Mass transport in humans

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  • Created by: emma
  • Created on: 17-04-14 16:11
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  • Mass Transport
    • Mass flow
      • Bulk movement of liquid and gases due to a pressure difference
    • Arteries
      • Endothelial layer- one cell thick, reduce friction as smooth
      • Elastic layer- Large amount of elastic to stretch and recoil as blood pulses through at high pressure, evens out pressure
      • Muscle layer- contractions restrict vessel to reduce volume of blood passing through
    • Arterioles
      • Smaller vessels than arteries and connect arteries to capillaries
      • Elastic layer is thinner as blood pressure lower and less need for elasticity as blood pulses through
      • Muscle layer is thicker as contract to constrict vessel and reduce blood flow or relax and dilate vessel to allow more blood flow to the organ
    • Veins
      • Thin muscle layer- no need for vaso-constriction as blood going back to heart
      • Valves- stop back flow of blood
      • Thin muscle layer- no need for stretch and recoil as low blood pressure
    • Capillaries
      • Only endothelial layer- very thin, short diffusion distance
      • Numerous and branched- increase surface area
      • Narrow- ensures RBC always in contact with wall, reduce diffusion distance and increase surface area
    • Tissue fluid
      • At beggining of capillary high hydrostatic pressure forces water out
        • Large proteins remain in capillary
          • At end a capillary, low water potential in capillary due to plasma proteins
            • Water enters capillary via osmosis
              • 10% returns via the lymph system


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