Ventilation

• how does a good blood supply maintain diffusion gradients?

  blood is always moving bringing CO2 to be exhaled and taking O2 away
• what happens to the diaphragm during inspiration and expiration?

  • contracts, flattens and lowers during inspiration
  • muscles relax so it moves up into its resting domed shape during expiration
• what happens to the internal intercostal muscles during inspiration and expiration?

  • relaxed during inspiration
  • contracts during expiration
• what happens to the external intercostal muscles during inspiration and expiration?

  • contract, moving the ribs upwards and outwards during inspiration
  • relaxes, moving ribs downwards and inwards during expiration
• what happens to the rib-cage during inspiration and expiration?

  • moves up and out during inspiration
  • moves down and inwards during expiration
• what happens to the volume inside lung during inspiration and expiration?

  • increases during inspiration
  • decreases during expiration
• what happens to the pressure inside the lungs during inspiration and expiration?

  • decreases during inspiration
  • increases during expiration
• what is the role of the plural membrane in ventilation?

  • lines the thorax surrounding the lung
  • the space between them (pleural cavity) is usually filled with a thin layer of lubricating fluid so the membranes slide easily over each other as you breath
• what is the difference between passive and forced expiration?

  Passive - expiration at rest

  Forced - expiration with force
• why is inspiration an active process?

  • requires ATP
• what direction does air move?

  from an area of high pressure to an area of low pressure
• what are the mechanisms of inspiration?

  • diaphragm contracts and external intercostal muscles contract
  • diaphragm flattens and moves down and ribcage is pulled up and out
  • volume of the chest cavity (thorax) increases
  • pressure of chest cavity decreases
  • air moves from higher pressure outside to lower pressure inside
• what are the mechanisms of expiration?

  • diaphragm relaxes and external intercostal muscles relax
  • diaphragm moves up and ribcage is pushed down and in
  • volume of the chest cavity (thorax) decreases
  • pressure of chest cavity increases
  • air moves from lower pressure outside to higher pressure inside
• what do the parts of the glass bell jar represent?

  • glass tube - trachea
  • bell jar - rib cage
  • balloons - lungs
  • rubber sheet - diaphragm
• why do the balloons inflate when the rubber sheet is pulled down?

  • when the rubber sheet is pulled down, volume inside the bell jar increases and pressure decreases
  • air is forced into balloons from an area of high pressure to an area of low pressure so the balloons inflate
• how does the glass bell jar show a realistic representation of expiration?

  it shows expiration as a passive process
• what are the limitations of the glass bell jar model?

  • bell jar is a fixed shape so can’t move like the ribcage
  • cant show forced expiration
  • diaphragm starts as a dome shape, not flat
• why might people struggle to breathe?

  • inflamed airways
  • narrow tubes leaving to lungs so less air gets out
  • structure of alveoli can break down - smoking
  • some are paralysed in accidents or disease so can’t breath
• what are the consequences of alveoli breaking down?

  • fewer big air sacs that have a small surface are for gas exchange than healthier lungs - less gas exchange
• what does the ‘iron lung’ do?

  • external negative-pressure ventilator which assists with people who can’t breath
  • air pumped out of chamber, lowering pressure inside to form a vacuum
  • chest wall of patient moved up as a result
  • increased volume and decreased pressure in chest allows air from outside to be drawn into the lungs
  • vacuum is then switched off and forces air out of lungs