Smoking and the airways sim
Set how many cigarettes a day, watch tar stop the cilia and mucus build up in the airway, and measure how much haemoglobin carbon monoxide takes away from oxygen.
Gas exchange: the effects of tar, carbon monoxide and nicotine · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Cigarette smoke harms the airways and the blood in three ways. Tar settles on the lining of the airways: it stops the cilia beating and later destroys them, and the goblet cells make more mucus. The cilia normally sweep mucus, with the dust and bacteria trapped in it, up to the throat; when they cannot, the mucus builds up, the smoker coughs to clear it, and infections such as bronchitis are more likely. Tar also contains the substances that cause cancer. Carbon monoxide binds to haemoglobin in red blood cells about 200 times more strongly than oxygen does, so the places on haemoglobin taken by carbon monoxide cannot carry oxygen: the blood carries less oxygen and the heart must work harder. Nicotine is the addictive drug in smoke; it raises heart rate and blood pressure. The model: about 1 % of a non-smoker's haemoglobin carries carbon monoxide, rising by 0.25 % for each cigarette a day (6 % at 20 a day; real smokers are typically 4 to 8 %); a dm³ of blood can carry about 200 cm³ of oxygen when no carbon monoxide is bound (150 g of haemoglobin × 1.34 cm³ per g); a healthy trachea clears mucus at about 5 mm a minute; smoke gives up to about 10 mg of tar per cigarette. How fast the cilia stop and how much more mucus is made are illustrative: at 20 a day, 50 % of the cilia still work and the mucus clears at 2.5 mm a minute. Time moves only when you press Wait 1 minute. Model limits: one person who has smoked this much for months; the damage to the cilia, the extra mucus and the carbon monoxide levels vary a lot from person to person, and lung cancer, emphysema and heart disease build up over years, which the model does not show.
- Airway lining: cilia sweep mucus up to the throat
- Monitor: the share of haemoglobin carrying carbon monoxide
- Haemoglobin (a diagram key): oxygen bright red, carbon monoxide grey
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