Hi, everybody. This is our first video for Chapter 17. Chapter 17 is the cardiovascular system one, the heart. So this video is just going to give you an overview and the basic structure of the heart, where it's located in the body, and like an overall pumping mechanism of the heart itself. The later on in Chapter 17, we'll get to a little bit more detail of how the heart.
functions, and, you know, the forces that allow blood to flow. But so far, we've discussed Chapter 19, the blood, and we know that the blood transports oxygen, does many other things, but a very important part of the function of blood, specifically our red blood cells, is that red blood cells will bind to and transport oxygen. Now, where does that oxygen go? The oxygen has to go to active tissue because active tissue will consume that oxygen in order to continue to make ATP or energy. The more energy a tissue has, the more ability it has to function.
So how does blood get from point eight? point B, it needs to be pumped through the body. And the function of the heart is essentially a pump. So this first slide here just shows you the orientation of the heart within the thoracic cavity, specifically within a space called the mediastinum.
The mediastinum is a space that houses the heart, as well as the great vessels of the heart. The great vessels of the heart are very large vessels. coming off of the heart that includes the superior vena cava, which is up top. Remember, superior means toward the head. And this little portion here, you can see a little bit of blue right here.
That's the inferior vena cava. And that vena cava is a large vein that's bringing blood from the bottom of the body up to the heart. Another great vessel is the aorta. The aorta is this red colored vessel here. So as you can see, the heart is the apex of the heart, which is the point is pointing down to sort of towards our left hip.
And the base is tilted up toward the right shoulder. Remember, when you're going through right and left, it's the patient's right and left, not your right and left. So you kind of have to think about it that way.
Don't forget to do that. Let's move on. See if I can do that. Okay. So the heart is essentially broken down into two separate pumps.
There's a pulmonary pump or a pulmonary circuit and a systemic pump or a systemic circuit. So if we were to divide our heart into two sides, the right side, which is this blue colored side, remember that's the patient's right, not your right. The right side is the pulmonary side.
So this is blue. And what happens here essentially is that blue blood or deoxygenated blood returns to the right side of the heart from our tissues. So the blood has lots of carbon dioxide and less oxygen. goes to the right side of the heart.
Then the right heart pumps that blue blood into the pulmonary circuit. Pulmonary refers to lungs. So the blood goes from the right heart to our lungs. Why would it go to our lungs?
It goes to our lungs to do two things. One is to pick up oxygen, right? So it was deoxygenated blood.
It goes to the lungs. and it picks up oxygen. So now it's oxygenated blood. The other thing that happens is that it releases that carbon dioxide.
It's bringing the carbon dioxide back from the tissues. Carbon dioxide is a waste product. It's a waste product from the Krebs cycle, from cellular respiration.
So it brings the carbon dioxide back to the lungs, and we breathe out the carbon dioxide. So two things are happening at the lungs. Once the blood is re-oxygenated, or we would just say once it's oxygenated, it turns bright red. That's why it's red over here. And it returns to the heart, but it returns to the left heart or the left side of the heart.
Now the blood is oxygenated, and then it will leave through the aorta. and go to the systemic circuit. So the right heart pumps to the lungs. That's why it's called the pulmonary circuit.
The left heart pumps to the body. And that's why it's called the systemic circuit. So two sides of the heart, right and left, two different circuits, pulmonary and systemic.
I am going to just remind you, we talked about this in Biology 109, that the heart sits in the pericardial cavity, and it has serous membranes associated with it. This is something we discussed in 109. And now we're actually going to see it and apply it in 110. So the pericardial, the pericardium, which is the serous membrane, has two layers. The parietal pericardium is the outer layer. The inner layer is the visceral pericardium. And in between those two serous membranes, we have serous fluid.
Specifically in the pericardium, we have what we call pericardial fluid. And that allows the two serous membranes, parietal and visceral, to easily slide past. one another every time the heart beats.
So that lubrication decreases friction, a decrease in friction, um, decreases heat. Uh, so we don't ever want the heart every time the heart beats, we don't want to overheat. So that Cirrus fluid allows for, um, that lubrication and allowing us for our heart to contract and relax without too much friction. This is just a side view.
Your chapter 17 part A outline goes through the layers of the heart wall and I just wanted to include this slide so you can see the layers. So this is a like a side view layer. This is the outermost layer of the heart wall and it's moving toward the innermost layer. So the outermost layer is the epicardium.
It's also considered the visceral pericardium. So the epicardium is outermost. The bulk of the heart wall is this muscular layer, and that's the myocardium, myo for muscle, and it's cardiac muscle. So this is the myocardium. And then the innermost layers, so this would be the layer that makes contact with the blood.
This is the endocardium. myocardium. So inner, middle, outer layer of the heart. And when you dissect the heart, you'll be able to see those layers.
It's very difficult to tell the anatomical boundary between outer, middle, and inner layer, but you'll, you'll appreciate, you'll at least be able to see the myocardium, the muscle layer in your dissection. This is just an, picture of the external anatomy of the heart, we will go through in great detail the external and internal anatomy of the heart in lab. I just wanted to include it here.
You can see the great vessels, superior vena cava, inferior vena cava, the pulmonary trunk, which gives way to the pulmonary arteries. And this is the aorta, which is a large artery. One way to remember Arteries versus veins.
Arteries always carry blood away from the heart, regardless of the type of blood they are carrying, oxygenated or deoxygenated. Blood is carried away. So you can remember A for away and A for artery.
If you remember it that way, you won't lose. Here's a picture of a cadaver heart. So you can see it's a little bit more difficult because it's not color coded.
But you can certainly see that this is the aorta. And these are the pulmonary arteries, the atria and the ventricles. This is the posterior view of the heart.
So we're looking at it from the backside. And you can see the pulmonary arteries. So the pulmonary arteries are bringing blood away from the heart toward the lungs. And then the pulmonary veins are bringing oxygenated blood from the lungs back to the heart.
So you can see those vessels here quite nicely. You can also see the inferior vena cava as well as, of course, the superior vena cava and the aorta. Let me show you. Oh, this is a, this is actually a really nice picture. This is a transverse cut.
Remember a transverse cut is a horizontal cut that separates a specimen into superior and inferior portions. And I like this, this view because you can see the thickness of the bottom chambers of the heart. So you went through your outline, I'm assuming, I'm hoping, and you know that the bottom chambers of the heart are called ventricles.
And here is the right ventricle. Remember the right ventricle pumps to the lungs, the pulmonary circuit, the left ventricle pumps to the system or the body's tissues. And I want you to take a look and see how much thicker the muscle is associated with the left ventricle. Do you see that the muscle around the left ventricle is thicker and the muscle around the right ventricle is thinner?
Now think about it. Where does the right ventricle have to pump? It only has to squeeze to pump blood to our lungs. Well, if your heart is right here and your lungs are right here, it doesn't need that much force to get the blood from the heart to the lungs. So the muscle doesn't have to be that thick, right?
However, the left ventricle has to contract and create force and squeeze that blood So the blood goes all the way to your active tissues, all the way up to your brain, all the way down to your toes. So that muscle has to be really strong. And because it has to be really strong, we have a thicker muscle associated with the left ventricle. So you can see that here. Here's the internal anatomy of the heart.
And again, you will be going over this in lab. You will be labeling. pictures. I just wanted to go over it with you quickly.
And then we will talk about, um, about the valves. So superior vena cava, inferior vena cava, pulmonary trunk, pulmonary arteries, large aortic arch, the upper or superior chambers of the heart are the atria singular is atrium. So here's the right atrium.
Here's the left atrium. Inferior to the atria are the ventricles, right ventricle, left ventricle. So we have right atrium, right ventricle, left atrium, left ventricle.
So far so good. Here we have an interventricular septum. That's just a divider between the right and the left ventricle.
Then we have four important valves to discuss. You'll have to label them. There are two types of valves.
There's four valves total, two types total. So first we have our atrioventricular valves, AV valves, atrioventricular. What are they between?
They're between the atria and the ventricle, AV valve. So here we find an AV valve. It's between this atrium and this ventricle. Here's another AV valve because it's AV because it's between an atrium and a ventricle.
Well, this is called the right AV valve because it's on the right side of the heart. Easy. This left AV valve because it's on the left side of the heart. That would be easy if we just ended there.
We know that. Scientists love to name the same structure, 10 different names. We don't simply just call this the right and left AV valves. We had to add something else.
So the right AV valve is also called the tricuspid valve. Tricuspid valve. I think your textbook author said you can remember it by you should always try to do right.
I don't know. I didn't make it up. I'm just telling you.
So. try cuspid on the right side. Always try to do right. I will not take credit for that one, but use it if it helps. Then the other one is on the left side.
This one is called the bicuspid valve. Bicuspid valve. I mean, it's named that because it has two cusps versus three cusps, but bicuspid valve is on the left side of the heart. It's also called the mitral valve. So this valve has three different names.
It's the left AV valve, also called the bicuspid valve, also called the mitral valve. It's all the same thing. It has three different names. You need to know all of the names. I don't care if I point to this in an exam and say, name it.
You don't have to list all three. You just name one. But if I refer to the mitral valve, you've got to know where it is. I hope that makes sense. Then we have the semilunar valves.
So these operate in a different way. Semilunar valves are between ventricle and a vessel. A ventricle, right, a lower chamber and a blood vessel.
So it's always named after the vessel it goes to. So here's a semilunar valve. This semilunar valve is between the right ventricle.
and the pulmonary trunk. So this one is called the pulmonary valve. This little one here, you can't really see because it's behind the pulmonary trunk, but this valve here is between the left ventricle and the aorta, the left ventricle and the aorta.
So this is called the aortic valve. So again, right ventricle and pulmonary trunk, that valve is called the pulmonary valve. Left ventricle and aorta, it's called the aortic valve.
Hopefully that makes sense. These are, this is just a cadaver heart. It's the same thing that we were seeing before. Here are your AV valves.
So this is the right AV valve. This is the left AV valve. Other names, tricuspid valve, bicuspid valve. Here you see the pulmonary valve and right in here between the left ventricle and the aorta would be the aortic valve.
Okay. So let me talk to you about how the valves work and then we'll... quickly trace blood flow, and then we'll be done with the overview of anatomy video. So the valves work, but I'm talking about the AV valves. So the valves between the atrium and the ventricle, they have different structures.
So they have these cusps, right? That's why they're called tricuspid and bicuspid. The one that you're looking at here is the bicuspid valve, but the tricuspid works the same exact way. So We have the flaps, right?
The cusps. Then we have these little cords. And these cords are called chordae tendineae.
They're little cords, right? And they attach to these muscles here called papillary muscles. So there are the three things that you need to know when you're thinking about how do these AV valves work. The cusps, the cords. the papillary muscles.
Now, when the atrium is contracting and moving blood into the ventricle, the valve is open. So blood is moving from atrium to ventricle and the valve is open. But when the ventricle contracts, we want all of the blood to go into the vessel, whether that vessel is the pulmonary trunk.
or whether that vessel is the aorta. So we do not want blood to go back into the atrium. When the ventricle contracts, we don't want blood to reverse and go up into the atrium.
We only want that blood to go out. the vessel. So these valves prevent backflow of blood.
This is how it works. Look down here, down here, we have the ventricle contracting. So you see it's getting, it's like squeezing.
Do you see how it's like relaxed here and it's squeezing there. So as the ventricle contracts, right, the blood kind of swooshes. Here are the, here are the, um, the valve cusps.
The blood swooshes up and closes the valve, the cusps. Do you see it? So the blood, when the ventricle contracts, the cusps close like that.
Hopefully you're with me. This is difficult online, but the cusps close at that same exact point. The papillary muscles pull down. So the blood is pushing the cusps up.
And the papillary muscles pull the cusps down via the cords. So what happens? You have a pressure pushing the cusps this way.
And then you have a counter pressure from the papillary muscles pulling the cusps this way. The pressure should be equal. So the valves close.
When the valves close, the blood can't go back to the atria. So the only option is that it goes out. the vessel. Does that make sense?
I hope it does. Okay. Again.
So the blood, when the ventricle contracts, the blood swooshes and causes the cusps to do this, right? If we didn't have the papillary muscles in the cords, that force of the blood would make the valves do this. And what would happen? The blood would go back to the atria.
So we need a counter pressure. Blood pushes the cusps close, chordae tendineae, papillary muscles. pull down, and then we have a beautifully closed valve.
That closed valve allows for blood to only move through the vessel. Cool, right? The semi-lunar valves are different. They work in a different manner.
They don't need muscles and they don't work on the muscle and cord, like counterpressure. So that's only with AV valves. The aortic valve, as well as the pulmonary valve, will just open because of the increased pressure. So they open because of the increased pressure. When the pressure decreases in the ventricle, they close again.
So they're pretty, pretty straightforward. OK, now the last thing that I want to do is. Trace the flow of blood through the two circuits. I'm going to switch my share to the whiteboard. I am going to start with a blue pen and we are going to do this together.
So get out your notebook or whatever you're going to write on and we're going to Trace, we're going to pretend we're we're tagging a blood cell, and we're moving through the heart and we're seeing where that blood cell goes. So we'll start with the superior vena cava. I'm sorry, might you know my handwriting is bad. You already know this.
It's only our like third video, superior vena cava and inferior vena cava. Again, I'm abbreviating because I'm talking. You don't abbreviate when you're practicing this.
So you write out all the words. It'll help you, I promise. So blood either returns to the heart from the superior or inferior vena cava. Then it goes to the right atrium. From the right atrium, it goes to the right ventricle.
From the right ventricle, it moves to the pulmonary trunk slash pulmonary. arteries. Then it goes to the lungs. What happens at the lungs?
It releases CO2 and picks up oxygen, right? So I wrote this in blue because Blood that is deoxygenated is actually dark red. It is not blue.
It is dark red. And in all of our textbooks, it's shown as blue. Once the, oh my goodness. Once the blood picks up the oxygen and it binds to hemoglobin, oxyhemoglobin is bright red. So now I'm going to switch my color to bright red.
Some fancy. So now the blood goes from the lungs and returns to the heart, but it goes to the left side. So it goes left atrium, left. ventricle out the aorta, and then it goes to the body's tissues.
So we'll right here. Oh my God. Hang on. Hang on. Sorry.
So it goes to the body's tissues. So we'll just right here. Tissues.
And then I want you to say what it does. So it releases the oxygen. It dumps the oxygen at the tissues because the tissues need oxygen to continue to make ATP. It also picks up carbon dioxide. And then where does the blood go?
Back to the. superior, inferior vena cava. It turns blue because it releases the oxygen. So it really turns dark red. It releases the oxygen.
It picks up that waste product, carbon dioxide. It goes back to the inferior or superior vena cava, depending on where the blood is coming from. And it returns to the heart, the right side, and it goes over and over and over again.
The last thing I want you to do, so keep it. repeating this, make sure that you're writing this out. You're understanding what's happening at the lungs.
You're understanding what's happening at the tissues. And I want you to add to this, the valves. So you should be adding tricuspid valve.
Where's the tricuspid valve? The tricuspid valve is right here, right? The tricuspid is between the right atrium and the right ventricle.
So you'll write that in. Where's the bicuspid valve? It's between the left atrium and the left ventricle. ventricle. Then I want you to tell me where the pulmonary valve is and the aortic valve.
I'll let you do that yourself. Keep going over this and over this and over this. Why? Pass. Okay.
Bye, everybody.