Hello, students, in this module we are going to be drawing a so called very difficult diagram of biology. Which is the diagram I am talking about? I am talking about human heart and that too the internal structure of human heart. But you are going to observe within minutes this diagram is not going to be staying difficult for you. In fact you will enjoy drawing this diagram. But before we start with the diagram, students, you must know which side is which one. Now, in biology, if this is a sheet of paper in front you. Now, this is going to be the right side and this is going to be the left side of the diagram. So, let’s start drawing our diagram with first drawing the upper chambers and which are the chambers I am talking about the right atrium, students. So, first draw the right atrium. Similarly, a beautiful curve for the left atrium also. Now, this completes the upper two chambers of the heart. Now, we need to draw the lower chambers of the heart. So similarly, a nice curve for the right ventricle in here and then the left ventricle, students, on the other side. Now, this completes the outline of our heart.

Now observe, students, this is the base of the heart and now here this is the apex of the heart. Apex should be slightly tilted towards the left side. That’s a structurally correct diagram. Now further, students, draw the septum in between the ventricles. This is the inter-ventricular septum, students. After this a beautiful blood vessel arising from right ventricle, which is the pulmonary trunk, students, we are needing to draw. Now, pulmonary trunk, this trunk is dividing into right and the left branch. At this stage you need to draw only the left side of the pulmonary trunk, like this branching it beautifully in here, this is the left pulmonary artery. Now how about the right side, not drawing right now, students, because we need to draw another vessel right now which is the vessel arising from the left ventricle. I am talking about your systemic aorta arching beautifully in here. Three branches you draw in here and then curve it beautifully down here like this. This is your systemic aorta. After this, students, draw the superior vena cava in here and once we have drawn superior vena cava, draw down in here the inferior vena cava here. Now after drawing superior and inferior vena cava, students, now you need to complete the pulmonary trunks right side and observe in here, students, now herein right side of the pulmonary trunk. This is the right pulmonary artery branching beautifully just like the left side. So, this completed the pulmonary trunks both the sides. Now, observe the walls of all the four chambers. You need to draw the walls and how to draw the walls. Make thinner walls of atria as you can see in here. Here the atria have got thin walls, students, compared to the ventricle. Observe the walls of ventricle in here, students, the wall is uneven because of muscular ridges present and there are three papillary muscles also present in here and observe right ventricle wall is thicker than the wall of the right atrium. Now, left ventricles, students, when we need to draw, observe the wall of the left ventricle. It is uneven having two papillary muscles in here. Now, also note, students, when you are drawing the four walls of these four chambers, the thickest wall you will be making of the left ventricle. And I talked about the uneven line, don’t make a smooth line here. Why this uneven line because there are muscular ridges called columnae carnae present in here, also the muscles down here these are the papillary muscles in here, students.

Now, we need to see, we need to draw in each chamber what structure has to be present. Right now starting with the right atrium here, you need to draw the opening of the superior vena cava. Similarly you will be drawing the opening of the inferior vena cava also in here and also, students, in the right atrium you observe a depression down here. Now this depression is called as Fossa Ovalis. Now this was the right atrium structure.

How about the left atrium, in the left atrium, students, you need to draw four openings in here, two on one side and two on the other side. Now, these are the opening of the four pulmonary veins. Now, students, observe another important structure you need to draw. At this stage you will be drawing the valves which are the semi lunar valves. Here you can see this is the semi lunar valve of the pulmonary trunk and another semi lunar valve here of aorta, students. Now, these are the two pocket like valves we call as the semi lunar valves, the half moon shaped valves you need to draw.

After this an important structure we are drawing which is the valve present in between the right atrium and the right ventricle. Now these valves, students, this is known as the tricuspid valve because it is got three flaps present in it. On the other side that means in the left ventricle you can see, say in between the left atrium and the left ventricle, the valve which is present, this valve is the bicuspid valve because there are two flaps present in here. Observe in here, students, this is the bicuspid valve in here. Now, bicuspid valve is attached to the papillary muscles. These are the papillary muscles. By some fibres, now these are the fibres which are present, these fibres are known as chordae tendinae. So, three structures in here, this is the bicuspid valve also called as mitral valve then chordae tendinae, these fibrous structures, and down here you can see the papillary muscles in here.

Now, students, here in we are going to be colouring our heart. You don’t need to colour the heart. You need to just draw the pencil sketch. But let’s see how beautiful our heart looks in here. Now, look at that, pulmonary trunks dividing into pulmonary arteries, that systemic aorta then superior vena cava and the inferior vena cava also observe, students, the walls of all the four chambers, the thickest being the left ventricle wall, the openings of the atria, the bicuspid and the tricuspid valve and the pulmonary veins.

Now, this is the diagram of internal structure of heart, students, and the labelling which are required by you are these labelling only.

So, enjoy drawing the structure of human heart, take care.