Your heart is the main organ of your cardiovascular system, a network of blood vessels that pumps blood throughout your body. It also works with other body systems to control your heart rate and blood pressure. Your family history, personal health history and lifestyle all affect how well your heart works.
The heart is a fist-sized organ that pumps blood throughout your body. It's the primary organ of your circulatory system.
Your heart contains four main sections (chambers) made of muscle and powered by electrical impulses. Your brain and nervous system direct your heart’s function.
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The inside and outside of your heart contain components that direct blood flow:
Inside of the Heart
Outside of the Heart
Your heart’s main function is to move blood throughout your body. Your heart also:
Your heart works with other body systems to control your heart rate and other body functions. The primary systems are:
Your heart is located in the front of your chest. It sits slightly behind and to the left of your sternum (breastbone). Your ribcage protects your heart.
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.
Everyone’s heart is a slightly different size. Generally, adult hearts are about the same size as two clenched fists, and children’s hearts are about the same size as one clenched 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.
The parts of your heart are like the parts of a house. Your heart has:
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:
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.
Your heart is divided into four chambers. You have two chambers on the top (atrium, plural atria) and two on the bottom (ventricles), one on each side of the heart.
Your heart valves are like doors between your heart chambers. They open and close to allow blood to flow through.
The atrioventricular (AV) valves open between your upper and lower heart chambers. They include:
Semilunar (SL) valves open when blood flows out of your ventricles. They include:
Your heart pumps blood through three types of blood vessels:
Your heart receives nutrients through a network of coronary arteries. These arteries run along your heart’s surface. They serve the heart itself.
Your heart’s conduction system is like the electrical wiring of a house. It controls the rhythm and pace of your heartbeat. It includes:
Your heart also has a network of electrical bundles and fibers. This network includes:
Heart conditions are among the most common types of disorders affecting people. In the United States, heart disease is the leading cause of death for people of all genders and most ethnic and racial groups.
Common conditions that affect your heart include:
If you have a condition that affects your heart, follow your healthcare provider’s treatment plan. It’s important to take medications as prescribed.
You can also make lifestyle changes to keep your heart healthy. You may:
You may want to ask your healthcare provider:
A note from Cleveland Clinic
Your heart is the primary organ of your circulatory system. It pumps blood throughout your body, controls your heart rate and maintains blood pressure. Your heart is a bit like a house. It has walls, rooms, doors, plumbing and an electrical system. All the parts of your heart work together to keep blood flowing and send nutrients to your other organs. Conditions that affect your heart are some of the most common types of conditions. Ask your healthcare provider how you can improve your heart health.
Last reviewed by a Cleveland Clinic medical professional on 08/26/2021.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy