T
he sun burns it. T e wind chaps it. You
scratch, scrape, and bruise it. Your skin takes a lot of abuse. T at’s all part of its job. T at’s because your skin is like a suit of
armor. It’s not hard and shiny. Yet skin does more to keep you safe than any clunky metal suit can. Skin protects your body. It keeps you at just
the right temperature. It gives you your sense of touch. It keeps all your insides, well, inside. People aren’t the only living things 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. It’s much more than that. Your skin is your body’s biggest organ. Zoom in for a closer look. You’ll see that it’s
made up of three main layers of tissue. T at’s a group of cells with a specific job. Each layer of skin plays an important role in protecting you and keeping you healthy. T e top layer is the epidermis. From the
outside, it looks pretty smooth. Try looking at it under a microscope, though. T en you’ll see lots of overlapping skin cells. T ey look like flattened cereal flakes. T e epidermis is thickest on the palms of
your hands and soles of your feet. T at makes sense. T ink about all the running, walking, grabbing, and holding these body parts do. T ey need a tough outer covering. T e epidermis is tough, but it’s also 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 thick. T at’s as thick as a dictionary.
18 NATIONAL GEOGRAPHIC EXTREME EXPLORER dermis
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 can do. T ey
can form a barrier. T ey block water, dust, chemicals, and germs from getting inside your body. T ey can shield your body from most of the sun’s harmful rays. T ey even help cushion your body against blows. T ese dead skin cells do a great job. T ey
don’t hang around long, though. In fact, as many as 40,000 of them fall off , blow off , or rub off your body each minute. In a year, you lose 4 kg of dead skin cells.
Don’t worry, though. T ere are plenty more skin cells where they came from. T at’s because the part of your epidermis that you can’t see is made up of living cells. And they have one job—make new skin cells.
epidermis
hypodermis
This photo shows the three main layers of tissue in your skin.
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