The circulatory system moves blood around our body. That is what we call blood circulation.

Our blood has 2 main functions:

  • It transports nutrients and oxygen to the different parts of our body.

  • It collects waste substances (the substances our body doesn't need).

Blood Vessels with Names.jpg

The heart is the organ that pumps the blood around our body. The heart is an involuntary muscle (you can't control it!!).

In the heart, you can find 4 chambers: 2 atriums and 2 ventricles. The atriums are in the upper part of the heart, and the ventricles are under the atriums.

Heart with Names.jpg

How does your heart work? Basically, there are 3 steps:

  1. The atriums recive the blood.

  2. Blood passes from the atriums to the ventricles.

  3. The ventricles pump the blood back to the body.

In this flash animation (from you can see the whole process.

A human heart looks like this: animation from

The blood is pumped through the blood vessels. There are 3 types of blood vessels:
  • Arteries: carry blood from the heart to the body. They carry oxygenated blood (blood with oxygen) that is bright red.

  • Veins: carry blood from the body back to the heart. They carry deoxygenated blood (blood with carbon dioxide) that is dark red.

  • Capillaries: are very tiny blood vessels that connect the arteries and the veins.

Time to review all this information on a video.

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