How are the lungs designed in human beings to maximise the area for exchange of gases?

Explanation

Within the lungs , the primary bronchi divides into smaller and smaller tubes which finally terminate into balloon-like structures called alveoli . These alveoli increase the surface area for exchange of gases . There are 750 million alveoli in the lungs of man . If the alveolar surface is spread out it would cover about `80 m^2` . Thus it makes efficient exchange of gases .
Each alveolus of air sac has a diameter of 75 to 300 microns and has a very thin wall. The walls of the alveoli are elastic and are supplied with capillaries . Through these thin walls gases are exchanged between the capillaries and the air sacs.