How the cardiovascular system works (and why it matters)

Most of us don’t spend much time thinking about our hearts unless something goes wrong. It just keeps beating in the background while we get on with our day — walking, working, sleeping, stressing, recovering. While it works quietly and constantly, it's allowing everything else in your body to keep functioning.

The cardiovascular system isn’t just about keeping your heart beating. It’s your body’s delivery system, transporting oxygen and nutrients to every cell while removing waste products. When this system functions well, you have energy, clarity, and vitality — when it doesn’t, the effects ripple through your entire body and can contribute to the development of cardiovascular diseases.

Understanding how your cardiovascular system works can make it easier to see why everyday habits — like how you move, eat, and manage stress — have such a powerful effect on how you feel.

What is the cardiovascular system?

The cardiovascular system, also known as the circulatory system, comprises the heart, blood vessels, and blood. Together, these components work as an integrated network that keeps your body functioning [1].

At its core, the cardiovascular system is responsible for circulation — the continuous movement of blood throughout your body. This system makes sure that oxygen-rich blood reaches your tissues and organs. At the same time, it collects and removes carbon dioxide and other waste products [1].

The average adult body has a blood volume of about five litres, which typically passes through the heart once every minute. This changes, depending on what your body needs — during exercise, for example, your heart pumps a lot more blood to deliver extra oxygen and nutrients to your working muscles [2]. The amount of blood pumped by the heart each minute is known as cardiac output. Cardiac output depends on heart rate and stroke volume — the amount of blood pumped with each heartbeat.

What are the components of the cardiovascular system?

The cardiovascular system consists of three main components that work together seamlessly: the heart, blood vessels, and blood itself.

The heart

Your heart is a muscular organ roughly the size of your closed fist, located slightly left of centre in your chest [3]. Despite its relatively small size, it’s one of the hardest-working organs in your body.

The heart contains four chambers: two upper chambers called atria and two lower chambers called ventricles [3]. These chambers work in a coordinated rhythm to pump blood efficiently. The right side of your heart receives oxygen-poor blood from your body and sends it to your lungs, where it’s expelled, while the left side receives oxygenated blood from your lungs and pumps it to the rest of your body [1].

Valves between the chambers ensure your blood flows in the correct direction, preventing backflow between heartbeats [3]. Your heart also has its own electrical conduction system that coordinates the timing of contractions, keeping the chambers contracting in the proper sequence [3].

Like any muscle, the heart has its own blood supply via the coronary arteries, which provide oxygenated blood to the heart muscle itself. Adequate coronary blood flow is essential for maintaining healthy cardiac function and supporting consistent cardiac output.

Blood vessels

Blood vessels form an extensive network that reaches every part of your body. There are three main types of blood vessels, each with a specific role [4]:

Arteries carry blood away from the heart. They have thick, elastic walls that can withstand the high pressure of blood being pumped from the heart. These walls contain vascular smooth muscle, allowing arteries to constrict and relax as needed. The largest artery, the aorta, branches into smaller arteries that deliver blood through your body [4].

Veins return blood to the heart. Unlike arteries, veins have thinner walls and contain valves that prevent blood from flowing backwards [4]. Veins push blood back up from your lower body to your heart, working against gravity with help from your surrounding muscles as they contract.

Capillaries are tiny, thin-walled blood vessels that connect arteries to veins. The capillaries are where the crucial exchange happens — oxygen and nutrients move from your blood into your tissues, whilst waste products move back into your bloodstream for removal [4].

Blood

Blood is the transport medium of the cardiovascular system. Blood delivers oxygen from your lungs to your tissues, transports nutrients from your digestive system to cells throughout your body, and collects waste products for removal [1].

Blood also helps to regulate our body’s temperature, supports immune function, and keeps the right amount of fluid in our tissues [4].

How does the cardiovascular system function?

The cardiovascular system operates through two connected circuits: pulmonary circulation and systemic circulation [1].

• Pulmonary circulation is the path blood takes between your heart and lungs. Oxygen-poor blood from your body enters the right atrium, moves to the right ventricle, and is then pumped through the pulmonary artery to your lungs. In the lungs, blood releases carbon dioxide and picks up fresh oxygen before returning to the left atrium through the pulmonary veins [1].
• Systemic circulation delivers oxygen-rich blood from your heart to the rest of your body. Blood leaves the left ventricle through your largest artery, the aorta, and travels through increasingly smaller arteries until it reaches those tiny capillaries. Oxygen and nutrients are delivered to your tissues, and waste products are collected for the return journey back to your heart [1].

This entire cycle happens with every single heartbeat — typically 60 to 100 times per minute at rest [1]. What’s remarkable is how adaptable this system is. During exercise, your heart pumps faster to deliver more oxygen to your working muscles. When you’re relaxing, it slows down. Your cardiovascular system is constantly adjusting to give your body exactly what it needs, when it needs it.

What are the main functions of the cardiovascular system?

Whilst most people know the cardiovascular system pumps blood, it actually performs several essential functions that keep you alive and well.

Transporting oxygen and nutrients

The cardiovascular system’s primary function is to deliver oxygen and nutrients to your cells [4]. Every cell in your body requires oxygen to function and produce energy. The cardiovascular system ensures a constant supply, picking up oxygen from your lungs and distributing it throughout your body.

At the same time, it transports nutrients absorbed from your digestive system — including glucose, amino acids, and fats — to cells that need them for energy, growth, and repair [4].

Removing waste products

As your cells work, they produce waste products like carbon dioxide and other metabolic byproducts. The cardiovascular system collects these waste substances and transports them to organs that can eliminate them: carbon dioxide to the lungs, and other waste to the kidneys and liver [1].

Without this waste removal, waste would build up in your tissues and interfere with how your cells function.

Regulating temperature and homeostasis

Your cardiovascular system plays a crucial role in maintaining your body temperature [4]. When you’re too warm, blood vessels in your skin dilate, allowing more blood to flow near the surface where heat can be released. When you’re cold, these vessels constrict, conserving heat by reducing blood flow to the skin [4].

This temperature regulation happens automatically as part of the body’s homeostasis — the process of maintaining stable internal conditions despite external changes.

Supporting immune function

Blood carries white blood cells and antibodies throughout your body, delivering immune defences wherever they’re needed [4]. When you get an infection or injury, your cardiovascular system rushes immune cells to the affected area and sends out chemical signals that tell your body how to respond.

The cardiovascular system also regulates inflammation, which is a key part of your body’s defence and healing processes.

What can affect cardiovascular system function?

Several factors can influence how well your cardiovascular system works.

Lifestyle factors

• Physical activity strengthens your heart muscle and improves circulation. Regular exercise helps your cardiovascular system work more efficiently, lowering your resting heart rate and blood pressure [5].
• Diet affects everything from your cholesterol levels to your blood pressure and body weight. A diet high in saturated fats can contribute to the build-up of fatty deposits in arteries, while a balanced diet rich in fruits, vegetables, and whole grains supports cardiovascular function [6]. What you eat directly fuels this intricate system.
• Smoking damages blood vessels and increases the risk of atherosclerosis — the build-up of fatty deposits in artery walls. It also reduces the amount of oxygen your blood can carry [6]. Smokers are almost twice as likely to experience heart attacks and strokes compared to non-smokers [7].
• Stress releases hormones that temporarily spike your heart rate and blood pressure. That’s fine for short bursts, but when stress becomes chronic, it can take a real toll on your nervous system and cardiovascular health [5].

Medical conditions

Certain health conditions directly affect cardiovascular function, so addressing them early is really important.

• High blood pressure forces your heart to work harder and can damage artery walls over time, increasing the risk of serious conditions [6]. It’s often called the “silent” condition because you might not feel unwell, but the effects are happening behind the scenes.
• High cholesterol can lead to atherosclerosis [6]. Lifestyle changes and appropriate treatment can significantly improve cholesterol levels.
• Obesity places extra demands on the cardiovascular system and is associated with increased risk of high blood pressure, high cholesterol, and other cardiovascular conditions [6]. Managing weight through sustainable lifestyle changes can support your cardiovascular system to work more efficiently.

Age and genetics

As you age, your cardiovascular system naturally changes. Blood vessels may become less elastic, and the heart muscle may thicken slightly [8]. These changes can affect how efficiently your cardiovascular system functions, so staying active and eating well becomes even more important as you grow older.

Your family history also plays a role. If close relatives have had cardiovascular conditions or heart disease, you might be at higher risk — but that doesn’t mean your future is set in stone. Understanding your genetic risk allows you to take proactive steps to support cardiovascular health.

Why understanding the cardiovascular system matters

Understanding how your cardiovascular system works can be empowering. When you know what’s happening inside your body, you can make choices that support it, rather than work against it.

Cardiovascular conditions are common, but many of the risk factors are actually within your control. Small, consistent improvements — eating more vegetables, moving your body regularly, finding ways to manage stress — can make a long-term difference to your cardiovascular health.

If you’re navigating perimenopause or menopause, paying attention to your cardiovascular health becomes even more important. Hormonal changes during this transition can affect your heart health, making it an ideal time to focus on supporting your cardiovascular system [5]. The habits you build now can shape how you feel for decades to come.

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