9781422276112

Humans breathe in oxygen and breathe out carbon dioxide. The process of taking in air into the lungs is called inhalation, or inspiration, and the process of breathing it out is called exhalation, or expiration. The whole process of the exchange of gases (oxygen and carbon dioxide) between the atmosphere and the cells of the body and vice versa is

known as respiration. The system supplies oxygen to blood and in turn to every cell in the body. The process of respiration continues even at night while the body is at rest.

WORDS TO UNDERSTAND

chest cavity: the cavity, or hollow space, in the chest enclosed by ribs between the diaphragm and neck. mucus: a thick fluid produced by some tissues that contains dead microorganisms. pathogens: infectious microbes capable of causing disease.

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