Two circulations in the body.

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So what you're looking at is basically kind of a mechanistic way of thinking about the heart.

Almost it´s a couple of pumps with pipes attached to the pumps.

And in the way, that´s not a bad way to think about the heart.

In fact we're gonna kind of move through this diagram.

I realize that it looks little bit scary. But, once I start labeling these stuff you'll start to see that it is actually not as bad as it seems.

So let´s get started in the upper part of the heart.

The Right atrium, It's right there.

And the blood goes down into the right ventricle.

And then, on the other side I´m going to label the last two chambers. The left atrium and the left ventricle.

We're gonna actually follow the path of blood after it leaves the right ventricle.

We're gonna start our journey here at the right ventricle.

So what´s the first thing that kind of comes across?

Well, blood leaves the right ventricle, goes through a valve and after, on the other side you´ve got, this area right here.

And I've drawn it as one tube with no split and this is the pulmonary trunk. Pulmonary trunk.

So blood is headed towards the lungs, going first through the trunk, and of course after the trunk, there is left and right --I write that up here-- pulmonary arteries are next.

And remember I call them arteries, because they´re going away from the heart.

And there are two arteries, so pulmonary arteries left and right pulmonary arteries.

And that´s why you see two things here, one here and you see one here and those are basically tubes.

So it´s going from the pulmonary trunk, it´s splitting into one of the two tubes and I´m drawing the left and right lung up top.

Of course you know that the lungs are actually not gonna look this way, so this is not anatomically correct.

But this is not --as I said in the beginning-- bad way of thinking about it.

So blood goes through the lungs and then comes out on the other side and there, we're gonna talked about the left and right pulmonary veins.

And actually here I´m gonna make the point that there aren´t just two pulmonary veins, one for each lung.

Actually they're usually more than that.

And so when I draw these two, I really wnat you to just think of the two sides, veins coming from both sides.

But the actual number could be a few pulmonary veins in total.

The pulmonary veins drain blood and into the left atrium, right.

So now we are on the other side of the heart.

And for the moment I´m gonna kind of pause the journey here. So we´ve gone from the right ventricle around to the lungs, back again into the left atrium.

And this is kind of the first part of our journey.

And this part of the journey is called the pulmonary circulation.

I´m actually just gonna write that here - Pulmonary circulation.

So the fact that this part starting from the heart and going back to the heart is one circuit.

And our heart actually has two circuits.

But I wanna point out these circuits one at a time.

We´ve already kind of completed one circuit.

So I´m gonna just take some blue paint to indicate deoxygenated blood or blood without oxygen,

I´m gonna paint in how it look.

--And actually it stop there because of my arrows, but you can actually see now-- deoxygenated blood kind of goes from the right ventricle, through the pulmonary trunk, through the arteries and into the left and right lung.

And once it´s there it´s gonna be kind of mixed in with the capillaries and it´s gonna start getting oxygen.

And then it´s gonna come out on the other side, in the pulmonary veins.

--And It´s again stopped a little bit there, but I can fill it in-- and the pulmonary veins are gonna deliver that oxygenated blood to the left atrium.

So what you see kind of colored in now, is the pulmonary circulation.

That´s the first part of our circuit.

Let´s now keep going and talk about the second part of the circulatory system, which is the systemic circulation.

So now the journey starts with the left ventricle. Let me start there.

For the systemic circulation, I´m gonna start in the left ventricle and it´s gonna go round to the body.

Right, the body is kind of the thing that's gonna be receiveing all the blood.

And when I said body, I really mean lots of things.

I mean things like the brain. So it coud be an organ, like the brain, the liver. Or it can also be maybe things like bones and your fingers, could be the toes, could be any part of your body that you can think of.

All these different organs and tissues are gonna be getting blood from the left ventricle.

It´s gonna be going initially through a giant vessel.

This vessel I´m gonna label --let's say here, as the Aorta.

So this large vessel, the Aorta. And of course it branches and splits and I haven't shown all the branches that come off the Aorta.

But there are many, many of them.

It goes to the various tissues and organs and then it comes back on the other side.

And at the end, kind of somewhere up here, it´s gonna go back to the right atrium.

And it generally travels through two major kind of vessels.

One is the Inferior and the other is the Superior, meaning lower and upper, and they both are called Vena Cava.

So Superior Vena Cava and Inferior Vena Cava. I just write that here.

So these are the two major veins that bring you back blood from the all the different parts of the body.

So now you´ve actually seen the second circulation, because it all ends up in the right atrium.

And this is the systemic circulation. I´m going to write [systemic circulation] here.

So now you can see that the heart is really two different system --err-- let´say two different circuit, rather.

And the first one, the pulmonary circulation, is really kind of relying on the right vetricle as the pump.

And the second one is relying on the left ventricle as the pump.

And actually I can --now you see, I can now color it in.

It would kind of deliver all the blood to the various organs, then the organs would use up the oxygene, so let me show it kind of now going back to blue.

That´s to indicate deoxygenated blood and it goes back to the right atrium as deoxygenated blood.

So this is kind of how we sometimes see it and again this doesn't show you or give you an appreciation for the anatomy exactly,

you know, where things branch off and where the different names make sense,

but you got kind of overall feel for the fact that we have two different circulations

and you can see where the blood is going for the two different circuits.

Now when you look at this picture you could say, well, okay, I guess you can see all the different tissues are getting the blood,

basically sounds like everything is coming from the oxygenated blood,

coming out of the left ventricle.

But, some tissues always kind of trick people out --err-- it's kind of a sparkle question.

I´m just gonna kind of try to target a couple of the tissues that I think people sometimes might have questions about.

And one of them, I woudn´t really call it tissue, but you can definitely call it cell type.

It´s the RBC, and RBC just stands for red blood cell.

So people sometimes wonder, you know, if the red blood cells are carrying oxygen to other parts of the body.

Then how do they themselves get oxygen?

You know, do they just kind of use up some of the oxygen they´re carrying, or what exactly?

And to answer this question, I would have to remind you that the red blood cell basically looks a little bit like this, right, in cross section.

And it doesn´t have any mitochondria, no mitochondria.

So, has no mitochondria. And remember, mitochondria are these tiny little organelles inside of cells that are using oxygen.

So that has no mitochondria, and it´s not really using oxygen.

So it´s not using oxygen and really these cells, we call them cells and there are many senses of the word,

but they don´t really have mitochondria, they also don´t have nucleus.

These are literally amazingly designed cells that are made for the purpose of carrying around oxygen to the body, because they literally are bags of hemoglobin.

So just remember, red blood cell don´t really need oxygen they´re simply carrying it around.

Another tissue or organ that makes people kind of wonder, is the heart.

The heart is pumping all the blood around, but does it actually get oxygen from vessels that are in the pulmonary circulation or from the systemic circulation or what?

And here the short answer is systemic circulation.

That´s kind of the quick answer.

And let me actually show you where the blood vessels come from.

These are called coronary vessels --I just write the word coronary here. Coronary vessels-- So, coronary artery and vein.

And these coronary vessles they actually come right off the aorta here and here.

So they kind of come off the aorta right away, they are the first branches off the aorta, actually.

So the first branches go and serve the heart.

So it´s kind of the first to get systemic circulation blood.

And the veins actually drain into a spot , directly into the right atrium.

There is actually a little spot right there that they drain in to.

So the blood from the arterial side is coming from the aorta

and on the venous side it´s actually not even dumping into the inferior or superior vena cava,

kind of little known fact that is coming directly into the right atrium.

And finally kind of tricky one, but the lungs.

Where do the lungs get their oxygen from?

And this is, I said tricky and I can not save this for last because there are actually blood vessels

and again don´t worry so much about the anatomy --in terms of where is it coming off exactly,

but it´s coming off of the systemic circulation and you´ve got a vessel going to the right lung.

Let´s say something like that. And you´ve got another vessel going, I´ve just drawn --kind of going to the left lung, like that.

So you´ve got a couple of arteries that are branching off and these are also part of the systemic circulation --systemic circulation.

And these are called the bronchial arteries.

And these bronchial arteries bring then, really --wonderful- oxygenated blood, right. These are the bronchial arteries.

And you might say, well that wasn´t so difficult.

I'll say bronchial vessels, because there are also some veins coming off.

Actually let me draw the veins now for you, so you can see how those kind of end up

and these veins come from -of course- the right lung and they actually end up -kind of- dumping in here.

I can't really show blue on blue, but you know, just try to see they kind of go there.

And you´ve got another vein from the other lung

kind of following a parallel path and going into the veins, as well.

And so they don´t dump necessarily directly into the inferior/ superior vena cava.

I´ve just wanna showed that they´re going to the venous side on the systemic circulation.

So if that was it, that would be really simple. But, actually lungs are kind of interesting in the sense that there is a lot of mixing going on.

You´ve got pulmonary arteries carrying blood,

you´ve got bronchial arteries carrying blood

and that blood mixes.

And then you´ve got the capillaries,

you´ve got some blood kind of from both places -

the pulmonary circulation and the blood from the systemic circulation again mixing.

And then on the other side where the veins are bringing blood back to the heart

most of the blood as it turns out, most of the blood actually goes this way into the pulmonary veins.

So even though you have the bronchial arteries bringing blood in, that would be right here,

you know the bronchial arteries bringing blood in, a lot of that blood ends up going into that pulmonary circulation.

So that´s kind of a intersting fact that not as much goes this way directly into that systemic circulation.

So that´s kind of the tricky thing to keep in mind

but the lungs then technically really are getting blood both from the systemic circulation

but also they are kind of mixing blood and they´re mixing blood with the pulmonary circulation.

We´ll talk a little bit more about this in another video

and I don´t feel like this kind of --got too confusing

but I just want you to be aware that there is mixing going on in the lungs with the systemic and pulmonary circulation.

That´s kind of a unique organ in that sense.