How, Exactly, Does Your Heart Work?

This illustrated guide walks you through how your ticker functions and explains what can happen when its valves aren’t pumping properly.

by Matt McMillen Health Writer

Your heart is the beating center of your circulatory system. It pumps blood—rich with oxygen and nutrients—to the rest of your body, which keeps your brain, kidneys, and other vital organs functioning as they should. And, if you keep your heart in tip-top shape, you’ll have a better chance that it—and you—function in great form for the long haul.

“Regular exercise and a healthy diet, like the Mediterranean diet, will help keep your cardiovascular risk factors, like high blood pressure and high cholesterol, in check,” says cardiologist Glenn Hirsch, M.D., of National Jewish Health in Denver.

Of course, many things can go wrong with your heart for different reasons. For example, your heart’s system of valves, which regulate blood flow through your ticker, can weaken and malfunction from aging, certain types of infections, high blood pressure or high cholesterol, and/or damage caused by a heart attack. This causes a type of heart disease called heart valve disease. Heart failure, genetic abnormalities, and cardiomyopathy (disease of the heart muscle), can also cause heart issues.

“There are lots of things that can happen if you have a problem with your heart,” says Dr. Hirsch. In fact, heart disease is the leading cause of death for both men and women in the U.S. The Centers for Disease Control and Prevention (CDC) estimates that 655,000 people die from heart disease every year.

But how, exactly, does your heart work? Let’s take a look at its important parts and all they do. And the best way to do that is to follow your blood flow.

Jason Hoffman

Your blood cycles through your body, delivering oxygen and other necessities to all the organs that keep you alive, before returning to your heart via your circulatory system’s network of veins. Once this now-depleted blood arrives back at your heart to be refreshed before it begins another round, its first stop is your right atrium, one of your heart’s two top chambers. (The other top chamber is the left atrium. Together, they’re known as the atria.)

“The right atrium collects all the venous blood, meaning all the deoxygenated blood after your body’s tissue and organs have had a chance to extract the oxygen for cellular functions,” explains Deepak Vivek, M.D., an interventional cardiologist at Orlando Health Heart and Vascular Institute in Orlando, FL. “A big vein called the vena cava dumps all that blood into the right atrium.”

Your heart has a total of four chambers. Below the atria are the left and right ventricles. Your blood will pass through each of your heart’s four valves. “The valves are very important to your overall health,” says Dr. Vivek. “The heart muscle is a pump that pumps blood throughout the rest of the body, and your valves need to open and close in a timed cycle to allow the appropriate flow of blood through the body to the brain, the liver, the lungs, the kidneys.” When your heart beats your right atrium contracts, and your tricuspid valve opens so that blood can move into your right ventricle.

Each of your valves performs a similar function, opening to allow blood to flow forward, and then closing so that none of your blood moves backwards. If you ever want to hear your heart at work, borrow a stethoscope: “That lub-dub sound that you hear when you listen to the heart through a stethoscope is the sound of the valves closing,” says Dr. Hirsch.

Listening to your heart can also reveal problems with its function. “Leaking has a different sound and timing, depending on the valve and whether it’s blocked or whether it’s leaking,” Dr. Hirsch explains. Blockage, or stenosis, happens when a valve thickens and stiffens, which prevents it from opening all the way. Leakage occurs when the valve can’t close fully. The medical term for this is regurgitation. Heart attacks and abnormal heart rhythms, or arrhythmias, can cause regurgitation.

Jason Hoffman

The right ventricle receives blood that has been depleted of oxygen during its journey through your body. Your lungs will restock its supply. To move your blood along, your right ventricle pumps it through the next valve on its pathway, the pulmonic valve. This valve opens to allow blood to be pumped into the pulmonary artery to blood vessels that connect to your lungs. “The right side pumps blood through the lungs,” says Dr. Vivek. “That’s its main job.”

Jason Hoffman

Once your blood arrives in your lungs, the carbon dioxide it carries leaves your body as you breathe out. When you breathe in, your blood becomes enriched with oxygen. “Once it picks up oxygen, it returns to your heart and into the left atrium,” explains Dr. Hirsch.

Jason Hoffman

The left atrium receives the freshly supplied blood and, when it contracts, pumps that blood through valve number three: your mitral valve. That valve opens to allow blood to flow from your left atrium into your left ventricle, the biggest, thickest, and strongest of your heart’s four chambers. Why does it need extra muscle? “Because it’s got to pump blood to the whole rest of the body, to your brain and all the way down to your toes and then back again to your heart,” says Dr. Vivek.

Jason Hoffman

The pressure created when your left ventricle contracts propels your blood forward through your heart’s fourth valve, the aortic valve, and into your aorta.

Jason Hoffman

“The aorta sends your blood everywhere,” says Dr. Vivek. It’s your body’s largest artery, and the first in the network of arteries that your blood flows through. Part of it extends down into your abdomen before branching off into smaller and smaller arteries. Your aorta also connects to arteries that deliver your blood to your upper body and to your brain. Your arteries handle the flow of blood from your heart, while your veins carry your blood on its return journey to your heart.

What keeps your heart pumping in a set rhythm and at a set rate? Your heart has its own electrical system that signals the muscles in your heart to contract and relax. “The heart is a muscle, but it has electrical conduction through the muscular tissue controlled by a wiring system throughout the heart,” says Dr. Hirsch.

Jason Hoffman

The electrical signals originate with pacemaker cells, located in your right atrium. As they travel downward, they cause your right atrium and left atrium to pump blood into your ventricles. When the signals reach another set of pacemaker cells called the atrioventricular (AV) node, located in the space between your heart’s upper and lower chambers, another signal tells your ventricles to contract and pump blood out of your heart. “This coordination of the electrical system and the contraction of the heart muscle helps the heart pump the blood through the body—up through the lungs, where it gets oxygen, before being pumped out of the left side of the heart to the rest of the body,” Dr. Hirsch explains.

Hats off to your heart for the big job that it does! Remember, though, that it can only keep up its vital work with your help. That means doing your best to support it: Eat a healthy diet, get regular exercise, manage your stress levels, and do everything in your power to quit smoking.

Matt McMillen
Meet Our Writer
Matt McMillen

Matt McMillen has been a freelance health reporter since 2002. In that time he’s written about everything from acupuncture to the Zika virus. He covers breaking medical news and the latest medical studies, profiles celebrities, and crafts easy to digest overviews of medical conditions. His work has appeared, both online and in print, in The Washington Post, WebMD Magazine, Diabetes Forecast, AARP, and elsewhere.