Inspiration / Expiration

• RIDVPA

  R - Ribs

  I - Intercostal

  D - Diaphragm

  V - Volume

  P - Pressure

  A - Air
• Inspiration (breathing in)


  Ribcage - moves up and out due to intercostal muscles contracting

  Diaphragm - contracts and flattens

  Volume (in thorax) - increases

  Pressure (in thorax) - decreases

  Air - rushes in
• Expiration (breathing out)


  Ribcage - moves down and in due to intercostal muscles relaxing

  Diaphragm - relaxes and returns to dome shape

  Volume (in thorax) - decreases

  Pressure (in thorax) - increases

  Air - rushes out
• Bell jar model

  The bell jar model is used to demonstrate inspiration and expiration in the lungs.
• Bell jar model flaws

  -In humans, the ribcage moves but the bell jar cannot.

  -The diaphragm should be a dome shape when breathing out but it is flat on a bell jar model.

  -The bell jar is hollow while the chest cavity has fluid .

  -There is an empty space in the bell jar but the thorax is filled with organs.