Gas exchange and lungs

• Alveoli


  • Adapted to carry out gas exchange
• All our cells carry out the process of cellular respiration
• Cells need oxygen for cellular respiration
• Function of the lungs

  Get oxygen from the air around us into our bloodstream where it can be transported to the rest of the body
• Air flow through the body

  1. Passes through mouth or nose

  2. Down trachea

  3. Divides between two bronchi

  4. Further divides into bronchioles

  5. Reaches the alveoli (the site of gas exchange)
• Alveolus


  Single alveoli
• Alveoli


  • Made up of one layer of thin cells
  • Creates a short diffusion pathway
  • Increases the rate at which carbon dioxide and oxygen can diffuse across
• Alveoli


  • Have a very large surface area
  • If spread out flat would cover half a tennis court
• Alveoli walls


  • Are moist
  • Allows the gases to dissolve
  • Increases their rate of diffusion
• Hemoglobin within the blood cells have already given up lots of its oxygen to the tissues
• Carbon dioxide can easily diffuse across
• Carbon dioxide isn't carried by red blood cells, it is dissolved in the blood plasma
• When you do exercise

  Your breathing rate changes
• Calculating breathing rate


  Number of breaths taken / Number of minutes = Breaths per minute