044 How Blood Flows Through the Heart
How does the blood move around the body? What is the role of the heart in bringing blood to all the different parts of the body?
Watch and see as Leslie gives an overview of the Circulatory System, the first in this series. Enjoy!
Transcript of Today’s Episode
Hello and welcome to another episode of Interactive Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 44, I am going to be talking about how blood flows through the heart.
This is going to be the first video in the Circulatory System series. So, let’s get right into it.
Here, we are looking at two pictures of the heart. On your left, we’re looking at the heart when it’s being filled with blood. On the right, we’re looking at the heart when it’s pumping the blood out of the heart. We’re going to look at a number of details here just to give an overview of how the blood flows through the heart.
In order to understand how the blood flows through the heart, we need to look at the valves that are found in the different parts of the heart. First of all, allow me to point out that this is the right side of the heart so, this is right. Over here, we have the left side of the heart. Now, that looks a little strange because when you’re looking at the screen, this is your left and this is your right. But, this is looking at it as an individual that’s facing you. This would be his right side and this would be the left side.
There are a number of valves that are found throughout the heart. There are a number of parts of the heart that we need to know. The first thing I want to point out is here, we have the right atrium and the left atrium. So, this chamber is the left atrium. This chamber is the right atrium. Then, we have the right ventricle and the left ventricle. Same thing over here, we have the right ventricle, left ventricle; right atrium and left atrium.
The next thing I want to point out is that between the atria and the ventricles, we have what we call the atrioventricular valve. And that makes sense since it’s between the atria and the ventricle. So, here we have an atrioventricular valve, here we have an atrioventricular valve. Now, on the right side, we also call this atrioventricular valve a tricuspid valve. We call it “tricuspid” because it has three cusps, in other words, three flaps. You’re only seeing two here but, that’s because this is a cross-section. Then, on the left side, we have what we call the left atrioventricular valve which is also known as the mitral valve or the bicuspid valve.
I’m just giving you these different names so that if you go and read a textbook and it says one of these, you know exactly what it’s talking about. So, we have the tricuspid or the right atrioventricular valve and the bicuspid or the mitral or the left atrioventricular valve.
Then, we have valves that allow blood to leave the ventricles. On the right side, we have the right semilunar valve and that is also called the pulmonary valve. The reason it’s called a pulmonary valve is because it leads into the pulmonary artery. On the left, we have this semilunar valve which we can also call the aortic valve. We call it the aortic valve because it leads into the aorta. So, these are the different names and I want you to know these names: tricuspid, bicuspid, mitral, atrioventricular, aortic, semilunar, which is the pulmonary and the aortic. Those are the valves that I want you to be familiar with.
The special thing about valves is that it allows for blood to flow in one direction. So, here you can see blood can flow into the ventricle but, it can’t flow back. If it tries to flow back, these valves are going to shut. So, all of these valves are one-way valves. They allow for blood to flow in one direction.
Now that we know the different valves, let’s look at how blood flow happens.
Blood comes back from the body and it enters into the heart via the vena cava. So, you can see blood is flowing into the vena cava. We have the posterior vena cava and we have the anterior vena cava. Blood is coming in, entering into the right atrium. As it enters into the right atrium, the atrium contracts and that pushes the blood into the right ventricle. Once the blood gets into the right ventricle, the ventricle contracts and that pushes the blood through the semilunar valve or the pulmonary valve into the pulmonary artery. And from here, that blood goes to the lungs. And, it goes also in this direction to the lungs. Once the blood goes to the lungs, it picks up, you guessed it, oxygen because you’re breathing in the oxygen. That oxygen aids the blood. Once the blood gets oxygen aided, it leaves the lungs and goes via the pulmonary veins into the left atrium.
The left atrium contracts sending the blood through the left atrioventricular valve into the left ventricle. Once the blood is in the left ventricle, the left ventricle contracts and that sends the blood through the semilunar valve or the aortic valve in this case, into the aorta, and then, that blood can go to the rest of the body. I know this looks a little confusing with all of these arrows but, let’s follow that one more time. Blood comes from the body. It enters via the posterior and anterior vena cava into the right atrium. The right atrium contracts and that pushes the blood through the tricuspid valve or the right atrioventricular valve into the ventricle. The ventricle contracts and that pushes the blood via the semilunar valve or the pulmonary valve to the pulmonary arteries that go to the lungs, picks up oxygen, then it comes back oxygenated via the pulmonary veins into the left atrium. The left atrium contracts and that pushes the blood into the left ventricle. The ventricle contracts, pushing the blood via the aortic valve or the semilunar valve to the aorta and out to the rest of the body. So, the function of the heart is basically to pump the blood to the body, to send the blood to the lungs to pick up oxygen, and then to send that oxygenated blood to the muscles and to the organs that need it.
Once the muscles and the organs that need it, once they use that oxygen, the blood comes back via the vena cava to the heart. The process can continue over and over again. I have these two over here and you can see, this shows the heart filling with blood and, this shows when the ventricles actually contract and send the blood out to the lungs and to the rest of the body via the aorta.
There’s one thing I’d like to emphasize though. I say that, first the right atrium contracts and then the right ventricle contracts, and I’m saying that just because I’m showing it one at a time. But, both atria contracts simultaneously and both ventricles contract simultaneously. So, that while this process is happening, this process is also happening. Blood is being pumped to the lungs. At the same time, it’s being pumped to the rest of the body. That gives you a general introduction into the circulatory system by showing you how the heart pumps blood.