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.

Topics to Explore

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The Endocrine System

The endocrine system comprises a number of glands that produce hormones with a varied array of vital functions. Hormones control or regulate the development or function of structures throughout the body.

Healthy Digestion

Healthy digestion involves the whole body. Learn about the processes and body parts that go into digestion.

The Heart: Introducing One Tough Muscle

The heart is one of the strongest muscles in the body. Learn about this extremely vital part of the body.

How Muscles Work

Muscles are one of those things that most of us take completely for granted, but they're the body's engine. Without our muscles, we couldn't walk or talk -- and our blood would stop flowing.

Are all blood types needed for for donation?

When you donate blood, your blood type is an important factor in how useful your donation may be. Just what are blood types?

What makes your arms, legs and feet fall asleep?

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.

How Your Kidneys Work

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.

How Your Lungs Work

You breathe in and out anywhere from 15 to 25 times per minute without even thinking about it -- it just happens naturally. Learn all about your lungs, various conditions and diseases, and what makes the breath of life so crucial.

How does your stomach keep from digesting itself?

Ever wondered how your stomach acid knows the difference between your stomach and the food inside it?

How Refractive Vision Problems Work

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.

What makes your knuckles pop?

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?

What does it mean when someone has 20/20 vision?

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

What is lymph?

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

What is an appendix and what causes appendicitis?

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

Why do my ears pop when I dive in the deep end of the pool?

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

Why are boogers sticky?

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

How much oxygen does a person consume in a day?

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

How Your Heart Works

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.

How Your Immune System Works

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.


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