How the small intestine and lungs in mammals are adapted for exchanging materials
-In the lungs, oxygen is transferred to the blood and carbon dioxide is transferred to the lungs to be removed.
-This takes place across the surface of millions of air sacs called alveoli, which are covered in tiny capillaries, which supply the blood
-Alveoli in the lungs create a very large surface area and the greater the surface area the more particles can move through, resulting in a faster rate of diffusion
-The alveoli and capillary walls are extremely thin, this provides a short diffusion pathway allowing the process to occur faster
-The lungs constantly supply oxygen to make blood from the alveoli oxygenated, by exchanging it for carbon dioxide that can be breathed out. This is a constant process meaning the concentration gradient is always steep