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

(N/A) The alveoli are small,balloon-like structures present in the lungs.
The walls of the alveoli consist of an extensive network of blood vessels (capillaries).
Each lung contains $300-350$ million alveoli,making a total of approximately $700$ million in both lungs.
When spread out,the total alveolar surface area covers about $80\, m^2$.
This large surface area and the thin,moist walls facilitate efficient gaseous exchange.