The Effects of Lung Disease (AQA A Level Biology)

The effects of lung disease

• There are several disorders or diseases that can prevent lungs from functioning properly

• They can affect the structure of the alveolar walls (gas exchange surface) and damage the airways involved in ventilation

• Examples of lung diseases that affect gas exchange include:

  • lung cancer

  • COPD

Lung cancer

• Cancer occurs if mutations affect the regulation of mitosis in cells

• Tumours develop if mutations occur in oncogenes or tumour-suppressor genes of the bronchial epithelial cells. This causes uncontrolled mitosis which develops into a mass of cells in the lumen of the airways

• The tumour becomes larger because it has no method of programmed cell death and survives because it develops its own blood supply (vascularisation)

• The tumour then starts to interfere with the normal working of the lungs, such as by squeezing against blood vessels or cancer cells entering into the lymphatic system, where they may develop another tumour

• 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 and sudden weight loss

COPD

• Chronic obstructive pulmonary disease (COPD) includes a range of lung-based diseases, such as chronic bronchitis and emphysema

• Symptoms of a COPD include shortness of breath, a chronic or persistent cough, chest tightness, wheezing and difficulty breathing when exercising or during any physical activity

• When goblet cells in the ciliated epithelium become enlarged they produce more mucus

• This destroys the cilia in the trachea and prevents them from sweeping mucus away from the lungs

• The mucus contains bacteria, dust and other microorganisms and can then block narrow bronchioles, causing coughing, scar tissue and infection

• The infection attracts phagocytes to the lungs and the phagocytes release elastase, an enzyme that damages the elasticity of the alveolar walls

• Without enough elastin, the alveoli break down and may burst. This creates large air spaces in the alveoli and patients become wheezy and breathless. Once the disease progresses, people often need a constant supply of oxygen to stay alive