How are the lungs designed in human beings to maximise the area for exchange of gases?
Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures called alveoli. The alveoli provide a surface where the exchange of gases can take place.
To maximise the area for exchange, the alveoli are arranged in a way that if the alveolar surface were spread out, it would cover about 80 m². This large surface area makes the exchange of gases efficient. The walls of the alveoli also contain an extensive network of blood-vessels for the transport of gases.
Additionally, during the breathing cycle, the lungs always contain a residual volume of air. This ensures there is sufficient time for oxygen to be absorbed and for carbon dioxide to be released.
Explanation
The answer is derived directly from the textbook context which explains the structure of alveoli and their large surface area (80 m²). It highlights the structural adaptations (balloon-like structures, extensive blood vessel network) and physiological mechanisms (residual volume) that facilitate efficient gas exchange.