We hear about hearts all the time. In songs and poems and especially on Valentine's Day. For centuries people thought their emotions came from their hearts. Now we know it's our brain that controls both our emotions and our hearts. But what does the heart do then and how does the heart work?

Blood Circulation, Illustration

Heart Beats

In fact your heart is kind of like a pump. By contracting and relaxing the cardiac muscles pump blood around your body. But you don't have to think about it! The cells in these muscles are programmed to do this contracting and relaxing by themselves, over and over again.

Think of it like this, before each beat your heart fills with blood. Then the cardiac muscles contract and squirt the blood along.

When the heart muscles contract they squeeze, kind of like when you squeeze your hand into a fist - try it and see! Your heart does this all day, all night, all the time.

The heart is a muscle

Yes, your heart is actually a muscle! One of the most important organ's in your body, it's about the size of your fist. You'll find it to the left of the centre of your chest.

Your heart may be a muscle but it's quite a special one. Made of some of the cleverest muscles you have - the cardiac muscles, it sends blood around your body. Your blood provides your body with the oxygen and nutrients you need. It also carries away waste products.





Breathing system





Heart Parts

Inside your heart are four chambers or blood filled areas. A chamber is just a room or a space. There are two on the bottom and two on the top.

The chambers on the bottom are called ventricles. Their job is to squirt blood around the body.

The chambers on the top are called atria. They fill with blood returning from around the body.

Running down the middle of your heart is a thick wall of muscle called the septum which separates the two sides.

You might be wondering how the blood knows which way to go when it gets pumped? Well your blood relies on valves inside the heart. Valves are a bit like doors. They let something in and keep it there by closing.

The mitral valve and the tricuspid valve let blood flow from the atria to the ventricles. The aortic and the pulmonary valves are in charge of controlling the flow of blood leaving the heart.

All the valves work together to keep the blood moving forwards. They open up to let it flow forwards and then quickly shut to stop it flowing backwards.

How does the heart work?

To resume

  • The heart is made up of super smart cardiac muscles
  • These cardiac muscles pump blood around your body
  • They do this by contracting and relaxing

Remember, your heart is a muscle and the more it works the healthier it will get. So get out there and do some exercise!

To find out more why not watch these videos:


Fun Kids Dr Hallux

Kids Health



And if you want to have a go at running this system for yourself - download our app Inside the Human Body!

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