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Cardiovascular system

Your cardiovascular system is made up of your:

  • heart
  • blood vessels – arteries, veins and capillaries (very small blood vessels)
  • blood

Your cardiovascular system is a network made up of blood vessels and your heart, which pumps blood and oxygen around your body. Your cardiovascular system also transports carbon dioxide, a waste product, from your body to your lungs. When you breathe out, carbon dioxide is removed from your body.

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How the heart works
Your heart is designed to last a whole lifetime
Image showing the main organs, arteries and veins in the cardiovascular system


  • How it works How does your cardiovascular system work?

    When you breathe in air through your mouth and nose, it travels to your lungs. Oxygen from the air is absorbed into your bloodstream through your lungs. Your heart then pumps oxygen-rich (oxygenated) blood through a network of blood vessels (arteries) to tissues all around your body. These include your organs (for example your liver and kidneys), muscles and nerves.

    When blood reaches your tissues it releases oxygen – your cells need this to function. Cells release waste products, such as carbon dioxide and water, which your blood absorbs and carries away. The used (deoxygenated) blood then travels through your veins and back towards your heart. Your heart pumps the deoxygenated blood back to your lungs, where it absorbs fresh oxygen, releases the carbon dioxide and the cycle starts again.

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  • Your heart Your heart

    Your heart is roughly the size of a clenched fist. It lies just to the left side of the centre of your chest and is surrounded by a protective layer called the pericardium.

    Your heart is a pump, divided into left and right sides. It has walls, made of muscle, which squeeze (contract) to pump blood into your blood vessels and around your body. You have around eight pints of blood in your body, and your heart beats about 72 times a minute to keep it circulating.

    Your veins deliver deoxygenated blood from your body to the right side of your heart. Your heart pumps this blood back to your lungs, where it absorbs more oxygen. This oxygenated blood then returns to the left side of your heart, which pumps it out to the rest of your body through your arteries. The muscle on the left side of your heart is slightly larger because it has more work to do than the right. The right side only pumps blood to your lungs, whereas the left side pumps blood around your whole body.

    Each side of your heart is divided into an upper chamber called an atrium and a larger, lower chamber, called a ventricle. Blood flows from each atrium to the ventricle below, through a one-way valve.

  • Your lungs Your lungs

    You have two lungs, one on either side of your heart in your chest. Your lungs are made of spongy tissue and have a rich blood supply. Air passes from your nose and mouth into your trachea (windpipe), before passing into each lung, through two airways called the bronchi. These divide into smaller airways, called bronchioles, which repeatedly divide and end in tiny sacs called alveoli.

    It's here in the alveoli that oxygen and carbon dioxide filter into and out of your blood. Oxygen passes through their thin walls and into the surrounding blood vessels. A substance called haemoglobin (found in red blood cells in your blood) helps move oxygen from the tiny air sacs to the blood. At the same time, carbon dioxide moves from the blood vessels into the air sacs. You then breathe this out through your lungs.

    Your chest and abdomen (tummy) are separated by your diaphragm. This is a sheet of muscle that forms the floor of your chest. When you breathe in, your diaphragm moves downwards, your lungs inflate and your chest cavity expands. In an average day, you breathe 10,000 litres of air in and out of your lungs.

  • Your blood pressure Your blood pressure

    Your blood pressure is an important part of how your cardiovascular system works. Your blood carries oxygen and nutrients and is pumped around your body by your heart. The pumping action of your heart and the size and flexibility of your arteries put your blood under pressure.

    Your blood pressure measurement is expressed as two numbers or levels. It’s measured in millimetres of mercury (mmHg). A blood pressure reading shows one number on top of another, such as 120/80mmHg.

    The first figure is called the systolic blood pressure. This is a measure of the pressure when your heart muscle is contracted and pumping blood out of your heart. It's the maximum pressure in your blood vessels. The second figure is called the diastolic blood pressure. This is the pressure between beats when your heart is resting and filling with blood, and is the minimum pressure in your blood vessels.

    Generally, the lower your blood pressure, the better it is for your health. However, very low blood pressure can make you feel dizzy or cause you to faint. If you're under the age of 80, doctors recommend your blood pressure is kept below 140/90 when measured in a clinic, or 135/85 if measured at home. If you're over 80, it’s accepted that your blood pressure may be slightly higher. If you have diabetes, kidney disease or cardiovascular disease, aim to keep your blood pressure lower than this – ideally less than 130/80.

    You can measure your blood pressure at home or go to a pharmacy. It's best to use a cuff that you put above your elbow. If your blood pressure is high or very low, see a doctor or nurse. They will check your health and may carry out tests, such as 24-hour blood pressure monitoring.

  • Your cardiovascular health Your cardiovascular health

    Your lifestyle plays an essential part in maintaining your long-term cardiovascular health. Eating a balanced diet, getting plenty of exercise and not smoking will help you to keep your heart healthy.

  • Heart treatment on demand

    You can access a range of our health and wellbeing services on a pay-as-you-go basis, including heart treatment.

  • FAQs FAQs

    What sorts of exercise can I do to keep my heart healthy?

    There is a range of different types of exercise that will help you improve the health of your heart (your cardiovascular fitness). Keeping active will also reduce your risk of heart disease, diabetes and stroke.

    The best kind of exercise for your heart is aerobic activity – this means that it involves or improves the use of oxygen by your body. This is essential for developing your cardiovascular fitness. Aerobic activity can be any sustained exercise that gets your heart to work more.

    Aim to do at least 150 minutes (two and a half hours) of moderate exercise each week. Try to do this in bouts of 10 minutes or more. It may help you to think of this as 30 minutes of exercise at least five times a week. Moderate exercise means your breathing becomes faster, your heart rate increases and you feel warmer. At this level of activity, your heart and lungs are working harder and this helps you become fitter.

    Good forms of cardiovascular exercise include brisk walking, cycling and swimming. But your exercise quota can also include all kinds of day-to-day activities, such as:

    • gardening
    • climbing stairs
    • vacuuming

    If you’re overweight or have a medical condition, check with your practice nurse or GP before you start an exercise programme. They will advise you on the best way to increase your physical activity.

    I have diabetes and have heard this can affect my heart. Do I need to take special precautions?

    If you have diabetes, you have a higher risk of developing heart disease. However, your diabetes specialist nurse or GP can advise you on how you can reduce this risk. This includes making changes to your lifestyle and controlling your condition.

    If you have diabetes, raised blood sugar levels can increase the risk of your arteries becoming narrowed or blocked. People with diabetes are also more susceptible to the other risk factors for cardiovascular disease, such as high blood pressure, raised cholesterol and smoking. Therefore, if you have diabetes, your GP will probably prescribe medicines to treat some of these risk factors. If you smoke, your GP will encourage you to stop and can give you help with ways to do this.

    High blood pressure is common in diabetes and it's important to control it. Aim for your blood pressure to be below 130/80mmHg, or lower if your kidneys are already damaged. You may be able to control your blood pressure by losing excess weight, doing more exercise and cutting down on alcohol and salt. However, you may need to take medicines too.

    If you have type 2 diabetes, you may have low HDL cholesterol levels, which is high-density lipoprotein, or 'good' cholesterol. You may also have high triglyceride levels (a type of fat) in your blood. Both these factors can increase the risk of heart disease. To help lower your cholesterol levels, you may need to take medicines. It will also help to cut down on fats in your diet, particularly saturated fats (which are found mostly in red meat and dairy products).

    Being physically active may help reduce the amount of medicine you take for your diabetes, and can help reduce the risk of heart disease. Monitor your blood glucose carefully as you build up your level of physical activity, as you may need to change the dose of your medicine. Ask your diabetes specialist nurse or GP for advice about this.

    Can too much stress in my life really cause heart disease?

    Stress is one factor that can increase your risk of heart disease. Others include smoking, lack of physical activity and high blood cholesterol.

    Many people think heart disease is caused by years of stress. In fact, it's unclear if stress alone causes heart disease, or if it affects other factors that make heart disease more likely. For example, stress can cause your blood pressure to rise, and this can increase your risk of heart disease.

    The way you try to cope with stress may also increase your risk of developing heart disease. Stress can encourage less healthy behaviour, such as smoking, drinking too much alcohol and over-eating.

    A good way to identify sources of stress in your life is to keep a diary. Keep a record of when you feel stressed and make notes about situations that cause this. This might help you work out why it’s worse on some days than on others. Once you have identified the possible causes of your stress, you can take steps to tackle them and respond differently.

    If you can't change a source of stress, aim to try and change your attitude towards it. Think about how you respond when you find yourself in a stressful situation. Then think about how you could change both your physical and mental responses to it.

    A balanced diet and regular physical activity can help you feel more ready to cope with potentially stressful situations. It's also important to learn how to unwind – yoga and other relaxation techniques may help.

    Try talking to friends, colleagues or family members about any worries you have, as sharing a problem may help. If you feel stressed or very anxious, talk to your GP. He or she will help you work out the best way to deal with it.

  • Resources Resources

    Further information


    • Cardiovascular system anatomy. Medscape., published 29 February 2012
    • Lung anatomy. Medscape., published 20 February 2013
    • Anatomy and function of the normal lung. American Thoracic Society., published 9 May 2014
    • Your cardiovascular system. Society for Cardiovascular Angiography and Interventions (SCAI)., accessed 9 May 2014
    • Your heart. Society for Cardiovascular Angiography and Interventions (SCAI)., accessed 9 May 2014
    • Heart anatomy. Medscape., published 19 March 2013
    • Hemoglobin concentration (Hb). Medscape., published 12 February 2014
    • What happens when you breathe? National Heart Lung and Blood Institute., published 17 July 2012
    • Pneumonia. American Thoracic Society., published 2010
    • What is high blood pressure? National Heart Lung and Blood Institute., published 2 August 2012
    • Hypertension. Medscape., published 31 March 2014
    • Hypotension. PatientPlus., published 15 October 2013
    • Prevention of cardiovascular disease. PatientPlus., published 17 December 2013
    • Management of hypertension. PatientPlus., published 17 December 2013
    • O’Brien E, Asmar R, Beilin L, et al. European Society of Hypertension recommendations for conventional, ambulatory and home blood pressure measurement. J Hypertens 2003; 21(5):821–48. doi:10.1097/
    • Physical activity: brief advice for adults in primary care. National Institute for Health and Care Excellence (NICE), May 2013.
    • Cardiovascular complications of diabetes. Society for Cardiovascular Angiography and Interventions (SCAI)., accessed 9 May 2014
    • Map of Medicine. Diabetes. International View. London: Map of Medicine; 2013 (Issue 3)
    • Hypertension. National Institute for Health and Care Excellence (NICE), August 2011.
    • Prevention of cardiovascular disease. National Institute for Health and Care Excellence (NICE), June 2010.
    • How does stress affect your health? Society for Cardiovascular Angiography and Interventions (SCAI)., accessed 9 May 2014
    • Coping with stress: information for young people. Royal College of Psychiatrists., accessed 9 May 2014
    • How to manage stress. Society for Cardiovascular Angiography and Interventions (SCAI)., accessed 9 May 2014
    • Acute stress disorder treatment and management. Medscape., published 4 November 2013
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