episode44

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.

As usual, you can visit the website at Interactive-Biology.com for more Biology videos and other resources. That’s all for this video, my name is Leslie Samuel and I’ll see you on the next one.

526 comments
Shahwalli
Shahwalli

Dear Leslie Thank you so much for your videos. They are great :)

Rana Shammas
Rana Shammas

This is extremely helpful. It helps me to picture it and understand it very well. This video is stuck on my mind. Will never forget the blood flow from now on :) Words can't thank you enough!!

adedayo Clement
adedayo Clement

pls how do I download these videos I'm a second year medical student and I'm greatly in need of them

Bop Beast
Bop Beast

Simply Amazing!! i cant believe i learned all this in 9 minutes when my teacher couldnt teach us in 75!!

al niebs
al niebs

and John Tan there are pulmonary veins on the right and left sides, just like the artery extends to both sides, for both the left and right lungs..

al niebs
al niebs

good vid but it bugs me that you call the inferior and superior vena cava the posterior and anterior vena cava...

trikampiukas
trikampiukas

Thanks a lot!! I do fitness and PT course, and I have anatomy class and I started circulatory system stuff. At the first class I couldn't absorb it, but now I have a clue how it works:D. Thanks once again for the simple explanation!

Roy Chang
Roy Chang

Were you aware that "Atrioventricular" in your slides are spelt incorrectly?

Rawdha Alkaabi
Rawdha Alkaabi

Thank you a lot , your video saved my life cuz tomorrow I have a test and I have to study about blood and other stuff , I didn't understand that part so I looked in YouTube and found you :) thanx again

mojo gamer
mojo gamer

thank you this video really helped me. it was well explained and really clear . thanks

Katherine Astaneh
Katherine Astaneh

The body is truly an amazing work. You have expressed this process to a level of understanding...thank you so much! I look forward to seeing more.

Debora Commins
Debora Commins

I am also fascinated!!! Anatomy was my favorite subject at University.

Suzane Tshibala
Suzane Tshibala

You're simply awesome. Thank u sooo much and keep up the brilliant work :D

LaTrina Treadway
LaTrina Treadway

See this video to learn how blood flows through the heart:

Shane holgate
Shane holgate

See this video to learn how blood flows through the heart:

John Tan
John Tan

aren't the pulmonary veins labelled wrongly? they should be on the left of the heart

Geraldine Molina
Geraldine Molina

Awesome explanation. You are the best!!!! The more I study the human body, the more I'm amazed by it.

sarah loutzenhiser
sarah loutzenhiser

Wow this is amazing! You make it easy to understand =) I will be watching more of your videos as I travel through my classes!

moniquedaleymd
moniquedaleymd

May God send down his many blessings upon you. You explained with such detail. This is coming from a student who was fighting to understand the functions of the heart. God bless! Monique D

alex biocanin
alex biocanin

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Glenda V.
Glenda V.

You are amazing! Keep up the good work! God Bless you!

bsa0852
bsa0852

Thanks for you .. It's very clear

kalpesh patel
kalpesh patel

Thank you so much, u have cleared my idea about blood circulation. I didnt understand when my tutor explain me. You are great

Lex
Lex

Thanks a lot! It's the little things that you say that makes such a huge difference. For example, "The antrioventricular is in the middle--and that makes sense because it is between the atrium and the ventricles." It's hard to see the obvious when you are so overwhelmed with everything else, so things like that really helps!

FRANCISCA NZEKWE
FRANCISCA NZEKWE

oh My God I enjoy the lecture; when I saw the cardiac cycle, I was scared, but now, I can teach it to other people myself. Thank you, you are a God saver

HentaiQueen
HentaiQueen

The blue ventricle looks an awful lot like a penis

fffashionjh
fffashionjh

Thankyou soooooomuch omg I have never learned the heart this easy! amen

Jan Amber Rose
Jan Amber Rose

Let's try to keep up on this stuff as we get older we should know this, especially for my family because we have a tendency to die from Heart problems.

Odiyanaa Ravi Swamukth
Odiyanaa Ravi Swamukth

hi samuel, thank you so much for your kind explanation.... you gave me a relax mind by going through details of each circulation.... wish you are my teacher at my class...

Leslie Samuel
Leslie Samuel

And I'm glad to hear that the videos are helping you :)