Out of all the muscles in the body, the heart works the hardest. It pumps continuously whether we are working out or relaxing in bed, keeping the rest of our organs working properly - and keeping us alive. Here is a two-minute guide to the human heart so that you can better understand how it works.

Heart basics

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The human heart is a fist-sized organ located just to the left of the center of the chest. In healthy adults, it beats around 80 times per minute, meaning that it beats around 115,000 times per day. This adds up to around 42 million beats per year. If you want to take that statistic even further, in the average 70-year lifespan of a human being, the heart beats more than 2.5 billion times. This beating is what pushes blood, oxygen, and other nutrients through the body.


The human heart has four distinct chambers, the top two of which are called the right and left atria. The two bottom chambers are the right and left ventricles. Blood from the rest of the body flows into the heart via the atria, and the ventricles pump that blood back out into the rest of the body, creating a constant, cyclical system.


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There are also four valves in the human heart. The two valves that are located between the atria and the ventricles are called atrioventricular valves, and are further divided into the tricuspid (right valve) and the mitral (left valve). There are also two semilunar valves located where the ventricles let out. These are called the pulmonary and aortic valves.

Pericardium and heart wall

The pericardium is a two-walled sac that surrounds the heart, protecting it and keeping it in its proper place inside the chest. Between the inner and outer layers of the pericardium is a fluid that lubricates the heart while it contracts, as well as protects it from the movement of the nearby diaphragm and lungs.

The wall of the heart itself helps to protect this important organ as well. It is made up of three layers: the epicardium, which is the inner wall of the pericardium; the myocardium, which contains the muscular part of the heart that contracts when it beats; and the innermost layer called the endocardium, which is the lining that comes in contact with the blood that flows through the heart.

Arteries and veins

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The final aspect of the heart's anatomy that needs discussing is the system of arteries and veins. Arteries are the vessels that carry blood away from the heart, with the largest and most important one being the aorta, which comes out of the left ventricle. The veins are the opposite of arteries, in that they bring blood back into the heart after it circulates through other parts of the body.

Cardiac cycle

As strange as it may sound, the heart has an electrical system as well, which sends cardiac impulses that cause it to beat. This beating is a part of what is called the cardiac cycle, and is divided into two parts. The first part is called systole, which is when the ventricles contract and send blood into the arteries to go to the rest of the body. The second part is called diastole, which is when the ventricles relax and take in blood from the atria. Incredibly, this all happens thousands of times a day, and as long as the cycle goes smoothly, it isn't necessary to give it a second thought.