What are the branches of bronchial tubes containing microscopic air sacs?

The correct answer identifies the branches of bronchial tubes that are specifically responsible for gas exchange in the respiratory system. Alveoli are the tiny, balloon-like structures found at the ends of the bronchioles, which are the smaller airways that branch off from the larger bronchi. These microscopic air sacs are critical for respiration as they provide a large surface area for the exchange of oxygen and carbon dioxide between the air we breathe and the blood.

While bronchi refer to the larger passages that lead from the trachea to the lungs, and bronchioles are the smaller branches that stem from the bronchi, they do not conduct gas exchange themselves. Instead, it is the alveoli that perform this essential function. The pleura, on the other hand, are membranes surrounding the lungs and do not play a direct role in the passage of air or in the gas exchange process. Therefore, alveoli are uniquely defined by their structure and function in alveolar gas exchange, which is why this answer is correct.