The main thing the heart does is pump blood. So, it’s a blood pump.

And it’s a pump that’s got to pump 24 hours a day, 7 days a week.

Sometimes it has got to pump a lot of blood, (like when you’re running). And then sometimes it’s got to pump not too much blood (like when you’re fast asleep).

The heart pumps blood by squeezing blood in its two main pumping chambers, the right and left ventricles. The right ventricle pumps blood to the lungs, where the blood picks up lots of oxygen. And the left ventricle pumps blood to the rest of the body (including the heart itself), where that oxygen is used up.

Click here for an anatomy  picture of the heart