The outermost layer of your skin, the epidermis, is the thin, tough part of your body that acts like a protective shell. Because they're also the first to encounter damage, the cells of the epidermis are constantly renewing themselves, with dead skin cells falling off by the tens of thousands each minute.
One of the most basic functions of the epidermis is waterproofing [source: The Merck Manuals]. Have you ever wondered why your body never absorbs water when you get caught in the rain or take a shower? That's because the epidermis contains a layer of cells called stratum corneum, which are packed tightly to protect your body against the absorption of harmful substances. This layer also protects your body from losing too much water [source: P&G].
When the epidermis is healthy, it protects the body from bacteria, viruses, infection and other unwanted substances [source: The Merck Manuals]. Protection starts with the natural layer of oil that appears on the outermost surface of the skin, providing the first barrier of protection. The stratum corneum also protects against the invasion of foreign substances. The epidermis also contains Langerhans cells, specialized cells that identify harmful substances and take them to white blood cells to be neutralized [source: P&G].
The epidermis layer also contains melanin, the skin pigmentation that helps filter dangerous ultraviolet (UV) rays and prevents the skin from absorbing them, which can cause wrinkles and skin cancer. However, studies have shown that the epidermis layer can't completely stop this type of damage, so it's beneficial to protect yourself with sunscreen, protective clothing and minimal sun exposure [source: The Merck Manuals].
Now that you know how your skin protects you, are you ready to find out what goes on under the surface of your skin? To find out how your skin regulates your body temperature, go to out the next page.