Biological basis of Lung Disease

Hey everyone

Here are some notes on everything you need to know about the Biological basis of lung disease for AQA Unit 1 this may also be of help to students studying with other boards 

Hope this helps :)



Attacks can be triggered by a wide variety of allergens such as pollen, dust, feathers...ect.
During an attack:
Muscle in the walls of the bronchi and bronchioles contracts, thus reducing the diameter of the airways.

Mucus secreting cells lining the airways go into slight over drive and start producing lots of mucus.

Mast cells resppond by producing histamine which causes the linings of the airways to become inflamed and swollen.

Blood vessels dilate and become leaky, causing the bronchi to fill with fluid.

Breathing becomes inccreasingly difficult and because less air can reach the alveoli there is a danger of lack of oxygen to the brain which could be fatal.

Avoiding exposure to allergens.

Using drugs such as antihistamines to relax muscles and reduce inflammation. 

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  • Fibrous lumps grow in the lungs which makes them stiff and so makes breathing shallow and difficult.
  • This usually arises due to breathing in dusty air- so people who work in places like mines are at a greater risk.
  • Dust accumulates in the aleoli stimulating white blood cells called macrophages to come and engluf these particles.
  • If there is a lot of dust the macrophages can get stuck in the connective tissue between the alveoli and eventually stimulate the formation of hard fibrous lumps.
  • The lumps cause a loss of elasticity in the lungs this reduces lung capacity.
  • The alveolar walls become thicker so diffusion distance is greater making oxygen absorption much more difficult.
  • Sufferers find exercise very difficult and get tired easily.
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  • This is a lifestyle disease and is caused by smoking.
  • Alveolar walls have a protein called elastin enabling them to recoil after being stretching during breathing.
  • In emphysema sufferers this elastin breaks down meaning less air can be breathed in and out.
  • The walls of the alveoli are also attacked by an enzyme which causes them to burst this greatly reduces their surface area.
  • The patient is constantly out of breath because there is reduced oxygen intake because of the reduced surface area.
  • Sufferers also have a chronic cough as their body tries to rid the lungs of damaged tissue and mucus.
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  • Caused by a single causative agent- Bacteria
  • Caused by overcrowded living conditions, HIV 
  • It is associated with third world countries.
  • Spread by coughing and sneezing.
  • A long exposure to the bacteria is needed for infection sometimes the bacteria lies dormant for ages.
  • Can also be spread through the milk of infected cows and also through badgers.
  • In more severe cases the bacteria causes cavities to appear in the lungs, these get filled with fluid so ventilation is very inefficient.


  • Coughing
  • Loss of apetite
  • Tiredness 
  • Weight loss

Treatment: Usually by antibiotics but many have now developed a resistance. 

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