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Students, we learnt that blood is a fluid connective tissue. And we also saw that a pumping organ is needed to push the blood across the body. And this pumping organ is nothing but the most important organ of the body which is the heart. Now heart is the involuntary pump, which means it functions without our will. Yes my dear students, heart is an organ of our body which works 365 days a year, 24 hours a day, it keeps on beating.

Now let us study about the human heart. The human heart is a muscular organ. That means it is completely made up of muscles. The size of the heart is that of the human fist approximately. Since heart is a very important organ, it requires protection. So students, our heart is covered by a covering which is called as a Pericardial Membrane. Now what do we mean by the word pericardial membrane? Let us see. The word peri means outer, the word membrane means covering, and the word cardial refers to heart. So it is the outer covering of the heart. As you can see the heart is protected by the Pericardial Membrane. Now the weight of the human heart is approximately 360 grams.

Now let’s go about to study the internal structure of the heart. Internally the heart is divided into a right side and a left side. And in all there are four chambers inside the heart. As you can see, there are four compartments in the heart which are called as the chambers of the heart. Now there are two upper chambers and two lower chambers. The upper chambers of the heart are called as Atria and in singular it is called as Atrium. Plural is Atria. And the lower chambers of the heart are called as Ventricles. Singular Ventricle. So students you can see the Atria which are the upper chambers, and the Ventricles which are the lower chambers. And our heart is divided into right side and left side. So in all these are the four chambers of the heart, the right Atrium, the right Ventricle, the left Atrium and the left Ventricle. Now students between the Atria and Ventricles of both the right and left hand side there is an opening. As you can see in the diagram there is an opening between the Atria and the Ventricles. And this opening is guarded by a structure which is called as a valve. You can see in the diagram valve present between the Atria and the Ventricles. Now what is the function of this valve? These valves they prevent the back flow of blood. Which means they allow the blood to flow only in one direction, that is from the Atria to the Ventricles. The blood cannot flow back from the Ventricles to the Atria.

Now one very important thing to note is, the right side of the heart always at any given point of time deals with deoxygenated blood, that is impure blood. And the left side of the heart always deals with oxygenated blood that is pure blood. Now going further this is the right Atrium. A big vein of the body enters the right Atrium from the upper part of the body. As you can see, a big vein entering the right Atrium from the upper part. This big vein is called as the Superior Vena Cava. Superior because it comes from the upper part of the body. Similarly a big vein enters the right Atrium from the lower part of the body. As you can see in the diagram, and this vein which enters from the lower part of the body is called as the Inferior Vena Cava.

Now moving to the right Ventricle, you can see in the diagram an artery leaves the right ventricle, and after coming out it divides into two branches. One branch enters the right lung and the other branch enters the left lung. Now this artery which leaves from the right Ventricle is called as the Pulmonary Artery. Pulmonary because it enters the lungs.

Now moving on to the left side, this is the left Atrium. Four veins enter the left Atrium. As you can see four veins entering the left Atrium, two from the right lung and two from the left lung. Now these four veins are called as the Pulmonary Veins. And this is the Left Ventricle. The largest artery of the body leaves from the Left Ventricle. You can see this large artery coming out from the Left Ventricle and this artery is called as the Aorta.