What is the primary role of the alveoli in the respiratory system?

The primary role of the alveoli in the respiratory system is gas exchange. Alveoli are tiny, balloon-like structures in the lungs where the exchange of gases occurs. They are surrounded by a network of capillaries, and it is here that oxygen from the air is absorbed into the blood, while carbon dioxide from the blood is expelled into the air to be exhaled. This process is critical for maintaining the body's oxygen levels and removing carbon dioxide, which is a waste product of metabolism.

The structure of the alveoli facilitates this process effectively, as they provide a large surface area relative to their volume, allowing for maximum gas exchange. Their thin walls (one cell thick) also ensure that gases can diffuse easily and efficiently. In addition, the moisture lining the alveolar walls aids in gas exchange, making oxygen molecules more permeable.

Understanding the function of the alveoli is crucial for grasping how the respiratory system maintains homeostasis and supports cellular respiration throughout the body.