The Heart

In this description, oxygen-rich blood means blood filled with oxygen, and oxygen-poor blood means blood lacking oxygen.

The heart is divided into four chambers. The upper chamber of the right side of the heart – that is the right as one can imagine looking down on one’s own heart – is known as the right atrium and it receives oxygen-poor blood from the body. The blood travels to the lower right chamber – the right ventricle – and when the heart beats, the blood is squeezed into the lungs, where it is reloaded with oxygen and carries on its way up to the upper left chamber of the heart..

When the heart relaxes, the oxygen-rich blood flows into the upper left chamber – the left atrium – of the heart. From there is moves down into the left ventricle and when the heart beats the oxygen-rich blood is pumped to the organs throughout the body, including to the muscle of the heart itself because it too needs oxygen-rich blood to keep functioning.