Lungs and Lung Disease

Chapter 4 - Lungs and lung disease of Biology Unit 1

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  • Created by: Ali
  • Created on: 04-05-12 17:46

Structure of the Lungs

Trachea - flexible airway supported by rings of cartilage, preventing collapse. Cilia in the trachea move the mucus to the throat. 

Bronchi - two divisons of the trachea, each leading to one lung.

Bronchioles - branching subdivisions of the bronchi.

Alveoli - minute air-sacs with a large surface area and thin wall (increasing the efficiency of gas exchange).

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  • The external intercostal muscles contract and the internal intercostal muscles relax.
  • The ribs are pulled upwards and outwards, increasing the volume of the thorax.
  • The diaphragm contracts, flattening it, increasing the volume of the thorax. 
  • The increased volume of the thorax decreases the pressure in the lungs.
  • Atmospheric pressure is more so air is forced into the lungs.
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  • The internal intercostal muscles contract and the external intercostal muscles relax.
  • The ribs are pulled downwards and inwards, decreasing the volume of the thorax.
  • The diaphragm relaxes, returning to it's original shape, decreasing the volume of the thorax.
  • The decreased volume of the thorax increases the pressure in the lungs.
  • Atmospheric pressure is less so air is forced out.
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Pulmonary Ventilation

Pulmonary ventilation - the total volume of air taken into the body in one minute.

Tidal volume - volume of air normally taken in at each breath, at rest.

Ventilation rate - number of breaths taken in one minute.

Pulmonary ventilation = tidal volume x ventilation rate

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Pulmonary Tuberculosis


Persisant cough, tiredness, loss of appetite, fever, coughing up blood.


Spread through the air in droplets.


  • The bacteria grow and divide in the upper regions of the lungs where there is a plentiful supply of oxygen.
  • White blood cells accumulate at the site of infection to ingest the bacteria.
  • This leads to enlargement and inflammation of the lymph nodes (primary infection).
  • Many years later these bacteria can re-emerge and they destory the tissue of the lungs which the sufferer coughs up (post-primary tuberculosis).
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Pulmonary Fibrosis


Shortness of breath, dry cough, weakness and fatigue.


  • Scars form on the epithelium lining, causing them to become irreversibly thickened. This reduces the efficiency of gas exchange.
  • It reduces the elasticity of the lungs making it difficult breathe out.
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Difficulty in breathing, wheezing sound, coughing.


Caused by air pollutants, pollen etc.


  • White blood cells on the linings of the bronchi and bronchioles release histamine.
  • The linings of the airways becomes inflammed.
  • The cells on the epithelium lining secrete more mucus.
  • Fluid leaves the capillaries and enters the airways.
  • Muscles surrounding the bronchioles contract, constricting the airways.
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Shortness of breath, cough,bluish skin coloration.


  • The elastin of the lungs becomes permanently streched.
  • Lungs aren't able to force all air of the alveoli.
  • Surface area of alveoli is reduced and they can burst.
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