How does the heart pump blood around the body

The heart is divided into four chambers: the right atrium, right ventricle, left atrium and left ventricle [insert diagram]. The right side of the heart pumps blood to the lungs. The left side of the heart pumps blood to the rest of the body.

First, deoxygenated blood arrives from the body, through the superior vena cava, into the right atrium. This is blood where all the oxygen has already been used up by the tissues of the body. It needs to get more oxygen, so it can be pumped around the body again and continue to provide oxygen to the tissues. To get more oxygen, it has to get to the lungs. So, it is pumped from the right atrium into the right ventricle, which then pumps it though the pulmonary artery to the lungs. Remember - Arteries carry blood Away from the heart, and pulmonary means relating to the lungs. So you know that the pulmonary artery carries blood away from the heart, to the lungs. 

This blood goes to the lungs and gets more oxygen. But, by this time it does not have the power to get all around the body to deliver the oxygen. So, it goes back to the heart, but this time it enters through the pulmonary veins (remember, if arteries go away from the heart, veins must go towards the heart - and pulmonary means lungs. So the pulmonary veins must take blood from the lungs, towards the heart). It goes through the pulmonary veins into the left atrium. The left atrium pumps blood into the left ventricle, which is a very muscular part of the heart. The left ventricle then pumps blood out, through the aorta (which is an artery), to the rest of the body, to supply the body with oxygen.