Which part of the lungs are described as tiny air sacs?

The correct answer is the alveoli, which are indeed the tiny air sacs within the lungs. They play a crucial role in the respiratory system by facilitating the exchange of oxygen and carbon dioxide between the air we breathe and the bloodstream. The structure of the alveoli is optimized for this gas exchange due to their large surface area and thin walls, allowing for efficient diffusion of gases.

In contrast, the bronchi are larger air passages that branch out from the trachea into the lungs but do not participate directly in gas exchange. Similarly, the lungs encompass the entire respiratory organ but are not specifically the air sacs themselves. The trachea serves as the windpipe connecting the throat to the bronchi, serving primarily as a passageway for air rather than as the site of gas exchange. Hence, alveoli are the only option that accurately describes the tiny air sacs critical for respiration.