Your Skin
Quick! What's the body's biggest organ?
You might be surprised to find out it's the skin, which you might not think of
as an organ. 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 our bodies
- helps keep our bodies at just the right temperature
- allows us to have the sense of touch
Don't Miss Your Epidermis
The skin is made up of three layers, each with its own important parts. The layer
on the outside is called the epidermis (say: eh-pih-DUR-mis). The
epidermis 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.
Bye-Bye 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. 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
(say: 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 Dermis Is Under the Epidermis
The next layer down is the dermis (say: DUR-mis). 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 your
skateboard?
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.
Dermis = Lots of Blood Vessels
Your dermis is also full of tiny blood vessels. These keep your skin cells healthy
by bringing them the oxygen and nutrients they need and by taking away waste. These
blood vessels are hard to see in kids, but you might get a better look if you check
out your grandparents' skin. As the dermis gets older, it gets thinner and easier
to see through.
The dermis is home to the oil glands, too. These are also called sebaceous
(say: sih-BAY-shus) glands, and they are always producing sebum
(say: 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
in your dermis. 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 Layer Is Subcutaneous Fat
The third and bottom layer of the skin is called the subcutaneous
(say: sub-kyoo-TAY-nee-us) layer. 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 (say: FAHL-ih-kul).
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.
Skin Can Warm and Cool You
Your skin can help if you're feeling too hot or too cold. Your blood vessels, hair,
and sweat glands cooperate to keep your body at just the right temperature. If you
were to run around in the heat, you could get overheated. If you play outside when
it's cold, your inner temperature could drop. Either way, your skin can help.
Your body is pretty smart. It knows how to keep your temperature right around 98.6°F
(37°C) to keep you and your cells healthy. Your skin can respond to messages sent
out by your hypothalamus (say: hy-po-THAL-uh-mus), the brain's inner
thermometer.
If you've been running around on a hot day, your blood vessels get the signal from
the hypothalamus to release some of your body's heat. They do this by bringing warm
blood closer to the surface of your skin. That's why you sometimes get a red face
when you run around.
To cool you down, sweat glands also swing into action by making lots of sweat to
release body heat into the air. The hotter you are, the more sweat your glands make!
Once the sweat hits the air, it evaporates (this means that it changes from a liquid
to a vapor) off your skin, and you cool down.
What about when you're ice-skating or sledding? When you're cold, your blood vessels
keep your body from losing heat by narrowing as much as possible and keeping the warm
blood away from the skin's surface. You might notice tiny bumps on your skin. Most
kids call these goosebumps, but the fancy
name for them is the pilomotor (say: PY-lo-mo-ter) reflex.
The reflex makes special tiny muscles called the erector pili (say:
ee-REK-tur pee-LEE) muscles pull on your hairs so they stand up very straight.
Keep It Clean!
Unlike other organs (like your lungs, heart, and brain), your skin likes a
good washing. When you wash your skin, use water and a mild soap. And don't forget
to cover scrapes and cuts with gauze or a bandage. This keeps the dirt out and helps
prevent infections. It's just one way to be kind to the skin you're in!
|
|
|