Heart is a vital organ of our body. If fulfills blood requirement of all the body organs. It keeps beating and pumping blood throughout the life for complete 24 hours. Until heart keeps beating, game of life can be played whereas once heart beat stops, life comes to an end i.e., a person dies. Thus, proper functioning of heart is essential for smooth running of life.

Today man is living in overpopulated areas and in polluted environment. Since he is living in crowded areas, he is neither able to breath pure air nor able to drink pure and clean water. His eating habits are also not very proper. His life has become inactive due to his laziness. Due to scarcity of playing grounds, he rarely performs any physical exercises. All these have exerted harmful effects on his body. But, more harm is caused to his heart. As a result, most of the world's population is suffering from high blood pressure, diabetes, heart diseases and many more such dreadful diseases.

In developed countries, number of heart disease patients have increased. Heart disease is not only affecting individuals of old age in fact number of youngsters suffering from heart diseases have also increased. Thus, it becomes essential that all should be informed regarding heart related disorders, their treatment as well as regarding their prevention.

Heart is a gift of nature to us. We cannot get it back even after spending millions. If it is kept healthy by following all the precautions and if proper care is taken then it will never cheat us and will keep functioning and beating properly, no matter what age an individual reaches. If we become careless towards heart then it is very likely that it will cheat us.

BLOOD:-

Blood is a red colored fluid. Its function is to supply nutrition and oxygen to various tissue system in our body. It carries oxygen from heart to various body organs and in return carries carbon-dioxide and impurities from various body organs to heart. Blood throughout the life keeps circulating in our blood vessels, nerve system and tissues.

Mainly, our blood contains 4 types of cells. They are:-

• Red blood cells,
• White blood cells,
• Plasma and 
• Platelets

Blood looks red in color due to the presence of red blood cells in it. They carry oxygen from one part to another in the body. They contain red pigment which is known as hemoglobin. This pigment is responsible to make our blood look red in color. Iron and protein are its main constituents. Deficiency of hemoglobin in body causes anemia. Blood when passes through lungs, oxygen gets incorporated in red blood cells, which is then supplied throughout the body. Each and every red blood cell remains active for 4 months. After 4 months, it dies and breakdown. These are replaced with new red blood cells. In this way, formation and destruction of red blood cells continue throughout the life.

Number of white blood cells in blood is very less. Its function is to immune body against organisms responsible for causing infections or diseases. For each 700 red blood cells, there is 1 white blood cell.

More than half of the blood contains plasma. It is a thick yellow colored fluid. Proteins, antibodies, fibrinogen, carbohydrate, fat, minerals etc..... are its constituents. Protein helps in building the body. Antibodies makes harmful bacteria and toxins inactive. Fibrinogen is essential to stop bleeding from an wound by formation of clot.

Size of platelets is very small. They play an important role to stop the bleeding from any wound formed.

BLOOD VESSELS:-

Blood vessels are the one which carries blood in the body. They carry pure blood from heart to the various organs of the body. From various organs of the body to the heart they carry impure blood.

There are 5 types of blood vessels. They are:-

• Artery,
• Arterioles,
• Capillary,
• Venule and 
• Vein

Artery is a big pipe like structure which carries blood towards heart. Arterioles which are small in size, branches out from artery. These arterioles further get divided into thin capillaries. These capillaries bend and take the form of venule. These venule join together to from a big vein.

Blood is pumped from right ventricle of the heart to the artery of the lungs. This artery carries blood to the lungs. Oxygen gets incorporated in the blood and carbon dioxide is left out. Left auricle of the heart carries this purified blood to left ventricle. From here, blood reaches aorta. This is the biggest artery of the body. From here, blood reaches various arteries. Nutrition gets incorporated in blood once it travels through small intestine. When traveling through kidneys, waste products are removed from blood. After supplying oxygen and nutrition to various parts of the body, blood through vena cava reaches heart with impurities and carbon-dioxide in it. Vena cava is the biggest vein of the body. Impure blood reaches right auricle of the heart. It gets purified and reaches left ventricle. In this way, cycle of blood circulation continues.

Arteries are made of thick and flexible matter. Through these arteries, excessively shining blood containing excess of oxygen flows. When heart beats, its pressure is seen on the whole of the circulatory system. Walls of blood vessels constricts and dilates. This regulates the amount of blood to be reached in arteries.

Walls of veins are made up of 3 layers. Veins are thinner than arteries. In case of hands and limbs, valves are seen attached to veins. This prevents reverse movement of blood flow and thus it do not get accumulated in any spot. Veins which are thick and dilated are called as varicose veins. These kinds of veins are found in limbs of older individuals who need to walk a lot. Pressure of blood is very less in veins and blood flow is also very slow. This blood contains very less amount of oxygen and thus its color looks a little bluish or light violet.

STRUCTURE OF HEART:-

Heart is a very important organ of our body. It is located on the left side in between lungs. It looks like a folded palm. It weighs approximately 300-400gm. Heart is covered by a layer known as pericardium. Heart constantly constricts and dilates. Through the process of constriction and dilation, it sends blood to various parts of the body through blood vessels.

Heart is divided into 2 parts. One is left and the other is right. A muscle wall separates these two parts. This muscle wall is known as septum. Because of this septum, neither blood from right side can reach left side of the heart nor blood from left side can reach right side of the heart. In this way, both right and left side of the heart acts as separate pumping organs. Thus, we often say that heart does the work of two pumps. Blood from the whole body through vein reaches right side of the heart and from here reaches the lungs. Left side receives blood from lungs and supplies it to the whole body.

Left and right side of the heart is further divided into two parts. Upper part is known as atrium. It receives blood. Lower part is known as ventricle. It pumps blood. In this way, heart consists of two atria and two ventricles.

Atrium has very little work related to pumping of blood. Thus, muscles of atrium are comparatively thinner. Muscles of ventricles are thick and strong because it has to pump blood with lots of pressure. To keep the direction of blood flow accurate, heart consists of two valves on the either side. One valve is located between atrium and ventricle. Tricuspid valve is on right side and mitral valve is on left side. Second valve is located between ventricle and arteries i.e., pulmonary valve on right side and aortic valve on left side.

Blood vessels which carry carbon-dioxide rich blood from various parts of the body to heart are called as veins. This work is done by two veins. One is superior vena cava and the other one is inferior vena cava, These veins from upper and lower parts of the body carries blood to the heart. Blood reaches right atrium of the heart. When right atrium gets filled with blood, it starts constricting. As a result, blood through tricuspid valve flows to right ventricle and from there through pulmonary artery reaches right and left lungs. Blood gets purified in lungs i.e., carbon-dioxide is removed and oxygen gets incorporated in it. Purified blood through pulmonary veins reaches left atrium.

Blood reaches to left ventricle through mitral valve on constriction of left atrium. When left ventricle constricts, blood reaches aorta and through its branches reaches to various parts of the body. This blood circulation continues throughout the life.

Since heart is a very important muscle, it too requires blood to carry out various functions. Muscles of heart is called as myocardium. Upper layer of muscular heart is known as epicardium and an inner layer is known as endocardium. Heart receives its blood supply through two coronary arteries. Both of them are attached with the lower part of aorta. Left coronary artery is divided into cirumflex anterior artery and left anterior descending artery. All three arteries get divided into small arteries throughout the outer portion of the heart. These arteries are responsible to supply blood to the heart and keep it healthy.

Serious heart disorder is formed when any of these arteries get obstructed. Blood of whole heart accumulates through cardium veins. All these arteries join a big artery which is known as coronary sinus. It opens in right side of the heart.

FUNCTIONS OF HEART:-

Heart is a pumping organ. It pumps pure blood received from lungs to each and every part of the body and impure blood received from body to lungs. These functions are carried out by heart without stopping even for a second throughout the life. Actually, right side of the heart sends impure blood to both the lungs for purification and left side of the heart sends pure blood received from lungs to the entire body. In this way, heart throughout the life continues blood circulation.

Apart from this, function of the heart is to regulate the pumping time along with the pace at which pumping is to be done. It also helps to keep synchronization between various parts of the heart. This synchronization is responsible for proper constriction and dilation of muscles of the heart. Each heart beat in the heart originates through sino atrial node in the right atrium near the superior vena cava. Constriction of muscles of the heart is done by two types of nerves. They are sympathetic nerves and para sympathetic nerves.

Blood flow through heart occurs in the form of constant waves. This can be detected in nerves. When heart constricts, aortic valve and pulmonary valve opens up and blood reaches arteries. At this time, mitral valve and tricuspid valve closes so that blood reached in arteries do not end up in atrium. During the process of constriction, pressure of blood in arteries is maximum. This is known as systolic pressure. During the process of dilation, aortic valve and pulmonary valve closes. At this time, pressure of blood is minimum. This process is known as diastol and the pressure is known as diastolic pressure. In this process, mitral valve and tricuspid valve open up.

Normally, heart of a healthy individual in young age beats for 70 times in 1 minute. In each beat, heart pumps 70 ml of blood. In this way, in 70 heart beats, heart pumps 5 liter of blood. Heart beat increases during exercise. With the increase in heart beat, amount of blood pumped also increases. In our body, total amount of blood present is 5-6 liter. If we calculate it for complete 24 hours, then our heart pumps 8000-10000 liter blood. Blood vessels whose function is to carry blood, if their length is measured then it comes to  approximately 1 lakh kilometer.

ELECTRIC DEVICE OF HEART:-

Heart is a self running device which beats on its own. It is not controlled by brain. Sometimes, signs are received to change pace of the heart. These signs can be identified in case of certain nerves and chemicals present in blood.

Pacemaker regulates constant and regular beating of the heart. Pacemaker is located between two atria. It is present amidst small group of muscles which sends regular electric signals. These signals constrict atrium. When they reach ventricle, it too constricts. Atrium always constrict before ventricle. Heart beat remains under control in certain definite circumstances. Constriction taking place is known as systole and the rest phase is known as diastole. Throughout the life, the activity of systole and diastole is carried out. In case of healthy individual, normally heart beats for 70 times in a minute. All these depend on electric signals present in heart. Through E.C.G. of heart, irregularities in these electric signals can be diagnosed. Irregularities in heart beats can be corrected by placing artificial pacemaker.