Inspiration and expiration

• Inspiration = breathing in

  expiration = breathing out
• RIDVPA = ribs, intercostal, diaphragm, volume, pressure, air

  (use purple sunglasses for memorisation)
• Process of inspiration:

  1. Intercostal muscles contract ---> ribcage moves up and out
  2. diaphragm (originally a dome) contracts and flattens
  3. Volume of thorax increases
  4. so pressure in thorax decreases
  5. Air rushes in
• inspiration/ expiration (use - to separate clauses)

  A) Inspiration

  B) diaphragm contracts and flattens

  C) intercostal muscles contract - ribcage moves up and out

  D) air rushes in

  E) volume increases - pressure decreases

  
• The diaphragm is a dome shape
• Bell Jar model:

  pulling down on the rubber sheet increases volume --> decreasing air pressure ---> drawing in air (balloons inflate)

  
• Limitations of bell jar =

  • 'ribcage' does not move: a human's does
  • Human diaphragm = dome shape in expiration: bell jar the rubber sheet is flat in expiration
  • Humans' chest cavity has fluid in: bell jar is empty.
  • Human's thorax is full of organs: bell jar is empty
• Use - to seperate clauses- expiration/inspiration for 1st

  A) expiration

  B) diaphragm relaxes - returns to dome shape

  C) intercostal muscles relax - ribcage moves down and in

  D) volume decreases - air pressure increases

  E) air rushes out