so we're moving on to the cardiovascular system and cardiovascular literally means the heart lead vessel system so whether or not you want to throw blood in there it kind of varies at least if you look from textbook to textbook but I just mainly think about the heart in the vessels thinking of the heart we usually call the heart of pump but really it operates as two pumps which we'll talk about in the next section the heart also separates the oxygen-rich from the oxygen poor blood and not all hearts in when you look across the animal kingdom not all hearts do that so we call our heart a closed circulatory system and it's pretty efficient the heart also creates blood pressure by just pumping its very nature it's putting pressure against the blood vessel walls and it can secrete its own hormone to help regulate that you learn more about that in Physiology here's a short video clip looking at a heart surgery open-heart surgery and you can read the YouTube comments this person just said hey Doc can you go ahead and take my phone and give me a little video clip on here got me opened up and the doc was like yeah no problemo shockingly yep great thank you so just a fun little intro some background on the heart and the cardiovascular system let's kind of take a more superficial to deep approach we'll look at where the heart is located the things that cover the heart and then we'll look at the anatomy of the heart wall so heart location is in the thoracic cavity but more specifically in the mediastinal remember this means a middle space so there's this region in the thoracic cavity roughly here where you have not just the heart but what we call the great vessels the superior inferior vena cava a Horta the trachea behind the trach is the esophagus so there's a lot of important mostly tubes in this middle space of your thoracic cavity called the mediastinal and the heart we know is not shaped like this it's actually maybe a little bit more like this and as the heart sits in the chest it's oriented obliquely so if you take that shape and then put it at a diagonal going down like this that's roughly how the hearts it's it's a little bit off-center right so if the heart was right in the middle it might be like this but it's a little bit off to the left side of the body it lies on its right side it's a little bit tricky to show in an image but if this is your heart we're saying that it's a little bit oblique a little bit to the left and kind of rolled you know it's ruled on that axis the heart sits on the diaphragm and it sits inside the cardiac notch of the left lung you can't make that out too well in this image but here you can see for sure this left lung has this big space right here cardiac notch where the heart sits so the next thing we'll talk about is the coverings of the heart and if you haven't seen this or if it's been a while in this video talking about serous membranes the main serous membrane I discuss is the pericardium so this will be a good review hey class let's talk about [Music] hey class let's talk about membranes there are four types in your body the cutaneous membrane is just the skin mucous membranes line lots of places where your body opens up to the environment synovial membranes are in some of your joints but I want to talk about saris membranes saris means watery so these are watery membranes but what do we mean by that well look at this ball imagine that this is a membrane of some sort let's say it's the pericardial sac the pericardium that the heart sits in if my fist was like the heart this delicate organ that's moving around a lot it needs a special protective layer maybe something very cushiony very slippery and sliding like a serous membrane so if this is my heart the pericardium is a serous membrane around the heart and it's double layered do you see how you can't quite see my fist anymore it's hidden inside the serous membrane which has two layers this is an outer layer but there's also some of the pink is touching my fist touching the heart that's the inner layer and these have different names in anatomy this outer layer is the parietal layer of the serous membrane parietal means wall you know these bones on your skull on the walls of your skull parietal bones ah means wall so the outer layers the parietal layer the inner or inner layer touching the organ touching the fist is the visceral layer and viscera are your organs so this is a serous membrane it has a parietal layer and a serous layer if tax organs like the heart the lungs and some digestive organs that move around a lot they need cushioning so that they're protected but they also need to be able to have some room to kind of squeeze and smush around to beat to get big and small as you breathe in and out or for your stomach let's say to churn up food inside this balloon right now is air but in your body there's a fluid inside these serous membranes called serous fluid there's a watery fluid again is to protect provide extra cushioning and just a nice friction free environment for some of your organs to move around a lot and those are saris membranes Wow thanks dr. H great job the other thing I want to mention before we move on from that is that that video clip was about serous membranes in general so now that we know for sure we're talking about the heart we're talking about the pericardium we can replace some of that generalised terminology with specific terminology meaning that serous membranes have a Sarris cavity but we could call it the pericardial cavity to be more specific and inside that cavity is fluid Sara's fluid but we can call it pericardial fluid to be more specific it's still the same thing we're just using precise terminology now if we look here we can see you know this is just a basic image version of the video that we just went through but looking at this slide there are references to a fibrous pericardium in a Sara's pericardium and in fact the other thing we'll talk about in this section is the heart wall and I really want to tackle those one at a time although there ends up being some overlap in between but I promise you it will make more sense if we think about these separate and then kind of combine all this information so let's talk about the fibrous pericardium this separate than the serous pericardium fibrous pericardium is very thick dense connective tissue it's going to protect for sure but a big role is anchoring anchoring the heart to the thoracic wall and because it's fairly tough it can prevent overfilling and it's not reducing friction so much that's the job of the serous pericardium all right so this outer layer is mostly really strong and protective and it can anchor the heart in place let's look at that on this slide here so there's a lot going on in this section right I don't want to get into all of it right now I just want to say where's the fibrous pericardium right there so it's the most superficial layer I can see where it's anchoring the heart to the thoracic wall that's the fibrous pericardium great if we go back the next thing we want to discuss is the serous pericardium and we just watch the video gave us a good recap about the serous pericardium its structure double layered memory and its function primarily we're talking about some protection but primarily a reducing friction to give it a nice friction-free environment for the heart to be so if we go ahead there's the fibrous pericardium but I want to see ah here is the serous pericardium got a parietal layer and a visceral layer with a pericardial cavity in between that would be full of pericardial fluid great the vestal leaves the heart wall the heart wall is made of these three layers of tissue epicardium meaning on top of the heart our most superficial layer myocardium referring to the muscular layer cardiac muscle tissue it's arranged in these bundles that kind of like squeeze or milk the heart and the endocardium the endocardium the most within inside heart wall layer and that's just simple squamous epithelium super thin super slippery lines the inside of the heart and the inside of blood vessels so if we go back to our very complex diagram here we want to jump ahead and find the heart wall there's three layers 1 2 3 we have the epicardium myocardium and the endocardium but what you may have noticed is that this number one looks an awful lot like the visceral layer of the serous pericardium because it is just as this Lea reads here it says the visceral layer of the serous pericardium and in parentheses at the car diem it's the same thing so work through that a few times think it over come back to this diagram a few times and see if you can name all these layers name their functions or what type of tissue they're made out of things like that but the other way you might want to think about this is like this if you were the heart surgeon in that video at the opening video you needed to cut through the pericardial sac to make that video where we could see the heart beating so you want to put your scalpel down through here all the way into the pericardial cavity out would leak the pericardial fluid and you would probably say okay I've made it through the pericardial sac I've cut through the pericardium well technically you didn't am i right because this thin thin thin membrane here that's still part of the pericardium it's the visceral layer of the serous pericardium they didn't cut all the way through but you know the heart has this outermost layer also called the epicardium you can't peel it off the surgeons not going to try to cut through that microscopically thin layer most of the time I tend to and I would suggest you tend to think about things like once you get to that pericardial cavity I start to call this usually epicardium myocardium and endocardium I won't refer to this as often as the visceral layer of the serous pericardium but it is also bad okay one last thing here to think about is the cardiac skeleton this is bands of dense connective tissue running through the heart it's not actually what you see here these are these spiral and circular bundles of myocardium the heart muscle but this dense connective tissue is kind of doing something similar it's running through the heart and it's doing several things it has a stabilization function so it's kind of here's a bit of it you can see these rings is keeping these valves in place along with some big blood vessels and some nerves it helps distribute the force of the contraction when the hearts contract it's kind of making sure that push is spread out evenly along the chamber it prevents over expansion it's also provides some elasticity to help spring the heart back down after it expands a bit really though the main thing we'll talk about not for a while here but much later in this exploration of the heart we'll talk about how the cardiac skeleton creates this electrically impermeable boundary between the atria and the ventricles and it's super important but it's something we'll save and we'll get into a little bit more later so those are the location of the heart the coverings of the heart including that very exciting exploration of the Sera's pericardium versus the fibrous pericardium versus the heart wall you really want to get down and dirty on that and just work through it and figure it out plus a little look at the cardiac skeleton which will become much more important later in our discussion see you for the next one