Circulatory Systems T1

  • Created by: tiasjw
  • Created on: 20-05-16 11:36
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  • Circulatory Systems
    • Open
      • Small organisms e.g. insects
      • Distances are short so substances can travel by diffusion
      • A simple heart pumps blood into cavities surrounding the animal's organs
      • Substances diffuse between the blood and cells
      • When the heart relaxes blood is drawn back into the heart through small valved openings
    • Closed
      • Multicellular organisms that are too large for diffusion; animals are usually larger in size and more active
      • Rely on a mass transport system to move substances by mass flow
      • The heart pumps blood and the blood and the particles in it move through blood vessels due to difference in pressure
        • Blood vessels generate higher blood pressures as the blood is forced along narrow channels instead of flowing into large cavities
      • The blood travels faster so the blood system is more efficient
      • Blood leaves the heart, flows along arteries and then arterioles, blood comes into close contact with capillaries where substances are exchanged, blood returns to heart by venules and veins
    • Single
      • For animals with closed systems
      • For example fish; heart pumps blood to gills, gaseous exchange takes place in gills, blood leaving gills then flows round rest of the body before returning to heart
      • Blood flows through the heart once for each complete circuit of the body
    • Double
      • For animals with closed systems
      • For example birds and mammals: right ventricle pumps oxygenated blood to lungs where it receives oxygen, the oxygenated blood then returns to heart to be pumped a second time by the left ventricle to the rest of the body
      • Blood flows through the heart twice foe each complete circuit of the body, giving blood returning from the lungs an 'extra boost'
      • Birds & mammals have a high metabolic rate, as substances can be delivered to cells more rapidly


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