Body Systems

Oh, to be a kid again. Plenty of summer vacation, plenty of mud puddles and plenty of osteoblasts? There's a reason your kid can spring back from any injury while you're laid up for weeks.

By Tom Scheve

At night, your eyes adjust to darkness after several minutes. Do you know why it takes that long? Take a look at how your eyes adjust to darkness.

Chances are rather good you've heard the news that you have a thyroid -- but chances are also pretty decent you're not completely up to speed on exactly why you have one. What can your thyroid do for you?

By Jessika Toothman

Instead of just giving in to your food cravings, how about nourishing your brain? Take a look at the foods that kick-start your smarts. Here's a hint -- that candy bowl's not going to help.

By Molly Edmonds

Every second of the day, blood bustles through your body, bound for your brain, toes and everything in between. How does your heart receive its fair share of the good stuff?

By Tom Scheve

When it comes to the heart, timing is critical. An irregular heartbeat is inefficient and deprives the body of blood. So what sets your ticker's rhythm?

By Julia Layton

Lub-dub, lub-dub, lub-dub, that's usually the sound of a happy heart. But what's responsible for that steady, comforting beat, and what if your heart doesn't sound like that?

By Tom Scheve

Everything we do is controlled and enabled by electrical signals running through our bodies. But how are those signals produced?

By Julia Layton & Mark Mancini

The heart is crucial to life and the focus of love. Explore the parts of the heart and how your heart works, plus take a look at real pictures of human hearts with this gallery.

A healthy brain works better longer, keeping memory accurate and thought processes clear. Learn more about the benefits and options of brain teasers and mind games on your health.

By Madeline Roberts Vann, MPH

The brain is a complex grouping of nerve cells and other structures that help us think, react to the environment, make decisions and carry them out. Take an in depth look into one of the most interesting parts of the human body.

By DiscoveryHealth.com writers

What does your brain really look like? It depends on how it's imaged. Take a look at all the different ways we can view the human brain.

By Sara Cheshire

Unfortunately for him, Humpty Dumpty was not blessed with the human skeletal system. Why can your skeleton do what all the king's horses and all the king's men can't?

By Robert Lamb

Everybody's stomach makes noises. Whether you call it growling, grumbling or gurgling, what is that sound and what is it trying to tell us?

By Jessika Toothman

Creatinine is a chemical molecule that is present in the serum (liquid portion) of the blood. The amount of creatinine produced depends on a person's muscle mass. But how is it measured?

By Jill Ferguson

"Don't cross your eyes -- they'll stick that way!" That's something most of us have heard from our mothers at one time or another. Can your eyes really get stuck?

By Marshall Brain

In the movie "WaterWorld," Kevin Costner's character has a mutation that gives him gills behind the ears. Could a mutation allow people to swim in the water just like fish --without having to use any sort of scuba equipment?

By Marshall Brain

Silica packets most likely contain silica gel or some other desiccant -- something that absorbs (collects) and holds water vapor. What would happen if you put that gel in your mouth?

By Katherine Neer

Back away from that speaker, turn down your music, and put down that power tool unless you want the ringing in your ears to be permanent. Sound can hurt you, and that ringing may be the first sign.

By Cristen Conger

What happens to your lunch after you eat it? As you read this, your digestive system is hard at work, taking it on a wild ride through your body.

By Melissa Jeffries

People expel gas by either burping or flatulating. Although it's an embarrassing thing to have happen, it's also a necessity. But what would happen if you just couldn't pass the gas?

By Katherine Neer

Eyebrows add expression to your face, and are often waxed and plucked in the name of beauty. But why do we have them in the first place, and what would happen if they went away?

By HowStuffWorks.com Contributors

Roses are red, violets are blue -- well, bluish. The sky is blue, too. Grass is green. These are things that most of us know for a fact and don't question. But what if you were colorblind? What would you see? Is life one long black-and-white movie?

By Katie Lambert

Why don't you have two hearts? Here's a hint: It's the same reason why you have one liver, but two eyes. Would a second heart help you live better?

By Josh Clark

You touch a hot object and immediately drop it. It happens so quickly you don't even think about it. How does this happen? Your nervous system coordinated everything.

By Craig Freudenrich, Ph.D.