Where in the respiratory system are oxygen and carbon dioxide exchanged?

The exchange of oxygen and carbon dioxide in the respiratory system occurs in the alveoli of the lungs. The alveoli are tiny air sacs located at the end of the bronchioles, which are the smallest branches of the bronchial tree. The walls of the alveoli are very thin and are surrounded by capillaries, which are tiny blood vessels. Oxygen from the air in the alveoli diffuses across the alveolar walls and into the capillaries, while carbon dioxide diffuses from the capillaries into the alveoli. The oxygen-rich blood from the capillaries then travels to the heart and is pumped throughout the body, while the carbon dioxide-rich air is exhaled.