[Music] now externally the heart is surrounded by a serus membrane referred to as the pericardium right the pericardium perryi is around cardium refers to heart so the heart is surrounded by these layers of membrane called the pericardium you can see in the picture here this and this in white forms the pericardium if we take a cross-section of the pericardium and wall of the heart and zoom in on that we can see the wall of the heart is composed of different layers so this layer here this is one of the layers of the pericardium and then here is another layer of the pericardium but this layer is is part of right outside of the heart it's attached you know it it follows the Contours right around on the heart we often include this layer of the pericardium as one of the layers of the heart wall itself so one name for this layer here is the epicardium Epi means upon because it's upon the heart it's the outer layer here of a heart wall the middle layer right here is the thickest part of the heart wall this is The myocardium this is mainly occupied by many cardiac muscle cells there we have blood vessels that run through here we have connective tissue as well but The myocardium is called that because this is where where the muscle mayo means muscle the muscle of the heart wall resides it's the thickest layer then the innermost layer of the heart wall is called the endocardium Endo means within the endocardium what's not shown here so besides the pericardium which surrounds the heart and the heart walls itself there's also some really tough strong connective tissue in the heart that forms its own structure that we refer to as the CC skeleton that I will discuss later let's first start with a pericardium so as I mentioned the pericardium is sort of a double layer membrane that surrounds the heart the outermost layer is spaced away from the heart but the the inner layer of the pericardium the second layer is is pressed right up against the heart itself and is often thought of as part of the heart wall so the functions of the pericardium would be to help stabilize the heart to protect it to Anchor it in place so it doesn't Sosh around and to prevent overexpansion when it's filling with blood so it's very tough strong material that and so it performs those types of functions related to its its Anatomy again stabilizing protecting the heart holding it in place and prevent it from over expanding when it fills with blood the pericardium can be thought of like you if you you have a balloon and you take your fist and you shove it in the balloon then this is basically the layout of the pericardium so shoving your fist in in a balloon from the outside from the outside of an inflated balloon part of the balloon going to cling right to the outside of your fist right that's the inner layer of the pericardium and then part and then there's going to be air in the balloon and then there's going to be the outer layer of that balloon latex there that's the outermost layer of the pericardium so we don't say latx or inner outer layers of the pericardium these different layers have their have different names so instead we say that the pericardium is divided up into the fibrous pericardium cus pericardium and the pericardial cavity fibrous pericardium that's the outermost portion the SAS pericardium is then further divided up into parietal and visceral layers so looking at the picture of the Fist and the balloon right here right this outer wall this outer portion of the pericardium that includes both the fibrous pericardium and the parietal layer of the CIS pericardium so this one layer here you have smashed together the fibrous pericardium on the outside and the parietal layer of the cus pericardium uh the next layer in deeper in right but again the fibrous pericardium and parietal layer of the cus pericardium are smashed together pushed together held together as a unit in to form this outer layer and then the visceral layer of the cus pericardium would be like this layer of the balloon that wraps around the fist now instead of being filled with air the actual material that fills in the space between the parietal and visceral layers of the sarus pericardium is called the pericardial cavity and that is filled with a fluid in this picture it's the same idea the heart would be your fist and this white area around the heart right that would be the part of the balloon touching your fist then this part right here right that would be the part of the balloon away from the Fist and then this Gap that you see here would be like the air between the two layers of balloon so if we zoom in on the outer portion here this is what we're looking at right here as I mentioned the outer most portion of the pericardium is composed of the fibrous pericardium and that is continuous and pushed right up against the parietal layer of the cus pericardium right here so it forms one one thick membrane let's say we have the space in here again referred to as the pericardial cavity and then this layer here that wraps directly around the heart would be the visceral layer of the cus pericardium visceral layer is always the layer that wraps directly around the organ and the parietal layer is always the layer that's farther away around the organs that line the body cavity itself let's go back to that picture of the heart wall and pericardium that we looked at earlier again we see here this fibrous layer here the fibrous pericardium incredibly strong all those fibers it's lots of for example collagen which is a very strong type of fiber and connective tissue and then in yellow and that purpley blue color here this would be the parietal layer of the sarus pericardium pericardio cavity which is filled with a fluid and then here we have the visceral pericardium in that same purpley blue color and yellow now the fluid that fills the space here in the pericardial Cav cavity is what is known as pericardial fluid it is a cus fluid which is fairly thin fairly watery and the the overall function of any kind of sarus fluid including the pericardial fluid is to reduce friction it acts as a lubricant since the heart is continuously contracted relaxing continuously beating right we don't want it to wear itself down from the outside by rubbing on the per cardium so that that fluid in the pericardial cavity here helps just reduce fra uh friction as the heart's beating boom boom boom boom boom boom boom boom boom so it doesn't wear itself out you can have disease with the pericardium itself one of the more common types of diseases associated with the pericardium is called pericarditis itis means inflammation so pericarditis is an inflammation of of the pericardium most often the reason that you would get inflammation in the pericardium is because it gets infected so due to infection you get inflammation which is pericarditis inflammation of the pericardium now what happens is the the pericardial cavity that space between the outer and inner layers it's not that big yes there's fluid to reduce friction but there's not that much space between the two layers so if the pericard inflames or swells up from that infection or or whatever is causing the inflammation then the layers rub against each other as the heart beats and it it's it becomes very painful um if you listen to somebody with pericarditis with a stethoscope you can hear sort of a scratching sound as the heart is beating to let you know that the layers are rubbing on each other and scratching each other as the heart is beating another problem we have with pericarditis is that inflammation can also cause the the pericardial fluid to back up all right it doesn't drain properly so the fluid builds up and you get more fluid accumulation and swelling in that pericardial space and it makes it a lot harder for the heart to expand uh and beat normally so it does restrict the movement of the heart so we call this idea cardiac tamponade when pericardial fluid build up in the pericardial cavity and that excess fluid that builds up kind of restricts the heart from moving properly and it doesn't P pump blood properly