 Hey everybody, Dr. O here. In this video we're going to talk about the location of the heart and then briefly talk about the different layers that make up the heart. So there's multiple ways to describe where the heart is. You could say it's in the thoracic cavity, which just tells you it's above the diaphragm. You could say it's in the mediastinum, which is the space between your two lungs. So that's going to have your heart, but also your thymus gland and your great vessels and your trachea and that kind of thing. The most specific location of the heart though is to say that it's in the pericardial cavity. So we'll come back to that in just a moment. But before, when I'm looking at this image here, I also want to remind you that the heart is actually shifted, so the right side of the heart is on the front, the left side of the heart is on the back. That's why you see a lot more of the right ventricle than you do the left ventricle. Same thing with the two atria. That's really important when you're listening, right? So that way you know where to put the stethoscope when you're listening to someone's heart because the heart is not sitting straight on, it's turned a little bit. So the right side is on the front. Another reason it's important to remember where the heart is, is if you're ever doing CPR, you want to make sure you're doing good compressions to help the heart pump, but you want to make sure that you don't damage the xiphoid process. So they always tell you to count up from the xiphoid process prior to doing CPR compressions. And that's because if you were to damage or break that xiphoid process, the tip of the sternum, you could drive it into the liver and that could be fatal. So it's always important to know where structures are if you're going to be pressing on another human being's body. Okay, the layers, let's just start on the outside and work our way in. So first we have the fibrous pericardium. That's going to be the tough fibrous pericardial sac that's in the heart, keeps the heart stabilized and hopefully protected. Then we have the visceral and parietal pericardium. We covered these way back in our first unit together. The parietal pericardium would be the layer that's lining the cavity of the heart is in, the visceral pericardium, which does have a second name, the epicardium. We never used that before, but the epicardium means the same thing as visceral pericardium. That's going to be the lining that's on the heart itself, it's actually part of the outside of the heart wall. So we'll come back to the cavity between those in just a moment. Then we have the myocardium, that's the heart muscle, obviously what we're really here to talk about since the heart is a muscular pump, then the inside of the heart would be lined with an endocardium, basically the same as the endothelium that lines your blood vessels. So remember that between the visceral and parietal pericardium you're going to have the pericardial cavity. It's not near as big as this picture shows it to you, it really barely exists, but just for representation. Inside that cavity is going to be a serious fluid, remember serious fluids are very watery, its job is to reduce friction. So every time your heart beats these two layers slide over each other rather than generating friction and that would be a pretty serious problem. If too much fluid were to get into this cavity that could make it difficult or impossible for the heart to beat, so that would be a serious problem. Okay so that's the basic location of the heart as well as the tissues and layers that surround it. I hope this helps. Have a wonderful day. Be blessed.