Lungs job is to transfer oxygen to the blood
and to remove waste carbon dioxide from it.
To do this the lungs contain millions of little air sacs
called alveoli where gas exchange takes place.
Alveoli are specialised to maximise diffusion of oxygen and
CO2. They have an enormous surface area (75m2), a moist
lining for dissolving gases, very thin walls, a ood blood supply.
The inside of the small intestine is covered in millions of
tiny projections called villi. They increase surface area in a
big way so that digested food is absorbed much more
quickly into the blood.
They have a single layer of surface cells and a vey good blood
suplly to assist quick absorption.