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  • Created by: tiacoles
  • Created on: 22-02-16 18:01



  • Intercostal and diaphragm muscles contract
  • This causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax (the space where the lungs are)
  • As the volume of the thorax increases the lung pressure decreases (to below atmospheric pressure)
  • This causes air to flow into the lungs
  • It is an active process - requires energy


  • The intercostal and diaphragm muscles relax
  • The ribcage moves downards and inwards and the diaphragm becomes curved again
  • The thorax volume decreases, causing the air pressure to increase (to above atmospheric pressure)
  • Air is forced out of the lungs
  • It is a passive process - doesn't require energy. 


  • Tidal Volume - the volume of air in each breath (0.4 dm3)
  • Vital Capacity - the maximum volume of air that


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