Gas exchange in humans

• What is the upper part of your body known as?

  Thorax
• What are your lungs protected by?

  • Ribcage
  • Separated from the lower part of your body (abdomen) by a muscular sheet called the diaphragm
• Breathing


  The mechanical way air is drawn into and passed out from our lungs (ventilation)

  
  

  Air moving down a pressure gradient, never sucked or blown
• How does the composition of air change?

  • From gas exchange in lungs
  • Air we breathe in consists of : 78% nitrogen, 21% oxygen, 1% argon and some trace gasses, Carbon dioxide 0.04%
  • Air we breathe out consists of : 78% nitrogen, 16% oxygen, Carbon dioxide 4%
• Oxygenation of blood

  • Oxygen in the air moves into capillaries
  • Blood is deoxygenated
  • Oxygen in lungs are at a higher concentration
  • The oxygen moves from your lungs into the blood
  • Blood becomes oxygenated
• CO2 in blood

  • When blood reaches your lungs first it has a high level of CO2 in plasma
  • The concentration of CO2 in blood is higher
  • The means it diffuses down a concentration gradient into the lungs for us to breathe out
• How does mouth to mouth resuscitation work?

  • Air breathed into lungs
  • A lot more oxygen that Carbon dioxide is present in the air we breathe out
  • If we ONLY breathed out Carbon Dioxide it would kill the patient
• Movement of thorax when breathing

  • Ribcage moves up and out
  • Muscles contract, diaphragm contracts and moves downwards
  • Space inside lungs is increased, reduces the pressure inside the lungs so air outside at a higher pressure moves into the lungs down the pressure gradient
  • Diaphragm relaxes and moves up
  • Ribs move inwards and down
  • Muscles relax
  • Space inside lungs decreases which makes the pressure higher inside the lungs than outside.
  • The air moves from a place of high pressure to one of low pressure and we breathe out