Lung Diseases


Pulmonary Tuberculosis

Cause: a rod-shaped bacterium

Transmission: the inhilation of droplets of water/moisture covered in the bacteria from an infected person

Symptoms: Cough, tiredness, short of breath - fever, coughing up blood

Course of infection:

  • Primary Infection

Immune response to bacterium - phagocytes (white blood cells) ingest bacterium and form hard lumps (tubercles) - bacteria are dormant

  • Secondary Infection

If immunosuppressed (immune system suppressed) bacteria activate - destroy alveoli - scar tissue forms - SA reduced + diffusion pathway increased

Bacteria can spread via blood as accessable due to damage

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Cause: Smoking or excessive exposure to air pollution

Symptoms: Cough, shortness of breath - bluish skin

Non contagious


  • Develops over long periods of time so undiagnosable
  • Causes inflammation which attracts phagocytes. They release enzyme which breaks down elastin
  • Elastic tissue is permanently stretched - more difficult to recoil and expel air - reduced diffusion gradient as less volume of air exhaled/inhaled
  • Alveoli are ruptured and walls thicken - SA reduced and Diffusion pathway increased
  • Less oxygen enters blood - less respiration so less energy released

All three of the diffusion actors are effected and gas exchange is less efficient

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Pulmonary Fibrosis

Scar tissue forms after the epithelial cells are damaged

Symptoms: Shortness of breath, Cough, Tiredness and Pain in chest

How it effects gas exchange

Concentration Gradient - Reduces elsasticity so lungs inhale/exhale a reduced volume of air (tidal volume) - lower concentrations of oxygen in comparison to what's in the blood

Diffusion Pathway - the scar tissue thickens the epithelial walls increasing the diffusion pathway so less oxygen can diffuse across in a certain amount of time

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Cause: Allergic Reaction - common allergens are pollen, fur + dust mites

Can be made worse by air pollution, cold weather, exercise, infection + stress

Effects: These all reduce the concentration gradient

  • Lining of the airways become inflamed  - reduce volume of air entering lungs
  • Cells produce larger amounts of mucus
  • Fluid leaves capillaries and enters airways
  • Muscles lining bronchioles contract constricitng airway

Symptoms: Short of breath, wheezing sound when breathing, tight chest, coughing

Asthma cases are increasing - more pullution, cleaner lifestyles, chemicals?

Can be passed on through genes

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