Double Circulation – Class 11 | Chapter – 18 | Biology Short Notes Series PDF

Double Circulation: The blood flows twice through the heart, once in an oxygenated state and the other in a deoxygenated state. This is called Double circulation and includes systematic and pulmonary circulation.


The heart is the key organ for blood circulation and the double circulation is an efficient way of circulation as it provides an effective way of circulation. The main difference is that the blood follows two routes – one for oxygenated blood and the other for deoxygenated blood. Hence, the name “double circulation.” The majority of mammals, including humans utilize a double circulatory system.

Double Circulation

The human heart is divided into four chambers:

  1. Left Atria
  2. Right Atria
  3. Left Ventricles
  4. Right Ventricles

Further, the heart is connected to the lungs through the pulmonary artery and vein. In double circulation, there are two pathways in which the blood flows. They are:

  • Systemic circulation

Systemic circulation carries oxygenated blood from the left ventricles to the tissue capillaries.

  • The oxygen-rich blood is transferred to the aorta for circulating into various parts of the body.
  • Later, the veins and venules collect the deoxygenated blood – which is rich in carbon dioxide from various parts of the body.
  • The deoxygenated blood is pumped back into the superior vena cava and then to the right atrium.
  • Once, after receiving the deoxygenated blood, the right atrium carries blood to the right ventricle for pulmonary circulation.
  • Pulmonary circulation

In the pulmonary circulation, the blood circulation starts from the right atrium to the left atrium. In this pathway:

  • The pulmonary artery collects the blood from the right ventricle and carries to lungs for oxygenation.
  • Once, after the purification process, the oxygenated blood is pumped back to the left atrium through the pulmonary vein which is carried to the left ventricles.
  • The left ventricles pump the oxygenated blood to the aorta for systemic circulation.

Double circulation supports a strict separation of both oxygenated and deoxygenated blood. Therefore, this circulation ensures that the body always has a dedicated supply of oxygen and also, it improves body efficiency. This is also one of the reasons why mammals can maintain their body temperatures.  Apart from the double circulation, a third portal system also exists to improve circulation efficiency.

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By Team Learning Mantras