Problem 17

Background and context

The smallest bronchioles terminate in little air sacs. These are known as alveoli. When a human breathes, they expand, and when a human exhales, they collapse.

Oxygen is transferred from the lungs to the circulation through the exchange of gases. Simultaneously, carbon dioxide is transported from the blood to the lungs. This occurs in the lungs here between alveoli and a network of microscopic blood arteries termed capillaries positioned in the alveolar walls.