By Sharon Fabian

All of the systems in your body work together. Each system has its own job to do, but each system also depends on the others. You will see how this works as you learn about the respiratory system.

The respiratory system is the system that takes in air, separates out the oxygen that you need to live, and gets rid of the carbon dioxide that is left. It includes your nose, nasal passages, windpipe, lungs, and diaphragm. Every minute, your respiratory system breathes in about thirteen pints of air.

It starts with your nose. You inhale fresh air about twenty times every minute. The air is drawn through your nasal passages, which clean the air by filtering out particles that you wouldn't want in your lungs. Mucus takes care of this part of the job. That's why it's so sticky, to capture unwanted stuff in the air. Sometimes, when your nose feels like getting rid of this yucky stuff fast, you sneeze.

After you breathe air in through your nose, it travels down your windpipe, also called the trachea. Since your windpipe is right beside the pipe that your food goes down, it has an interesting feature; a little flap called the epiglottis that can close really quickly to keep food from getting into your windpipe.

Below your ribs, your windpipe splits into two parts, which attach to your two lungs. Your left lung is a little smaller than your right one, to leave space for your heart. Your lungs fill up most of the space in your ribcage. Here is one example of your systems helping each other out. Your rib cage protects your lungs.

Your lungs are pink, spongy organs. Inside each of them there are tubes, called bronchi, that branch out into smaller and smaller tubes. They must get really small, because all together you have about 1,500 miles of airway tubing! At the very end of the tubes are tiny sacs called alveoli. You have about 300 million of these!

Sample

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