MSD Manual

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Gas Exchange Between Alveolar Spaces and Capillaries
Gas Exchange Between Alveolar Spaces and Capillaries
Gas Exchange Between Alveolar Spaces and Capillaries

The function of the respiratory system is to move two gases: oxygen and carbon dioxide. Gas exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them. As shown below, inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli.