 So this is going to be a demonstration of the cardiac chambers. I'm holding the e-viscerate heart in my hand just to bring up to speed This is the right atrium and we can see the opening of the superior vena keva And we can see the opening of the inferior vena keva in this particular cadaver There are not one but two openings of the inferior vena keva I've turned it to show the posterior aspect of the right atrium and this is the left atrium And we can see the opening of the pulmonary vein On the left side and the opening of the pulmonary veins on the right side again in this cadaver Instead of two pulmonary veins on the left side We can see only one opening of the pulmonary vein on the left side. So this is the left atrium There's the right atrium now I'm going to turn to the cart to show where we have split it open If you were to take a look at the exterior surface, you will see a groove Joining the superior vena keva to the inferior vena keva This is the groove which I'm tracing. This is called the sulcus terminalis And corresponding to this groove we have made an incision And now I'm reflecting the right atrium Straight away we can see that right under the sulcus terminalis There is a ridge on the interior surface And that ridge is referred to as the crista terminalis This crista terminalis is a useful landmark It divides the heart interior of the right atrium into an anterior portion and a posterior portion And the anterior portion we can see is muscular and it's got ridges And that portion is referred to as the muscular pectinate eye or the pectinate muscles Deep inside we can see the opening of the right oracle which is here First straight to the crista terminalis we have this smooth portion here This is called the sinus venarium This smooth portion is derived from the sinus venosis And this is the smooth inflow portion of the superior vena keva And the inferior vena keva Wherever there is inflow of blood or outflow of blood The endocardium has to be smooth so as to prevent turbulence So this crista terminalis importantly separates the anterior muscular part from the posterior smooth part At the upper end of the crista terminalis Near the opening of the superior vena keva Where my instrument has gone in in this region Is the location of the sinoatrial node Though it cannot be seen because it is more functional than anatomical Now let's take a look at some other structures We can see the opening of the coronary sinus And my instrument has gone into the opening of the coronary sinus And we can see the tip of the instrument here in the coronary sinus So this is the opening of the coronary sinus This is the opening There may be a few valvular structures, filmy valves Around the opening of the coronary sinus And we can see one of that film here This is known as the thebiscin valve Or the valve of the coronary sinus It is of not much functional use My instrument has gone into yet another opening This is the atrioventricular orifice Communicating the right atrium with the right ventricle And we can see the three valves here The anterior posterior and the septal valve Which constitute the tricuspid valve We'll talk about the details of the valve when we open out the right ventricle Near the opening of the coronary sinus On the interatrial septum There is again atrioventricular node Which we cannot see because it's more of a functional location Now my finger is touching a depression on the right atrium And I'm going to trace the location of the depression here with my instrument This is known as the fossa ovalis This is the remnant of the foramen ovale So on the right atrial side we see the fossa ovalis Which is now covered This marks the location of the foramen ovale And this is the area of atrial septal defect Persistent atrial septal defect So these are the structures that we can see on the interior of the right atrium Now I'm going to turn the heart Show the interior of the left atrium For that we have split open the orifices of the pulmonary veins As I mentioned there was only one left pulmonary vein And there were two right pulmonary veins So we split them open in the form of a Y incision And now we are looking at the interior of the left atrium We notice that the atrium of the left atrium is all smooth Because this marks the entry point of the pulmonary veins So therefore there is no specific landmark to be seen on the interior of the left atrium Except this orifice where my instrument has gone in This is the left atrial ventricular orifice And we can see it is lined by the two valves Which is the mitral valve We'll talk more about the mitral valve when we open the left ventricular I will draw your attention to this place where my finger is located My right index finger here And my left index finger here I am touching the inter atrial septal My left finger is inside the right atrium And my right index finger is inside the left atrium Left atrium is the valve of the fossa ovalis Which is the remnant of the septum prima And the right atrium is the fossa ovalis So this is the location of atrial septal defect Atrial septal defect is a congenital condition Where there is a persistence of the foramine ovale Sometimes we can have a pinhole defect The so called normal atrial septal defect Which does not require any surgery However, if the atrial septal defect is significant Then it requires surgical closure That's all the point which I want to mention pertaining to the interior of the atrial chambers Thank you very much for watching Dr. Sanjo Sanyal signing out David who is the camera person If you have any questions or comments Please put them in the comment section below Have a nice day