Do you have any idea what is the largest organ in your body? You might be surprised to find out it's the skin, which you might not think of as an organ, according to KidsHealth.org. No matter how you think of it, your skin is very important. It covers and protects everything inside your body. Without skin, people's muscles, bones, and organs would be hanging out all over the place. Skin holds everything together. It also protects your body, helps keep your body at just the right temperature, and allows you to have the sense of touch.
According to EnchantedLearning.com, the skin is an organ that forms a protective barrier against germs (and other organisms) and keeps the inside of your body inside your body, and keeps what's outside of your body outside. Skin also helps maintain a constant body temperature. Human skin is only about 0.07 inches (2 mm) thick. Skin is made up of two layers that cover a third fatty layer. The outer layer is called the epidermis; it is a tough protective layer that contains melanin (which protects against the rays of the sun and gives the skin its color). The second layer (located under the epidermis) is called the dermis; it contains nerve endings, sweat glands, oil glands, and hair follicles. Under these two skin layers is a fatty layer of subcutaneous tissue (the word subcutaneous means "under the skin"). On average, an adult has from 18-20 square feet (about 2 square meters) of skin, which weighs about 6 pounds (2.7 kg).
Your skin doesn't just cover you. It does a whole lot more. According to Discovery.com, skin functions as protective wrapping. Along with a layer of fat underneath, it insulates you against all kinds of bumps, bangs and wear and tear. It keeps germs and water OUT (unless you have a break in your skin) and keeps your body's fluids and salts IN. Skin manufactures and oozes out all sorts of wonderful liquids. Waxes and oils act as your body's natural waterproofer and a protector against germs. They make your skin softer; but they can also give you pimples. Your skin also contains glands which manufacture sweat. With sweat, not only does your body get cooled by its evaporation, but it has a convenient way to get rid of chemicals it doesn't need. Skin is alive. It's made of many thin sheets of layers of flat, stacked cells in which you'll find nerves, blood vessels, hair follicles, glands, and sensory receptors. Older cells are constantly being pushed to the surface by new cells which grow from below. When the old ones reach the top, they become wider and flatter as they get rubbed and worn by all your activity. And, sooner or later, they end up popping off like tiles blown from a roof in a strong wind. In approximately a month's time, your body has made a whole new layer of skin cells!
The skin is made up of three layers, each with its own important parts, according to KidsHealth.org. The layer on the outside, called the epidermis (eh-pih-dur-mis), is the part of your skin you can see. Look down at your hands for a minute. Even though you can't see anything happening, your epidermis is hard at work. At the bottom of the epidermis, new skin cells are forming. When the cells are ready, they start moving toward the top of your epidermis. This trip takes about 2 weeks to a month. As newer cells continue to move up, older cells near the top die and rise to the surface of your skin. What you see on your hands (and everywhere else on your body) are really dead skin cells. These old cells are tough and strong, just right for covering your body and protecting it. But they only stick around for a little while. Soon, they'll flake off. Though you can't see it happening, every minute of the day we lose about 30,000 to 40,000 dead skin cells off the surface of our skin. So, just in the time it took you to read this far, you've probably lost about 40,000 cells. That's almost 9 pounds (4 kilograms) of cells every year! But don't think your skin might wear out someday.
According to KidsHealth.org, your epidermis is always making new skin cells that rise to the top to replace the old ones. Most of the cells in your epidermis (95%) work to make new skin cells. And what about the other 5%? They make a substance called melanin (mel-uh-nun). Melanin gives skin its color. The darker your skin is, the more melanin you have. When you go out into the sun, these cells make extra melanin to protect you from getting burned by the sun's ultraviolet, or UV, rays. That's why your skin gets tan if you spend a lot of time in the sun. But even though melanin is mighty, it can't shield you all by itself. You'll want to wear sunscreen and protective clothing, such as a hat, to prevent painful sunburns. Protecting your skin now also can help prevent skin cancer when you get older.
The epidermis consists mainly of cells called keratinocytes, made from the tough protein keratin (also the material in hair and nails), according to NationalGeographic.com. This covering of dead skin is known as the stratum corneum, or horny layer, and its thickness varies considerably, being more than ten times thicker on the soles of the feet than around the eyes. The epidermis harbors defensive Langerhans cells, which alert the body's immune system to viruses and other infectious agents.
The next layer down is the dermis (dur-mis), according to KidsHealth.org. You can't see your dermis because it's hidden under your epidermis. The dermis contains nerve endings, blood vessels, oil glands, and sweat glands. It also contains collagen and elastin, which are tough and stretchy. The nerve endings in your dermis tell you how things feel when you touch them. They work with your brain and nervous system, so that your brain gets the message about what you're touching. Is it the soft fur of a cat or the rough surface of sandpaper? Sometimes what you feel is dangerous, so the nerve endings work with your muscles to keep you from getting hurt. If you touch something hot, the nerve endings in your dermis respond right away: "Ouch! That's hot!" The nerves quickly send this message to the brain or spinal cord, which then immediately commands the muscles to take your hand away. This all happens in a split second, without you ever thinking about it.
As the dermis gets older, it gets thinner and easier to see through, according to KidsHealth.org. The dermis is home to the oil glands, too. These are also called sebaceous (sih-bay-shus) glands, and they are always producing sebum (see-bum). Sebum is your skin's own natural oil. It rises to the surface of your epidermis to keep your skin lubricated and protected. It also makes your skin waterproof — as long as sebum's on the scene, your skin won't absorb water and get soggy. You also have sweat glands on your epidermis. Even though you can't feel it, you actually sweat a tiny bit all the time. The sweat comes up through pores, tiny holes in the skin that allow it to escape. When the sebum meets the sweat, they form a protective film that's a bit sticky. An easy way to see this film in action is to pick up a pin with your fingers. Then wash your hands well with soap and water and dry them off completely. Now try to pick up that pin again. It won't be so easy because your sticky layer is gone! Don't worry — it will be back soon, as your sebaceous and sweat glands create more sticky stuff.
The third and bottom layer of the skin is called the subcutaneous (sub-kyoo-tay-nee-us) layer, according to KidsHealth.org. It is made mostly of fat and helps your body stay warm and absorb shocks, like if you bang into something or fall down. The subcutaneous layer also helps hold your skin to all the tissues underneath it. This layer is where you'll find the start of hair, too. Each hair on your body grows out of a tiny tube in the skin called a follicle. Every follicle has its roots way down in the subcutaneous layer and continues up through the dermis. You have hair follicles all over your body, except on your lips, the palms of your hands, and the soles of your feet. And you have more hair follicles in some places than in others — there are more than 100,000 follicles on your head alone! Your hair follicles rely on your sebaceous glands to bring on the shine. Connected to each follicle in the dermis layer is a tiny sebaceous gland that releases sebum onto the hair. This lightly coats the hair with oil, giving it some shine and a little waterproofing.
According to NationalGeographic.com, skin acts as a waterproof, insulating shield, guarding the body against extremes of temperature, damaging sunlight, and harmful chemicals. It also exudes antibacterial substances that prevent infection and manufactures vitamin D for converting calcium into healthy bones. Skin additionally is a huge sensor packed with nerves for keeping the brain in touch with the outside world. At the same time, skin allows us free movement, proving itself an amazingly versatile organ. Taking care of it is of critical importance for your overall health. When your skin is damaged or becomes diseased, it affects many other parts of your body and can lead to other health care problems.
Until next time. Let me know what you think.