The alveoli are designed to maximize gas exchange through several key adaptations:
- They have a large surface area owing to millions of tiny alveoli sacs, providing about 70 square meters in adults, which allows more gas to be exchanged at once.
- The walls of alveoli are extremely thin (one cell thick) , minimizing the diffusion distance for oxygen and carbon dioxide between the air and blood.
- They are surrounded by a dense network of capillaries , ensuring a rich blood supply to maintain concentration gradients for efficient diffusion.
- The inner surface is moist , allowing gases to dissolve and diffuse more easily.
- The alveoli produce surfactant , a substance that reduces surface tension, preventing collapse and keeping alveoli open for gas exchange.
Together, these features — large surface area, thin walls, rich blood supply, moist lining, and surfactant production — optimize the alveoli for rapid and efficient gas exchange between the lungs and blood.
