Effects of Tobacco Smoke
- Smoking causes chronic obstructive lung disease, coronary heart disease and increased risks of several different types of cancer, including lung cancer
- Chemicals in cigarettes include:
- Tar - a carcinogen (a substance that causes cancer))
- Nicotine - an addictive substance which also narrows blood vessels
- Carbon monoxide - reduces the oxygen-carrying capacity of the blood
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| Section through a normal lung | Section through a smoker’s lung |
Tar
- Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs
- Tar also contributes to COPD, which occurs when chronic bronchitis and emphysema, two different diseases which are frequently linked to smoking, occur together
- Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus
- Tar destroys cilia, inhibiting the cleaning of the airways, and mucus (containing dirt, bacteria and viruses) builds up blocking the smallest bronchioles
- A smoker's cough is an attempt to move the mucus but it damages the epithelia resulting in scar tissue
- The scar tissue narrows the airways and makes breathing difficult
Emphysema
- Emphysema develops as a result of frequent infection, meaning phagocytes are attracted to the lungs where they release elastase - an enzyme that breaks down the elastin in the alveoli walls, to enable them to reach the surface where the bacteria are
- Without adequate elastin, the alveoli cannot stretch, so they recoil and many burst
- The breakdown of alveoli results in the appearance of large air spaces, reducing the surface area for gas exchange and making sufferers breathe more rapidly
- As it progresses, patients become breathless and wheezy - they may need a constant supply of oxygen to stay alive
The breakdown of alveoli in emphysema diagram
The breakdown of alveoli in emphysema reduces the surface area for gas exchange
Carbon monoxide
- Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen
- This puts more strain on the breathing system as breathing frequency and depth need to increase in order to get the same amount of oxygen into the blood
- It also puts more strain on the circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes
Nicotine
- Nicotine narrows blood vessels so puts more strain on the circulatory system and increases blood pressure
- Narrow blood vessels are more likely to become clogged with fat, including cholesterol - if this happens in the coronary artery, this causes coronary heart disease
- This means the heart muscle cells do not get sufficient oxygen and so less aerobic respiration takes place
- To compensate the cells respire anaerobically, producing lactic acid which cannot be removed (due to lack of blood supply)
- This creates a low pH environment in the cells causing enzymes to denature and eventually, heart muscle cells will die
- If enough die this can cause a heart attack
- Another effect of nicotine is low birth weight in babies born to mothers who smoke during their pregnancy
- Nicotine narrows the blood vessels in the umbilical cord, which reduces the supply of oxygen and important food molecules to the fetus
- The placenta can also separate from the uterus, causing bleeding, premature birth and sometimes, miscarriage or stillbirth
