Which of the following best describes the role of alveoli in the respiratory system?

The role of alveoli in the respiratory system is primarily related to gas exchange, making the description of them as the site where the majority of oxygen is absorbed and carbon dioxide is expelled the most accurate. Alveoli are tiny air sacs located in the lungs that provide a large surface area for diffusion due to their numerous small structures and extensive capillary networks surrounding them.

When air enters the lungs, oxygen from the inhaled air passes through the thin walls of the alveoli and into the bloodstream, where it binds to hemoglobin in red blood cells for transport to tissues throughout the body. Simultaneously, carbon dioxide, which is a waste product of metabolism, diffuses from the blood into the alveoli, where it is expelled from the body when we exhale. This efficient exchange of oxygen and carbon dioxide is critical for maintaining the body’s normal physiological functions.

The other options refer to functions that are not primarily associated with alveoli. While air passages do lead to the lungs, they do not engage in gas exchange. The filtering and humidifying of inhaled air are functions of the upper respiratory tract, and mucus production is related to different structures in the respiratory system, like goblet cells and mucous glands, rather than the alve