Types of Circulatory Systems

• Single closed circulatory system

  Consists of one circuit from the heart, the blood passes through the heart once per cycle and there is only one circuit that the blood takes
• Single closed circulatory system

  • Fish
• Single closed circulatory system in fish


  1. Blood passes through two sets of capillaries immediately after being pumped out of the heart

  2. Blood flows through capillaries in the gills to become oxygenated

  3. Blood flows through capillaries delivering the blood to the body before returning it back to the heart
• Single closed circulatory system would not enable efficient gas exchange for mammals but it does work for fish because they have that counter current flow mechanism
• Double closed circulatory system

  The blood passes through the heart twice per cycle and there are two separate circuits the blood would take
• Circuits in double closed circulatory system

  • Blood vessels carrying blood from the heart to the lungs for gas exchange (pulmonary circuit)
  • Blood vessels carrying the blood from the heart to the rest of the body to deliver oxygen, nutrients and collect waste (systemic circuit)
• Closed circulatory system


  The blood stays within blood vessels, kept separate from body tissues and doesn't come directly in contact with cells, the transport medium is blood and it always remains inside of blood vessels
• Closed circulatory system


  • Gas and small molecules can leave the blood by diffusion or due to high hydrostatic pressure
  • The blood is pumped under pressure and molecules leave through walls of the blood vessels
  • The amount of blood flowing can be adjusted by widening or narrowing the blood vessels
• Open circulatory system


  The transport medium, the hemolymph or blood, is usually pumped directly to the body cavity called the haemocoll from the heart, there are few transport vessels so the transport mediums are pumped at low pressure, food and nitrogenous waste will be transported but not gases which are instead transported via their tracheal system, once exchange has taken place at the cells and tissues the transport medium returns the heart through an open-ended vessel
• Open circulatory system


  • Invertebrates like insects