Human Body

The human body is an amazing structure made up of many fascinating parts and systems. Learn about the human body and how its systems work together.

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Having a limb fall asleep can range from annoying to downright painful. See what's going on inside your arm or leg when it falls asleep.

The kidneys spend 24 hours a day, seven days a week filtering gallons and gallons of blood. But that's not all these little bean-shaped organs accomplish in a day.

By Craig Freudenrich, Ph.D.

You couldn't breathe without your lungs and you do it without even thinking about it. So, how do your lungs manage this amazing feat?

By Craig Freudenrich, Ph.D.


Ever wonder how your stomach acid attacks the food inside it but not the stomach itself?

By Contributors

Millions of people have refractive vision problems -- when the eyes get blurry or can't focus on an object. Learn about four major types of refractive vision problems.

By Craig Freudenrich, Ph.D.

If you've ever laced your fingers together, turned your palms away from you, bent your fingers back and heard a loud crack or pop, you know what knuckle-popping sounds like. So, what would happen if you popped your knuckles all the time?

By Katherine Neer

We all know 20/20 vision is a good thing, but just what do those numbers mean?


Lymph is a commonly-used medical term, but what's it mean exactly?

Your appendix is really a pretty mysterious organ. Find out why you have an organ that's not necessary to your survival.

Your ears are very sensitive to the air or water pressure around them. But just what happens when you dive into that pool?

You may never have thought about it (unless your child asks), but boogers are sticky for a perfectly logical scientific reason.

By writers


You breath all day, every day. How much oxygen does this process consume?

When you cut yourself accidentally, do you ever wonder what makes up this thing we call blood? It's pretty amazing stuff, considering how it wards off infections while supplying nutrients to every cell in the human body.

By Carl Bianco, M.D.

The heart is a vital organ that basically serves as a pump. Learn about heart chambers and valves, blood flow, the heart's electrical system and blood supply. Read more about how this amazing organ works.

By Carl Bianco, M.D.

There are millions of bacteria, microbes, viruses, toxins and parasites that want to invade your body. And they'd happily do it, too -- if it weren't for your immune system.

By Marshall Brain