human respiratory system
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Articles from Britannica encyclopedias for elementary and high school students.
- respiratory system - Children's Encyclopedia (Ages 8-11)
All animals need a steady supply of oxygen in order to live. Oxygen is a gas found in air. It helps to turn food into energy. This process creates another gas-carbon dioxide. Because carbon dioxide is a waste product, it must be removed from the body. The respiratory system is the body’s way of breathing in oxygen and breathing out carbon dioxide.
- respiratory system - Student Encyclopedia (Ages 11 and up)
All living things need oxygen. Oxygen enables them to metabolize, or burn, nutrients, releasing the energy required to grow, reproduce, and maintain life. In the metabolic process, oxygen combines with the carbon in food and forms carbon dioxide as a waste product. The respiratory system is an organism’s apparatus for taking in oxygen and expelling carbon dioxide and water vapor.