What are the air sacs of the lungs where the exchange of oxygen and carbon dioxide takes place called?

The air sacs of the lungs where the exchange of oxygen and carbon dioxide occurs are called alveoli. These small, balloon-like structures provide a large surface area for gas exchange, facilitating the transfer of oxygen into the bloodstream while allowing carbon dioxide to be removed. Each alveolus is surrounded by a network of capillaries, which are tiny blood vessels that play a critical role in this process.

In contrast, the bronchi are branching tubes that direct air into the lungs, but they do not participate directly in gas exchange. The term "capillaries" refers to the blood vessels that surround the alveoli and are essential for transporting gases, but do not themselves serve as the location for gas exchange. While the lungs encompass both the bronchi and the alveoli, it is specifically the alveoli that are responsible for the vital function of oxygen and carbon dioxide exchange. This precise interaction between alveoli and capillaries is fundamental to respiratory physiology.