process of gaseous exchange at the alveolus

1. Inhaled air in the alveolus contains more oxygen and less carbon dioxide compared to the quantities in the blood capillaries of the lungs.
2. hence the partial pressure of oxygen is higher in the air of the alveolus compared to the partial pressure of oxygen in the blood capillaries.
3. the higher partial pressure of oxygen in the alveolus causes the oxygen to dissolve in the layer of moisture on the wall of the alveolus and diffuse out of the alveolus into the blood capillaries.
4. during respiration, carbon dioxide is produced. the blood capillaries in the body transport the carbon dioxide to the alveolus.
5. hence the partial pressure of carbon dioxide in the blood capillaries entering the alveolus is higher than the the partial pressure of carbon dioxide in the alveolus.
6. as a result, the carbon dioxide in the blood capillaries diffuses out of the blood capillaries into the alveolus and is expelled during exhalation.

itu sahaja.. kalau ade salah tu tolong la perbetulkan.. 

kalau tak faham pulak tu .. buat buat faham je lah..