Gas Exchange

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  • Gas exchange
    • Diffusion
      • Passive movement of particles
        • No energy is needed
      • Net movement of particles from an area of high concentration to a low concentration
        • Particles diffuse down a concentration gradient
        • Net movement is the overall direction
        • Continues until particles are evenly distributed throughout liquid/gad
    • Exchange surfaces are adapted for efficient diffusion
      • Common factors in gas exchange surfaces
        • 1) Gives gas exchange organs a large surface area to volume ratio
          • Increases rate of diffusion
            • 2) Thin, which provides short diffusion across the gas exchange surface
        • 2) Thin, which provides short diffusion across the gas exchange surface
    • The smaller the surface area to volume ratio, the slower the rate of exchange
    • In the Lungs
      • Gas exchange surface in lungs is called the Alveolar Epithelium (AE Surface is a layer of thin, flat cells)
      • Oxygen diffuses out of the alveoli. across the AE Surface, then the capillary endothelium, and into the blood
        • Carbon dioxide diffuses into the alveoli from the blood and is breathed out
      • Features in the lungs
        • A lot of alveoli means larger surface area for diffusion
        • The AE surface and Capillary endothelium are one cell thick, short diffusion pathway
        • Alveoli all have good blood supply from capillaries, they maintain the centration gradient by taking oxygen away and bringing more carbon dioxide
        • Breathing in and out refreshed the air in the alveoli


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