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How Your Heart Works and How Things Go Wrong

Your heart is one of the most important organs in the body. The average adult heart is about the size of a fist. It’s the central part of your circulatory system, which is made up of your heart, your blood vessels (arteries, veins, capillaries) and your lungs. Your heart is made up of four chambers, four valves, a system of blood vessels, and tissue that separates the chambers.

How the heart works – an overview

With each heartbeat, your heart provides oxygen and nutrient-rich blood to the lungs and the rest of the body through your blood vessels so your organs and other tissues can use it to function. At the same time, your heart receives the blood that has fed oxygen and nutrients to your body organs; moves that blood to the lungs where it removes carbon dioxide and picks up more oxygen; and then pumps the re-oxygenated blood back to the body where the whole process starts over again. This circulatory process happens approximately one hundred thousand times per day. Each heartbeat you hear is the sound of your heart expanding and contracting with each beat, moving blood throughout the body to do what it needs to do.

How does blood move through the heart?


Blood moves through the heart (and the rest of the body) in an intricate system of blood vessels, which are flexible tubes that are all connected. The three main types of blood vessels are arteries, veins, and capillaries. Arteries carry oxygen-enriched blood away from the heart to the rest of the body. Veins take blood back to the heart, then to the lungs to get rid of carbon dioxide and pick up oxygen. Capillaries are tiny blood vessels that connect the arteries and veins. Their walls are thin and porous, so they allow oxygen, carbon dioxide, nutrients, and more to pass to and from the cells of our organs and other tissue.

The aorta is the largest artery in the body. It leaves the heart to deliver blood to our bodies. The aorta branches out to other arteries, and those arteries branch out again to smaller and smaller arteries and capillaries until oxygen and nutrients are delivered all over the body.

The superior vena cava is the large vein that brings blood to the heart from the head, arms, and brain and the inferior vena cava brings blood to the heart from the abdomen and legs. This blood has been stripped of oxygen and nutrients and has been filled with carbon dioxide and other waste products.


How does the blood get pumped through the vessels?


There are four sections of the heart called chambers. The two upper chambers are the atria, and the two lower chambers are the ventricles. The right atrium is the chamber that accepts the blood returning from the body. This blood enters the right atrium through the superior and inferior vena cava. This is the blood that has been depleted of oxygen during the process of delivering that oxygen to the body tissues. Once the right atrium is full of blood, it pumps the blood into the right ventricle through the tricuspid valve. The right ventricle then contracts, which pumps blood away from the heart to the lungs through the pulmonary artery where it receives more oxygen. Once that happens, the blood is again full of oxygen and nutrients that can be delivered to the body tissues.

At the same time the right atrium is receiving blood and moving it into the right ventricle where it gets pumped to the lungs, another process is occurring. In that process, the left atrium is accepting the newly oxygenated blood from the lungs through the pulmonary veins. The left atrium then pumps the blood into the left ventricle through the mitral valve. When the left ventricle contracts, it moves blood through the aortic valve and into the aorta so the aorta can provide the oxygenated blood to the rest of the body.


Where do the heart valves come in?


There are four valves in the heart – the aortic valve, the tricuspid valve, the mitral valve, and the pulmonary valve. The two valves that do the most work are the aortic and the mitral valve. In a normal heart, each of the four valves has flaps. The flaps are called cusps or leaflets. Three of the valves have three cusps, and the mitral valve has two cusps. The cusps are attached to the valves by fibrous tissue that helps support the cusps. This tissue is called the annulus. The mitral and tricuspid valves have additional supportive tissue called chordae tendineae. This tissue is made up of fibrous strings that extend from the cusps of the valves to the small muscles in the ventricles (the lower chambers of the heart).

The job of the valves is to open and close as the heart pumps blood from chamber to chamber within the heart. The mitral and tricuspid valves move blood from the atria to the ventricles when the atria contract. When the ventricles contract, the mitral and tricuspid valves close and the pulmonary and aortic valves open. This opening and closing of valves is meant to keep blood flowing only in the direction it’s meant to flow. The cusps on the valves help create a tight seal so the blood doesn’t leak, which also helps blood move in the right direction.


What’s the job of the lungs? How does the blood move through them?


When blood leaves the right ventricle through the pulmonary valve and into the pulmonary artery, it enters the lungs where it circulates throughout your lungs. This process is called pulmonary circulation. From the pulmonary artery, your blood moves into the tiny capillary vessels in the lungs.

The oxygen you inhale during breathing fills air sacs in the lungs, and it travels from the air sacs through the capillary walls into the blood. At the same time, the waste products and carbon dioxide pass from the blood to the air sacs, and the carbon dioxide leaves the body when you exhale. The oxygenated blood then travels back to the heart, going into the left atrium through the pulmonary veins.


How does the heart muscle receive blood? 


The blood that pumps through the body via the heart and lungs does not nourish the heart muscle. The heart has its own system of arteries that bring oxygen and nutrients to the heart. Those are the coronary arteries. There are two major coronary arteries that branch off the aorta – the right coronary artery and the left main coronary artery.

The right coronary artery supplies the right side of the heart with blood. It also branches into the posterior descending artery, and that artery provides blood to the bottom of the left ventricle and the back of the septum (the wall that separates the chambers).

The left main coronary artery branches off into two arteries – the circumflex artery and the left anterior descending artery. The circumflex artery supplies blood to the left atrium and the side and back of the left ventricle, and the left anterior descending artery provides blood to the front and bottom of the left ventricle and the front of the septum. Branches of these arteries provide blood throughout the muscle that makes up the heart.


What makes the heart beat?

The four chambers of the heart work together by contracting then relaxing to keep blood pumping through the heart. These contractions are made possible by electrical impulses.

Your heart has what is basically an electrical system. It powers the heartbeat with electrical impulses that trigger the muscles to work. The electrical impulses travel through a pathway in the heart.

The sinoatrial node (SA node)

The SA node is like the conductor that keeps your heart beating. It consists of a small bundle of cells on the right atrium. It’s commonly known as your heart’s pacemaker. From the SA node, the electrical impulses travel through the walls of the atria, which causes them to contract.

The atrioventricular node (AV node)


There is a second cluster of cells in the center of the heart that sits between the atria and the ventricles. This is called the atrioventricular node (AV node). The AV node is like the gatekeeper. It slows the electrical impulses down before they enter the ventricles, which gives the atria time to contract before the ventricles do.

There is a pathway of fibers within your heart that sends electrical impulses from the AV node to the ventricle walls, which causes the ventricles to contract. This pathway is called the His-Purkinje network.

The normal resting heart rate is between 50 and 99 beats per minute. Many things can cause your heart to beat faster, including exercise, stress, fever, medications, and certain foods and drinks. Having a heart rate higher than 100 can be normal under certain circumstances, but if your heart beats more than 100 times per minute when you’re resting, that’s not normal. A fast heart rate is called tachycardia.


What happens if parts of the heart don’t work well?

Heart disease is an umbrella term that covers many diseases and conditions that affect the heart. If any part of your cardiovascular system doesn’t work well, you may be diagnosed with heart disease. Here’s a brief overview of some of the types of heart disease that can develop when different areas of your heart are damaged or aren’t functioning well.

Coronary arteries

The coronary arteries supply the heart with oxygen and other nutrients. When the coronary arteries are blocked, damaged, or weakened, they cannot effectively bring blood to the heart. And when the heart isn’t nourished with blood and nutrients, it doesn’t work well, so it can’t do its job of pumping blood to and from the rest of the body. That is considered coronary artery disease.

The coronary arteries are most often damaged by a buildup of fatty deposits called plaque. There are many risk factors for plaque buildup in the coronary arteries, including smoking, having a sedentary lifestyle, eating a poor diet, having diabetes, being overweight, and more.

Heart valves

The heart valves are an important part of the cardiovascular system. If the valves don’t work properly, blood flow can be inhibited, and blood can also leak or flow in the wrong direction. There are two main types of heart valve disease – stenosis and regurgitation. Any valve can be affected by stenosis and regurgitation, but the mitral and aortic valves are the most commonly affected valves. Some valve disease is congenital, which means it was present at birth. And some valve disease is acquired, which means it developed over time.

If valves are damaged, they cannot open and close properly, which can inhibit blood flow among other things.

Acquired valve disease may be preventable. Making heart-healthy lifestyle choices is important for preventing heart valve disease as is following your doctor’s recommendations and having heart screenings.

Heart rhythm problems

Heart rhythm problems, otherwise known as arrhythmias, can be caused by many factors. Congenital heart defects can lead to dangerous arrhythmias, as can certain health problems, heart conditions, medications, food and drinks, drugs, and more. Atrial fibrillation is a potentially deadly arrhythmia that often occurs in damaged hearts. Heart attacks, damaged heart tissue, coronary artery disease, high blood pressure, thyroid disease, smoking, drinking too much alcohol, drinking too much caffeine, uncontrolled diabetes, cardiomyopathy, and other conditions can all cause arrhythmias.

Choosing a heart-healthy lifestyle can possibly prevent many heart problems, including arrhythmias.

How to keep your heart healthy

Taking steps to prevent heart disease is the best thing you can do for your heart health. While there are effective medications and surgeries that can treat heart disease once it occurs, there are always risks and potential complications. Choosing a heart-healthy lifestyle can go a long way toward ensuring your heart is healthy for years to come. Here are some tips for heart-healthy living.

  • If you smoke, quit.
  • Make heart-healthy food choices.
  • Keep your cholesterol levels in check.
  • Monitor your blood pressure. If it’s high, talk to your doctor about how to reduce it.
  • If you have diabetes, make sure it’s managed well.
  • Keep a healthy weight. If you’re overweight, take steps to lose weight.
  • Stay active. Exercise is important, but it’s also important to move throughout the day. If you sit at a desk for work, get up every hour and move around to improve your circulation and help keep your heart healthy.
  • Take steps to reduce stress and manage unavoidable stress.

Also, make sure you get all recommended screenings to keep on top of your heart’s health.