exchange surfaces

• Lungs adaptations:

  • Many alveoli provide a large surface area
  • Capillaries and alveoli are one cell thick, providing a short diffusion pathway
  • Lungs are well ventilated, maintaining the concentration gradient by allowing fresh O2 to be brought in and removing waste CO2
  • Good blood supply maintains the concentration gradient by removing oxygenated blood and bringing CO2-rich blood to the lungs
• Small intestine adaptations:

  • Many projections called villi provide a large surface area
  • Walls of villi and capillaries are one cell thick, providing a short diffusion pathway
  • Cells have many mitochondria, allowing energy transfer from aerobic respiration for active transport of food molecules
  • Good blood supply maintains the concentration gradient
  • The small intestine is very long, increasing the time for absorption
• Alveoli are small air sacs that have thin walls with many blood capillaries close to them.