How a healthy heart works

Your heart is a muscle about the size of a fist. It is in the middle of your chest tilted slightly to the left.

Each day, your heart beats about 100,000 times. It pumps about 23,000 litres (5,000 gallons) of blood around your body.

This blood delivers oxygen and nutrients to all parts of your body, and carries away unwanted carbon dioxide and waste products.

Your heart is a vital part of your cardiovascular system.

Watch our short animated guide to your heart and how it works:

The structure of your heart

Diagram showing the four chambers of your heart

Your heart is made up of three tissue layers:

  • Pericardium – a thin outer lining that protects your heart
  • Myocardium – the thick muscular tissue that contracts and squeezes blood out of your heart
  • Endocardium – a thin inner lining that also provides protection.

Inside the heart there are four chambers – two on the left side and two on the right.

  • The two small upper chambers are called the atria.
  • The two larger lower chambers are called the ventricles.

The left and right sides of the heart are divided by a muscular wall called the septum.

For your heart to keep pumping regularly, it needs an electrical supply. This is provided by a special group of heart cells called the sinus node - also known as your heart’s natural pacemaker.

As your heart beats, it pumps blood to every part of your body. This is called your circulatory system.

What can go wrong?

Some people are born with hearts that have not developed properly before birth - this is called congenital heart disease. Sometimes you can inherit a heart condition from your family.

Some heart conditions may develop later in life, including coronary heart disease and atrial fibrillation.

People who have coronary heart disease are at risk of having a heart attack. Damage to the heart muscle because of a heart attack can lead to heart failure which can affect you for the rest of your life.

However, there's plenty you can do to keep your heart healthy.

Play our interactive game, Know your heart, to better understand your heart.