Your muscular heart, the main organ in your cardiovascular system, is vital for life. Its parts work together to move blood through your body in a coordinated way. It constantly sends oxygen to your cells and takes away waste. Many conditions can affect this organ and keep it from working well.


The heart and the major arteries and veins going into and out of it.
Your heart is a muscular organ that pumps blood to your body.

What is the heart?

The heart is a fist-sized organ that pumps blood throughout your body. It’s your circulatory system’s main organ. Muscle and tissue make up this powerhouse organ.

Your heart contains four muscular sections (chambers) that briefly hold blood before moving it. Electrical impulses make your heart beat, moving blood through these chambers. Your brain and nervous system direct your heart’s function.


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What is the function of the heart?

Your heart’s main function is to move blood throughout your body. Blood brings oxygen and nutrients to your cells. It also takes away carbon dioxide and other waste so other organs can dispose of them.

Your heart also:

Your heart works with these body systems to control your heart rate and other body functions:

  • Nervous system: Your nervous system helps control your heart rate. It sends signals that tell your heart to beat slower during rest and faster during stress.
  • Endocrine system: Your endocrine system sends out hormones. These hormones tell your blood vessels to constrict or relax, which affects your blood pressure. Hormones from your thyroid gland can also tell your heart to beat faster or slower.


The chambers and valves of the heart.
Blood moves through chambers inside your heart.

What are the parts of the heart?

The parts of your heart are like the parts of a building. Your heart anatomy includes:

  • Walls.
  • Chambers that are like rooms.
  • Valves that open and close like doors to the rooms.
  • Blood vessels like plumbing pipes that run through a building.
  • An electrical conduction system like electrical power that runs through a building.

Heart walls

Your heart walls are the muscles that contract (squeeze) and relax to send blood throughout your body. A layer of muscular tissue called the septum divides your heart walls into the left and right sides.

Your heart walls have three layers:

  • Endocardium: Inner layer.
  • Myocardium: Muscular middle layer.
  • Epicardium: Protective outer layer.

The epicardium is one layer of your pericardium. The pericardium is a protective sac that covers your entire heart. It produces fluid to lubricate your heart and keep it from rubbing against other organs.

Heart chambers

Your heart has four separate chambers. You have two chambers on the top (atrium, plural atria) and two on the bottom (ventricles), one on each side of your heart.

  • Right atrium: Two large veins deliver oxygen-poor blood to your right atrium. The superior vena cava carries blood from your upper body. The inferior vena cava brings blood from your lower body. Then the right atrium pumps the blood to your right ventricle.
  • Right ventricle: The lower right chamber pumps the oxygen-poor blood to your lungs through the pulmonary artery. The lungs reload the blood with oxygen.
  • Left atrium: After the lungs fill your blood with oxygen, the pulmonary veins carry the blood to the left atrium. This upper chamber pumps the blood to your left ventricle.
  • Left ventricle: The left ventricle is slightly larger than the right. It pumps oxygen-rich blood to the rest of your body.

Heart valves

Your heart valves are like doors between your heart chambers. They open and close to allow blood to flow through. They also keep your blood from moving in the wrong direction.

Atrioventricular valves

The atrioventricular (AV) valves open between your upper and lower heart chambers. They include:

  • Tricuspid valve: Door between your right atrium and right ventricle.
  • Mitral valve: Door between your left atrium and left ventricle.
Semilunar valves

Semilunar (SL) valves open when blood flows out of your ventricles. They include:

  • Aortic valve: Opens when blood flows out of your left ventricle to your aorta (artery that carries oxygen-rich blood to your body).
  • Pulmonary valve: Opens when blood flows from your right ventricle to your pulmonary arteries (the only arteries that carry oxygen-poor blood to your lungs).

Blood vessels

Your heart pumps blood through three types of blood vessels:

  • Arteries carry oxygen-rich blood from your heart to your body’s tissues. The exception is your pulmonary arteries, which go to your lungs.
  • Veins carry oxygen-poor blood back to your heart.
  • Capillaries are small blood vessels where your body exchanges oxygen-rich and oxygen-poor blood.
Coronary arteries

Your heart receives nutrients through a network of coronary arteries. These arteries run along your heart’s surface. They serve the heart itself and include the:

  • Left coronary artery: Divides into two branches (the circumflex artery and the left anterior descending artery).
  • Circumflex artery: Supplies blood to the left atrium and the side and back of the left ventricle.
  • Left anterior descending artery (LAD): Supplies blood to the front and bottom of the left ventricle and the front of the septum.
  • Right coronary artery (RCA): Supplies blood to the right atrium, right ventricle, bottom portion of the left ventricle and back of the septum.

Electrical conduction system

Your heart’s conduction system is like the electrical wiring of a building. It controls the rhythm and pace of your heartbeat. Signals start at the top of your heart and move down to the bottom. Your conduction system includes:

  • Sinoatrial (SA) node: Sends the signals that make your heart beat.
  • Atrioventricular (AV) node: Carries electrical signals from your heart’s upper chambers to its lower ones.
  • Left bundle branch: Sends electric impulses to your left ventricle.
  • Right bundle branch: Sends electric impulses to your right ventricle.
  • Bundle of His: Sends impulses from your AV node to the Purkinje fibers.
  • Purkinje fibers: Make your heart ventricles contract and pump out blood.


Where is your heart located?

Your heart is in the front of your chest. It sits slightly behind and to the left of your sternum (breastbone), which is in the middle of your chest.

Your heart is slightly on the left side of your body. It sits between your right and left lungs. The left lung is slightly smaller to make room for the heart in your left chest. Your rib cage protects your heart.

What does your heart look like?

Your heart looks a little bit like an upside-down pyramid with rounded edges. Large blood vessels go into and out of your heart to bring blood into and away from your heart. They connect your heart to the rest of your body, which it supplies with blood and oxygen.

How big is your heart?

Everyone’s heart is a slightly different size. Generally, your heart is about the same size as your fist. On average, an adult’s heart weighs about 10 ounces. Your heart may weigh a little more or a little less, depending on your body size and sex.


Conditions and Disorders

What are the common conditions and disorders that affect your heart?

Heart conditions are among the most common types of disorders. In the United States, heart disease is the leading cause of death.

Common conditions that affect your heart include:

Common signs or symptoms of heart conditions

Symptoms of heart conditions include:

Common tests to check the health of your heart

Tests to check your heart health include:

Common treatments for the heart

Treatments for heart conditions include:


How can I keep my heart healthy?

If you have a condition that affects your heart, follow your healthcare provider’s treatment plan. It’s important to take medications at the right times and in the right amounts.

You can also make lifestyle changes to keep your heart healthy. You can strive to:

  • Achieve and maintain a weight that’s healthy for you.
  • Drink alcohol in moderation.
  • Eat heart-healthy foods like plenty of fruits, vegetables and whole grains.
  • Be physically active for at least 150 minutes per week.
  • Limit how much sodium you consume.
  • Manage your stress with healthy strategies like meditation or journaling.
  • Quit smoking and/or using tobacco products and avoid secondhand smoke. If you smoke, ask a healthcare provider for resources to help you quit.

Additional Common Questions

What should I ask my doctor about my heart?

You may want to ask your healthcare provider:

  • How does my family history affect my heart health?
  • What can I do to lower my blood pressure?
  • How do my cholesterol levels affect my heart?
  • What are the symptoms of a heart attack?
  • What foods should I eat to prevent heart disease?

A note from Cleveland Clinic

As the main organ of your circulatory system, your heart keeps you alive. It pumps blood throughout your body, bringing oxygen to your cells and tissues. Since your heart plays such a vital role, it’s important to take care of it. Conditions that affect your heart are very common, but you have the power to make changes for a stronger heart. Ask your healthcare provider how you can improve your heart health.

Medically Reviewed

Last reviewed on 01/26/2024.

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