What is exchange of gas?
This is when the red blood cells , sent from the heart, pass
through the alveoli and the breathed in oxygen is diffused into the
cell and carbon dioxide is diffused out. The cells then travel
around the body in the blood vessels where the oxygen is needed,
before returning to the heart in the veins.
The red blood cells have a substance in them called haemoglobin
. When the red blood cells pick up oxygen in the lungs, it becomes
oxhaemoglobin