Lungs / Breathing

• Breathing in causes the ribs to move up and out

  The diaphragm flattens from its normal domed shape forcing air out of the lungs
• Alveoli

  
  

  Tiny air sacs with large surface area for diffusion of gases

  Have a rich blood supply - maintained high concentration gradient
• Oxygen is constantly removed into the blood and more CO2 is delivered

  Gas exchange is fastest across the steepest concentration gradients