Skip to main content

What is the cardiovascular system?

The cardiovascular system, or circulatory system, is made up of your heart, blood and blood vessels. Your heart uses the network of blood vessels (arteries, veins and capillaries) to deliver oxygen and nutrients to the cells in your entire body, as well as to take away waste.

These three key parts of the cardiovascular system maintain blood flow to all the cells in your body, so you can survive:

1. The heart

At the centre of the cardiovascular system lies the heart, a muscular organ that pumps blood to all parts of your body. Positioned slightly left of the body's midline, the heart consists of four chambers: two atria (upper chambers) and two ventricles (lower chambers). The atria receive blood returning to the heart, while the ventricles pump blood out to the body and lungs.

2. Blood

Blood is the fluid that circulates through the cardiovascular system, carrying oxygen, nutrients, hormones and waste products to and from cells throughout the body. Blood is composed of various components, including:

- Red blood cells (erythrocytes): Red blood cells transport oxygen from the lungs to tissues and carry carbon dioxide back to the lungs for exhalation.

- White blood cells (leukocytes): White blood cells play a crucial role in the immune system, defending the body against infections and foreign invaders.

- Platelets: Platelets are cell fragments involved in blood clotting, helping to prevent excessive bleeding when blood vessels are damaged.

- Plasma: Plasma is the liquid portion of blood, composed mostly of water, in which blood cells are suspended. It carries nutrients, hormones and waste products throughout the body.

3. Blood vessels

Blood vessels form the intricate network through which blood travels, connecting the heart to every tissue and organ in the body. There are three main types of blood vessels:

- Arteries: Arteries carry oxygen-rich blood away from the heart to various parts of the body. As arteries branch out, they become smaller arterioles, which further divide into microscopic capillaries.

- Capillaries: Capillaries are tiny, thin-walled vessels where the exchange of oxygen, nutrients and waste products occurs between the blood and surrounding tissues.

- Veins: Veins return oxygen-depleted blood from the body's tissues back to the heart. As veins converge, they become larger vessels that eventually empty into the heart.

The cardiovascular system has two divisions in the body. The first is the systemic circulatory system. This is the main blood circulatory system that transports blood to the organs, tissues and cells throughout the body.

The second is the pulmonary circulatory system. This system moves blood between the heart and lungs. It is where oxygen enters the blood and carbon dioxide leaves the blood.

Arteries carry blood away from the heart, and veins carry blood towards the heart. With the exception of pulmonary blood vessels, arteries carry oxygenated blood and veins carry deoxygenated blood.

Arteries have thick walls with muscle tissue. Veins have thinner walls and use valves to keep your blood flowing.

How the heart, blood vessels, and blood work together

The heart and blood vessels work together to continuously pump blood throughout your body. The walls of the heart are thick muscles that contract (beat) when they receive an electrical signal, about once per second. Valves inside the heart open and close exactly on time to keep blood flowing smoothly in the right direction.

Using the network of arteries, veins and capillaries, blood carries carbon dioxide to the lungs (for exhalation), where it then picks up oxygen. This oxygen-rich blood goes to the left side of the heart, which then pumps it out to the rest of the body. The blood returns to the right side of the heart, which then pumps it back to the lungs.

To work properly, the heart needs precise electrical timing of each beat, proper opening and closing of the valves, and plenty of energy from its own blood supply.

The function of a healthy cardiovascular system

The cardiovascular system delivers oxygen, nutrients, hormones and other important substances to cells and organs throughout your entire body. It plays an important role in helping the body meet the demands of activity, exercise and stress, and ensures your body gets what it needs during exercise and rest. It also carries carbon dioxide and other waste away for disposal, and keeps your temperature at a normal level.

Your cells depend on your cardiovascular system to be able to function properly. For example, food nutrients are gathered from the small intestine by blood in the cardiovascular system and delivered to every cell.

That’s why it’s vital to take care of your heart with exercise, a healthy diet and controlled blood pressure and cholesterol levels.

What happens when things go wrong?

The cardiovascular system is often considered the lifeline of the human body, so when things go awry with this intricate network of heart, blood vessels and blood, the consequences can be serious.

From common ailments to severe diseases, understanding what happens when the cardiovascular system falters is paramount for safeguarding health and wellbeing.

Many of the problems with the cardiovascular system are related to slowdowns or blockages in the blood vessels.

Since your blood vessels supply your entire body with oxygen, a blockage in any of the blood vessels makes it harder to deliver that oxygen.

Common cardiovascular conditions and treatments

The cardiovascular system is susceptible to various conditions that can impact its function and overall health. From common ailments to more complex diseases, understanding these conditions and their respective treatments is crucial for maintaining cardiovascular wellbeing.

Some of the most prevalent cardiovascular conditions include the following.

1. Hypertension (high blood pressure)

Condition: Hypertension occurs when the force of blood against the artery walls is consistently too high. It's often referred to as the "silent killer" because it typically presents with no symptoms but can lead to serious complications such as heart disease, stroke and kidney failure.

Treatment: Lifestyle changes, including a healthy diet low in sodium, regular exercise, weight management and stress reduction, are typically the first line of defence. If lifestyle modifications alone are insufficient, medications may be prescribed to lower blood pressure.

2. Coronary artery disease (CAD)

Condition: CAD is a common type of heart disease characterised by the narrowing or blockage of the coronary arteries, which supply oxygen-rich blood to the heart muscle. It often develops over time due to the buildup of plaque (atherosclerosis) within the artery walls.

Treatment: Treatment for CAD aims to relieve symptoms, prevent complications, and reduce the risk of heart attack or stroke. Lifestyle changes, including smoking cessation, dietary modifications, regular exercise and stress management, are crucial. Medications such as statins, antiplatelet drugs, beta-blockers and nitroglycerin may be prescribed. In some cases, procedures such as angioplasty with stent placement or coronary artery bypass surgery may be necessary to restore blood flow to the heart.

3. Heart failure

Condition: Heart failure occurs when the heart is unable to pump enough blood to meet the body's needs. It can result from various conditions, such as CAD, hypertension, or damage to the heart muscle (cardiomyopathy).

Treatment: Treatment for heart failure focuses on improving symptoms, slowing disease progression and prolonging life. Lifestyle modifications, including limiting salt intake, managing fluid intake and regular exercise, are important. Medications may be prescribed to improve heart function and reduce symptoms. In advanced cases, devices such as pacemakers, defibrillators or heart transplantation may be considered.

4. Arrhythmias

Condition: Arrhythmias are irregular heartbeats that can manifest as a slow, fast or irregular heart rhythm. They can occur due to various factors, including heart disease, electrolyte imbalances and congenital abnormalities.

Treatment: Treatment for arrhythmias depends on the type and severity of the condition. Mild cases may not require treatment, while more serious arrhythmias may be managed with medications such as antiarrhythmics, beta-blockers or calcium channel blockers. In some cases, procedures such as catheter ablation, pacemaker implantation or cardioversion may be necessary to restore normal heart rhythm.

5. Stroke

Condition: A stroke occurs when blood flow to part of the brain is interrupted or reduced, depriving brain tissue of oxygen and nutrients. This can result in permanent brain damage or death.

Treatment: Treatment for stroke depends on whether it is ischaemic (caused by a blocked artery) or haemorrhagic (caused by bleeding). Ischaemic strokes may be treated with medications such as tissue plasminogen activator (tPA) to dissolve blood clots, or procedures such as mechanical thrombectomy to remove clots from the arteries. Haemorrhagic strokes may require surgery to repair or remove abnormal blood vessels or to relieve pressure on the brain.

6. Peripheral artery disease

Condition: Peripheral artery disease (PAD), also known as peripheral vascular disease, is a common circulatory condition that occurs when narrowed arteries reduce blood flow to the limbs, typically the legs. This narrowing is often due to the buildup of fatty deposits (plaque) on the artery walls, a process known as atherosclerosis. PAD can result in symptoms such as leg pain, numbness, weakness, and even tissue damage in severe cases. PAD affects almost one in every five Australians. Approximately 50 per cent of people with PAD show no symptoms, leading to under-diagnosis and under-treatment. In addition, the reduced blood flow to the limbs can lead to the limb developing gangrene, where it starts to decay and die. There is no cure for gangrene. The only treatment option is to amputate the affected limb to prevent the gangrene from spreading further in the body. Shockingly, every two hours in Australia, one person has an arm or leg amputated due to PAD.

Treatment: By adopting healthy lifestyle habits, adhering to prescribed medications and undergoing appropriate interventions as advised by their healthcare professional, individuals with PAD can improve their quality of life and reduce the risk of cardiovascular events and limb loss.

Support HRI

Today's research is tomorrow's cure.

Every donation to the Heart Research Institute is an investment into the lives of millions. Help make a lasting difference by donating today.

Other ways you can help