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OK. Now, we're going to learn uh how the heart is located in situ. So you imagine that this is the right border of the heart. This is the inferior border of the heart and this is the left border of the heart. This is the apex of the heart. Uh Here you have the atrioventricular groove. This is the interventricular groove, the anterior interventricular groove. These two grooves will separate the three chambers that are predominantly seen when you look at the anterior view of the heart of the heart in situ, this is the right atrium, this is the right ventricle. So you can see that the right atrium and the right ventricle is separated by this groove. This is the atrial ventricular groove and the right ventricle is separated from the left, left ventricle by this groove. This is the anterior interventricular groove. Now, uh the right atrial chamber will give off a a pocket. OK, a pocket that will run like this. This is called the right auricle, also called the right atrial appendage. This looks like the PNA that is why it is called the auricle. Uh This is just a pocket, an extension of the right atrial chamber. On the left side, this is the left border of the heart. On the left side. On the upper part, you can see a small another auricle, this is the left auricle or the left atrial appendage. This is the only part of the left atrium that you can see the left atrium is actually behind. So you can see that the anatomical position of the Heart institute is a little bit confusing unlike the Valentine Heart that you might have learned in your lower classes. So I'm drawing a Valentine heart, a much more easier disposition of the chambers uh to help you correlate how these chambers are located in the anatomy. So this is the Valentine heart. And uh you imagine that this, these are the, this is the septum that is going to separate the right side of the heart from the left side of the heart. And this is the septum or the or the separation that is going to separate the atrium from the ventricle. In that case, this will be the right atrium. This will be the right ventricle, this will be the left atrium and this will be the left ventricle. This is a a pretty easy disposition of the heart and usually the uh first diagrams is that we learn in lower classes. So this is the interatrial septum separating the right atrium from the left atrium. This is the interventricular septum separating the right ventricle from the left ventricle and these are the atrial ventricular acceptor or the partition that separates the atrium from the ventricle. This is the right part of that partition and this is the left part of that partition. And you can easily note that there is a cross over here. So I'm going to use hand gestures to help you identify to, to help you imagine how this can be transposed into this form in the human anatomy. This is the cross that you can evidently see. OK. I'm going to show that cross with my hand gestures. Uh This is the right, this is the interatrial septum. This is the interventricular septum. So this is the vertical limb of the cross shown by this hand. This is a horizontal limb which I'm placing like this, that is showing the right component and the left component of the atrial ventricular partition. OK. So you can easily identify this cross with my hand gestures. And in within this space, you have to imagine that this is the right atrium. This is the right ventricle, this is the left atrium and this is the left ventricle. Now, I'm going to shift this Valentine heart into the human anatomical heart by placing this in my body orientation. So you have to follow how the septa and how these chambers are going to be transposed. I'm going to move it like this like this and place it like this. This is how the heart will be oriented in my body. This is the atrioventricular partition and this is the interatrial and the interventricular septum. You can see how this interventricular septum is oriented in my body. So in this case, you can see that the right atrium is over here, this is the right ventricle, this is the left ventricle and here you have the left atrium. So you can imagine that this is the right atrium. This is the right ventricle. This is the left ventricle and this is the left atrium in my body orientation. And this is the interventricular septum and this is the inter atrial septum. OK. So this is the reason why you have right atrium here, right ventricle here, left ventricle forming the apex and the left border and the left atrium, you cannot see the left atrium in this picture because it is behind the only part of the left atrium that you can see from the front view is the small left atrial appendage that tries to peak from the left border, upper part. That is the structure that you are seeing here. That is the only part of the left atrium that you can see. Ok. Now, coming to the great vessels that are entering and leaving from these, this is the right ventricle. OK. Going if you trace this right ventricle at bo you can see the pulmonary trunk going upwards. This is the pulmonary trunk, pulmonary trunk can be, you can trace the right ventricle onto the pulmonary trunk easily. And you can see that the right auricular appendage and the left auricular appendage is somewhat flanking the pulmonary trunk. Over here, you have the ascending arch of ascending part and the arch of the iota, the proximal part of the arch of the iota. So you can see that the right ventricle continues on to the pulmonary trunk, but you can't see the continuation of the left ventricle onto the ascending iota and the arch of theta. So you can imagine this like this right ventricle pumps blood towards the pulmonary trunk. But the left ventricle will pump blood through a stream that runs behind it and goes towards the iota. OK. So this stream is going behind the right ventricle stream like this. So you can see the continuation of RV towards the pulmonary trunk, but not the continuation of LV towards the aorta that you have to understand that it is there is a spatial element inside it. Now, you're seeing the anterior view of the media sternum. This is the right side of the cadaver. This is the left side of the cadaver. Uh This is the fibrous pericardium in the media sterum. Now, if I lift the fibrous pericardium, uh you can see the heart that is located in situ. So now I'm inside the pericardial cavity, ok? This plane is inside the pericardial cavity. Uh This is the right border of the heart, this is the inferior border of the heart and this is the left border of the heart. This corresponds to the cardiac shadow that you see in a conventional chest x-ray, the chambers that you can view here are on the corresponding to the right border. This is the right atrium. You can see how compressible the atrium is. This is the right atrium. This is actually the atrial ventricular groove. OK. So on the right side of this, you have the right atrium. This is the right ventricle. You can see how less compressible. The right ventricle is corresponding to the right atrium. The right atrium is highly compressible. The right ventricle is less compressible and this is the corresponding to the interventricular groove. And onto the left side of that, you have the left ventricle. So this is the left ventricle, the left ventricle is less compressible when you compare it with the right ventricle. So the chambers that you can see here are the right atrium, the right ventricle and the left ventricle and the grooves that you can appreciate here are the atrial ventricular groove and the anterior interventricular groove which separates the right ventricle from the left ventricle. This is the apex of the heart. This is a sternal costal surface or the anterior surface of the heart. This is the right border, this is the left border and this is the inferior border. Ok. Now, you may be wondering where is the left atrium? The left atrium is actually behind the heart. You can't see the left atrium from front unless except this small part that you can see on the left border. The left border is predominantly found by the left ventricle, but the small part is contributed by this small structure. This is the left atrial appendage or the left auricle. Now, you can see that the right ventricle pumps its blood into the pulmonary trunk and you can see how pulmonary trunk is flanked by this auricle. This is the right auricle and this a this is the left auricle. The right auricle is an extension of the right atrial chamber. The left auricle is an extension of the left atrial chamber that is behind, you can't see it from here. Now, the right ventricle, as I mentioned before, the right ventricle pumps its blood into the pulmonary trunk. This is the pulmonary trunk and this is the left ventricle. The left ventricle pumps it blood into this great vessel. This is the aorta. Now, this can be understood by this analogy, the right ventricle pumps it blood into the pulmonary trunk from the left ventricle. You can see the blood will be pumped behind the stream. The stream is the right ventricle stream that from behind the right ventricle stream, the left ventricle will pump blood into the aorta. So that is going behind. That is why you can't see the continuity of the left ventricle into the aorta. Now, the lower part of the aorta is covered by the right auricular appendage. These are all important landmarks by which you can identify different structures. Now, the right atrial chamber, if I go into the pericardium, you can see the right atrial chamber about that, the vein that is draining into the right atrial chamber from above. This is the intrapericardial part of the superior vena cava. You can see how compressible the superior vena cava is compared to the IOTA. Now, if we review this from the chest x-ray perspective, this is the right border of the heart found mainly by the right atrium. The inferior border is mainly by the right ventricle. The anterior surface is by the right ventricle. The apex of the heart is found by the left ventricle. The left border is predominantly found by the left ventricle, contributed by the left atrial appendage and the pulmonary trunk.