Merck Manual

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Gas Exchange Between Alveoli and Capillaries
Gas Exchange Between Alveoli and Capillaries
Gas Exchange Between Alveoli and Capillaries

The function of the respiratory system is to add oxygen to the blood and remove carbon dioxide. The microscopically thin walls of the alveoli allow inhaled oxygen to move quickly and easily from the lungs to the red blood cells in the surrounding capillaries. At the same time, carbon dioxide moves from the blood in the capillaries into the alveoli.