Double Circulation

What is Double Circulation?

The majority of mammals including humans have a double circulatory system, i.e. we have two loops in our body where the blood circulates. Double circulation is the movement of blood in the whole body and it involves the flow of

  • Oxygenated blood: Oxygen-rich

  • Deoxygenated blood: Little to no oxygen, and a lot of carbon dioxide  

Why is Blood Circulation in the Human Heart Called Double Circulation?

It is important for human bodies as it ensures our tissues and muscles receive blood full of oxygen instead of the impure mixture of oxygenated and deoxygenated blood. The organ powering double circulatory system is the heart that pumps blood through four chambers that include two Atria and two Ventricles. The four valves present in the heart keep blood moving in one direction and help in preventing the backflow of blood into the heart. The two valves are found in the heart itself and the other two valves are found in the major arteries in the heart. The major arteries of the heart are Aorta and Pulmonary Artery. All of these parts can be understood if we see the diagram of the heart with all labelings. 


As we can see above in the picture, humans have four chambers in their hearts (whereas some organisms have two or three-chambered hearts such as in reptiles and fish). The human heart can be separated into two halves, separated by a muscle tissue called septum; each half having an atrium that sits on the top of one ventricle.


It is referred to as a double circulatory system because here, the blood passes through the heart twice per circuit. The left pump sends the fresh oxygenated blood around the body and on the other hand, the right pump sends deoxygenated blood to the lungs where it becomes oxygenated and flows back to the heart. It is important for the separation of oxygenated and deoxygenated blood in human beings as it makes the circulatory system more efficient and also helps in maintaining the constant temperature of the body. Below are the four chambers of the heart playing an important role in the double circulation in human beings.

  • Left Atrium: Receives oxygenated blood from lungs which contain oxygen.

  • Right Atrium: It receives deoxygenated blood that contains CO2 as the byproduct of metabolism.

  • Left Ventricle: It also receives oxygenated blood coming from the left atrium via a bi-cuspid valve.

  • Right Ventricle: It receives deoxygenated blood consisting of CO2 from the right atrium via tricuspid valve.

Below are the Blood Vessels Responsible for Carrying Out Double Circulation:

  • Pulmonary Artery: It takes deoxygenated blood to the lungs.

  • Aorta: It carries oxygenated blood to the body tissues.

  • Pulmonary Vein: It carries oxygenated blood 

  • Vena Cava: It takes deoxygenated blood 

Two Types of Circulation: Double Circulation in Human

  1. Pulmonary Circulation

  •  Lungs are involved in this type of circulation.

  • In this pathway, when deoxygenated blood is transferred to the lungs via the pulmonary artery and that deoxygenated blood comes from the right atrium to the right ventricle and then pulmonary artery. 

  • Now, carbon dioxide is removed and oxygen enters as a result of which blood carries oxygenated blood. 

  • This oxygenated blood is carried by Pulmonary Vein to the Left Atrium. Further, this blood goes to the Left Ventricle.

  1. Systemic Circulation

  • All systemic organs and tissues are involved in this type of circulation. 

  • Oxygenated blood will go to the tissues and organs via Aorta when then becomes deoxygenated as a result of by-products (CO2) of metabolic and respiration processes.

  • This deoxygenated blood is carried by Vena Cava to the right atrium and then further into the right ventricle. 

And the cycle follows, the deoxygenated blood from the right ventricle goes to the lungs via the pulmonary artery. The CO2 is exhaled out from the lungs at that spot. If anyone asks to define double circulation, you can easily talk about pulmonary and systemic circulation and describe how blood enters twice to the heart and escapes twice out of the heart in the whole process. Therefore, it is known as double circulation.

What is the Advantage of Double Circulation?

Talking about the significance of double circulation, one can understand from the following points how an efficient circulation is important for our bodies.

  • It helps in maintaining higher blood pressure.

  • It allows a greater flow of blood to the tissues.

  • It helps in creating more pressure to pump blood around the whole body tissues and organs. 

  • A separation of oxygenated and deoxygenated blood is possible that leads to taking in oxygen-rich blood and removal of carbon dioxide from the blood through the lungs.

  • It helps in producing a large amount of energy to maintain life processes.

FAQ (Frequently Asked Questions)

1. Why is Blood Circulation in the Human Heart Called Double Circulation?

Circulation in the human heart is referred to as double circulation because having four-chambered hearts, the blood enters twice to the heart and blood escapes twice from the heart via arteries and veins. Therefore there is the double-entry and double exit of blood in the whole circulation and hence the name- double circulation.

2. Why is the Double Circulation of Blood Necessary in Human Beings?

Double circulation in human beings allows the separation of oxygenated and deoxygenated blood in the body. It helps in maintaining a high blood pressure required for essential processes. It enables pure blood to reach the different tissues and organs of the body like kidney, liver, etc.

3. What Do You Mean by the Double Circulation of Blood?

Double circulation takes place with the help of two types of circulation in the human body that includes

  • Pulmonary Circulation: In this, lungs receive deoxygenated blood from the pulmonary artery which is then oxygenated and sent to other parts of the heart.

  • Systemic Circulation: Here, the oxygenated blood goes to the tissues and organs which in turn supply deoxygenated blood further to go to the other parts of the heart.

Double circulation involves blood flow to the four chambers including the left atrium, left ventricle, right atrium, and right ventricle. Blood vessels like a pulmonary artery, aorta, vena cava and pulmonary vein are equally responsible to successfully complete the blood circulation.