Bodily Defenses Image Map

The whistle blows and practice is over, so you run in from the field.  You’re out of breath from all the running you’ve been doing for the past hour.  But have you ever wondered what causes you to become out of breath or even why breathing faster seems to help you recover?

When you run, your body uses energy that is taken from the food you eat every day. Cells can only obtain the energy from your food if there is a special gas called oxygen in your body. (Click here for a review of how cells use oxygen). Oxygen in the air is brought into your lungs when you inhale. Blood picks up the oxygen from your lungs and carries it through the bloodstream to every cell in your body.

Cells use the oxygen and produce another gas, called carbon dioxide, as a waste product. It is very dangerous if carbon dioxide builds up in your body, so your blood carries the carbon dioxide to your lungs where it is released into the air when you breathe out or exhale.

This module will help you understand how gas exchange occurs in the body and why it is so important.

After completing this lesson, each student should be able to:

  • Diagram and label the anatomy of the lungs and the circulatory system.
  • Explain how the processes of gas exchange occurs and what purpose it serves.
  • Explain the harmful effects that smoking and air pollution have on the body


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