer covering. T e epidermis is tough, but it can also be
as thin as a sheet of paper. In fact, on most places on your body, all the layers of your skin together are no thicker than this magazine. Compare this to the skin of some animals.
Rhinoceros skin, for instance, is up to 5 cm (2 inches) thick. T at’s as thick as a dictionary.
18 NATIONAL GEOGRAPHIC EXPLORER
Dead Cells Now here’s something that really might surprise you. All of the cells that form your outer skin are dead. Yet you couldn’t live without them. Look at what these dead cells do. T ey form
a barrier. T ey block unwanted water, dust, chemicals, and germs from getting inside your body. T ey shield your body from most of the sun’s harmful rays. T ey help cushion your body against blows. T ese dead skin cells do a great job, but they
don’t hang around long. As many as 40,000 of them fall off , blow off , or rub off your body each minute. Run your hand over your arm. You just brushed away about a thousand dead skin cells. Don’t worry, though. T ere are plenty more where they came from.
Layer by Layer
This close-up photo shows three layers of skin.
epidermis dermis
hypodermis
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