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The Human Heart Explained So That Even A 5 Year Old Can Understand
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Galen’s Controversial Studies

Greco-Roman Physician Galen has been mentioned by Science Sensei in the past in both positive and negative ways. While it is true that Galen did discover a lot of useful things that are still true in medical science today, some of it was later disproven. It is likely down to the fact that Galen never once dissected a human being. Instead, he only dissected animals.

Therefore, when it came to the human heart or other organs, it was clear he did not know how they worked. That was likely due to the fact that getting a body to open up and dissect during his time was not as easy as one would want. It was also looked down upon. In some places, it was even illegal to open one up after a person’s death.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Galen Might Be Controversial, But He Wasn’t Completely Wrong

However, in spite of the controversy surrounding Galen, he did discover one very important thing. Regarding the human heart, he was able to discover that arteries carried blood. He managed to discover this while operating as a surgeon for Roman Gladiators. In this area, he was surely able to come across several men who were heavily injured.

It’s unsurprising you’ll find out more information about the human body when operating on, well, humans. Seeing as Galen mostly dissected animals, and opening up dead bodies was still taboo in his time, injured gladiators were the perfect test subjects. They’d have wide open, exposed areas to examine for Galen. Allowing him to figure out the key point on arteries.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Andreas Vesalius Spiked On Everybody

Unlike Galen who never dissected a human to know how the heart worked, Andreas Vesalius actually did. He was a fan of Galen’s originally, but when he discovered the many errors he made…Andreas spent the rest of his life trying to correct the wrongs. His impact on the study of our hearts is massive.

Outside of possibly Hippocrates, no one discovered more than Vesalius about our bodies. Yet no one discovered more about the heart than him. His work mostly revolved around the Hippocratic theories on the heart, as well as those that Hippocrates proved during his time.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Andreas Vesalius Pushed Against Hippocrates, And He Was Right

Vesalius did make the discovery that went against Hippocrates a bit. Although he respected him as a physician, especially given his time, a lot of the theories Hippocrates had were pretty spot on. Others, however, were not. Regarding the heart being labeled as a muscle, Vesalius believed the criteria for muscles were that they needed to be voluntarily moved.

If this is true, then the heart working involuntarily meant it could not be a true muscle. Today, we’ve reclassified the muscular system into 3 parts including cardiac muscles. In addition to Hippocratic principles, Andreas also went against religious beliefs that claimed the human heart was the center of our soul. He never drew a specific conclusion on this to avoid religious backlash. This was something Hippocrates himself also avoided.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Vesalius’ Full Heart-Related Discoveries

Andreas was the first to identify two chambers and two atria. He found that the right atrium was a continuation of the inferior and superior venae cavae. Meanwhile, the left atrium is a continuation of the pulmonary vein. He destroyed Galen’s theory regarding a hole being in the septum or heart. Perhaps his greatest discoveries in the world of medicine involve the vascular and circulatory systems.

A fellow physician named Michael Servetus disproved Galen’s theory on a porous intraventricular septum but it never reached the major public due to where it was published. First in the Manuscript of Paris and next in the Christianismi Restitutio. The latter of which was declared a heresy by The Inquisition with the Catholic Church of the time.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Vesalius Proved Servetus and Estienne Right

Vesalius found one of only three remaining copies, then published Servetus’s findings along with his own. He proved the septum is waterproof, then discovered and named the mitral valve while explaining blow flow. He then proved Charles Estienne’s findings on the valves of the hepatic veins.

Vesalius added information on the Azygos Vein, then discovered the canal that connects to a fetus between the Umbilical Vein and Vena Cava. All of this is considered factual to this day and is taught to medical students all over the world. Without Andreas, we would have believed old thoughts for perhaps hundreds of more years.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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What Does The Heart Actually Do?

Essentially, your heart is a muscular organ that is critical to the function of your body due to doing several different jobs. First, it pumps blood through our blood vessels that are part of our circulatory system. This same blood carries oxygen as well as nutrients to areas throughout our body. It manages to do all of this while carrying metabolic waste such as carbon dioxide to the lungs.

We then, of course, blow the CO2 out as we breathe. The number of things our blood has to do in our bodies alone can be intense. This is why when the heart does not operate or work well, our entire body feels it. We need it to pump blood properly just to remain conscious alone! It was not hard for people to figure out that our heart was critical to our bodies. This is why we’ve always tried to protect it for thousands of years.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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The Heartbeat and Pulse

In humans, most believe the first instance of life happens with a person’s heartbeat showing up. This is what you often see in an unborn child when soon-to-be mothers go to check up on the health of their child. Our heartbeat is often heard at the spot of our heart but people can actually feel this elsewhere too.

When your “pulse” is taken at the doctor’s office, hospital, or by the EMT, they might check it in several ways. What they are looking for is your heart rate, which is basically the number of times your heart is beating per minute. A pulse can be taken in several ways. On the neck, the wrist, or simply the heart itself among other places. There are also machines that can take this automatically.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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There Are A Lot Of Things That Affect Our Heartbeat/Pulse

While your doctor will likely tell you that you need to be around a specific number for your heartbeat/pulse, these are only the recommended numbers. That is because we’ve judged how normal people happen to be, and make numbers to fit this accordingly. That is often why the acceptable numbers in this territory can be wide-open. However, a lot of things can affect these numbers.

The average heart rate or pulse will differ from person to person. It is determined by your sex, age, medication you’re taking, or if you have any conditions such as ADHD. Newborns, in fact, have the fastest heartbeats of any human being. The average heart should beat up to roughly 100,000 times in a 24-hour period. Knowing your heartbeat and the rate at which it beats can be a huge asset to your overall health.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Parts Of The Human Heart

We will be breaking this down into specific sections for you as there are quite a lot of parts to the heart. Each also does something highly important for your body. Since your heart is part of the circulatory system, the job it does cannot be understated. You need it to live for a reason.

We’ll explain the sections of the heart, what these areas do, and why they are key for your body to operate normally. Keep in mind that our heart helps our blood flow properly throughout the body. Anytime a part of the heart does not operate as it should…you could experience sometimes severe problems.

Your heart is made up of specific Arteries, Veins, Chambers, Valves, Heart Walls, and Nerves. These sections are quite vast with some having more to do than others. Of course, the size as well as what each side of the heart happens to do is important as well. Let’s examine all of that now!

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Size

The size of the human heart can differ somewhat. Most hearts grow along with the person as they age. Hearts range around 5 inches (12 cm) in length, 3.5 inches (8 cm) wide, and 2.5 inches (6 cm) in thickness. Male and Female hearts weigh a bit differently. Male hearts range from 10 to 12 ounces (280-340 grams) while Female hearts range from 8 to 10 ounces (230-280 grams)

While some sizes can be problematic and be a sign of sickness, this is not always the case. In fact, many athletes have bigger hearts. Since our hearts often work like muscles, a well-trained athlete can have a larger heart than average due to the amount of exercise they get. Like a skeletal muscle, the heart will get a bit larger the more exercise a person puts it through. Yet you do not want it to get too large, which is why you might hear about being healthy enough for specific activities.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Shape and Location

The shape was described as “like a pyramid” by Hippocrates but it’s often described as a Cone shape today. They aren’t too different clearly. Therefore no, the shape of our actual heart is not “heart-shaped,” funny enough. The location of our heart is toward the middle of our chest and lies behind the sternum and ribcage.

However, the lower tip of the heart is toward the left side of the sternum between our 4th and 5th ribs. This is likely why so many assume it’s located on the left side when it’s not. For years, we assumed the left side made the most sense. Yet there is no real reason for this except for how nerves made us feel it was toward the left. Therefore, when you pledge allegiance to the flag, your hand should go over the middle of your chest, not the far left.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Chambers

Our heart has four total chambers. They are comprised of two upper chambers and two lower chambers, with the upper and lower doing different things. The upper chambers, known as the right and left atria, receive incoming blood from the body. Yet the lower chambers, known as the right and left ventricles, pump out blood from the heart to the body.

Our valves then serve as gatekeepers that allow proper flow with our blood and keep it going in the right direction. This is essential because if the valves did not do this our bodies could literally shut down. That is why, when even one does not operate correctly, surgery is required to fix it.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Valves

There are also four valves too, one for every chamber. These are comprised of the Mitral Valve, Tricuspid Valve, Aortic Valve, and Pulmonic Valve. The Mitral and Tricuspid valves are located between the upper chambers while the Aortic and Pulmomic Valves are located between the lower chambers.

Perhaps something you may not know here is that the sound of our heartbeat is produced by the opening and closing of our heart valves. This can be quite weird and partly, even kind of trippy to the heart. One would assume the beat of the heart comes from other factors. Yet this is why doctors check your heartbeat when you go in to be seen. Valve issues result in several heart-related illnesses, and that means hearing your heartbeat can be critical for doctors to know how to help you.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Walls and Layers

While most naturally assume there is only one heart wall, there are actually three total heart walls. They come together to help form a thick heart that protects itself from possible damage. The external layer of the heart wall is called the Epicardium while the middle layer is known as the Myocardium. Finally, the inner layer is called the Endocardium. The Epicardium is thin and transparent, made from delicate connective tissue. The Myocardium is made of cardiac muscle tissue and tends to make up the majority of our overall cardiac wall. It’s also responsible for its own pumping action.

Meanwhile, the Endocardium is made of a thin layer of endothelium that overlies another thin layer of connective tissue. This provides a smooth overall lining for the four chambers of the heart, while also covering all four heart valves too. The Endocardium is also connected to and is continuous with the endothelial lining of the large blood vessels that are attached to the heart itself.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Arteries Of The Human Heart Part 1

The arteries of the human heart are as follows: The aorta, pulmonary trunk, right and left pulmonary arteries, right coronary artery, and the left main coronary artery. The aorta is located near the top section of the heart and happens to be the heart’s main artery. It supplies oxygenated blood to our circulatory system.

When blood leaves the aortic valve, it travels through the aorta itself where it then exits our brain, muscles, and cells. Whenever you see “pulmonary” it tends to mean something related to the lungs. That is exactly what the pulmonary trunk, as well as the right and left pulmonary arteries, affect.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Arteries Of The Human Heart Part 2

The pulmonary trunk is located usually near the top right of the heart and then splits off into the right and left pulmonary arteries. The left is a bit smaller than the right but it does just as well as its “right” neighbor. They both pretty much do as you’d imagine, carry blood to the lung the name suggests.

The right coronary artery and left main coronary artery each feed blood into their designed sections of the heart itself. The left is pumping to the left side and the right is pumping to the right. They both come out of the aortic valve with the left coming out of the left cusp of this valve and the right coming from the right cusp of the same valve.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Veins Of The Human Heart Part 1

The veins of the human heart are as follows: Superior Vena Cava, Inferior Vena Cava, right and left pulmonary veins, Great Cardiac Vein, Middle Cardiac Vein, Small Cardiac Vein, and Anterior Cardiac Veins. The Vena Cava veins are pretty straightforward. The Superior returns deoxygenated blood from the systematic circulation to our right atrium.

It receives a venomous return from the upper half of the body. Meanwhile, this happens at the lower end regarding the Inferior. The Inferior also takes blood to the right atrium but it comes from the middle and lower parts of the body. Both of the Vena Cava are crucial to the function of our hearts.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Veins of The Heart Part 2

Of course, our Pulmonary Veins are similar to Pulmonary arteries. The right and left veins essentially make up four veins, with two flowing to each lung. They drain into the heart’s left atrium and are part of our pulmonary circulation. The Great, Middle and Small Cardiac Veins return deoxygenated blood from the myocardium to the right atrium.

This same blood flows back to the lungs for reoxygenation and removal of carbon dioxide. All end at the Coronary Sinus too. The Anterior Cardiac Veins mostly are comprised of between two and five small vessels that collect blood from the right ventricle and open into the right atrium. Yet it does not end at the Coronary Sinus but rather drains into the anterior wall of the right atrium.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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The Human Heart Nerves and Sinus Node Part 1

There are technically only two main nerves in the human heart. They are known as the Accelerans Nerve and Vagus Nerve. Each is pretty important and likely does a lot more than you might think. Each nerve is affected by the nervous system, of course. Yet the heartbeat we have is set up by something known as a sinus node.

This node is made up of a group of cells located in the wall of the right atrium. They have the ability to randomly produce electrical impulses that travel through the heart via its electrical conduction system. Ultimately, that causes our heart to contract. When a sinus node is not in play for someone, a pacemaker does the job for them.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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The Human Heart Nerves and Sinus Node Part 2

When it comes to nerves, they are also affected by hormones in the blood and the amount of blood being returned to the heart. The Vagus Nerve is what slows down our heart rate, as it uses acetylcholine to accomplish this. Meanwhile, the Accerlans Nerve speeds it up by using noradrenaline.

This actually increases blood flow helping a person prepare for an increase in possible activity. These nerves are also part of the autonomic nervous system, which is part of the infamous “Fight or Flight” System. Medical professionals even have both Acetylcholine and Noradereline on hand to help in needed situations.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Interesting and Surprising Heart Facts

One thing we always like to do when explaining an organ, especially one such as the heart, is to mention some compelling information you may not know. For example, did you know that the human heart pumps 2,000 gallons of blood per day on average? You may also not know that a woman’s heart beats faster than a man’s on average.

Men and women are both capable of having heart trouble yet men are more likely to have heart attacks than women. Yet women are more than 40% of all heart attack deaths annually, meaning heart attacks affect them far worse. Women are also older than men are when they get heart attacks, which could also be a key reason for the higher fatality rate.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Differences In Men and Women Part 1

A woman’s heart tends to be smaller than a man’s. The walls that divide some of the chambers of the heart are thinner for women versus men too. While a woman’s heart pumps faster than a man’s, it also ejects around 10% less blood with each squeeze of the heart. This can, sometimes, affect a woman’s cardio versus a man’s. However, as mentioned previously, a woman who exercises her heart can make it larger.

Theoretically, this can even her up with a regular man’s heart size. You already know that men might be more likely to get a heart attack while women die more from them. However, did you know the way in which each sex has a heart attack differs? Men often will have chest pain as well as pain radiating down the left arm. Meanwhile, women might get shortness of breath but could also have pain in the back, neck, or jaw accompanied by major fatigue or tiredness.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Heart Differences In Men and Women Part 2

Why are men more likely to have a heart attack or high blood pressure? This could be due to how stress impacts men differently. When a woman is stressed, her pulse rate will rise while her heart pumps more blood. Yet when a man gets stressed, the arteries of the man’s heart constrict, raising his blood pressure.

Due to societal pressures as well as those men put on themselves, stress is an issue among men worldwide. Therefore, high blood pressure is also higher among men too. This makes sense in theory. Of course, untreated long-term high blood pressure can lead to heart attacks. More and more women are also seeing heart problems directly related to stress. Yet due to most women being able to handle stress in a slightly healthier way heart-wise, heart attacks from stress are not as common.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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How The Heart Became Associated With Love Part 1

For a, seemingly, endless period of time, we have connected the heart with love. However, there is no reason for this as we proved centuries ago that consciousness and emotions were all brain-driven. Ancient Egyptians, Chinese, and Romans all believed the heart and love had some connection.

In fact, the Romans believed that a vein of the heart extended to the fourth finger on a person’s left hand. This is, of course, not actually the case. However, that is why when a person gets engaged or married, it is now a tradition to put the ring on a person’s left hand, on the fourth finger.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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How The Heart Became Associated With Love Part 2

Some believe love became connected to the heart due to how we react to someone we find attractive. When this happens, our brain releases hormones. This sends a message to our blood and heart that can cause hormones to be released from the autonomic nervous system. That is why men, for example, might get an erect penis.

At the same time, both men and women might experience faster heartbeats due to the noradrenaline released. It’s easy to see how, knowing this, ancient people believe there was a connection. While people did eventually realize the differences between the heart and brain, we continue to associate our hearts with the emotion of love. Sometimes, old habits die hard, or they don’t die at all.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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You Really Can Have A Broken Heart and Die From It

While some believe that there is no such thing as a broken heart, the facts say otherwise. You can actually have a broken heart, but it’s technically not the cartoonish break. There aren’t any arrows in it either, cupid fans. We have already established in the past that there are connections between the brain and the heart.

However, this is a pretty big deal because it means that things like depression can affect your heart too. Doctors refer to this as “Broken Heart Syndrome.” Yet it’s also called Stress-Induced Cardiomyopathy. It can affect anyone, even those with a completely or relatively healthy heart, as well as those young and old.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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How Broken Heart Syndrome Affects Us

As one of the names suggests, it is typically triggered by stress. This is due to a sudden increase in stress hormones that put a lot of harmful pressure on the heart. Women are more likely than men to experience Broken Heart Syndrome but men CAN still experience it. The Syndrome typically causes horrific chest pain and often gets mistaken for a heart attack.

This is due to symptoms being incredibly similar, of course. However, there are thankfully no blocked arteries with Broken Heart Syndrome. That means most people tend to survive this and recover in a few weeks. In others, it can be deadly as it can cause sudden and severe heart muscle failure. Therefore, when your friend says they have a broken heart, take it seriously.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Ways You Can Protect Your Heart Part 1

If you want to properly protect your heart so that you can live for many years to come, there are a few ways that can be accomplished. First, you should be sure to get proper sleep. In fact, prolonged lack of sleep has been known to cause irregular jumps in a person’s heartbeats. This is known as Premature Ventricular Contraction and it can be a big problem.

When they say laughter is the best medicine, it’s technically not a lie. It’s also a great preventative too. Laughter has been known to reduce stress and even boost your immune system. Therefore, when you feel down, avoid sad music. Instead, watch a comedy movie or stand-up special. Your heart will thank you later.

The Human Heart Explained So That Even A 5 Year Old Can Understand
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Ways To Protect Your Heart Part 2

Be sure to eat as healthy as you can and go each year to proper check-ups from your doctor to make sure everything is working as it should. Do your best to stay away from hardcore drugs as well as recreational drugs, even those such as cannabis. When you use marijuana, it puts stress on your heart.

It can cause some issues with the heart such as increased blood pressure, arrhythmias, and even put you at greater risk of heart attack and stroke. Clearly, hardcore drugs like cocaine, meth, and more are obviously bad for you too. While cannabis is nowhere near as bad as those, it still can be bad for your heart. Therefore, it’s best to avoid it if you have any heart condition. Also, things like exercise can be incredibly helpful for your heart long-term!