The Effects of Smoking (WJEC GCSE Biology)

The Effects of Smoking

• Smoking leads to emphysema and an increased risk of several different types of cancer, including lung cancer

  • There are strong links between cigarette smoking and lung cancer and emphysema

  • The majority of cases of lung cancer are caused by smoking

Graph showing a correlation between numbers of adults who smoke and lung cancer rates over time

• Note that as the general trend shows that as the number of adults who smoke decreases, so does the lung cancer rates a few years later (as cancer takes some time to develop)

• The trend in the rate of developing lung cancer for women has been increasing, while in men it is decreasing

• This is because the number of female smokers – unlike men – continued to increase in the 1950s and 1960s before starting to fall

• As cancer takes some years to develop, a fall in female rates of lung cancer is likely to occur later

• Chemicals in cigarettes include:

  • Tar - a carcinogen (a substance that causes cancer)

  • Nicotine - an addictive substance which also narrows blood vessels

Tar

• Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs

• It also contributes to the lung disease emphysema 

Nicotine

• Nicotine is addictive 

• It narrows blood vessels leading to increased blood pressure

• It also increases heart rate

• Both of these effects can cause blood clots to form in the arteries leading to heart attack or stroke

Lung cancer

• Tumours can develop in the respiratory system which is a consequence of the chemicals found in cigarette smoke

• Tumours can interfere with the normal working of the lungs

• Symptoms of lung cancer include:

  • Coughing up blood

  • A persistent cough

  • Coughing an increased amount of mucus

  • Back or shoulder pain

  • Wheezing and breathing difficulties

  • Sudden weight loss

Emphysema

• Emphysema is a lung disease that can develop as a result of the chemicals found in cigarette smoke

• Frequent infections can develop in the lungs of smokers which results in phagocytes (a type of white blood cell) being attracted to the tissues of the lungs

• Phagocytes release enzymes that damage the alveolar walls which create large air spaces in the alveoli resulting in a smaller surface area for gas exchange

• The consequences of this are breathlessness and wheezy breathing

  • Once the disease progresses, people often need a constant supply of oxygen to stay alive

Emphysema diagram

The breakdown of alveoli in emphysema reduces the surface area for gas exchange

Cilia and mucus

• The effects of smoking also damage the cilia cells and the mucus that line the airways of the respiratory system

• The chemicals in cigarette smoke paralyse cilia which prevents them from working

• The small particles found in cigarette smoke clog the mucus which prevents it from moving up and out of the airways instead it builds up blocking the smallest bronchioles

• A smoker's cough is the attempt to move the mucus but it damages the epithelia resulting in scar tissue, which narrows the airways and makes breathing difficult

• Dirt and pathogens contained within the mucus are not removed from the airways so frequent infections of the respiratory system can occur