An explanation that makes reference to three of the following:
1. oxygen use lower in smokers / lower rate of oxygen use / eq
2. tar (in cigarettes)
3. causes emphysema / mucus builds up / mucus not removed / cilia damaged / eq
4. less surface area (of alveoli) / eq
5. less diffusion of oxygen (into blood)
6. carbon monoxide binds to haemoglobin (reducing oxygen) /eq
7. causes narrowing of arteries / blocks blood vessels (reducing flow of oxygenated blood) / eq
Accept less oxygen uptake / eq Accept converse
Accept alveoli walls break down / deform / are damaged
Ignore gas exchange
Ignore veins