Question

how are alveoli designed and why

Answer 1

The alveoli are adapted to make gas exchange in lungs happen easily and efficiently. ... they give the lungs a really big surface area. they have moist, thin walls (just one cell thick) they have a lot of tiny blood vessels called capillaries.

Answer 2

alveoli provide and area for the exchange of gases. A large network of blood if found in the alveoli. Alveoli have thin membranes which allow the exchange of gases to take place more swiftly.