The human body is magnificent. It is a single structure but it is made up of billions of smaller structures either cells, tissues, organs, or systems. It works wonders all day long and even when we are asleep without us noticing or worrying about any physiological process or function.

Our stomach digests the food, our lungs exchange gases, our heart pumps blood, and the maestro, the brain, controls all these functions and regulates them. 

There are ten major systems in any human body and they are:

• The skeletal system
• The muscular system.
• The nervous system.
• The endocrine system.
• The cardiovascular system.
• The lymphatic system.
• The respiratory system.
• The digestive system.
• The urinary system.
• The reproductive system.

Each system represents an organization of varying numbers and kinds of organs. Those organs are arranged in a particular way so that together they can perform complex physiological functions of the body. 

 

Body functions are either physiological or psychological. The survival of the body depends on the body's ability to restore the normal state of the internal environment. 

All systems of the human body are necessary for life. 

Let's have a look at the cardiovascular system. Let's talk about all you need to know about the heart.

The human heart is an incredible organ. It serves the whole body and pumps blood to all the body's organs and tissues. It beats around 100,000 times per day, pumping the 5 liters of blood over and over again throughout the body 24/7.

 

How can we define the Heart?

It is a small muscular organ around the size of a closed fist and it lies in the chest slightly to the left.

It delivers oxygen and nutrient-rich blood to various body's tissues and organs and carries away waste products.

The heart also takes the deoxygenated blood and delivers it to the lungs where the blood loads up with oxygen and unloads carbon dioxide and other metabolic waste products.

This circulation, including the heart, blood and blood vessels, is called the cardiovascular system or the circulatory system. 

The mechanism of action of the heart depends on its anatomical structure. Each chamber and each vessel work in a certain way to keep the blood flowing throughout the body.

 

What is the Anatomical structure of the heart? 

The heart consists of four chambers: 

• Two atria. They are the upper two thin-walled chambers that receive the blood from the veins.
• The ventricles. They are the two lower thick-walled chambers that forcefully pump or discharge blood out of the heart.

Each ventricle and atrium are separated from the other ventricle or atrium by a wall of tissue called the septum.

And each atrium is separated from the ventricle by valves.

The differences in thickness in different chambers' walls are mainly due to the different amounts of myocardium in different walls. This is an indication of the different amounts of force each wall or chamber is required to generate to do its function.

That's not everything about the anatomical composition of the heart.

The heart walls themselves consist of three layers of tissue:

• The endocardium. It is the innermost layer. It lines the inside of the heart and protects the various valves and chambers.
• The myocardium. It is the muscular layer of the heart walls. It is thicker in the ventricles.
• The pericardium. It is a thin protective coat that surrounds the heart from the outside.
• The epicardium. It is a part of the pericardium; it is the innermost layer of the pericardium. It is a protective layer that consists mostly of connective tissue.

 

Valves of the Heart

Any pump will need a set of valves to keep the fluid it pumps flowing in one direction and prevent returning back of the fluid. The heart is no exception.

The heart has two types of valves to keep the blood flowing in the correct direction.

The first type of valve is the valve between the atria and the ventricles. They are called the atrioventricular valves or the cuspid valves. 

The right atrioventricular valve is called the tricuspid valve, while the left atrioventricular valve is known as the mitral or bicuspid valve.

On the other hand, the valves at the base of the large vessels getting out of the ventricles, such as the aorta, are called the semilunar valves.

The valve between the pulmonary trunk and the right ventricle is called the pulmonary semilunar valve. As for the valve between the aorta and the left ventricle, it is called the aortic semilunar valve.

So, again, the heart has four valves: 

• Aortic valve. It is between the left ventricle and the aorta. 
• Mitral valve. It is between the left atrium and the left ventricle. 
• Pulmonary valve. It is between the right ventricle and the pulmonary artery. 
• Tricuspid valve. It is between the right atrium and the right ventricle.

As we explained, those valves are very important to keep the blood on its right pathway. When the ventricles contract, the atrioventricular valves close to prevent the flow back of blood into the atria. And when the ventricles relax, the semilunar valves close so that blood doesn't flow back into the ventricles.

This way the blood flows to the tissues and organs to supply them with the essential nutrients and oxygen.

Many people are aware of the sound of the heart.

But the heart makes many types of sounds, and the closing and the opening of the valves are key contributors to the sound of the heartbeat.

 

But if you think for a minute, you will wonder, what about the heart? How does it feed? How does the heart get its oxygen and nutrient requirements?  

The myocardium of the heart is the muscular part that works and contracts all the time, that's why it needs a continuous supply of nutrients and oxygen or else it wouldn't work efficiently. For this reason, the heart has an extensive network of blood vessels to deliver oxygen and nutrients to the working muscle cells and remove waste products.

The ascending aorta sends two branches, the right and left coronary artery, to supply the walls of the myocardium.

After the blood passes through the capillaries of the myocardium, it becomes part of the coronary veins system. Almost all of the cardiac veins drain into the coronary sinus, which drains into the right atrium.

This is all you need to know about the heart's structural anatomy.

 

Now it is time to get to know the Physiology and mechanism of action of the heart.

 

How does the Heart work? 

Let's talk about the two sides of the heart, the left and right sides.

The left and right sides work together in an organized way. The atria and ventricles contract and relax in a certain way taking turns to produce the rhythmic heartbeat.

So, how does that happen? 

The right side of the heart is the side that receives the deoxygenated blood and sends it to the lungs. 

The right atrium receives the deoxygenated blood from the body through the largest veins in the body, the superior and inferior vena cava. 

When the right atrium contracts, the blood is pumped to the right ventricle. Once the right ventricle is full, it contracts to pump the blood to the lungs through the pulmonary artery.

In the lungs, the gas exchange happens, the blood takes up oxygen and offloads carbon dioxide. This is the simple function of the lung we all learned in biology class. While, in fact, it is sort of a complex process. 

When the blood enters the lung through the pulmonary arteries, it passes through tiny capillaries. Those capillaries connect at the surface of the alveoli, the lung’s air sacs.  Oxygen enters the blood while carbon dioxide leaves it through the capillaries of the alveoli. 

After this cycle on the right side, the left side turn comes. The function of the left side is to receive the oxygenated blood coming from the lungs and pump it throughout the whole body. 

When the oxygenated blood returns from the lungs through the pulmonary veins, the left atrium contracts to push the blood to the left ventricle. When the left ventricle is full, it contracts and pushes the blood back to the body through the aorta. 

Most doctors and scientists when they talk about the cardiac cycle, they divide it into two parts, the right-side part and the left side part. But that’s just for an easy explanation. It all happens at the same time. Both atria and ventricle contract at the same time.

In other words, the heart works as two pumps, one on the right and one on the left, working simultaneously. 

We measure those cycles by heartbeats. 

Each heartbeat has two parts: 

• Diastole. In this part of the cycle, the ventricles relax and fill with blood while the atria contract to empty all blood into the ventricles. 
• Systole. In this part, the ventricles contract to pump the blood out of the heart while the atria relax to fill with blood again. 

Those two parts are very important when someone is measuring blood pressure. When you take the blood pressure the machine will give two readings, high and low numbers. The higher number represents systolic blood pressure while the lower number represents diastolic blood pressure. 

The systolic blood pressure indicates the pressure the blood creates against the artery walls during systole. The diastolic blood pressure shows how much pressure is in the arteries during diastole. 

Blood pressure measurement is very important because blood pressure readings are vital data. 

Some readings mean that the patient is currently having an emergency, and other readings mean that the patient is having a certain condition and needs treatment and follow-up.

 

What else is important? Have you ever heard about the Heart Electrical system?

Have you ever been to the emergency room and a doctor asked you to do an electrocardiogram or ECG for short? 

 

What is ECG? 

To understand the concept of ECG, you need to know about the heart's electrical system.

To pump the blood throughout the body, muscles of the heart must work together to pump the blood in the right direction at the right time with the right force. 

To coordinate this activity, there must be electrical impulses that control the action of those muscles.

Electrical signals coming from a specific part in the heart known as the sinoatrial node, or SA node. It is the heart's natural pacemaker. It is located at the top of the right atrium.

Electrical signals begin at the SA node causing the atria to contract to push the blood down to the ventricles.

When the signals reach the area of cells at the bottom of the right atrium, a slight delay occurs.

These cells at the bottom of the right atrium, between the atria and ventricles, are called the atrioventricular node or AV node. They act as a gatekeeper as they coordinate the electric signals so that the atria and ventricles don't contract at the same time.

After that, signals travel through a bundle of fibers that lies within the ventricle walls called Purkinje fibers. Those are specialized fibers that pass the impulses to the heart muscles so that the ventricles contract. 

 

But what about the pulse? It is also one of the important vital data about a heart condition.

It is time to talk about the pulse we feel when the arteries pass close to the skin's surface. 

A person can easily feel their pulse at certain points where the arteries are closest to the skin's surface such as on the wrist or the neck.

The pulse we feel represents the rush of blood as the heart pumps it throughout the body.

When doctors feel the pulse, they count it in a minute because it represents the times the heart beats in one minute.

Pulse rates vary from one person to another. Pulse rate even varies in the same person. It is lower at rest and increases with exercise. 

If you know how to take your pulse, you can easily evaluate your exercise program.

If you are curious and want to know how to measure your pulse, let us tell you briefly how.

First, you have to place the tips of your index, second and third fingers on the palm side of the wrist of the other hand below the base of the thump. Or you can also feel it on the lower neck on either side of the windpipe.

Second, you have to press your fingers lightly until you feel the blood pushing your fingers and pulsating beneath your fingers.

If you don't feel it, you can move your fingers around or slightly up or down until you feel it.

Use a watch with the second hand to count the beats you feel for 10 seconds, then multiply the number by six to get your heart rate per minute.

 

But when you get that number, how can you know it is normal? What is the normal heart rate? 

A healthy pulse is usually from 60-100 beats per minute, and as we explained, what is normal can change from one person to the other. This is called normal or resting heart rate.

The normal heart rates for different age groups are:

• Children (ages 6-15) from 70 to 100 beats per minute.
• Adults (age 18 and above) from 60 to 100 beats per minute.

 

Some people might think that women's heart rates might be different from men's heart rates.

In fact, for most healthy adults, men and women, the resting heart rate ranges from 60 to 100 as we mentioned.

But as for pregnant women, it is a different case.

During pregnancy, the amount of blood the heart pumps, or called the cardiac output, increases by 30% to 50%. As the cardiac output increases, the resting heart rate speeds up from the normal rate of about 70 beats per minute to as high as 90 beats per minute.

Also, during exercises, the cardiac output and heart rate increase more when a woman is pregnant than when she is not.

However, generally, a lower heart rate at rest implies more efficient heart function and better fitness of the cardiovascular system. For example, a well-trained athlete might have a normal resting heart rate close to 40 beats per minute.

Also, a 2010 report from the Women's Health Initiative (WHI) indicated that a resting heart rate at the low end of the spectrum may offer some protection against heart attacks.

But keep in mind that many factors can affect the heart rate, including:

• Age.
• Fitness and activity level.
• Being a smoker.
• Having a cardiovascular disease.
• High cholesterol levels.
• Diabetes.
• Emotions.
• Body size.
• Medications. Some medications such as hypertension and arrhythmia medications can influence the heart rate.
• Air temperature.
• Body position.  Heart rate can change according to body position, standing up or lying down, for example.

But this wide range of heart rates can be tricky because despite this wide range of normal heart rate measures, an abnormally high or low heart rate indicates an underlying problem or health condition.

 

So, when should you consult a doctor about your heart rate?  

If your resting heart rate is consistently above 100 beats per minute, it is called tachycardia, and you should consult your doctor about it, especially if you are not a trained athlete.

Or if your resting heart rate is consistently below 60 beats per minute, it is called bradycardia and you should consult your doctor about it, especially if you have other signs or symptoms such as fainting, dizziness or shortness of breath.

 

You can hear people saying the term "Maximum heart rate" at the gym or health clubs, so what is the maximum heart rate? 

It is the rate at which your heart is beating and working its hardest to meet your body's oxygen needs.

It is the highest achieved heart rate during maximal exercise.

The maximum heart rate plays a major role in the aerobic capacity of a person. Aerobic capacity means the amount of oxygen one can consume.

Several studies have indicated that a high aerobic capacity is associated with a low risk of heart attacks and death.

 

So, how can someone improve their maximum heart rate? 

First, you have to know your maximum heart rate.

One simple method to calculate your predicted maximum heart rate is to use this formula: 

220 - your age = your predicted maximum heart rate.

However, there is a way to know the accurate maximal heart rate. It is most accurately determined by a medically supervised maximal graded exercise test.

So, the best way to both lower your resting heart rate and increase your maximum heart rate and aerobic capacity is vigorous exercise.

And because it is almost impossible to maintain your maximum heart rate for more than a few minutes, doctors recommend setting a percentage of your maximum heart rate as a target as you exercise.

For example, you can set your target rate at 50% of the maximum heart rate and gradually increase the intensity of the workout until reaching 70% to 80%.

This way you can gain the most benefits and reduce the risks.

But if you don't exercise regularly, you should check with your doctor before setting a target heart rate.

Some people will also benefit the most from high-intensity interval training, but this should also be discussed with a healthcare professional.

And as a general rule, always check with your healthcare provider before starting any exercise program so that he or she can find you a target heart rate and a training program that matches your needs.

The heart is an essential and powerful organ, it works day and night constantly to supply the whole body with oxygen and nutrients.

If it stops, one can't survive for long.

So, staying active and regularly exercising is the best way to keep your heart safe and healthy.

A don't forget to maintain a healthy diet to protect your heart from disease, because, as you know, you are what you eat.