What is the primary function of the alveoli?

What is the primary function of the alveoli?

• A. Gas exchange
• B. Air conduction
• C. Mucus production
• D. Immune defense

Answer: (A)

Gas exchange is the primary function of the alveoli. These tiny air sacs are positioned at the ends of the respiratory tree and have walls that are extremely thin, surrounded by a dense network of capillaries. This setup provides a large surface area and a very short diffusion distance, so oxygen from the air inside the alveoli readily moves into the blood, while carbon dioxide from the blood diffuses into the alveolar air to be expelled. The diffusion is driven by differences in gas partial pressures between the alveolar air and the blood. Surfactant produced by type II cells helps keep the alveoli open by lowering surface tension, maintaining the surface area needed for continuous gas exchange. In contrast, air conduction occurs in the larger airways, mucus production happens in the mucous membranes of those airways, and immune defense involves immune cells like alveolar macrophages.

Gas exchange is the primary function of the alveoli. These tiny air sacs are positioned at the ends of the respiratory tree and have walls that are extremely thin, surrounded by a dense network of capillaries. This setup provides a large surface area and a very short diffusion distance, so oxygen from the air inside the alveoli readily moves into the blood, while carbon dioxide from the blood diffuses into the alveolar air to be expelled. The diffusion is driven by differences in gas partial pressures between the alveolar air and the blood. Surfactant produced by type II cells helps keep the alveoli open by lowering surface tension, maintaining the surface area needed for continuous gas exchange. In contrast, air conduction occurs in the larger airways, mucus production happens in the mucous membranes of those airways, and immune defense involves immune cells like alveolar macrophages.