where does the actual gas exchange happen?

The actual gas exchange in the respiratory system occurs in the alveoli, which are tiny air sacs in the lungs. The alveoli are lined with capillaries, which are tiny blood vessels. Oxygen from the air diffuses across the alveoli and into the capillaries, while carbon dioxide diffuses from the capillaries and into the alveoli. The oxygen-rich blood is then pumped by the heart to the rest of the body, while the carbon dioxide-rich blood is pumped to the lungs to be exhaled.