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Heart Anatomy and Function
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0:00
In today's video, we're going to do a deep dive into the anatomy and structure and function of one of the coolest organs in the entire human body -- the heart. The heart is an incredible organ. And that's like the biggest understatement that I could possibly say about the heart because this thing beats about two and a half billion times over your lifetime. This thing is capable of self-excitation. You could take a heart from someone, stick it on a table, and it would beat
0:30
for like 3 minutes on its own. It's wild. This is an absolutely incredible organ. But when you stop and think about it, it needs to be. Like, so for example here, if the heart required the brain to tell itself when to beat, how to operate no matter what, like let's kind of like just play through that in a scenario. Like, let's say, someone gets a head injury. It's not enough to kill them, but at the same time,
0:58
you know, it could be enough to start temporarily shutting down certain structures in the body. Like if your pancreas stops working temporarily, it's not the end of the world. You know, liver, kidneys; like, obviously, none of that is ideal. Obviously. But if the heart stops working even for a second, that's all she wrote. So, the heart needs to be capable of regulating itself. No matter what. It can't really depend on other organs. Again, it could be influenced,
1:28
but your brain has all sorts of influences over the beating of the heart. It's just that it's not an outright requirement, which is a really important thing about the heart. So, what I want to do in today's video is go over some of the anatomy of the heart. Now, we're not going to necessarily go over everything you see in this list here, and we're going to be using multiple images. We have a lot of different views of the heart that we can look at. And by the way,
1:53
I'm- we're going to be doing this in a 100 percent free Kenhub article that we're going to go ahead and link in the description below. So, you can go ahead and follow along with me and then you'll be able to see all of this for yourself and get a real robust understanding. You can pause the video, you can do whatever you need to, and then we can kind of go from there. So, but I think like the heart, like understanding how the heart is,
2:15
why the heart is, all of that stuff is so important if you really are looking to, I guess, just understand the human body better because the heart is such a core element of it. So, with that said, what I want to do is just kind of orient you to what we're looking at here because this is the right side of the heart. And it's important to understand that the heart is essentially divided into left and right. Obviously, there's going to be four chambers, but
2:41
you could just divide it straight down the middle and say, "Hey, you got a right side, you got a left side," and that is also going to be distinct in their functions, whereas the right side of the heart is going to be deoxygenated while the left side of the heart is going to be oxygenated. Now, interestingly, that wasn't always the case because if we come right here, you can see this thing. It says the fossa ovalis. This is a remnant of the foramen ovale,
3:06
which was a hole that connected the two atria of the heart. And I'll explain exactly what the atria are in just a second. But when you were developing inside of mom, there was a connection between the oxygenated and deoxygenated side of your heart. What's fascinating is this foramen ovale closes upon your first breaths. So, as soon as you're born and you're breathing oxygen, it slams shut. Now, it takes like, you know, around a year or so for this thing to fully close.
3:38
And if it doesn't, then obviously that can be very problematic and so there's a whole series of clinical steps that would need to be taken in that event. But you can see though, it's interesting to think like it wasn't always divided between oxygenated and deoxygenated. At one point in time like blood could mix and go this way and that way. But once you start moving around, you know, once you're walking and talking and doing things, you really,
4:01
really need that clear distinction between oxygenated and deoxygenated. So, this is a right view of the heart, which means we are looking at the deoxygenated side. And so you can see this blue structure here and another blue one down here and what's happening is they are blending into this tissue right here. What we're basically doing is seeing blood flow, deoxygenated blood flow, coming from the upper body is going through this tube here called the superior vena cava and then
4:32
deoxygenated blood from the lower body coming through the inferior vena cava. Now I'm using those terms really loosely. I mean, obviously, you have chest, you have abdomen, there's all sorts of things, and how we distinguish these are going to be a little nuanced. But I think you get the idea here that basically once your body uses the blood, you got to get it back to the heart, and it puts it through these gigantic blood
4:52
vessels called the venae cavae. And then it's going to enter into the right atrium. So, an atrium is basically like a gathering center. I always tell my students, you know, think about like, you know, atria for a bird, right? Like a… like a bird atrium type of thing. Like you can think of it like this gathering center. And what's going to happen here is it's going to just kind of pull in this waiting staging area inside of the atrium.
5:17
Now, the atrium is mostly going to be very smooth, but if you also see here, like we've cut this window, right? The illustrator cut this window and then like peeled it back, you can also see what's called the pectinate muscle. And so the pectinate muscle is really interesting because when this is -- so this is muscular, I should also say. Like because the atria is going to have to contract and push the blood into a deeper
5:40
cavity called the right ventricle but it's very thin muscle here, but it is muscular. But what's fascinating is this architecture of pectinate. You can see it's like very branched. What'll happen is just as the muscle contracts, it very efficiently and effectively like pushes the blood down towards this valve here that we're going to see here called the tricuspid valve or the right atrioventricular valve. So, this structure doesn't just look cool. It serves
6:07
a function. What it does is it just helps to efficiently funnel and push that blood in the correct direction. But you're also going to see a lot of smoothness and that is just going to also help just with less friction just deliver the blood where it needs to go. You can think of this as, you know, again, just the staging area. And then it's going to go through this valve here called the tricuspid valve, or you could also say the
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right atrioventricular valve. And we're going to get a better view of this type of valve in just a moment. But just understand this is going to push it down into that area, which the right ventricle is going to be behind here. So, this view is more so about that right atrium. That's like really what it's going for. So, to see the right ventricle, we'd have to just go deeper. But we have an alternative
6:55
view here. Now, this is actually going to be switching to the left side of the heart. However, we can still understand the basics of how the ventricles are going to work. So, once again, we can see the left atrium and now we can see inside of the left ventricle. But again, there is a left atrium and a right atrium. These are gathering centers. So, to kind of go back up here, actually, what's happening in the right atrium again
7:21
is we're gathering all the deoxygenated blood from everywhere in the body. But the left atrium, which is this structure here, is gathering oxygenated blood that is returning from the lungs. So, the lungs give all that blood oxygen and then it's going to return in these structures called the pulmonary veins and it's going to drop into that left atrium. So, we have blood gathering on either side of the heart, on the right and the left side of the
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heart, and what they're doing is just waiting. And then those atria are going to contract and squeeze it. And inside of the left atrium, you're also going to see pectinate muscle. You're going to see smooth muscle. When I say smooth muscle, I mean like it's physically smooth. The shape of it is smooth; not the actual type of smooth muscle. And then what's going to happen is both sides contract at the same time and push the blood through these atrioventricular valves.
8:16
So, if I go back up here, again, you can see the top of this right atrioventricular valve, also called the tricuspid valve. Here is a better view of the left atrioventricular valve, also known as the mitral valve or the bicuspid valve. It's never fun when there's like three or more names for a particular structure, but this is basically, this flap of connective tissue. And then you can see these little heartstrings attached to it. These are called the chordae tendineae.
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So, when you ever hear someone say like you're tugging on my heartstrings or something like that, well, this is what they're talking about. Granted, that's a figure of speech. I don't think anyone's actually reaching into your heart and tugging on your heartstrings. If so, that's an intense… that's an intense thing you're experiencing. So, the point here is the blood is going to push through this cusp and it's now going to enter into
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this really large structure, this open space called the left ventricle, or if it was on the right side, the right ventricle. And what I want you to take note of is just how thick the muscular wall is in the left ventricle. And now it's not going to be as thick on the right ventricle, but it's still going to be far thicker than -- let's come back up here -- look at how thin this muscle is here, right? Like you are looking at the actual like depth of that muscle,
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the thickness of the atria. These are very thin, but they don't need to be very thick because when they contract, it goes and squeezes the blood right below it into the ventricles. But where do the ventricles need to pump the blood to? The rest of the body. So, in like specifically, if we're talking about the left ventricle, this thing is going to pump its blood and it's going to go out -- and we're going to
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see a different view of this in a moment -- this structure here called the aorta. Now you have an ascending aorta. You have an aortic arch and then this thing is even going to loop all the way down to essentially where your bellybutton is. This is kind of wild. People don't realize how big the aorta is and how long it is. It's the size of a garden hose. And then it's going to curve around and go all the way down to around the area
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of your bellybutton before it starts splitting into the iliac arteries. Really, really wild. But then I want you to understand, you also have these offshoots, right? You have like the brachiocephalic and the subclavian. You have all these different offshoots. You're going up to the common carotids. My point is this. The left ventricle is so thick because it needs to pump blood to the head, to the shoulders,
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to the arms, right? Like, everywhere else in the body it needs to be delivered here. The right ventricle, on the other hand, is going to pump blood and it's going to go to the lungs which are right next door. Is it still going to be strong? Like, is the muscle there going to be thick? Yeah. Just not as thick as you'll see in the left ventricle because it doesn't have to travel as far. But what's also really interesting is you can see these tiny little muscles here.
11:08
These are called the papillary muscles. So, it's kind of hard to see. I'm going to try to outline it as best I can here. So, there's one. Here's another one back here. You can see another one right here. So, papillary comes from papilla, which means nipple. These are your heart nipples. And what they're doing is they are attaching with those chordae tendineae to the cusps. They're like physically attaching to the cusps.
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Now, we used to think, before we had really good medical imaging of all of this, that what would happen is these muscles would contract and it would pull those valves open. It would be like, "Hey," you know, like you're opening the door from someone, "Come on in, blood; come on in right here." But what we then saw when we could see through, you know, complex medical imaging, these things working in action,
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is that they're not really doing that, because you have to understand, valves prevent backflow. Back flow is never good when you're talking about the circulatory system because you want blood to go in one direction. It's all a one-way street. So, if we have blood coming from the left atrium into the left ventricle, when that ventricle contracts, you don't want it going backwards. It defeats the entire purpose. And that's where you're starting to have valve disorders and that's
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a whole other, you know, topic for another day. My point is simply, you don't want this. So, what'll happen is this valve is there to prevent blood from going back into the atria. So, to do that, these muscles are desperately holding on to these chordae tendineae on these cusps and just holding on and just being like… it's like -- I always liken it to the same thing is that it's like a guy holding on to a kite in a windstorm, just desperately holding on,
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just like, "Ahhh!" You know, that type of thing. That's what's happening every single time the ventricle contracts two and a half billion times over the course of your lifetime. The heart is wild. This is such an amazing thing that it's doing. And these strings are just holding it back. So, but then you'll also look back here. You'll see this really interesting architecture. This is called the trabeculae carneae, which literally translates to little beams of meat, which is wild.
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But again, like this architecture is going to actually allow the branched cells, because what you can't really tell here is you can see this muscle tissue here, the cardiomyocytes -- so cardiac muscle -- is branched, and by being branched at a cellular level, it can actually intertwine on itself and so when it contracts, it can contract in, right? So, it's like lub-dub, or more appropriately, atria contract -- lub, ventricles contract -- dub.
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But the point here is it's all twisted. This architecture allows the heart to like to actually contract in on itself and twist. And what that's going to do is push the blood out the aorta. Or if you were the right ventricle, it's actually going to pull- push it out the pulmonary trunk and then it's going to go to the pulmonary arteries and it's going to go to the lungs. But it's not that -- so this muscle is shaped this way intentionally. That's
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the whole point of it. So, the whole point of it is so that it can just very forcefully push and eject the blood out of the heart. Now, you also see down here where it says apex of the heart. So, the apex is just going to be this point. And what's really, really cool is -- now we can't see it in this image, but there is like actual pathways -- conductive pathways. You've probably heard,
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and I want to do a whole separate thing on this in a different video of like the sinoatrial node or atrioventricular node or the bundle of His or, you know, like the Purkinje fibers. Basically, when the heart beats -- this is one of my favorite things -- is just that the signal will go all the way down to the apex of the heart first, and this will be the area of the heart that contracts initially, which makes sense because then if this is slamming shut, it's going to help
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to push blood out like that. Isn't that cool? I love it. It's just it's absolutely wild. And then it's going to go out of the aorta. It's going to go to the head. It's going to go everywhere you can possibly think of in the body. Just absolutely fascinating how it's able to do that. So, let's now look at one of my favorite views of the heart and that is a horizontal or transverse section through the heart. And you do this towards the most superior part of the heart because that
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way you can see on top of the valves. That's what all of these are. These are those one-way valves that are basically saying, okay, like blood is allowed through here but not back through here. And so, you can see there are two large valves and then there are two smaller valves. So, if we take a look at the larger ones first, we can see that there are two like sections to it. But on this one, you can see there are three sections to it. And this is going to make perfect sense to
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you because this is the tricuspid valve and this is the bicuspid valve. Again, they have different names like you could say right atrioventricular or left atrioventricular or mitral valve, but I'm actually personally a fan of saying bicuspid and tricuspid because of this. It, to me, is just like the most efficient and effective way to think about it, but it's personal preference. I don't really have anything beyond that as a reason.
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But then if we look at these other valves here, this one is the aortic valve and this is the pulmonary valve. So, the aortic valve is going to be at the base of the aorta. So where the left ventricle turns into the ascending aorta, we have this little valve here. And you can also see, by the way, what's really cool, the coronary arteries splitting off of it. So, a real interesting thing about the heart is that like, I like to think of it
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like an airplane. You know, if the oxygen mask comes down, then what you're going to do is put that on yourself before you, say, put it on a child or an elderly person or someone who would need some help. And that is because you need to be able to function in order to help other people. The heart will supply itself with oxygenated blood before it supplies anything else. And so, it's just a kind of interesting thing is it's branching off of the ascending aorta there.
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But this aortic valve is at the base of the aorta. And so, it prevents blood when the ventricles relax temporarily from blood pouring back in to the left ventricle. And then the pulmonary valve is going to do a very similar thing except it's going to be at the base of the pulmonary trunk. Now pulmon- means lungs. And so, what's happening is this tube would then split into the pulmonary arteries and then those would go to the left and the right lung.
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So, again, all of these are preventing backflow, but they're going to do it in slightly different regions, obviously, and in slightly different ways between, right, these separating the atria and the ventricles and then these separating the tubes leaving the heart and back into those ventricles. So really, really cool, and in fact, I can even slide down here and you can see a cadaveric image of this. And so,
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you can see the pulmonary valve, aortic valve, bicuspid and then the tricuspid right here. Again, they're highlighted, but you can see this is just a phenomenal view to look at for the heart. But what I want to do is we're going to actually come back and take a quiz in just a second. So, we're going to do that because I think quizzing yourself after a study session is the best way to make sure that you're retaining the information.
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What I want to do now is I want to highlight through here some of the individual structures that we just mentioned because the images I was showing you were kind of like all in one and here we can kind of individualize them and just highlight them by themselves. And so here you can see the inside of that left ventricle. So, everything you see there in green is going to be that left ventricle. And again, this is going
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to be the part of the heart that pumps the oxygenated blood to the rest of the body, whereas here, it's highlighting the ascending aorta. So, remember that like the aorta is actually rather big, like really, really big. So, you have to separate it into different sections, and this right here is what we would call the ascending aorta. Then we flip back to the other side. You can see the right atrium. So, you can see just everything
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involved inside of that right atrium because we've peeled back that wall. Then from here, now we have a clearer view of the right ventricle or inside of it. And so, yes, it's highlighted in green but we can still see, you know, like the base of the pulmonary valve here. You can see the tricuspid valve. You can see the papillary muscles. You can see the trabeculae carne. So, everything is still going to be the
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exact same in terms of like the view like we saw with the left ventricle. Not like it's the exact same as the left ventricle, just that it has the same components. That's a better way to say it. But you can also see the thinness of the ventricular wall. And so, when we -- if I quickly go back; in fact, I want you to take a mental note of this, right? So, let me get that text out of the way. You can see just how thin this is. So,
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I want you to take a mental note of that because I'm going to go back to images. And woo! Did I go back too far? There we go. You can see how thick that the myocardium of the heart is on that left ventricle. And again, that's because it has to pump to the rest of the body. Whereas, you know,
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if we come back here, you can see that the right ventricle only needs to pump the blood to the lungs. Just really, really cool to see it from that view. So you can see the pulmonary trunk. This is again the part that is branching off of the right ventricle and then it's going to split into the pulmonary arteries. And what you can't really see because it's sliding underneath the aorta is going to be a pulmonary artery that's going to be
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going to the right lung. And then over here you can see the pulmonary veins. Remember veins are always bringing blood back to the heart whereas arteries are taking blood away from the heart. So, a lot of times people will think arteries are always oxygenated and veins are always deoxygenated. Not true. There are exceptions. Like another clear exception you can find inside of the kidney. So what's happening here is we have pulmonary veins because
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they're bringing blood back from the lungs that are oxygenated. Whereas if we were to go here, you see this purple thing? That would be the pulmonary artery. So, the pulmonary trunk turns to pulmonary artery -- well, those are deoxygenated because the blood is going away from the heart to go to the lungs which is why you really want to be more distinct with arteries and veins based on where are they going in relation to the heart.
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So then, again, come over here and you can see the entire left atrium from this view. Now I didn't really have time, or, you know, it's not really I didn't really have time, I just haven't mentioned, this right here, this little appendage coming off, that is called an auricle. So, it's basically like this ear-like appendage that is kind of draping off of the atria. Now, there is one for the right atrium and one for the left atrium. And they're even functional in
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utero. As the heart is developing, they can help to contract and just kind of push blood. But, you know, as you're born and then as you grow, they just kind of don't really function in that unique novel way, but they just kind of still hang around. So, super, super cool. And then we're right back to this left ventricle view. So, what I want to do now because I feel like we have a decent understanding of how the heart works. I want to take a short quiz and I
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feel like that's just the best way again for us to figure out exactly how well we are retaining this information, so let's go ahead and take that right now. All right, so I've gone ahead and customized a quiz specifically based off of what we just discussed. Again, this is one of my favorite features we have here at Kenhub is the ability to craft your own quiz in the event that, you know, there's just certain times and certain
22:30
structures you just want to be quizzed on those. You want to kind of dial that in. So, we have 20 unique structures that we could possibly face inside of here so we're going to go ahead and do this and we're going to click on a study session. That reason being is because these have this spaced repetition-type quizzes which here at Kenhub we are a huge fan of because these have been shown to be one of the most effective ways to actually learn information.
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Study session quizzes are there to teach you things, whereas the exam quiz is there to test your knowledge on it. So, spaced repetition basically says, "You know what, we're going to show you this again, but we're going to show it to you in a slightly different way." And over time, that familiarization occurs and you just become more comfortable with it and you do a better job with it. So, I'm going to lower the time down to 5 minutes. We're going to hit start quiz
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and let's see what happens. I'm excited to see what we have here. So, it says, which image shows the right atrium of the heart? Now, what's going to be fun is that this is going to show you images that we did not see, but I believe in you. I believe in you because I want you to be able to pause this video if you need. You can take the extra time and look and see how this is coming along. So,
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and then we can kind of discuss it. So, I'll give you a second, but again, feel free to pause.
23:51
The answer is going to be this one here. And what I want to do is zoom in on it. And we can see when you push this "i" icon, you can see that there are so many other images. Not always; it kind of depends on how many illustrations we have. But here we have so many different illustrations that can help you to figure this out. So, let's say, like, because again, you're like, "I don't know what is this going to be." So,
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you can click on it and then you can start cycling through these different images and be like, "Wait a minute. Ah, I remember that view. I don't remember this view." So, this is, I think, this is the view we were looking at. It might be a little bit -- oh, no. It was this one. Like, we were seeing this view and it's like, "Well, I didn't see that view." Luckily for you, you can come on in and you can find an additional view that might be the one you're familiar with.
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What this is doing is it's trying to show you just different ways to look at it. And that's one of the biggest, you know, advantages I personally believe that anatomy has for the human mind is that what it forces you to do is think analytically through spatial problems. So, you know, this is a posterior view of the heart. We never saw a posterior view of the heart. So, you'd have to figure out that this is a posterior view of the heart. You have
25:02
to start twisting the heart in your mind. And when you do that, that's when you can start to maybe piece this together. Like, well, maybe that's the right side. Ooh, what are these things? Are these the pulmonary veins? And so, yes, this would require you to have some understanding of the heart to really efficiently and effectively pull it off. But still, this is a great, you know, mindset to get into so we can get the correct answer.
25:26
So, next, which image shows the right ventricle of the heart? So, again, I'll give you a moment. We haven't seen either of these images, but you can pause this if you need. That is going to be this one right here. And again, if we click the "i" icon, I want to see if I can find that particular image, which is this one right here. So, you can see that what's -- I love this image. This is really cool. You can see there's probes
25:52
actually like pulling on the lungs to show the mediastinum, which is this large area here. You can even see the thymus in here. There's a lot of anatomy going on here. And I think this is one of my favorite ways to start introducing students like the fact that -- I mean, like look. These things don't exist in isolation. Not only do you need to be able to orient yourself, you need to be able to see what else is around there; even things that you
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may not recognize immediately. But yeah, this is going to be that right ventricle. Which image shows the apex of the heart? What do you think? It's going to be this, right? The apex is going to be this point. So, this point is, remember, this is where blood is being ejected out from first. So, the signal for the heart to contract goes all the way down to the apex and then the heart will contract from the bottom up, essentially squeezing out that fluid.
26:49
All right, right atrium of the heart. And now you can see that the quizzes… the quiz questions are starting to get a little more challenging. What do we got here? Right atrium. We've already seen this image. Now, it's going to be this one. Now, here's the interesting part is the auricle, the right auricle, is attached and kind of belongs to the right atrium, but it is its own unique structure. So, I could see how you might
27:15
have been like, "I think it's one of these," or even think it's this. But the best answer is going to be this one right here, which is indeed the view that we've already seen. Which image shows the right atrium of the heart? And now you're starting to see the spaced repetition aspect of this quiz, right? It's showing you or asking you the same type of question what's this going to be from a slightly different view.
27:40
That is going to be this one here. I actually don't want to spoil it in case we see it asks what that is next. It's asking for the right ventricle of the heart. Funnily enough, that was the right ventricle, but they're at- they're showing it in a different view. So, let's see if we can hurry and pull this off.
27:59
So again, we've seen this view. It's this one down here. And I want to be really quick because we're running out of time. But if you look at it from, here, you can see right ventricle. That is definitely going to be it. Now granted, this is in situ, but still had to hurry and go on. Okay, this will be the last question we have and then we'll run out of time. So once again, it's asking for the apex of the heart. And so I know I keep on, you know, mentioning
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spaced repetition, but there's so much value in this and just drilling it in. It's kind of similar to running through flash cards over and over and over. It's just going to imprint that into your mind. So, what is the apex of the heart? It's going to be this one right here. So, we did pretty good on this, but we also didn't, you know, go over many questions. We're not going to save, but I love the fact that you have an option to save this. Again,
28:47
you can see, you know, you could retake it. You can edit it. You can -- we have- we give you options. You can also see how your progress is going with this, you know, especially… because as you do this, you know, you want to also see if you're just getting better. It's not always about being able to pass it or get the correct answer in the moment. You want to make sure that you can always get the correct answer. And that
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is something you can start seeing and you can even start seeing how well you are improving, how quickly you're improving. Those are all metrics that we like to track here, so. Thanks for watching. I just want you again, you can find the link to this down in the description below. So, if you want to go ahead and go through this exact article that has so you can read about the heart so you can get a better understanding based off of that.
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You can see those exact images. So, go ahead and click that link in the description below. And while you're down there, why don't you go ahead and leave us a comment of what you want to see us talk about next. It's always easier from a creative standpoint to give the people what they want. So, tell us what you want. What do you want to see? What other videos in the future do you want us to discuss and structures? So, be sure to leave a comment down below.
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And also, while you're down there, hit that like button. It helps. It really does. It helps people see this in their recommended algorithm. So, do us a favor. If you enjoyed this video, be sure to hit that like button. We would very much appreciate it. But, thanks for hanging out with me, and I will see you in the next video.
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