Your heart is a pump that keeps blood moving around your body. It works 24 hours a day to keep you alive. Each day, your heart beats about 100,000 times.
Every part of your body needs a fresh supply of blood in order to work normally. It’s your heart’s job to make sure that this is pumped out regularly.
The movement of blood around the body, pumped by the heart, is called circulation. Your heart, blood and blood vessels together make up your cardiovascular system (or heart and circulatory system). Your body contains about five litres (eight pints) of blood, which your heart is continuously circulating.
The two sides of your heart are separate, but they work together.
The right side of the heart receives dark, de-oxygenated blood which has circulated around your body.
It pumps this to your lungs, where it picks up a fresh supply of oxygen and becomes bright red again. The blood then returns to the left side of the heart, ready to be pumped back out to the rest of your body.
There are four valves in your heart. They act like gates that open and close, making sure that your blood travels in one direction through your heart – a bit like a one-way traffic system. They are called the tricuspid valve and the pulmonary valve on the right side of the heart, and the mitral valve and the aortic valve on the left.
Like every other living tissue, the heart itself needs a continuous supply of fresh blood. This comes from the coronary arteries which branch off from the main artery (the aorta) as it leaves the heart. The coronary arteries spread across the outside of the myocardium, supplying it with oxygen and essential nutrients.
As your heart muscle contracts, it pushes blood through your heart. With each contraction, or heartbeat:
So what can go wrong?