B3- Exchange Surfaces: Alveoli + Villi

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  • B3- Exchange Surfaces
    • The Lungs- Alveoli
      • 1 cell thick, enables a shorter diffusion path.
      • Have a large surface area, increases the rate of diffusion
      • Have a good + efficient blood supply.
        • Blood must be oxygenated and have its CO2 removed continuously
      • Are well ventilated
        • So that you inhale fresh oxygen for the blood, and exhale carbon dioxide
    • The Small Intestine- Villi
      • Moist and Large surface area
        • There are thousands of villi within the inner walls of the small intestine
          • Allows more digested nutrients (amino acids) to diffuse into the blood capillary
      • 1 cell thick
        • Means digested food  needs only to travel through 1 cell to reach the blood capillary
      • Have a good + efficient blood supply
        • There is a dense network of blood capillaries within each Villi
          • To carry away the oxygenated blood and the de-oxygenated blood aound the body
      • The Micro-villi contain Mitochondria as they release energy which is needed for digested nutrients to be absorbed from the low concentration outside the cell to the high concentration on the otherside of the micro-villi
        • Active Transport


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