2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

Alveoli are adapted for gas exchange by diffusion because:

-        there are many of them

-        they increase the surface area

-        only one cells thick (to reduce the distance gases have to travel)

-        surrounded by capillaries (ensures a good concentration gradient)

-        moist (allows gases to dissolve easily