6.8 Exchange of gases in the lungs

Question 1

What are the 6 reasons as to why diffusion of gases between the alveoli and blood will be fast?

Answer 1

1. red blood cells are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
2. the distance between the alveolar air and rbc is reduced as the rbc are flattened against the capillary walls
3. the walls of both alveoli and capillaries are very thing and therefore the distance over which diffusion takes place is very short
4. alveoli and pulmonary capillaries have a v very large total surface area
5. breathing movements constantly ventilate the lungs and the action of the heart constantly circulated blood around the alveoli. Together these ensure that a step concentration gradient of the gases to be exchanged is maintained.
6. blood flow through the pulmonary capillaries maintains a concentration gradient.