Your Heart

How does my heart work?

Your heart is located under the ribcage in the centre of your chest between your right and left lungs.

Its muscular walls beat, or contract, pumping blood continuously to all parts of your body.

The size of your heart can vary depending on your age, size and the condition of your heart.

A normal, healthy adult heart is generally the size of a clenched adult fist. However, some diseases of the heart can cause it to become larger.

How does my heart pump blood?

There are two sides to the heart (left and right) and both sides act as pumps.

The two sides are further divided into two chambers - so four chambers in total.

The upper chambers are called ATRIA: they collect blood.

The lower chambers are called VENTRICLES: they contract to pump the blood out.

Why does it pump blood?

The left side of the heart is larger than the right and pumps blood, rich in oxygen and nutrients, out through blood vessels (arteries) to the head and body.

The oxygen is used by the body and then your veins carry the blood, which is now low in oxygen, back to the right side of the heart.

The right side of the heart then pumps this blood to the lungs where it receives more oxygen.

This blood returns to the left side of the heart and is pumped around the body again.

Blood is pumped at high pressure so it can reach all the body's parts. For this to happen, the heart has to be very strong and needs a very good blood supply. This is provided by the coronary arteries.

The Coronary Arteries

The coronary arteries branch off  the aorta - the main artery taking blood away from the heart to the rest of the body.

The coronary arteries are the first to receive the blood, which is rich in oxygen.

The two coronary arteries pass around the heart, meet at the back and almost form a circle.

The left coronary artery and its branches supply blood to most of the left ventricle (lower chambers). The left ventricle is the more muscular and larger of the two ventricles, as it has to do the hard work of pumping blood all around the body.

The right coronary artery supplies the right ventricle and the underside of the heart.

The Conduction System

The heart has its own electrical conduction system, which allows impulses to travel through the heart's muscles causing them to contract and pump blood around the body.

The electrical impulse is produced by a special part of the right atrium (the top chamber) called the sinus or sinoatrial (SA) node. This is frequently called the heart's natural "pacemaker".

The electrical impulse travels from the SA Node through the muscle of the atriums causing them to contract and push the blood into the ventricles. The impulse then comes to the atrio-ventricular node or AV node.

The AV node acts like a junction box, delaying the impulse momentarily before it enters the muscles of the ventricles via fibres, which act like wires. This is known as the Purkinje fibres.

As the impulse travels along these fibres, the ventricles both contract, pushing the blood out of the heart to the lungs and body.  These impulses make the heart beat 60-80 times every minute.  Sometimes our heart beats faster or slower depending on how healthy we are and whether we are exercising or resting.

Occasionally things go wrong with the electrical system of the heart. This results in an irregular heartbeat is called an arrhythmia.