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Circulatory system

4-minute read

What is the circulatory system?

Your circulatory system, also called the cardiovascular system or vascular system, transports oxygen, nutrients and hormones to your body's cells to use for energy, growth and repair. Your circulatory system also removes carbon dioxide and other wastes your cells do not need.

These key parts of your circulatory system maintain blood flow to your body so you can survive:

  • blood, made up of cells and plasma
  • the heart, a muscular organ that pumps blood to all parts of your body
  • blood vessels, a network of arteries, capillaries and veins to carry blood pumped by your heart
Illustration showing the circulatory system.
Illustration showing the circulatory system.

How does the circulatory system work?

Blood that is low in oxygen collects in your heart's right atrium, one of the heart’s 4 chambers.

It moves into the right ventricle, which pumps this blood to your lungs where your red blood cells pick up oxygen and get rid of carbon dioxide. You exhale the carbon dioxide.

The oxygen-rich blood returns to your heart's left atrium, then into your left ventricle. The left ventricle pumps oxygen-rich blood through your aorta, into your arteries, then to all parts of your body. Along the way, the blood gathers food nutrients from your small intestine

As it enters the capillaries, your blood makes close contact with tissues and cells. It delivers oxygen and nutrients and removes carbon dioxide and wastes. Now low in oxygen, the blood travels through the veins to return to your heart's right atrium, where the circuit starts all over again.

Cardiovascular disease

Cardiovascular disease (CVD) refers to all diseases of the heart and blood vessels.

Most CVD occurs when fatty substances, called plaque or atheroma, build up in the lining of blood vessels, causing them to narrow and allow less blood to pass through. This process is called atherosclerosis

Atherosclerosis causes coronary heart disease, also known as ischaemic heart disease. The slowing of the blood flow reduces the oxygen and nutrients available to the heart muscles. This can cause angina or a heart attack, which will require emergency medical attention. The most common symptom of heart attack or angina is chest pain.

When the supply of blood to part of the brain is interrupted because of a blocked or burst artery, a person will have a stroke. A stroke is also an emergency and will require urgent medical treatment.

Read more about heart problems and cardiovascular health here.

High or low blood pressure

As your heart pumps blood into your arteries, the blood pushes against the artery walls. This is what determines your blood pressure. Most doctors consider that a healthy blood pressure is higher than 90/60mm/Hg and lower than 140/90mm/Hg.

High blood pressure, also known as hypertension, can raise your risk of cardiovascular disease. It is the most common condition of the circulatory system. 

Low blood pressure, also known as hypotension, is a sign of good health for some people but can be a problem for others. If you have symptoms of low blood pressure, such as dizziness or fainting, you should see a doctor. 

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: April 2021

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