Gas exchange in the lungs

• What are the alveoli?

  Small air sacs that are the site of gas exchange in the lungs
• Adaptations of the alveoli:

  • RBCs are slowed as the pass through capillaries, allowing more time for diffusion
  • reduced distance between alveoli and RBCs
  • microvilli increase the surface area of the alveoli
  • steep concentration gradient