What is the heart?

Your heart is a muscle located in your rib cage, behind and to the left of your breastbone. It’s about the size of your fist when you make it into a ball.

What is the function of the heart?

Your heart’s function is to pump blood around your body, to give your cells the nutrients and oxygen they need.

Your heart pumps blood to your lungs, where it picks up oxygen. This oxygen-rich blood then returns to your heart to be pumped to the rest of your body through arteries.

The heart also sends blood to its own muscles through the coronary arteries.

What are the different parts of the heart?

The parts of the heart include:

• heart muscle
• 4 chambers (2 atria and 2 ventricles)
• valves
• blood vessels — arteries, veins and capillaries
• the electrical conduction system

The major artery coming from your heart is called the aorta.

Heart muscle

Your heart muscle is divided into 3 layers:

• the endocardium (inner layer)
• the myocardium (middle layer)
• the epicardium (protective outer layer)

The muscle of your heart contracts and relaxes to pump blood around your body.

Heart chambers

Your heart has 4 chambers. The upper chambers are the right atrium and left atrium. The lower chambers are the right and left ventricles. Your heart is divided into 2 sides (the right and left sides) by a thin wall called the septum.

Heart valves

There are 4 valves in your heart that act like doors between the different chambers inside.

• The atrioventricular (AV) valves act as the doors between the atria and the ventricles. The right AV valve is called the tricuspid valve. The left AV valve is known as the mitral valve.
• The semilunar valves which include the pulmonary and aortic valves, act as the doors between the ventricles and the major blood vessels leaving the heart.

Blood vessels

Blood is pumped to your heart, lungs and around your body via blood vessels. There are 3 types of blood vessels:

• arteries — carry oxygenated blood from the heart to the body
• veins — carry deoxygenated blood from the body back to the heart and lungs
• capillaries — where oxygen and other nutrients are exchanged

Electrical conduction system

Electrical pathways in your heart muscle make it pump. The heart has special cells called pacemaker cells that automatically start each heartbeat. The heart muscle then squeezes, which makes the blood flow.

Electrical impulses start at the SA node (pacemaker) in the right atrium. This spreads in a coordinated way through the atria so that the heart muscle pumps in a synchronised way (happens together).

The AV node, which is between the atria and ventricles, slows the electrical activity before it enters the ventricles. This is so that the atria pump first — to pump blood into the ventricles. Then the ventricles pump afterwards — to pump the blood around the body.

Your heart is kept beating by the heart’s electrical system.

How does the heart work?

This is how your heart pumps blood:

1. The right atrium receives blood that has been around your body.
2. The blood then flows through valves into the right ventricle, where it is pumped to the lungs to get more oxygen.
3. Oxygenated blood returns from the lungs to the left atrium. It’s then pumped from the left ventricle to the rest of your body via the aorta.

Heart valves stop the blood from flowing backwards from the ventricles in the atrium. When the valves shut, they make a sound that can be heard with a stethoscope.

What medical conditions are related to the heart?

There are many different health conditions related to the heart — here are a few:

• Coronary artery disease happens when the coronary arteries become clogged with fatty deposits.
• Angina is chest pain caused when an area of heart muscle is not getting enough blood. Discomfort can spread to the shoulder, neck or jaw.
• A heart attack (myocardial infarction) happens when a blockage in a coronary artery reduces the blood (and oxygen) supply to the heart muscle, usually due to coronary artery disease.
• Heart failure happens when the heart doesn’t pump well, it can make you feel tired, short of breath and sometimes cause swelling in your legs.
• Heart valve disease happens when the valves do not open or close properly, causing problems with blood flow.
• Arrhythmias happen when the heart is not beating in the usual pattern. The beat can be irregular, too fast or too slow.

How can I take care of my heart?

You can lower your heart disease risk by:

• keeping physically active
• keeping a healthy weight
• reducing stress
• eating a healthy diet
• quitting smoking or vaping, if you smoke

It’s also important to manage your:

• blood pressure
• cholesterol level
• blood sugar levels — if you have diabetes

The things you do to keep your heart healthy can also help protect you from other diseases, such as type 2 diabetes and kidney disease.

Resources and support

For more information about how your heart works, heart conditions and how to keep your heart healthy, visit:

• The Heart Foundation
• Heart Research Australia

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.

Languages other than English

Read more on heart health in a range of community languages on the Heart Foundation website.

Information for Aboriginal and/or Torres Strait Islander peoples

Visit the St Vincent's Hospital NSW and Heart Foundation Aboriginal heart health website for information for Aboriginal and/or Torres Strait islander people.