TYPES OF CLOSED CIRCULATORY SYSTEM


  • In all vertebrates, higher molluscas and annelids, the blood is circulated all over the body through a network of blood vessels.
  • In this type of circulation, blood flows within the blood vessels and does not come in direct contact with cells and body tissues.
  • Exchange of material between blood and body tissues is through an intermediate fluid celled lymph.
  • Blood flows with high pressure and contains respiratory pigments like haemoglobin for transportation of respiratory gases.
  • Close circulation is of two types- single and double circulation.

Single circulation

  • In single circulation, the blood passes through heart only once during each cycle. ex. Fishes
  • Deoxygenated blood is pumped from heart towards gills, where it undergoes oxygenation.
  • This oxygenated blood moves towards various body parts, gets deoxygenated and returns back to heart for next cycle.
  • The heart of Fish carries only deoxygenated blood, it also called 'Venous Heart'.


Double Circulation

  • In double circulation, blood passes through heart twice during each cycle.
  • It occurs in birds and mammals.
  • In these animals, heart pumps deoxygenated blood to lungs for oxygenation and it returns to heart as oxygenated blood.
  • This is 'Pulmonary Circulation'.
  • The oxygenated blood is pumped for the heart towards various body parts and returns back to the heart as deoxygenated blood.
  • This is 'Systemic Circulation'.
  • Human heart shows double circulation.




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