Mass transport

The blood systme and the passage of water through plants

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  • Rapid blood flow
  • Oxygenated blood
  • High blood pressure
  • Carries blood from the heart to the tissues
  • Thick muscle layer - Arteries can be constricted and dialated to control volume of passing blood
  • Thick elastic layer - elastic wall is streched in systole and spring back during diastole  which helps to maintain high and smooth pressure surges
  • Thick wall - to resist the vessel bursting
  • No valves - blood does not flow backwards in the artery
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  • Blood flow slower than arteries
  • Oxygenated blood
  • Lower pressure
  • Controls flow of blood (slows it down)
  • Thicker muscle than artery - controls blood movement into the capillaries
  • Elastic layer thinner than artery - becasue blood pressure is lower
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  • Very slow blood flow
  • Both oxygenated and de-oxygenated blood
  • Low blood pressure
  • Exchanges metabolic materials between the blood and the cells of the body
  • Extremley thin - diffusion distance is short
  • Numerous and highly branched - large surface area for diffusion
  • Narrow diameter - permeate tissues
  • Narrow lumen - red blood cells are squeezed flat against side of capillary
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  • Slow blood flow
  • De-oxygenated blood
  • Very low blood pressure (due to valves)
  • Transport blood from tissues to heart
  • Thin muscle layer - constrictions and dialations cannot control blood flow
  • Thin elastic layer - Low pressure of blood won't cause them to burst
  • Thin wall - No need for thick wall - no risk of bursting
  • Vavles throughout - to stop blood flowing backwards
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Muscle layer

  • Thickest = Arteriole
  • Middle = Artery
  • Thinnest = vein


  • Muscle layer contration allows constrcition of the lumen in the arterioled. This contricts bloow flow and conrols blopd movement into the capillaries
  • Smaller arteries can be constricted to controll the volume of blood passing through
  • Constrction and dialation in the veins can't control bloow flow to the tissues
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Elastic layer

  • Thickest = Arteries
  • Medium = Arterioles
  • Thinnest = veins


  • Thick elasitc in the artery helps to maintain high and smooth pressure surges by the beating of the heart
  • Arterioles elastic layer is thinner than arteries because blood pressure is lower
  • Thin in veins because they have a blood pressure so no risk of bursting
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