Week 5 · Lesson 3 Smoking and Its Hazards: what tobacco and its smoke contain, effects on the body, types of smoking, active and passive exposure, damage to the environment, how to say no · 3 lessons
2
How smoking harms the body
Science Prep 3 Term 1, Unit 1: pp. 25–33
GoalExplain how smoke harms the lungs, the blood, the heart and the brain, and why quitting is hard.
New words
emphysema · lasting damage to the air sacs (alveoli) of the lungs, so less oxygen reaches the bloodhaemoglobin · the substance in red blood cells that carries oxygenaddiction · a strong craving that makes it very hard to stop, even when someone knows the harm
Explanation
Smoke harms many parts of the body. In the lungs, long-term smoking darkens the tissue with tar and the lungs lose elasticity, so people become short of breath, cough and cannot exercise as much; the risk of lung cancer rises. In emphysema there is lasting damage to the air sacs, the alveoli, so less oxygen reaches the blood. Carbon monoxide binds to the haemoglobin of the blood much faster than oxygen does, so the blood carries less oxygen. Nicotine speeds up the heart, raises blood pressure and makes the blood vessels narrower, so the chance of heart disease and hardened arteries goes up. The nervous system is also affected, with anxiety, trouble sleeping and concentrating, especially in teenagers. Smoking can also harm fertility, an unborn baby, the immune system, the skin and the hair. Nicotine reaches the brain quickly and gives a short feeling of well-being that fades, so the person craves another dose: this is addiction, and it is why quitting is hard. Cigarette butts also litter soil and water. For medical help, talk to a doctor, a parent or the school nurse.
carbon monoxide enters the blood→binds to haemoglobin→blood carries less oxygen→body tissues get less oxygen
Worked examples
Haemoglobin carries oxygen. If carbon monoxide binds to it first, fewer places are free for oxygen. Imagine a bus with 40 seats: if 10 are taken by people who will not leave, only 30 are free. The blood carries less oxygen in the same way.
Two balloons: a new one and one that has been stretched many times. The stretched one is slack and does not spring back well. This is only a model of an idea: lungs that lose elasticity do not push the air out as easily. Real lungs are very different from balloons.
Emphysema is long-term damage to the air sacs. Fewer air sacs work well, so less oxygen enters the blood. Say “long-term damage”, not “a hole made by tar”: the exact process is more complex.
Class activity
Balloon model, with a grown-up. Blow up one new balloon a little and let the air out; observe how quickly it shrinks. Stretch another balloon many times, then blow it up and let it go. Compare. Say what idea the model shows (lungs that lose elasticity) and what it does not show (alveoli, haemoglobin, nicotine). Then make a card sort: carbon monoxide, nicotine, tar against what each one does to the body.
Practice
1
How does carbon monoxide reduce the oxygen the blood carries?
It binds to haemoglobin faster than oxygen does.
2
What is emphysema?
Long-term damage to the air sacs (alveoli), so less oxygen reaches the blood.
3
Name two effects of nicotine on the heart and blood vessels.
It raises heart rate and blood pressure and narrows blood vessels.
4
Why is quitting hard?
Nicotine gives a short feeling of well-being that fades, so people crave another dose: addiction.