6.4.3 Describe the features of alveoli that adapt them to gas exchange

·      Great quantity increases surface area for gas exchange

·      Spherical shape to increase surface area

·      Surrounded by capillaries

·      Surface is moist to make diffusion easier

·      One celled layer to allow faster diffusion

·      Membranes are short, which result in a short distance for diffusion

(http://1.bp.blogspot.com/aUWSNlVi7N4/T7pGJHOvYqI/AAAAAAAABpk/2OSjn9gxVck/s1600/alveoli.png)