ch4.3 gas exchange

• how are lungs well suited to their function of gas exchange?

  • Millions of alveoli provide large internal surface area
  • Each alveolus is surrounded in a capillary network
  • Walls of the alveoli are one cell thick
  • Membrane of alveoli covered in thin layer of moisture
  • Lungs are positioned deep inside the body to prevent excess evaporation
• gas exchange = the transfer of oxygen and carbon dioxide between the alveoli and the capillaries in the lungs
• oxygen

  • high concentration in alveoli
  • low concentration in capillaries
  • = diffuses from alveoli into the capillaries to oxygenate the blood stream
• carbon dioxide

  • high concentration in capillaries
  • low concentration in alveoli
  • = diffuses from capillaries into alveoli where we breath it ou
• concentration gradient = difference in gas concentration between air in the alveoli and blood in the capillaries
• concentration gradient is maintained by

  • constant flow of blood in the capillaries
  • movement of air into and out of the alveoli