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Current time:0:00Total duration:10:11

Layers of a blood vessel

Video transcript

let's talk about blood vessels I'm going to talk to you about the different types of blood vessels that there are and we're going to see if we can come up with some general patterns so let's start with the let's say we take a blood vessel out of your body and we examine it under a microscope it would look something like this where you have the middle and called out the lumen and right outside of the lumen you have cells and these cells are going all the way around the lumen and they're the first type of cell that any blood would interact with right because that's right immediately outside of the limit and on the other side of the cells on the back side of the cells if you think of the lumen as the front side is a little line I'm going to draw here to represent protein that sits there and acts as a scaffold kind of like keeping all the cells in place so you have all these endothelial cells endothelial cells and then you have that little basement membrane like a thin line of membrane called a basement membrane that keeps everything from falling out of place and the thing that's in the basement membrane is mostly protein so think about things like collagen which you can find in bones and your gums that same protein is actually lining all of these blood vessels that are in your body and together the basement membrane in the endothelial cells they make up a layer called the tunica writing it nice and big intima then make up a layer called the Tunica intima and that's kind of the the word we use because Tunica comes from the word for coat or cloak and intima is kind of the intimate layer the intimate coating of the vessels so Tunica intima now right outside of this is another layer and I'm going to draw that here in red and this bill layer of muscle so imagine these little lines represent smooth muscle cells so this would be muscle this would be the layer of Tunica called tunica media or middle and the most important thing here is that they're smooth muscle in this layer smooth muscle and finally on the very outside you have another layer and I'm going to draw it as a yellow line and this yellow line represents more protein this is another layer protein just like the basement membrane but different composition of proteins but again you see actually a lot of collagen just as before and some other proteins as well and this is called the Tunica externa for external layer Tunica externa actually another word that they sometimes use for this is called adventitia adventitia so you might see that word too and the really interesting thing about the Tunica externa is that you actually on the large vessels you find that they need blood to supply themselves and so some of these large vessels have little blood vessels on them now you might think well this is just go on endlessly you know vessels with vessels on them and then those little vessels have more vessels on them and so on and so forth actually no it's just a large vessels that have this so you sometimes not always see what's called visa vis orem and this is kind of a fancy name for but there are little blood vessels on blood vessels which I always thought was kind of a cool thing so the Tunica externa has the blood vessels and it also has nerve endings and I'm not going to actually draw that in because it'd be kind of hard to show that but nerve endings actually can be in that layer in that Tunica externa layer so you've got 3 layers each of them has some pretty cool things in them and now I thought what we'd do is we'd go and think about each vessel type and how this could look for that vessel so let's start with the veins and I'll do the veins over here so let's say you have a vein on the inside it has that Tunica intima layer and I'm not going to draw the cells out because now you know what that represents that purple line represents the endothelial cells and the basement membrane and you also have a smooth muscle layer so kind of a red line to represent tunica media and veins have a Tunica externa a third layer so veins kind of follow this general pattern they have these three layers and they're pretty straightforward in terms of following exactly what I just talked about fair enough now arteries let me do a different color for arteries let's say red I think of arteries in two different groups so I think of large and middle sized arteries a little differently that I think about small arteries or arterioles and you'll see that these small arteries and arterioles actually look quite similar to one another so let's start with the large and middle sized arteries so there you have let's say an inside and then on the outside of that in the tunica media layer you start seeing a difference from the veins you see that it's much larger much larger and in the vein you just had to kind of a thin layer smooth muscle here you have a nice large layer of smooth muscle and in addition to having these smooth muscle cells in the large and middle arteries you have an interesting new thing you have something called elastin protein in elastin is going to be in here and this is a protein that helps make these very elastic right because they're going to have such high pressures that they have to be able to not break when these pressures are going through so this elastin this green elastin protein helps make the arteries more elastic more elastic for high pressures or high pressures and I'll write p4 pressures so that's what the middle layer looks like and of course you still have your outer layer as before ok so you've seen one key difference now right with these large and middle sized arteries okay now let's go to the small arteries and arterials so here let's start out with a lumen you have that as before and you also have a large tunica media so unlike the vein the tunica media and the arteries in both types of arteries is actually quite large except here instead of having elastin in this area you have just tons and tons of muscle lots of muscle so they're very very strong in the sense that you can actually very easily squeeze down on the lumen if you wanted to by having all this muscle contract and that makes sense because we know that the arterioles look at all that muscle the arterioles are actually going to be the ones that are going to create resistance so here you have a lot of muscle and this is to help create lots of resistance if you need it to change your blood pressure so that's why the small arteries and arterioles are really helpful in squeezing down and changing blood pressures and on the outside they as before have that layer of Tunica externa and this again is where the nerve endings go and where the blood vessels are the vase of Zoram go so that's where that layers okay and you might be thinking well there's got to be one more cell or one more vessel type and there is and it's the capillary so let me draw the capillary and so I'll do that over here and the capillary is actually going to look different from all this other stuff that we've done because the capillaries are actually really really unique in the sense that unlike we had for the veins and the arteries this is down to the single cell level right so you still have a lumen but on the outside instead of having a lot of endothelial cells you actually have at times one cell one cell will actually form the entire wall of the tube so you actually have a cell traveling within a cell almost like the cell is giving the little red blood cells floating through a big hug or something like that so that that capillary looks actually quite different as you can see from the other things that we've drawn the veins and the arteries but I want you to just take a look at this again and see the the key differences between the veins and the arteries the vein follows the general pattern but the larger middle arteries have a lot of elastin in the tunica media and the small and small arteries and arterioles have a lot of muscle in that tunica media