Q. How are lungs designed in human beings to maximize the area for exchange of gases?
In the lungs, the air passage (wind pipe) divides into smaller tubes, called ‘bronchi’ in turn form ‘bronchioles’. The bronchioles which terminate in balloon – like structures, are called ‘alveoli’. Each lung contains 300 – 350 million alveoli. The alveoli present in the lungs provide maximum surface for exchange of gases. The alveoli have very thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.