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How The Heart Works - Heart Health

An explanation of how the heart works can help you understand what's going on with different heart diseases.

The heart is a complex arrangement of muscle with four chambers inside. The upper chambers are called the atria (singular: atrium) and the lower chambers are called the ventricles. Between these chambers are one-way valves which ensure the blood flows only in one direction.

The names and placement of these valves are:

  • The valve between the right atrium and the right ventricle is the tricuspid valve
  • The valve at the exit from the right ventricle is called the pulmonary valve
  • The valve between the left atrium and the left ventricle is the mitral valve
  • The valve at the exit from the left ventricle is the aortic valve.

The heart takes blood from the body into the right atrium and from there the blood flows through the tricuspid valve into the right ventricle – a more powerful pump which sends the blood to the lungs to pick up oxygen.

This oxygen-laden (oxygenated) blood returns to the left side of the heart to the left atrium – and then through the mitral valve into the left ventricle. The left ventricle is the heart’s most powerful pump which is responsible for pumping blood around the body to keep us alive.

It’s essential to ensure there is a good supply of blood to the heart muscle itself so it can keep pumping. This supply comes from the coronary arteries. As blood exits the heart in the aorta, some of that oxygenated blood goes into a network of coronary arteries to be delivered to heart muscle.

The heart muscle, if you think about it, is truly amazing. It contracts a bit more than once a second – more if you’re exercising – day in, day out, from the day you’re born. However, its continuous action can be interrupted by conditions that damage any part of it.

Two of the ways the heart can be damaged is by blockages and narrowing (stenoses) that occur in the network of coronary arteries – the arteries that specifically supply the heart muscle with blood – and also in the valves.

Blockages and narrowing can occur anywhere in the coronary arteries, though the risk of a coronary artery narrowing depends on where the artery is. Blockages and narrowing in some arteries are more critical than others.

A complete blockage results in the death of the cells in the part of the heart which that artery supplies with blood and oxygen.

If any of the valves becomes narrowed (stenosed) the heart has to pump harder to push the blood out. The valves can also lose their seal for varied reasons which means blood can flow backwards – this is known as incompetence or regurgitation – and again, it can increase the load on the heart muscle.

If untreated, the heart will be more likely to eventually fail. Since the left side of the heart is where the high pressure is, that’s where heart valve problems mostly occur.


Next: What is Coronary Artery Disease?

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This information has been developed and reviewed for Bupa by health professionals. To the best of their knowledge it is current and based on reputable sources of medical research. It should be used as a guide only and should not be relied upon as a substitute for professional medical or other health professional advice.

Bupa Australia Pty Ltd makes no warranties or representations regarding the completeness or accuracy of the information. Bupa Australia is not liable for any loss or damage you suffer arising out of the use of or reliance on the information. Except that which cannot be excluded by law. We recommend that you consult your doctor or other qualified health professional if you have questions or concerns about your health. For more details on how we produce our health content, visit the About our health information page.

Last published 31 October 2010