diffusion of gases

3. • The concentration of oxygen in the
alveolus is higher than that in the
blood.
• The oxygen dissolves in moist lining
of the alveolus
• Then oxygen diffuses into the blood
capillary
• In the blood, oxygen combines with
haemoglobin in the RBCs to form
oxyhaemoglobin

4. • This oxygen-rich blood is then
transported to the heart and pumped
to all part of the body
• In the body cells, the concentration of
oxygen in low.
• Thus, oxyhaemoglobin which is an
unstable compound in the blood
capillary decomposes to release
oxygen which diffuses into the body
cells for cellular respiration.
• At the same time, carbon dioxide
diffuses out of the body cells into the
blood capillaries and is transported to
the alveolus to be removed.