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
• The alveoli are a cluster of air sacks found in the lungs where gas exchange occurs
• O2 diffuses from air in the alveoli into blood in the capillaries
• CO2 diffuses from blood in the capillaries into air in the alveoli