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Okay let's talk about the arteries and the veins

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and I'm actually going to talk about the both of them

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and simultaneously because there are some interesting

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differences I want to point out between the two. You know that they're both vessels but

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there are some really important differences between how they work and what they do.

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So this is your heart and coming out of your heart is the aorta

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and before this video I have been drawing the aorta quite differently,

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kind of showing its branches and here I am showing it kind of stretched out.

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and I'll show a few of the branches but really the point of the drawing is not to make it anatomically correct,

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you can tell that definitely it's not anatomically correct,

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because that wouldn't make any sense at all,

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that blood going off to one side.

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But really, I want to show you a concept in this video.

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A few concepts, actually. So, here we have --let's say, the vein.

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And I'm gonna stretch that out as well, and let's imagine that

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all of the veins are dumping into this one final vein.

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It gets back to the --to the heart.

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So I'll draw the branches kind of coming in to the vein here and here.

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And we know that the arteries and the vein are trying to get blood out to the capillaries.

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So these show you what a zoomed in version may look like of the capillaries.

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So we've got --let's say, some capillaries, 
here and maybe some here and here.

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And you know of course in real life you don't have three such a capillary beds,

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which is what I'm drawing here, but really of thousands and thousands, right?

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And let's not to forget, you know,

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these capillaries are basically found in different parts in the body,

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so you might have --for example, a bone, and some capillaries in the bone,

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you may have this second capillary, may be, going to your face,

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let's say even specifically, your nose.

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And this third capillary bed, may be going down to your foot.

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So you have blood in your foot.

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So you have different parts of the body all getting capillaries and

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the blood is gonna start at the heart, go to the capillaries through the arteries,

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and then return through all those beds.

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And we've kind of lumped it together.

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And what I want to show you now is, that these very very simply is the systemic circulation.

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Systemic circulation.

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Now, of course you know that there is also the pulmonary circulation.

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So what is that look like?

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I mean to draw that here --pulmonary circulation.

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So pulmonary, you know, means lungs.

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And I've shown you previously, in another video, that there is blood going to these lungs.

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In a very low pressure system. So we talked previously about low pressure and high pressure system.

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And now I just remember that this is kind of how it gets there,

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you have deoxigenated blood, or the --the blood in the blue vessel,

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kind of going up like that, and this should be the pulmonary artery.

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Pulmonary artery.

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All right, {Art.} for artery. And we have the pulmonary vein,

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bringing that blood back to the heart with oxygen in it.

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Pulmonary vein.

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So that's your pulmonary circulation, so your pulmonary circulation in your systemic circulation.

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And I'll get back to why I drew the pulmonary artery in blue,

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and pulmonary vein in red, in just one second.

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Let's put that on the side for a momment.

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And let's get into exactly how to think about arteries and veins in general.

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So in general, I think of arteries as taking blood {AWAY} from the heart.

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That's the easiest and most clear way of figuring out what an artery is exactly.

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So, arteries are taking blood AWAY from the heart.

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So let me just draw a little arrow here.

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And veins are bringing blood {BACK}. And so this becomes our first point.

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Point number one, and this's the point of difference between the two of them,

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is the direction of flowing, and even if you see at pulmonary system,

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you can see that --that remains true, that the arteries are taking blood away,

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and the vein is bringin the blood back.

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Okay. Point number two. Now you see that the arteries are drawn in red, for the most part.

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And so usually arteries have oxygenated blood, that they're bringing out to the tissues.

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And then the veins carry the deoxygenated blood, that they bring back from the tissue.

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So point number two, is really about the colour.

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And so we write that in here.

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So this should be like a little red blood cell with hemoglobin in it.

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And this is a little red blood cells --

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still called the red blood cell eventhough its colour is more blue,

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but it still got the hemoglobin in it,

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but the hemoglobin down here --down here, actually doesn't have any oxygen left,

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and so the colour looks quite different.

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So the colour of arterial blood is usually red, because of the fact that oxygen is bound to the hemoglobin.

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And less oxygen bound in the venous side, so that's why it turns blue.

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Now, I want to --just a little star there, because that's not always true.

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And you can see where clearly it's not true, it's over here.

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So I'd like to --let me star the pulmonary circulation,

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where you can see that the pulmonary artery and vein --I'll star that,

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that's just really emphasize the point, or actually the reverse of what I've just said, right.

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Because the pulmonary artery is actually gonna carry deoxygenated blood,

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and the pulmonary vein is carrying oxygenated blood.

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So clearly that's the reverse of what I've just side.

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But that is one exception to the general rule,

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which is that arteries definitely look red, and veins generally look blue.

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Okay, so that --those are two points of difference between the arteries and veins.

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Let's keep going. So now you know, that arteries are high pressure, right.

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because the heart is pumping the blood out, and it's gonna be in a very very high pressure.

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And so I kind of think the arteries as being like a river, a fast flowing river.

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So you can think of this as fast flowing, high pressure.

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So that is the third difference. This is a high pressure system.

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Third difference, it's that it's high pressure system.

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In fact, maybe I'll even emphasize the point by writing the word very large:

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HIGH PRESSURE.

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And actually, the other thing we think about with these arteries is that there is not so much volume in the arteries.

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So if you actually look at --let's say, first time now,

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you should try figure out where all the blood was located,

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not too much of it is in the arteries.

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So it's very low volume system, right, its volume is very small.

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And the veins are the opposite. They're kind of a large volume-- system.

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And they have really kind of a low pressure.

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Alright, pressure is very small over here.

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And if you actually figure out what percent is where,

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in terms of the amount of blood, about 5% of the blood, at any point time,

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would be in the heart. And --let's say, about 5% would be in the capillaries.

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and then about 10% or so, would be in the lungs.

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So what we have to --now we're 5 and 5 is 10, 10 plus 10 is 20.

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And then we have another about 15% in the arteries. So about 15%.

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So that's actually not too much blood.

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And so the remaining --what is that, 65% of the blood, is actually in the vein, in any point of time.

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So that's remarkable, right. About two third of the blood in any point time is actually sitting in all the vein combined.

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And so the way I've drawn it, isn't really --not really a best way to draw it.

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I should really erase this. And really redraw this to make it much more accurate.

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It should look a lot more like this, right, like a big giant lake of blood.

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And so this is actually how to think about of the vein.

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It's actually very very low pressure but high volume system.

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So that may be the third point. I'll bring up on the blood side --or, on the vein side.

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it's that it's a high volume system. so, high volume.

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Now, we've talked about the direction of flow,

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we've talked about the fact that one side carries more oxygen than the other,

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and we've also talked about the fact that arteries are high pressure-low volume system.

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And the veins are high volume-low pressure system.

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So what are some other differences?

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So, one other difference is that in the arteries, you actually don't have any valves.

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Now --I don't know how to label that to make it super clear, but let me just find some sort open spot here,

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and write number four, there're no valves in the arterial system,

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whereas on the venous side, you actually do have valves.

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You have these valves come together --we make it very clear, but making the two sides touch.

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And the blood kind of goes through like that.

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So you have these valves keep the blood going in the right direction.

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So that would be the fourth point of difference between the two.

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So you have these valves. And you might get confused, because you think,

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"well, doesn't the heart also have valves?"

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And it does, the heart also has valves.

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But the veins have a different type of valves, and that's actually keep the blood flowing in the right direction.

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You can imagine that you probably don't even need that on the arterial side,

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because the pressures are so high, that the blood is forced to go one way.

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Or, it's in the vein, because it's kind of a giant lake.

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Water can kind of swirl around and around and around,

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and so it's helpful to have valves keeping going in the right direction.

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So that's the fourth point of difference.

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So now think about of the fact that you might have, a break in the arterial system.

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So let's say that you have an accident, and you cut an artery --or, a big artery, let's say.

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What would it look like? So if you have a break right here,

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you would actually have like a fountain of blood, coming out, right there.

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Because it's under such high pressure, it's gonna spew up, right.

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And so this is basically what it looks like when you actually cut your artery,

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again, because of the fact that it's under such high pressure.

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And on the venous side, on the vein side, if you have a break. It looks really different.

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Because you have --let's say your break is right here,

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you'd actually get a kind of --a pool of blood, just locally, before it clots off.

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Because again, you have a very low pressure. So it's just gonna kind of quietly pool and,

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you might get a bruise right there.

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But it's really won't look like a fountain of blood.

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And that's actually another final point of difference which,

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really gets back to the high pressure system on the arterial side,

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and the high volume-low pressure system on the venous side.

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~o0o~