Describe and explain the adaptations of the alveoli for gas exchange. (4 marks)

The alveoli are highly folded in order to increase the surface area available for gas exchange. The thins walls of the alveoli and the supplying capillaries allow for a short diffusion distance, thus increase the rate of gas exchange. The alveoli have a rich blood supply from the capillaries which maintains a steep concentration gradient and thus faster gas exchange. The lining of the alveoli is moist which allows the gas to easily dissolve before diffusing through.