Blood Flow Through the Heart

What is the role of blood flow through the heart and body?

You need continuous blood flow through your heart and body to stay alive. Your heart is a powerful muscle that pumps oxygen-rich blood out to your body. Once it leaves your heart, this blood flows through many blood vessels to reach every part of your body, from the major organs (like your brain) to the smallest tissues at the tips of your toes. Your blood is always on the go, and it has two main jobs while it’s flowing through your body:

• It delivers oxygen and nutrients to all your organs and tissues.
• It removes carbon dioxide and other waste products from those same places.

The blood then returns to your heart once it’s low on oxygen and full of waste products. It needs to get filled with oxygen and get rid of carbon dioxide so your heart pumps it out to blood vessels in your lungs. Your blood gains oxygen and gets rid of waste in your lungs before flowing back to your heart. Your heart gratefully accepts this refreshed blood and pumps it back out to your body.

In addition to its role in delivering oxygen and nutrients, blood also contains infection-fighting cells called white blood cells. White blood cells are crucial in protecting the body from infection. Your white blood cells circulate throughout your body and respond to infections and foreign materials.

This circulation of blood continues over and over, every second of every day. Your heart and blood vessels make it all happen, and that’s why together they’re known as your circulatory system. The many parts of your circulatory system work together like a top-notch delivery service to keep blood moving through your body on schedule.

Blockages in your blood vessels (like blood clots) or other slowdowns can disrupt this system and lead to health issues. So, it’s important to learn how blood flows through your heart and body. You can then do whatever you can to keep this powerful system — invisible to you as you go about your day — going strong.

Where does blood flow through the heart?

Your heart has four chambers, which you can think of like rooms in your home. Two are on the right side of your heart (right atrium and right ventricle), and two are on the left side (left atrium and left ventricle). Your blood flows through all four chambers — just not all in a row.

Like returning home after a long day at work, your blood returns to your heart after circulating through your body. It enters your right atrium and then directly flows into your right ventricle. (It’s like when you enter your living room and immediately keep going to your kitchen to grab a bite to eat.)

From your right ventricle, your blood can’t immediately go to the two chambers on the left side of your heart. It first needs to make a pit stop at your lungs to get rid of waste and pick up more oxygen. So it leaves your heart and goes to your lungs. (It’s like when you dash into your bathroom to take care of business and also take a quick shower.)

After leaving your lungs, your blood enters your left atrium and from there flows into your left ventricle. Your left ventricle then pumps this blood out to your body, where it makes the rounds before returning to your heart. (You go to your bedroom and get some sleep before waking up the next day and heading back out to work.)

Heart valves

Like rooms in your home, your heart chambers have doors. These doors — your heart valves — open and close to manage blood flow and keep it moving in the proper direction. You have four main heart valves:

• The tricuspid valve connects your right atrium and right ventricle.
• The pulmonary valve connects your right ventricle and main pulmonary artery (large artery that carries blood to your lungs).
• The mitral valve connects your left atrium and left ventricle.
• The aortic valve connects your left ventricle and aorta (large artery that carries blood away from your heart to the rest of your body).

What is the order of blood flow through the heart, step by step?

The right and left sides of your heart work together to make sure blood flows throughout your whole body. Blood flows through your heart in a series of steps. These steps take place in the space of one heartbeat — just a second or two.

On the right side

1. Oxygen-poor blood from all over your body enters your right atrium through two large veins, your superior vena cava and inferior vena cava. These veins drain blood from your upper body and lower body, respectively, and directly empty it into your right atrium.
2. Your tricuspid valve opens to let blood travel from your right atrium to your right ventricle.
3. When your right ventricle is full it squeezes, which closes your tricuspid valve and opens your pulmonary valve.
4. Blood flows through your main pulmonary artery and its branches to your lungs, where it gets oxygen and releases carbon dioxide.

On the left side

1. Oxygen-rich blood travels from your lungs to your left atrium through large veins called pulmonary veins. These veins directly empty the blood into your left atrium.
2. Your mitral valve opens to send blood from your left atrium to your left ventricle.
3. When your left ventricle is full it squeezes, which closes your mitral valve and opens your aortic valve.
4. Your heart sends blood through your aortic valve to your aorta, where it flows to the rest of your body.

How much blood does your heart pump?

Your heart pumps about 2,000 gallons of blood each day. That’s enough to fill an 8-by-10-foot swimming pool.

It beats around 100,000 times daily. In an average life span of almost 79 years, your heart beats nearly 2.9 billion times.

What conditions affect blood flow through the heart?

Certain conditions can affect the pathway of blood flow in your heart. Some of these conditions include:

• Arrhythmia: An irregular heartbeat like atrial fibrillation or ventricular fibrillation.
• Congestive heart failure: Damage or weakness in your heart muscle, making it harder for your heart to pump blood to the rest of your body.
• Coronary artery disease (CAD): Hardening and narrowing of the arteries that carry blood to your heart muscle due to plaque buildup.
• Peripheral artery disease (PAD): Hardening and narrowing of the arteries that carry blood to the rest of your body due to plaque buildup.
• Heart attack: A sudden blockage in your coronary artery that cuts off oxygen to part of your heart muscle.
• Heart valve disease: A heart valve that doesn’t work properly. For example, it may be narrowed or leaky.
• Structural congenital heart defects: Problems with your heart structure that are present at birth, including bicuspid aortic valve disease.
• Sudden cardiac arrest: Sudden loss of heart function because of a malfunction in your heart’s electrical system.

How does blood flow through the body, step by step?

Your heart pumps oxygen-rich blood through your aortic valve and into your aorta. Your aorta is your body’s main artery, and it has many branches that go in different directions to reach various areas of your body. Picture a tree with one main trunk (your aorta) and lots of branches (all the arteries that connect to your aorta). Your aorta and its branches are responsible for delivering blood to your entire body.

Here’s what happens once blood is in your aorta:

1. Blood passes from your aorta into other arteries that directly branch off your aorta (aortic branches).
2. The first aortic branches are your coronary arteries, which nourish your heart muscle.
3. Many more arteries branch off your aorta as it travels through your chest and belly.
4. Ultimately, your aorta splits (bifurcates) into two terminal branches called your iliac arteries. Your aorta and your iliac arteries form an upside-down Y near your belly button.
5. Many of your aorta’s branches have their own branches, which you can think of like twigs. These arteries meander through every part of your body.
6. Blood flows from your arteries into even smaller blood vessels called arterioles.
7. Your arterioles link up with vessels that are smaller yet, called capillaries. Your capillaries have very thin walls that allow oxygen and nutrients to pass into your organs and tissues.
8. After swapping the oxygen and nutrients for the waste products, your capillaries connect with venules. Your venules are small blood vessels that link up with veins.
9. Your veins carry blood that’s now low in oxygen and full of waste back toward your heart.
10. Blood from all your veins ultimately ends up in your superior vena cava and inferior vena cava. These two large veins empty the blood directly into your heart’s right atrium.
11. Your blood then cycles through your heart and lungs before going back out to your body all over again.

Blood flow through your body is a complex and beautiful system. It operates 24/7, whether you’re awake or asleep. This constant blood flow allows you to think, speak, move and interact with your environment.

What conditions affect blood flow through the body?

Many different circulatory system diseases can disrupt normal blood flow through your body. For example, you may develop:

• Weak spots in your artery wall (aneurysms).
• Plaque buildup in your arteries (atherosclerosis).
• Weakened or damaged veins (venous disease).
• Abnormal connections between arteries and veins (arteriovenous fistulae).

Sometimes, you can prevent or at least lower your risk of these conditions. Other times, factors like heredity (the genes you inherit from your biological parents) and aging take over, and there’s not much you can do about it.

Even if you can’t prevent all the conditions affecting blood flow, you can work with a healthcare provider to manage any problems that come up and keep them from getting worse.

How can I improve blood flow in my heart and body?

Here are some things you can do to support healthy blood flow:

• Reach and keep a weight that’s healthy for you.
• Eat a heart-healthy diet.
• Exercise for about 150 minutes per week (that’s 30 minutes, five days a week).
• Limit alcohol intake.
• Manage stress with healthy coping techniques such as talk therapy or meditation.
• Quit smoking or using any tobacco products.

A note from Cleveland Clinic

Close your eyes and imagine what you could see from an airplane window as you prepare to land near a big city. Picture complex networks of roads and highways, connecting and diverging at various points. Long lines of cars all move along, intent on keeping up with the flow of traffic and reaching their destinations. A similar hustle and bustle goes on inside your body all the time, on a much smaller scale, as blood moves through your heart and blood vessels.

The tiny inner workings of your body are easy to forget about because you don’t see them every day. Yet this constant blood flow keeps you alive day in and day out. You may not need to know every detail of how it all works. But knowing the basics can help you talk with your healthcare provider about any issues that come up or simply about ways to stay healthy. Don’t hesitate to reach out to your provider with questions or concerns about blood flow or any aspect of your health.