Download Have you ever counted how long you could hold your breath for? In

Have you ever counted how long you could hold
your breath for? In May 2007, a trained diver broke
a world record. He held his breath underwater for 9
minutes and 8 seconds! Most people can't hold their
breath for nearly that long. That's because the
human body needs an almost constant supply of
oxygen to live. And oxygen comes from the air you
breathe.
Every cell in your body needs oxygen. Cells use
oxygen to get energy from food. During this process,
cells also produce a waste material called carbon
dioxide. Breathing allows you to bring oxygen into
your body and send carbon dioxide out of it. Your
respiratory system makes breathing possible.
It is made up of air passages, lungs, and muscles that help you
breathe.
Function of the Lungs
The lungs are an important part of your respiratory system.
They take up most of the space inside your chest and are protected
by your rib cage. When you breathe, special muscles pull fresh air
into your lungs and push used air out of them.
When you inhale, air travels down a passageway to your lungs.
In the lungs, oxygen passes into your blood. The blood delivers this
oxygen to your cells. Then the blood brings carbon dioxide from
your cells back to your lungs. When you exhale, carbon dioxide is
pushed out of the lungs. It travels up the passageway to get out of
your body.
Passageway to the Lungs
When you breathe, air enters your nose and mouth. It travels
through your throat and down your trachea. Your trachea, or
windpipe, is a tube that runs down your neck and into your chest.
In your chest, the trachea splits into two tubes, called bronchi.
Bronchi lead into your lungs.
Discovery Education Science
© 2007 Discovery Communications, LLC
Page 1 of 2
Lungs: Catchin' Air
Structure of the Lungs
Inside your lungs, the bronchi branch into smaller and smaller
tubes. They fill your lungs with thousands of air passages that look
like branches of a tree. At the end of each air passage are tiny air
sacs called alveoli.
The alveoli are like tiny bubbles of air. Each adult lung contains
about 300 million alveoli. They give lung tissue a spongy
appearance.
Alveoli are surrounded by tiny blood vessels. Here, oxygen from
the air enters the blood, and carbon dioxide from the blood enters
the alveoli. Because of their round shape, alveoli allow lots of
oxygen and carbon dioxide to be delivered to and from your cells
in a short time.
And it's a good thing, too! There are always trillions of cells in your
body that need oxygen and trillions of cells that need to get rid of
carbon dioxide. So it's important to take good care of your lungs—
your cells are counting on them!
Discovery Education Science
© 2007 Discovery Communications, LLC
Page 2 of 2