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Current time:0:00Total duration:8:52

Video transcript

so we've gotten kind of used to drawing the heart with four chambers I'm going to draw it with four chambers here something like this with two chambers on top those are the atria and then I'm going to draw some slightly larger chambers down below these are the ventricles right and just to kind of label it this would be the RA this would be the left atrium the right ventricle and the left ventricle and we've we've kind of always tended to view the heart basically this way kind of looking at it from the front but now what if I wanted to actually change things around let's say I actually erase this bit for us and instead of looking at it from the front let's say actually I'm going to draw a pair of eyes here and draw it like this and let's say you actually could view it instead of from the front you actually can look down on it look from the top what would you see if you're looking down on let's say you cut away the atria what would it look like so I actually did this I actually took a picture or drew it rather and it would look like this so you look at this and you think oh my gosh this is so different from how we've used to how we're used to seeing it so the first thing you want to do is kind of get oriented right so let's let's orient ourselves and we're going to use little clues so for example let's start with this valve right here we know that it has three cusps one two three and it has these little cords right you can see these little tiny cords right here that it has and right there and there so think about the fact that it has cords chordae tendineae that's what they're called and chordae tendineae if it has chordae tendineae you know there are only a couple of valves that have chordae tendineae and those are the atrioventricular valves atrioventricular valves so it's one of the two right it's got to be one of the two atrioventricular valves and one of the two atria ventricle valves has three cusps in fact we call it tricuspid and that's what this is this is the tricuspid valve and the other atrioventricular valve and you can see there are a couple of chordae tendineae here that kind of Clues us in that this is definitely one of they two atrioventricular valves and this is the other one this is actually only has two cusps one two so this must be the mitral valve mitral valve which means that these other two are are left and you know one's got to be the aortic valve and one's got to be the pulmonary valve so how do we figure out which is which well let's let's use another clue so you can see that there's a little hole here for blood and actually Bloods flowing this way from there and it's flowing that way from there so if blood is going into these little vessels and these vessels that are wrapping around the heart and you remember they're called the coronary vessels in this case they're the arteries the coronary arteries these coronary arteries are getting blood and it's coming from just outside of one of the valves well let's think about this this is I've drawn it in red and whenever I use the color red I'm trying to signify oxygen so we've got oxygenated blood that's going into these arteries and where would it be coming from well if it was the pulmonary valve that would make no sense because that blood is definitely not oxygen in it yet and we know that the blood here is so this must be the aortic valve and the aortic valve has usually three flaps as well so this is our a or tech valve and I didn't actually draw the aorta because we've literally kind of cut the aorta out but if you were to draw it if you were to imagine how it would look it would basically look like this it basically kind of go on top like this and blood would be going out the aorta right but I've cut that part away now the last valve also has three flaps one two three so really them is that just the mitral valve has two flaps usually all the other ones have three and this is your last valve and this is your pulmonary valve pulmonary valve so it's pretty cool we actually were able to orient ourselves just by using some of the clue is that kind of drawn in here now if I've talked about the coronary arteries you're probably also wondering what these blue things are down here these are the coronary veins coronary veins and a very cool thing about coronary veins is that these veins actually drain directly into the right atrium you know most veins in our body you know vein from our let's say kidney or a vein from your toe all those veins drain into where they drain into one of two large vessels either your superior or inferior vena cava right inferior and superior I'm going to call them VC vena cava and these are the two large veins that kind of drain the whole body but one unique little vein or set of aims is the coronary veins the veins that actually supply the heart they kind of on their own drain into the right atrium because this is the right atrium right this chamber that we've chopped away and so they drain directly into that right atrium they don't actually go into either one of these so that's actually an interesting kind of feature and you can see that here as well so that brings me to kind of my final point about this picture and that is that in the very very center you have a little blue circle what is that so this right here is a very unique bit of tissue and this is something we've talked about differently in different kind of settings and this is our atrial ventricular node atrioventricular node now the AV node is going to connect kind of connect the two atria to the ventricles and send a signal right it's going to send a depolarization signal through it so if your atria contract I'm just going to kind of sketch out the atria and your ventricles one of the things that kind of always comes up is well when the signal goes from the SA node it has to go through this AV node and then it goes down and splits into the left and right side and also of course it sends a signal to the other atrium so this is kind of a rough scheme of what it looks like but just keep in mind now so we're look directly at this box right this box right in the middle now if you could actually get a signal to go a different way let's say you can actually get a electrical conduction signal to go I don't know maybe through the walls maybe from the atrial wall to the ventricular wall or maybe it could go right through the valve let's imagine go through the valve well then your AV node isn't doing a very good job because the whole point of the AV node was to create a delay remember that's one of the kind of the interesting things that it does is it creates a delay of it was about 1/10 of a second well this delay wouldn't happen if you could actually just send the signal some other way right if you could just go around or circumvent that node but the fact is that this entire area and I'm going to just show you this entire area all this stuff is actually unable to send any electrical signal no charge signal can go through there you're not going to get any depolarization through any of these spots not even through the valves and that's really important because if you didn't have that then basically signals would go through any which way but now because all this stuff around this AV node is inert you know really not going to let any signal through the AV node is the only passageway from the atria down to the ventricles and you can see that very clearly when I cut it this way so the final kind of outstanding question in your mind might be well well what is it made of you know this this stuff it's inert but what is it made of and most of this stuff is collagen so a lot of this kind of inert stuff is collagen where should I write that maybe I can make a little space right here this is mostly collagen so you get collagen and here the rings of the valves are actually fibrous these are fibrous rings so between the fibrous rings of the valves and the collagen you basically aren't getting any sort of electrical conduction it's not actually myocytes it's not electrical conduction tissue it's neither of those two types of cells it's primarily protein and that's that's why you can't get a signal through there