I am sure this will come up for the exams. It hasn't come up for quite a few years now.
Okay this isn't the best. I originally did it for my personal revision, so I didn't bother writing it well
1. It is a combination of chemicals
2. Tar settles on the lining of the airways and alveoli and this increases the diffusion distance for oxygen to enter and carbon dioxide to leave the blood.
3. The presence of chemicals in the airways may cause an allergy reaction.
4. This causes the smooth muscles in the walls of the airways to contract.
5. the lumen of the airways get smaller and restricts the flow of oxygen to the alveoli
6. Tar paralyses or destroys cilia so that mucus is not moved. The bacteria and dust laden mucus is trapped in the airways.
7. the bacteria multiply in the mucus and may block the bronchioles
8. The presence of bacteria and viruses…