The primary function of the heart is to pump blood. It pumps blood twenty four hours a day seven days a week. Sometimes it has got to pump a lot of blood (like when you are running) and then sometimes it has to pump less blood (like when you are fast asleep)
The diagram on the right shows Toby, he is pointing to where the heart is located in the body, between your lungs in the middle of your chest.
The heart has four chambers, though there are many children born whose hearts don’t have all these chambers. The upper chambers are called the left and right atria and the lower chambers are called the left and right ventricles. A muscle called the septum separates the left and right atria and the left and right ventricle.