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Lungs and Breathing

in Science

ImageTake a deep breath. Feel how your chest swells. Lungs inside your body are filling up with air. Every time you breathe in, or inhale, your lungs fill up with air. When you breathe out, or exhale, your lungs empty out. You probably breathe about 20 times every minute. If you are running or playing hard, you might take 80 breaths a minute. What happens to all this air?

It goes to your lungs. Your lungs are like two big sponges inside your chest. Lungs are the body organs you use for breathing. All mammals, birds, reptiles, most amphibians, and even some fish have lungs.

Your lungs are inside a big cave in your body called your chest cavity. One lung is on the right side of your chest cavity. The other is on the left side. Your heart is in between your lungs. The sides, or walls, of this cavity are made of thick muscles and bones called ribs. The muscles make the walls move out and in when you inhale or exhale. This makes your lungs fill up or empty out. The muscles and ribs also protect your lungs from getting hurt.


When you inhale air through your nose or your mouth, that air takes off on an incredible journey. First it goes down the back of your throat, past your voice box, and into your windpipe, or trachea. Your trachea is like a tunnel that branches off into two more tunnels called bronchial tubes or bronchi. Each bronchial tube goes off to one of your lungs. It doesn’t matter whether the air goes to the right lung or the left lung. Both lungs do the same job.

Inside your lungs, the bronchi are like upside-down trees. They split into smaller and smaller branches and then into many twigs. The twigs end in tiny air sacs called alveoli. So far, the air has just been along for the ride. Inside the alveoli the air really goes to work. Its job is to keep you alive.

The job of the air in your alveoli is to bring oxygen into your body and take carbon dioxide out. Oxygen and carbon dioxide are two invisible gases in air. The secret to doing this job is blood.


The air in your alveoli sends oxygen into your blood. Your blood flows through a system of tubes called blood vessels. First, blood full of oxygen goes to your heart. Your heart is like a big pump. It sends the oxygen-filled blood whooshing off to all parts of your body.

The blood vessels that deliver oxygen are called arteries. Arteries branch off into smaller and smaller tubes. The tiniest blood vessels are called capillaries. Capillaries reach every cell in your body and drop off the oxygen. In your cells, the oxygen works with food to make energy for you.


After your blood drops off the oxygen in your body’s cells, it picks up carbon dioxide. Carbon dioxide is a waste product. It is created when your body cells use oxygen and food to make energy. This waste has got to go. So your blood carries it back to your lungs.

The blood vessels that carry blood full of carbon dioxide are called veins. Veins carry blood back to your heart. Your heart pumps the blood into your lungs. Finally, your blood drops off the carbon dioxide in your alveoli.

The carbon dioxide leaves the opposite way that the oxygen came in. Your lungs push carbon dioxide out of your body when you exhale. Taking oxygen into your body and giving off carbon dioxide is called respiration.

The story gets even better. Plants use the carbon dioxide that you and other animals exhale. Carbon dioxide and sunlight help plants make food. A waste product that plants give off is the oxygen that you need for life.


Germs can cause lung diseases such as tuberculosis and pneumonia. These are serious health problems. Smoking tobacco causes other lung diseases, such as lung cancer and emphysema. People with emphysema have trouble getting enough oxygen in their blood. Diseases caused by smoking can be deadly. Smoking also makes asthma and chronic bronchitis worse. These conditions make breathing difficult.

It is very important to keep your lungs healthy. The best thing you can do for your lungs is to not smoke.

Source: Microsoft ® Encarta