Gas exchange

• Respiration


  A chemical reaction which releases energy from food
• Respiratory system


  Exchanges the gases which are involved in respiration
• Compared to atmospheric air, exhaled air contains less oxygen, more carbon dioxide, and more water vapour
• Alveoli


  • Thin walls (just one cell thick) to reduce the diffusion distance
  • Large surface area for maximum exchange of gases
  • Moist surface for the dissolving of gases in alveolar air so that they can diffuse across the alveolar walls
  • Rich blood supply to remove diffused gases and maintain a concentration gradient for further diffusion
• Gas exchange in the lungs happens in the alveoli