Site of gas exchange in mammals = epithelium of alveoli.
Alveoli - minute air sacs 100-300um in diameter.
Essential features of exchange surfaces
- Large surface area to volume ratio - speeds up rate of exchange.
- Very thin - short diffusion pathway so materials can cross rapidly.
- Partially pemeable - selected materials diffuse through easily.
- Movement of environmental medium e.g. air - maintain a diffusion gradient.
- Movement of internal medium e.g. blood - maintain a diffusion gradient.
Diffusion is proportional to: (surface area x difference in concentration…