Heart Functions an Overview

Heart Functions an Overview

Heart fnctions incessantly throughout our life. The heart is one of the organs in our body that never stops working from the moment we are conceived until we die. In fact, the heart beats at around 100.000 times every day (72 beats per minute on average), pushing approximately 5.000 gallons of blood every time it beats.

What is the heart and its function?

The heart is a muscular organ located in the left side of the chest, which has about the size of a closed fist. It is one of the most important organs in our body because heart functions to pump the blood to all the organs and tissues in order to provide them with oxygen and nutrients, including its own muscles and tissues. In fact, little dysfunctions or abnormalities in the heart can cause severe consequences.

Likewise, when the blood passes through the different tissues, it also takes the carbon dioxide and other wastes to transport them to the lungs and kidneys to be excreted from the organism. Said more specifically, when the heart functions to pump the deoxygenated blood to the lungs, the blood passes through tiny capillaries to get in contact with the surface of the lung’s alveoli (air containing parts). There, the carbon dioxide is removed from the blood to be expelled to the atmosphere through expiration, and the oxygen passes from the alveoli to the blood to be transported to other organs and tissues.

On the other hand, when the blood reaches the kidneys, all the wastes are removed from it and excreted through the urine. The functions of the kidneys are explained in more detail in another article.

What is the anatomy/structure of the heart?

The anatomy of the heart is complex, but all its parts operate together to fulfill its function. It is made up of four chambers, each one of them with different functions, but in general, they are in charge to receive the deoxygenated blood, transport it to the lungs and then receive the oxygenated blood to pump it to the rest of the body. Likewise, the heart is connected to the veins and arteries to carry the blood to all organs and tissues.

Heart anatomy

The four chambers of the heart are divided in two auricles (or atria) and two ventricles. The auricles are the two upper chambers, the right one receives the deoxygenated blood from all the body’s tissues through the cava veins (superior and inferior, they are the largest veins of the body). The left auricle receives the oxygenated blood from the lungs through the pulmonary veins.

The ventricles are the two lower chambers, the right one receives the deoxygenated blood from the right atria and pumps it into the lungs through the pulmonary arteries. The left ventricle receives the oxygenated blood from the left atria and pumps it to the rest of the organs and tissues through the aorta artery. The coronary arteries leave the aorta to carry oxygenated and nourished blood to the structures of the heart itself.

Because the left ventricle makes a greater effort than the other chambers to pump the blood, under normal conditions, the muscles of their walls are thicker and stronger than the muscles of the walls of the right ventricle and atria. At this point, it is very important to say that left chambers (atria and ventricle) are separated from the right chambers (atria and ventricle) by a wall of muscle called septum.

Other important structures in the heart are the valves. In fact, these are the structures in charge of ensuring that blood only flows in one direction inside the heart. Each valve has a name according to the other structures with which it relates. The tricuspid valve is between the right atrium and the right ventricle, the pulmonary valve is between the right ventricle and the pulmonary artery, the mitral valve is between the left atrium and the left ventricle and the aortic valve is between the left ventricle and the aorta artery.

The closure of the tricuspid and mitral valves produces a sound described as “lub” and the closure of the pulmonary and aortic valves produces a sound described as “DUB”, so the closure of the valves is what produces the famous sound “lub-DUB” every time that our hearts beats. When the heart valves do not work properly, blood circulates in more than one direction and murmurs appear.

To protect the muscles in the heart’s walls, the septum and the valves, the heart has three layers of tissue called epicardium, myocardium and endocardium. The epicardium is the outermost layer, it has protective functions, and it is mainly made of connective tissue. The myocardium is the middle layer, composed by the muscles of the heart. The endocardium is the inner layer, it covers the myocardium and lines the chambers, septum and valves of the heart to protect them. Finally, all these layers and heart structures are externally covered by a thin coat that protects them, called pericardium.

How does the heart pump blood?

The heart rate varies from a person to another and, in turn, it can vary throughout the day according to the activities that the person is performing. For example, when a person is at rest, his/her heart can beat about 60 times per minute, but it increases during the exercise to 100 beats per minute, or more. The heart rate expresses how many times the heart gets contracted per minute, but, in every beat, many perfectly synchronized steps occur to properly pump the blood.

When the atria are full of blood, they get contracted, the tricuspid and mitral valves open and the blood passes to the ventricles. This is the beginning of the cardiac cycle. Once the ventricles are full of blood, the tricuspid and mitral valves close and the muscles in the ventricles’ walls begin to contract to generate the force necessary to push the blood to the lungs and the rest of the body respectively. Once these muscles have generated enough force to open the pulmonary and aortic valves, the heart walls contract and the blood is pumped through the pulmonary and the aortic arteries. Finally, the muscles in the ventricles’ walls relax and the cardiac cycle starts again.

Summarizing, the cardiac cycle can be divided in two phases, the diastole and the systole. The diastole refers to the moment when the atria and ventricles relax and fill with blood, while the systole involves the atria contraction, to push the blood into the ventricles, and the ventricles contraction to pump the blood out of the heart once the atria start to relax.

Every time you feel your pulse, it means that a cardiac cycle has been completed.

In conclusion, the heart is an organ with a complex structure in which parts must work very synchronously to properly fulfill itsfunction and pump the blood to the rest of the organs and tissues of our body. Any abnormality in the heart structures and functioning can cause severe damages in other organs and trigger the apparition of many symptoms. Heart health is extremely important to maintain an adequate quality of life.

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Author: Dr.Aurelysmar GrimandecollantesDr.Aurelysmar is 29 years old MD and medical writer. Medical degree from the Universidad Centroccidental "Lisandro Alvarado", Venezuela, 2014. Diploma in Occupational Health and Safety, Venezuela, 2015. Course: Specialized Health Training for Physicians, Spain, 2017.