Question

how are the lungs designed in human beings to maximize the area for exchange of gases

Answer 1

Respiration in human beings takes place through a special system called as respiratory system.This involves nostrils, nasal cavity, larynx, bronchi, bronchioles ending in alveoli inside the lungs. Lungs are designed in such a way that they are lined by a thin membrane to facilitate the exchange of gases. 
Bronchi and bronchioles are the parts of respiratory system located in the lungs. 

*Primary bronchi are the structures which arise by the bifurcation of the wind pipe before entering the lungs. Primary bronchi divide and give rise to secondary bronchi. Bronchioles are the small tubular extensions of repeatedly dividing secondary bronchi inside the lung.

*Bronchi end in bronchioles. Each bronchi divides at least 20 times to form smaller bronchioles    Bronchioles end in small tubular structures called as alveolar tubes.Bronchi are made up of fibrocartilaginous layer. Bronchi serve as tubes of air conductors. Bronchi are larger in diameter  

*Bronchioles branch into many alveolar tubes. Bronchioles are lined by smooth muscles. Bronchioles are air conductors and others are respiratory gas exchangers. Bronchioles are smaller in diameter.
*Alveoli are richly supplied by blood vessels which help in exchange of gases on the alveolar membrane. 

Answer 2

The lungs is designed to exchange of gases in humans. the alvieli takes part in exchange of gases in alveoli the co2 and o2 will be exchanged to blood. When we inhale more air the chest muscles and diagphram helps to increase the volume of lungs to inhale more air..