How your heart works

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Your heart is a muscle that pumps blood to all parts of your body. The blood gives your body the oxygen and nourishment it needs to work properly. 

Explore the heart by selecting a dot

Right coronary artery The right coronary artery supplies blood to the right side of the heart, and the sinoatrial node, which regulates the heart rhythm.

Left main
coronary artery
The left main coronary artery supplies blood to the left side of the heart muscle (the left ventricle and left atrium).

Left circumflex artery The circumflex artery branches off from the left main coronary artery. It supplies blood to the back of the heart.

Left anterior descending branch The left anterior descending artery branches off the left main coronary artery and supplies blood to the front of the heart.

Explore the heart by selecting a dot

Vena cava The large veins that carry deoxygenated blood from your body into the heart.

Aorta The aorta is the largest artery in the body, it carries oxygenated blood from your heart to your body.

Right atriumThe chamber that receives blood from your vena cava before pumping it into your right ventricle.

Left atriumThe chamber that receives blood from your lungs before pumping it into your left ventricle.

Right ventricleThis chamber pumps the blood to your lungs to enable your blood to receive oxygen.

Left ventricle This chamber of the heart pumps oxygenated blood into your aorta. It is the largest chamber in your heart.

The heart has two sides separated by a muscular wall.

  • The heart has two sides – left and right, separated by a muscular wall. 
  • There is an upper and lower chamber on each side connected by valves that direct the flow of blood. 
  • The smaller upper chambers are known as the atria and the larger lower chambers are the ventricles. 
  • The pumping of the heart is controlled by special fibres that conduct electrical signals to the various chambers. 
  • The right side of the heart pumps the blood to the lungs, where it receives oxygen. 
  • Blood enters the left side of the heart from the lungs and the heart pumps the oxygen-rich blood around the body. 

Coronary arteries 

Coronary arteries supply the heart muscle with blood. The left and right coronary arteries divide many times to spread over the heart muscle wall and give it blood and oxygen. 

The coronary arteries get blood from the aorta, the major artery taking blood to the rest of the body. 

Coronary heart disease

Coronary heart disease affects many people. It’s a chronic condition – that means it is long term. 

Coronary heart disease happens when fatty material builds up in your arteries. This makes them narrower. The fatty material is called ‘plaque’. Plaque builds up slowly, and this process is called atherosclerosis. It can start when you are young and be well advanced by middle age. 

Stable plaque is generally not harmful but if the arteries narrow too much it can cause angina.  

Unstable plaque has more fat, a thin cap and is inflamed. It does not have to be associated with severe narrowing of the artery. Unstable plaque can develop a crack on the surface, exposing the contents of the plaque to the blood. Blood cells try to seal the gap in the surface with a blood clot. The blood clot partially or completely blocks the artery.  

If your arteries become too narrow, less blood can reach your heart muscle. This may lead to symptoms such as angina.

If a blood clot forms in a narrow artery and blocks the blood supply to part of your heart, it can cause a heart attack. While atherosclerosis (a hardening and narrowing of the arteries) develops slowly over decades, the major consequences can appear to be sudden. 

Some people may not know they have coronary heart disease until they have a heart attack

Learn more about coronary heart disease

Recovering from a heart attack?

Learn more about heart attack recovery, including information on what happened to your heart, heart attack treatment and how you can recover sooner.


Your heart (PDF)

How it works - all you need to know

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