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- What is the circulatory system?
- How does the circulatory system work?
- What are the common conditions related to the circulatory system?
- Related information on Australian websites
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
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.
The cardiovascular system consists of the heart, blood vessels, and blood. Its primary function is to transport nutrients and oxygen-rich blood to all parts of the body and to carry deoxygenated blood back to the lungs.
Abnormalities or injuries to any or all parts of the cardiovascular system can result in serious health complications. Common conditions that can affect the cardiovascular system include coronary artery disease, heart attack, high blood pressure, and stroke.
This article explores the cardiovascular system, including its components and their functions. We also outline some common cardiovascular system diseases and their associated treatments.
The cardiovascular system is the system responsible for delivering blood to different parts of the body. It consists of the following organs and tissues:
- The heart: A muscular pump that forces blood around the body.
- A closed system of blood vessels: These vessels include:
- Arteries: Vessels that carry blood away from the heart.
- Veins: Vessels that bring blood back to the heart.
- Capillaries: Tiny vessels that branch off from arteries to deliver blood to all body tissues.
There are two blood circulatory systems 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 circulatory system moves blood between the heart and lungs. It is where oxygen enters the blood and carbon dioxide leaves the blood.
Click on the BodyMap above to interact with a 3D model of the circulatory system.
The heart consists of four distinct chambers: two upper chambers called “atria” and two lower chambers called “ventricles.” A wall or “septum” separates the atria and ventricles. Valves control the flow of blood within the different chambers.
Blood follows the following path through the heart:
- Blood lacking oxygen returns from the body and enters the right atrium (upper right chamber) via the inferior vena cava and superior vena cava veins.
- Blood flows through the tricuspid valve and enters the right ventricle (lower right chamber).
- The right ventricle pumps blood through the pulmonary valve and out of the heart via the main pulmonary artery.
- The blood then flows through the left and right pulmonary arteries into the lungs. Here, the process of breathing draws oxygen into the blood and removes carbon dioxide. As a result, the blood is now rich in oxygen.
- The blood returns to the heart and flows into the left atrium (upper left chamber) via four pulmonary veins.
- Blood flows through the mitral valve and enters the left ventricle (lower left chamber).
- The left ventricle pumps the blood through the aortic valve into a large artery called the “aorta.” This artery delivers blood to the rest of the body.
The heart pumps blood through closed vessels to every tissue within the body. The blood itself then delivers nutrients and oxygen to all cells in the body. Without blood, the cells and tissues would not function at their total capacity and would begin to malfunction and die.
The cardiac cycle consists of two phases.
The first phase is diastole, in which the ventricles fill with blood. It begins when the aortic or pulmonary valve closes and ends when the mitral or tricuspid valve closes. During diastole, blood vessels return blood to the heart in preparation for the next contraction of the ventricles.
The second phase is systole, in which the ventricles contract and eject blood. It begins when the mitral or tricuspid valve closes and ends when the aortic or pulmonary valve closes. The pressure inside the ventricles becomes greater than the pressure inside adjacent blood vessels, thereby forcing the blood from the ventricles to the vessels.
Cardiovascular diseases can be severe and potentially life threatening. Understanding conditions that can affect the cardiovascular system may help people seek appropriate and timely medical advice.
Overviews of some common cardiovascular diseases are below.
Heart attack
A heart attack happens when a part of the heart muscle does not receive enough blood. This can occur due to a blockage, a tear in an artery around the heart, or if the heart requires more oxygen than is available.
Symptoms of a heart attack include:
- chest pain or discomfort
- feeling lightheaded
- pain or discomfort in the jaw, neck, or back
- pain or discomfort in one or both arms or shoulders
- shortness of breath
Three of the main risk factors of a heart attack are:
- high blood cholesterol
- high blood pressure
- smoking
People who have had a heart attack can lower their chances of future cardiovascular problems by engaging in the following:
- regular physical activity
- reaching or maintaining a moderate weight
- following a heart-healthy diet
- quitting smoking
- undergoing cardiac rehabilitation
Stroke
A stroke is a medical condition in which the blood supply to a part of the brain becomes cut off. This lack of blood supply triggers the death of brain cells.
There are two types of stroke. Ischemic stroke occurs as a result of a blood clot blocking blood flow to the brain. Hemorrhagic stroke occurs as a result of a bleed in or around the brain.
Some significant risk factors of a stroke include:
- high blood pressure
- diabetes
- heart disease
- smoking
- personal or family history of stroke
- older age
- being of African American heritage
Symptoms of a stroke begin suddenly and may include:
- one-sided weakness or numbness of the leg, arm, or face
- vision problems in one or both eyes
- difficulty speaking or understanding speech
- confusion
- dizziness, loss of balance, or difficulty walking
- severe headache
The treatment for stroke will depend on the type. A person who experiences ischemic stroke may receive medications to help break up the blood clot and restore blood flow to their brain. A person who experiences a hemorrhagic stroke may require surgery to fix the blood vessel that is bleeding out.
Follow-up treatments for stroke may include:
- antiplatelet or anticoagulant medications to help prevent the formation of new blood clots
- medications to lower blood pressure
- medications called statins to reduce levels of cholesterol in the blood
- physical therapy
- rehabilitation therapy
- speech therapy
Heart failure
Heart failure occurs when the heart is unable to pump enough blood to satisfy the body’s needs.
Some symptoms of heart failure include:
- persistent coughing or wheezing
- shortness of breath
- exercise intolerance
- increased heart rate
- nausea
- lack of appetite
- swelling
- fatigue
- confusion
Risk factors of heart failure include:
- high blood pressure
- coronary artery disease
- personal history of one of the following conditions:
- heart attack
- diabetes
- sleep apnea
- congenital heart defect
There is no cure for heart failure. But treatments can help to slow the progression of the disease and alleviate symptoms. Examples include:
- lifestyle changes, such as dietary and exercise changes
- devices and surgical procedures
- medications to manage blood pressure or cholesterol levels
- diuretics to reduce swelling, or edema
Arrhythmia
An arrhythmia is an abnormal heart rhythm. It may present as a heartbeat that is too quick, too slow, or has a distinctive pattern. Symptoms may include:
- fast or slow heartbeat
- skipping beats
- lightheadedness
- dizziness
- fainting
- chest pain
- shortness of breath
- sweating
The risk factors of arrhythmia include:
- heart disease
- congenital heart defect
- high blood pressure
- high cholesterol
- older age
- alcohol use
- untreated sleep apnea
For dangerous arrhythmias, doctors may insert a device called a pacemaker to restore a regular heart rate.
As a person ages, their heart begins to work less effectively than it used to. For example, it cannot beat as fast during physical activity, although the resting heart rate remains steady. Arrhythmias can also develop as the heart ages.
Another common condition of aging is more stiffness in the large arteries and stiffness of the heart muscle. This stiffness can cause high blood pressure, increasing the risk of heart attacks, stroke, and heart failure. Stiffness of the heart can also cause congestive heart failure.
The cardiovascular system consists of the heart, veins, arteries, and capillaries. These components make up two circulatory systems: the systemic and pulmonary circulatory systems. The cardiac cycle consists of two phases: systole (relaxation) and diastole (contraction).
Some conditions that can affect the heart include heart attack, stroke, heart failure, and arrhythmia.
As the body ages, the heart functions less effectively, especially during periods of high physical activity. The arteries also have a higher likelihood of becoming stiff with age, which increases the possibility of high blood pressure and associated cardiovascular issues.