What are the small air sacs at the end of bronchioles called?

The small air sacs at the end of bronchioles are called alveoli. These structures are crucial for the process of gas exchange in the lungs. Alveoli provide a large surface area relative to their volume, which allows for efficient diffusion of oxygen and carbon dioxide between the air in the alveoli and the blood in the surrounding capillaries. The thin walls of the alveoli facilitate this gas exchange, making them vital for respiratory function.

The other choices refer to different parts of the respiratory system. Bronchi are larger air passages that branch off from the trachea and lead to the bronchioles but are not responsible for gas exchange themselves. The trachea is the windpipe that connects the throat to the bronchi, serving as an airway for air to enter the lungs. The larynx, often referred to as the voice box, is involved in phonation and is situated above the trachea but does not perform gas exchange functions. Thus, alveoli are specifically identified for their role in the respiratory process, distinguishing them from the other structures mentioned.