How does the heart work: Basic structures and their function

Want to know how does the heart work? Good. It is very simple. Although the heart is basically just a pump, the way it works and the way it is built is a little bit more complex. 

In order to explain its mode of action, I have divided its blueprint into several sections. This should help simplify the explanation. 

Besides four chambers, two ventricles and two atriums, human heart has other basic structures which make this organ such an amazing creation of nature.


FOUR HEART VALVES regulate the blood flow through the cardiac muscle. These valves are made of strong tissue and controlled by blood pressure changes within each heart chamber.

As one valve closes, the other one opens. Besides letting the blood flow forward, they also prevent the blood from flowing backward, when they are working properly. 

CORONARY ARTERIES are part of separate circulatory system which fuels cardiac muscle, by providing oxygen and nutrients rich blood to the heart. 

When they are clogged, the heart doesn't gets its fuel as it should. Because of this, it is important to know how does the heart work, in order to prevent blockades, coronary heart disease or heart attack.

SINOATRIAL NODE is primary pacemaker of the heart muscle. It is under control of nervous system and part of the brain known as medulla oblongata.

SA node sends electrical signals to the heart muscle and stimulates  contractions of the atrial muscles, while regulating heart rate.

ATRIOVENTRICULAR NODE is secondary pacemaker of the heart. Electrical signal travels from the SA node to the AV node. AV node sends it through the bundle of his, down the bundle branches to the purkinje fibers which causes ventricules to contract.

Bundle of his, bundle branches and purkinje fibers are part of heart's conduction system through which the electrical signals travels thereby completing the circle.


Right side of the heart is composed of right ventricle, right atrium, tricuspid valve and pulmonic valve.

This side of the heart receives deoxygenated blood from the body and sends it through the pulmonary arteries into the lungs where it's re-oxygenated.


Left side of the heart is composed of left ventricle, left atrium, mitral valve and aortic valve.

It receives oxygen rich blood from the lungs and pumps it through the aorta to the rest of the body. This cycle repeats over and over.


Left side of the heart can get enlarged in people with some kind of heart disease and in top level athletes, especially endurance athletes. However, some people have genetic predisposition towards heart enlargement.

For instance, my left atrium was 4 cm wider, while my left ventricule was 5,9 cm wider. Although I have genetic predosposition towards heart enlargment, heart disease made it even bigger.

However, with healthy diet and especially cardio exercises, I managed to improve the function and reduce the size of my heart muscle. On the other hand, my heart will always be a little bit bigger, due to my genetic blueprint.


Besides genetics, other factors such as hormones, nervous system reactions and stress, infections and immune system, cholesterol levels and body compositon all have an effect on the heart function and size.

First of all, if your immune system is weak, then some kind of infection can damage the valves. Damaged heart valves don't close properly which causes the blood to flow backward. We don't want that.

On the other hand, hormonal imbalance can lead to heart enlargement and weaken its function. Sometimes, hormonal imbalance is the main cause behind cardiac arrhythmias.

When it comes to nervous system reactions, chronic stress and anxiety can over stimulate natural pacemaker of the heart muscle, by sending irregular electrical signals to the sinoatrial node. This kind of mental state usually leads to heart palpitations but it is not life threatening.

Lastly but not least, high body fat percentage and elevated cholesterol levels can lead to coronary heart disease and blood clots. If blood vessels that supply the heart muscle with nutrient rich blood get clogged, the tissue will die off, due to ischemia.

In this case, even if all other parameters are in check, it won't matter since we can't revive or regenerate dead tissue. Because of this, your chances of needing heart transplant surgery in near or distant future, go up significantly.

So, knowing how does the heart work and keeping these tips in mind will help you avoid the surgery.

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