AS biology smoking


Cigarette Smoke

What does cigarette smoke contain?

Cigarette smoke contains over 4000 different chemicals, many of which are harmful. The harmful substances include:

  • Tar (a mixture of chemicals including carcinogens)
  • Carbon Monoxide
  • Nicotine 
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Short Term Effects

  • The tar settles on the lining of the airways and alveoli, increasing the diffusion distance.
  • The tar on the surface of the airway can cause an allergic reaction. This causes the smooth muscles to contract. The lumen of the airway will get smaller which restricts the flow of air into the alveoli
  • Tar paralyses or destroyes the cilia on the surface of the airway. This means that the cilia is unable to move the mucus away to the back of the mouth.
  • Goblet cells and mucus secreting glands enlarge and release more mucus which collects in the airways
  • Bacteria and viruses become trapped in the mucus cannot be removed. They can then multiply the mucus.
  • Smokers are more likely to catch diseases lik influenza and pneumonia
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Longer Term Effects

  • Smokers cough
  • Delicate lining of the airways and alveoli become damaged and will be eventually be replaced by scar tissue which is thicker and less flexible
  • Smooth muscle in the bronchioles thicken which reduces the lumen of the airway and the flow of air is permanently restricted
  • Damage to the epithelium
  • Inflamation of the lining of the airways
  • Elastic tissues damaged in the lungs
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  • Causes addiction 
  • Releases the hormone adrenaline which increases the heart rate and breathing rate
  • Blood pressure is raised in the arterioles
  • Causes constriction of the arterioles leading to the extremities which reduces blood flow and oxgyen in the extremities. This can lead to the need for amputation
  • Platelets are made sticky which increases the risk of a blood clot or thrombus
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Carbon Monoxide

  • Enters the blood and binds with haemoglobin. It combines much more readily than oxygen and forms the stable compound carboxyhaemoglobin. This reduces the oxygen-carrying capacity of the blood
  • The body will detect a lower level of oxygen and so the heart rate will rise
  • Damage to the lining of the arteries
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Lung Cancer

  • Cigarette smoke contains a number of carcinogenic compunds which cause cancer. 
  • Carcinogenic compounds enter the cells of the lung tissue. They enter the nucleus of a cell and have a direct effect upon the genetic material.
  • If the mutation affects the genes that control cell division then uncontrolled cell division may take place- causing cancer!
  • Cancer often starts at the entrance to the bronchi.
  • Often takes 20-30 years to develop and may develop for years before being discovered
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Chronic Bronchitis

  • Inflamation of the lining of the airways
  • Damage to cilia and over production of mucus
  • Symptoms- lung irritation, continual coughing and coughing up mucus
  • Increases risk of lung infection
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  • The loss of elastcity in the alveoli which causes them to burst
  • Reduced surface area of the lungs asd larger air spaces are formed
  • Causes shortness of breath
  • Harder to exhale
  • Blood less oxygenated 
  • Fatigue
  • Breathing can become shallow and rapid
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Chronic Obstructive Pulmonary Disease (COPD)

Combination of diseases that includes chronic bronchitis, emphysema and asthma. There are a number of symptoms.

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  • Damage to the arteries and smooth muscle
  • The deposition of fatty substances
  • The deposition increases and therefore decreases the size of the lumen
  • Plaque also sticks to the artery wall which makes it rough and less flexible
  • The decrease in the lumen size decreases the blood flow
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  • Blood flowing past plaque cannow flow smoothly which increases the chance of a blood clot.
  • The stickiness of the platelets caused by nicotine will significantly increase the risk of a blood clot
  • Red blood cells also stick to the deposits
  • Blood clot also known as Thrombus 
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  • A stroke is the death of the brain tissue which is caused by the loss of blood flow to that part of the brain
  • One cause is a blood clot  which will lead to a part of the brain
  • Another cause is an artery that leads to the brain bursting (haemorrhage)
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