- Numerous alveoli in the lungs → provide a very large surface area
- walls of the alveolus → is only 1 cell thick → which provides a short diffusion distance → ensuring higher rate of diffusion
- thin film of moisture covers the inner wall of the alveolus → which allows O2 to dissolve in it.
- walls of alveoli → richly supplied with blood capillaries → which ensure continuous flow of blood → which maintain the concentration gradient of gasses
diffusion gradient is maintained by:
- continuous flow of blood through blood capillaries
- continuous breathing of air in and out