01.08 Blood Flow Through The Heart

Hey guys, in this lesson we're going to talk about blood flow throughout the heart. So let's go ahead and get started and hopefully you guys will get a good understanding of this because I love cardiac and I hope that all this makes sense. So it is imperative to know the blood flow throughout the heart so that you can comprehend other cardiac diseases such as heart failure. My most important piece of advice that I can give you guys is to keep it simple. If you understand the anatomy of the heart, then the blood flow should just be easy to comprehend. Don't make it harder than what it's gotta be. So let's go ahead and get started and talk about it. So here is a heart, right atrium, right ventricle, left atrium left ventricle.

So usually most books when they start talking about the blood flow throughout the heart, it starts in the superior or inferior vena cava. And that looks something like this. And this is supposed to be on the back of the heart. I just gave you a picture of the front of the heart. So this is a superior vena cava, and this is the inferior vena cava. Blood is coming from the body and it dumps into the right atrium. Typically this blood is coming from the brain, and it dumps into the right atrium. So after the superior and inferior vena cava, it goes into the right atrium as it enters the heart. Once it enters the right atrium, then it crosses a valve that we have right here, which is called the tricuspid valve. So this valve opens when the atria contract and it goes into the right ventricle.

So superior and inferior vena cava, right atrium crosses across the tricuspid valve and into the right ventricle. And this is all poorly oxygenated blood because it comes from the body. So let's go onto the next slide and keep going. So again, here's our heart. Now after it has entered the right ventricle, it has to go through the pulmonary valve, which is about right here. And it looks something like this. Well, the valve looks like this and then it goes through the pulmonary arteries. One goes to the left and one goes to the right. Okay. After the blood goes through the pulmonary arteries, one to the left lung, one to the right lung, that is where gas exchange occurs. So this is where oxygen and CO2 diffuses. And so after this happens, then we have the left and the right pulmonary veins and they are coming back to the left atrium. If you're thinking about behind the heart, it would just kind of come somewhere like this. So afterward it goes into the left atrium.

So let's go on to the next slide cause it keeps going to the left side of the heart. So again, here is the heart and here is our lungs and the pulmonary veins are now entering the left atrium. And really quickly, how is this, is this oxygen-rich blood? Yes it is because it has already gone through the lungs. And so the blood that's coming to the left atrium is full of oxygen. So once it goes through the left atrium, it has to pump it to the left ventricle. But first we have a little valve right here called the mitral valve. That valve opens up and it allows the blood to enter the left ventricle. Remember, this is all oxygen rich blood. We have a little aortic valve right here. So after the left ventricle contracts, the aortic valve opens and the blood goes right here.

So in this slide, let's back up a little bit again. I know y'all love the heart and my little drawing. So here's the aorta and from the aorta, if y'all remember A&P days, we have the aortic arch, we have these little arteries that go and supply blood to the brain and the upper part of the body and all that type of stuff. And this right here is the can go into the acsending and then descending aorta. It brings blood to the kidneys, liver. It goes throughout the body. Here's the arms. So it sends blood through the body all the way down.

Wow. This is why I became a nurse and not an artist all the way down to the legs, and so the blood just gets distributed everywhere. And so what happens when it reaches the tissues? Remember we have little capillaries right here. And so the blood that is full of oxygen goes to the capillaries and this is where it delivers the oxygen to the tissues. And and then it goes back into the veins and eventually it all circles back to the inferior vena cava or the superior vena cava. So let's do a little recap about all this.

Okay. It's important to understand the blood flow throughout the heart. Keep it simple. And if you understand the anatomy of the heart, then this will all sense. So I'm going to do it one last time all together, and hopefully, this will help. Here's a superior vena cava, and it's a vein that enters the top atria.

Here's the inferior vena cava. And the reason why it's right here is because it's behind the heart, but it would come and it would dump right here into the right atrium. Okay, so superior and inferior vena cava, it goes into the right atrium and then it crosses the tricuspid valve so that the blood goes into the right ventricle. When the right ventricle contracts, it opens up the pulmonary valve. Blood goes through the pulmonary valve into the pulmonary arteries. Also, just a side note, if y'all remember, the pulmonary arteries are the only arteries in the blood without oxygen because they're going to the lungs. So once it goes from the pulmonary arteries, it's going to go straight to the lungs. And this is where gas exchange occurs after it goes back to the lungs it's got to come back to the heart. So it's going to do that through the pulmonary veins.

And one from the right side, one from the left side, and it takes it right into the left atrium. From there, it crosses a little valve called the mitral valve. That valve opens when the atria contract and then the blood goes in here into the left ventricle. From there when the left ventricle contracts, we have a little aortic valve right here that opens and the blood goes through the aortic valve and it goes through the aorta and into the body. And this is where oxygen enters the capillaries and then it comes back to the heart from the inferior and the superior vena cava. I really hope that my little drawing has helped. So here's our heart, remember blood goes this way and then it's going to go to the lungs and then it enters in and blood goes this way and when the left ventricle contracts, blood goes this way and it goes to the body.

When somebody has congestive heart failure, right side or left side sided heart failure, and if the left ventricle does not pump like it should. So all this blood that's trying to go to the body, it's not able to because the pump, remember the heart is a muscle and so the pump is not able to pump out the blood. So it kind of backtracks. So if you think about it, blood comes from the left atrium before it goes to the left ventricle. So if the ventricle can't pump like it should, everything starts going backwards. So it backs up into the left atrium. So think about it for one second. Where's is it going to back up into now? Right into the lungs. As a heart failure gets worse, it can affect the right ventricle and the right atrium and then everything backs up into the body.

So sometimes depending on whether it's systolic or diastolic or left or right-sided heart failure, you'll see people that are short of breath and have fluid retention and it's all in their lungs. That usually means that the left ventricle is not working. Or have you had people with, fluid in their legs and their legs were swollen or they have the ascites or JVD, the jugular vein distension. It can usually means that it's right-sided heart failure. It used to be called left-sided, right-sided heart failure or congestive heart failure. Now it's just called heart failure with reduced ejection fraction or systolic heart failure or heart failure with preserved ejection fraction or diastolic heart failure. But that is for another lesson. This lesson is just to get you guys to understand the basic blood flow throughout the heart. And I hope that this has helped. I hope that you have a basic understanding of it and are more intrigued on how the heart works and you guys would want to go out and learn everything there is about it now. Make sure that you guys go out and be your best self today. And as always, happy nursing.