In this module, you will learn:

  • how the blood circulates in the body

Resources to help you:

Textbook: page 41

Double circulation in humans

Credit: @Maryna_Melnyk via Depositphotos

Blood circulation


The function of the heart is to pump blood throughout the body. In humans, blood circulates through the heart twice. We call this double circulation.

How does this work?

The heart pumps blood to the lungs to get oxygen before the blood comes back to the heart. Then this blood full of oxygen is pumped to the rest of the body, to the cells that need them.

Right side of the heart


Let's start at point A. This is the right atrium.

The right atrium receives blood from the body through the vena cava. The blood has less oxygen because other cells have used the oxygen.

This is called deoxygenated blood. It has less oxygen and more carbon dioxide.

The heart pumps this blood to the lungs via the pulmonary artery.

Blood circulation on right side of the heart

Left side
Both side

Blood circulation on left side of the heart

The circulation of blood in the heart

Left side of the heart


The blood then picks up oxygen from the lungs and returns to the heart's left atrium via the pulmonary vein. This blood is rich in oxygen and is called oxygenated blood.

Oxygenated blood has more oxygen and less carbon dioxide.

And lastly, the heart pumps this oxygenated blood to all the rest of the body through the aorta.

Watch the video

See how the blood flows between the heart and the lungs


You can change the speed to 0.75x to make it easier to listen.

Ready for the next module?

In the next module, we will look at the blood vessels.

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