How are the alveoli designed to maximise the exchange of gases?

Explanation

There are millions of alveoli (thin-walled air-sacs) in the lungs. The presence of millions of alveoli in the lungs provides a very large area of the exchange of gases. And the availability of large surface area maximises the exchange of gases. For example, if all alveoli from the two human lungs are unfolded, they would give an area of about 80 square metres (which is nearly the size of a tennis court).