What is the primary function of alveoli in the lungs?

The primary function of alveoli in the lungs is to facilitate oxygen and carbon dioxide gas exchange. Alveoli are tiny, air-filled sacs located at the end of the bronchial tubes and are surrounded by a network of capillaries. The structure of alveoli allows oxygen from the inhaled air to diffuse into the blood, where it binds to hemoglobin in red blood cells for transport to the body's tissues. Simultaneously, carbon dioxide, which is a waste product produced by cellular metabolism, diffuses from the blood into the alveoli to be exhaled.

This efficient gas exchange process is crucial for maintaining the body’s oxygen supply and removing carbon dioxide, which is essential for normal respiratory function. The large surface area provided by the numerous alveoli, along with their thin walls, optimizes this exchange process, making it a fundamental aspect of respiratory physiology. Other options, while related to the respiratory system, do not capture the primary purpose of alveoli as accurately or relevantly as the chosen answer.