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4.1. The airways and lungs

The airways and lungs

In addition to the nutrients obtained by the digestive system , cells need oxygen to carry out cellular respiration. Nutrients, with oxygen, are transformed into other simpler substances and energy is released, in addition to other waste substances, such as CO2, which have to be eliminated.

Respiration is the process by which the body obtains the oxygen necessary to live from the air and expels carbon dioxide from cellular metabolism, thus carrying out the  exchange of gases between air and blood.