Cardiovascular System 101

The human body is an extremely complicated system where a vast array of cells and organs play an essential role in normal body function – however, there are none more important than the heart! Information or news about heart disease and complications are often advertised in the media, but how much do you actually know about the basics?

What is the ‘Cardiovascular System’?

As most people know, the heart is responsible for delivering oxygen and nutrients , as well as other substances, to body tissue. However, the  cardiovascular system as a concept describes more than simply the heart, with it made up of the heart, blood vessels and blood. In simple terms, the heart acts as a muscular pump that creates the pressure gradient needed for blood to flow into the tissues (Sherwood, 2006). The blood vessels are responsible for carrying blood around the body, with them divided into arteries, capillaries and veins, all of which have different functions (Wynsberghe et al. 1995). Finally, blood is termed as the transport medium, which substances such as gases and nutrients are dissolved in, whilst being transported to various parts of the body (Sherwood, 2006).

The basic anatomy

The heart is a hollow muscular organ about the size of a clenched fist situated in the midcenter of chest between the sternum and the vertebrae (Sherwood, 2006). The heart is divided into right and left halves, with 4 chambers in total and in an average sized adult male weighs about 11 oz. (McArdle et al. 2015). The top two chambers are the atrium, with the bottom two ventricles, with a wall of muscle called the ‘septum’ separating the left and right sides (Wynsberghe et al. 1995). As well as chambers, there are also 4 heart valves which allow normal flow on blood through the system and prevent backflow of blood.

Despite the heart being at the centre of the cardiovascular system, it is the blood vessels that are responsible for carrying blood throughout the body. As most people know, blood vessels come in three different shapes and sizes, with these being arteries, veins and capillaries. In simple terms, arteries carry blood away from the heart (to organs and tissues), whilst veins are responsible for bringing the blood back to the heart (Wynsberghe et al. 1995). Capillaries are slightly different, as they are microscopic vessels with very narrow walls, usually one cell thick. This is to allow the passage of water and small particles to pass through, so are therefore vital for gas exchange (Wynsberghe et al. 1995).

The final component of the cardiovascular system is blood itself, with it consisting of a mixture of a liquid known as plasma (55%) and formed elements (45%), which is mainly made up of red and white blood cells (Wynsberghe et al. 1995). Blood has three main functions within the human body, with these consisting of transport, regulation and protection. Red blood cells are predominately responsible for the transport of nutrients and waste products, whilst blood cells in the body help to fight infection and disease (Wynsberghe et al. 1995).

How does the heart work?

Unlike all other type of muscle, cardiac muscle is able to contract automatically, displaying ‘pacemaker activity’ (Sherwood, 2006). This allows for electrical signals (depolarization) to occur repeatedly, which is responsible for the continual flow of blood through the body.

The depolarization originates in the sinoatrial (SA) node, with the electrical signals spreading through the left and right atrium causing them to contract and hence ejecting blood into the corresponding ventricles (ACSM, 2010). The SA node is therefore referred to as the ‘normal pacemaker’ of the heart. Once the atria have contracted, the electrical impulses pass through the atrioventricular (AV) node and underneath the ventricles within the purkinje fibres (ACSM, 2010). The contraction of the ventricles results in the blood being pumped out of the heart in either the pulmonary artery (pulmonary circulation) or aorta (systemic circulation) depending on the side (McArdle et al. 2015).

What is the importance of cardiovascular function?

Now you know the basics regarding your cardiovascular system, you may be wondering the importance of how healthy it is. Having a healthy heart in particular is very important, with cardiovascular disease (CVD) a main cause of death in the United Kingdom. Simply, CVD is a general term for conditions affecting the heart or blood vessels and is usually associated with a build-up of fatty deposits inside the arteries (NHS, 2016). According to statistics from the British Health Foundation (2015), 27.4% of male deaths and 25.2% of female deaths in the United Kingdom during 2015 were due to CVD. It is therefore important to be able to monitor how healthy you are and if needed receive the advice to decrease your risk.

As you would expect, it has been found that there is a strong connection of lifestyle, diet and physical activity to CVD (Perk et al. 2012). The current NHS guidelines (NHS, 2016) suggest that by exercising moderately for 150 minutes per week and by eating a healthy balanced diet you will decrease your risk.

How can we help?

At Surrey Human Performance Institute we currently offer tests that examine the healthiness of your heart during rest and at exercise. We provide a service called the CV risk assessment for £35, which involves a finger prick blood sample and lifestyle questionnaire, with the data used to calculate your risk of CVD in the next 10 years.  For a slightly more in depth analysis of your heart, we also offer a Cardiopulmonary Exercise Test, or CPET for short. This prices at £149 and involves placing ECG electrodes on your chest and analysing the electrical response of your heart during rest and exercise. For more information or to book into a session, please get in contact!


  1. ACSM (2010). Resource Manual for Guidelines for Exercise Testing and Prescription, 6th edition, Wolters Kluwer Health, Lippincott Williams & Wilkins, pp.428-432.
  2. British Health Foundation (2017). Cardiovascular Disease Statistics,, last accessed 10.10.17.
  3. McArdle, W.D., Katch, F.I. and Katch, V.L. (2015). Exercise Physiology: Nutrition, Energy and Human Performance. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th Edition, Wolters Kluwer Health, Lippincott Williams & Wilkins, pp.731-763.
  4. National Health Service (NHS), (2016). NHS choices: Cardiovascular disease,, last accessed 10.10.17.
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