Exchange and transport in Animals

• How does gas exchange happen in the alveoli of mammals?

  1.Lungs transfer oxygen to blood and remove CO2.

  2.Lungs contain millions of alveoli.

  3.Blood arrives from rest of body to alveoli in lungs. Contains lots of CO2, not much O2.

  4.O2 diffuses out of air into alveoli (O2 concentration high) and into the blood (O2 concentration low). CO2 diffuses in opposite directions to be breathed out.
• What are adaptations of the alveoli?

  -moist lining for dissolving gases.

  -a good blood supply to maintain concentration gradients of O2 and CO2.

  -very thin walls which minimise distance gases have to move.

  -large surface area.