Final answer:
The alveoli are adapted for gas exchange due to their thin walls, large surface area, moist lining, and rich blood supply, which collectively facilitate the efficient diffusion of gases between the air and the bloodstream.
Step-by-step explanation:
Alveoli are specially adapted structures in the lungs that enable the exchange of gases between the air and the bloodstream. There are three main factors that make the alveolus highly adapted to its function of gas exchange:
- Thin walls: Alveoli are composed of thin-walled parenchymal cells, usually just one-cell thick. This thin barrier allows gases such as oxygen and carbon dioxide to easily diffuse across.
- Large surface area: Each human lung contains approximately 300 million alveoli, contributing to a total surface area equivalent to that of a tennis court. This extensive surface area is crucial for providing sufficient space for gas exchange.
- Moist lining: The alveoli have a moist lining that helps to dissolve gases, thereby facilitating their diffusion across the alveolar and capillary membranes.
- Rich blood supply: Each alveolus is surrounded by a network of capillaries with a one-cell thick endothelial layer. This proximity to the blood supply allows for efficient uptake of oxygen and removal of carbon dioxide.
Together, these adaptations ensure that the alveoli are highly efficient at transferring oxygen into the blood and removing carbon dioxide from it.