The circulatory system

The human circulatory system is made mainly of a pump, the heart, and a network of blood vessels: the arteries, veins and capillaries that carry blood around the body.

📖 In short

The circulatory system is a network that carries blood all through your body. It has three parts: the heart, which pumps blood; the blood vessels, which it travels through like roads; and the blood, which carries oxygen and food to every cell.

🤩 Did you know?

If all the blood vessels in your body were laid end to end, they'd go around the Earth more than twice!
Blood makes a full trip around the body in less than a minute.
High blood pressure makes the heart work harder.
Ibn al-Nafis discovered the pulmonary circulation more than 700 years ago.

🔎 Find out more

🌟 Blood's roads

Arteries are vessels that carry blood from the heart to the body, veins bring it back to the heart, and capillaries are very thin vessels joining them, where the blood gives cells what they need.

🔍 Two circuits

In the small circuit, blood goes from the heart to the lungs to pick up oxygen and comes back. In the big circuit, it goes from the heart to the whole body and comes back.

💡 The pulse

When the heart pumps blood, the arteries swell a little. Put two fingers on your wrist or the side of your neck and you'll feel these beats, which match your heartbeats.

🎯 A strong heart

Exercise, running and playing make the heart stronger, and healthy food with little salt and fat keeps the blood vessels clean.

📸 More pictures

In breathing, blood carrying carbon dioxide (“blue”) goes to the heart, which pumps it to the lungs. In the lungs the blood gets rid of carbon dioxide and takes in oxygen. Then the oxygen-rich blood (red) returns to the heart to be pumped all around the body.

In nutrition, the circulatory system carries tiny bits of digested food to the body's cells; these bits enter the bloodstream through the walls of the small intestine.

Getting rid of waste. Blood carries waste from the body's tissues to the kidneys, which filter it out and pass it in urine.

🧩 Test yourself

1 Which vessels carry blood from the heart to the body?

2 Where can you feel your pulse?

3 Ibn al-Nafis discovered the pulmonary circulation more than ?? years ago.

4 Which picture shows “The circulatory system”?