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Current time:0:00Total duration:12:54

Video transcript

so I wanted to talk to you a little bit about atherosclerosis and I have already cheated a little bit and I started drawing I wanted to make it slightly nicer drawing because I wanted to make sure that the important things we can actually see them and that it's pretty clear so in the top left I have a small vessel and I have the three layers and in the middle is the lumen and on the outside is the the outside so this little white box I've drawn I've tried to blow it up for you a little bit here so again over on this side we have the lumen just to orient you again and this is the outside of a blood vessel so we know blood vessels have three layers and this particular blood vessel is actually let me label it is a middle or large artery so I'm specifically talking about large and middle sized arteries here and the reason that this makes a difference I'll point it out specifically again but there are these green little coils I've drawn here like these little green squigglies and this is a little protein called elastin and I specifically want to talk about these arteries because these large and middle arteries that have in them in the walls elastin are very very susceptible to atherosclerosis this process and so I thought that it makes sense to point it out just so you know exactly which vessels are being affected by this process so let's go through and very quickly refresh ourselves and talk about the three layers of the vessel we have the intima the Tunica intima and I'm just writing T for Tunica and then the that's the innermost layer the middle layer right here in red is the tunica media and i remember that because it's the middle layer so media middle and on the outside right here is the Tunica externa external kind of the external layer and sometimes you'll see that as adventitia another word for it so these are the three layers and we know this and the way that atherosclerosis happen this is a process and it's a it's a process that affects millions and millions of people the way this happens is that it usually affects these large vessels large middle arteries and actually these vessels just to give you a little bit of an orientation I'm talking about one millimeter sized vessels all the way to about 25 millimeters in diameter so kind of a kind of biggish vessels that you can actually see with your naked eye this could be like the artery that maybe maybe the aorta the largest artery could be an artery that goes out to my arm the brachial artery so any of these larger middle sized arteries fit in this category and they're affected by atherosclerosis and so the first step in atherosclerosis let's just jump into it is that you have an irritant some irritant and that could be I'm not talking about maybe someone's annoying little brother or sister or a knowing neighbor but some irritant like let's say you have here I'll draw it in red a toxin from cigarette smoke so let's say you have some toxin that's swimming through your blood vessels and that could be an irritant another irritant could be so I'll put smoking up here for that another irritant could be maybe having too much lipids so maybe a hyperlipidemia hyperlipidemia and when I say lipid I mean specifically fats and cholesterol so you could have little droplets that's show little yellow droplets that I think of yellow is fat of LDL this is a protein LDL stands for actually I'll write that out low density that's what the L and the D are low-density lipoprotein this is basically something that carries fat and cholesterol around your blood so you could have too much of it you could have too much LDL in your blood in the in the blood vessels and the arteries and that could be an irritant or it could be maybe I'll use a dart and then maybe a white color here maybe it could be high blood pressure high blood pressure pushing out on these vessels could be an irritant so any of these things could be an irritant hyperlipidemia smoking or hypertension or high blood pressure could be an irritant and what is being irritated what is the thing that is being irritated that's number two is the layer of cells right here this inner layer of cells in the Tunica intima and that layer of cells we know is the endothelial layer endothelial cells so that's the layer that's being offended somehow so it's being upset or angry it's getting upset at these irritants so I'm going to show some unhappy faces here maybe some unhappy faces down here from the LDL maybe some unhappiness from that high blood pressure and right behind it just to orient you is the basement membrane but really again it's the endothelial cells that are being irritated right so that would be step two is endothelial as you leave in the same color endothelial dysfunction they stopped working the way that they'd like to work and I'll try to be a little bit more specific endothelial cells are basically a barrier right there they're creating a barrier between what is flowing through the blood and the wall itself right there the first thing that molecules and cells in the blood are going to see and so if you have endothelial dysfunction what you get is that this barrier starts breaking down and so this barrier let me erase some of this stuff now just to make some space we know that LDL is low density lipoprotein I'll erase that and I'll erase these white arrows for the hypertension and I'll even erase the cigarette smoke the toxin and I'll leave the LDL for a second you'll see why but basically me show you that these cells start getting unhappy and they start breaking down and I guess I erased a lot of it but I'll draw some of it back and what you get is something like this you basically have now a breach a breach so you have these cells here but now they're letting stuff through and the stuff that gets through primarily and this is of importance to us is the LDL so even if something else was the irritant let's say cigarette smoke was the major irritant here and you got endothelial dysfunction from that the next step in atherosclerosis is step three is LDL goes in - I'll just write into T or Tunica intima this is kind of the next major step is that LDL decides that it wants to go inside it likes to be inside of this layer so you get LDL hanging out over here I'll just write LDL here just so you know what we're talking about so all these little molecules of LDL which again get you bring with them a lot of fat and cholesterol and they're all now in this Tunica intima layer so they're all within this Tunica intima layer let me make sure I make that very clear all within this layer of Tunica intima so they're not usually there and that's step three now step four really really interesting this is where things get really kind of wild is you have cells in your immune system that are right here called macrophages macrophages and these macrophages they have huge mouths and they are actually macrophage really means big eater so macrophage macro big and phage meaning to eat macrophages actually swims through the blood and are patrolling the blood almost like police officers and they sense that hey something is not right with this wall there's LDL in there and they go in pursuit they go after that LDL and now they go into the wall so now you've got LDL on the wall I've got macrophages in the wall and so I'm going to draw these macrophages not to scale as again they're they're bigger than this but they're now in the wall they're hanging out in this area right and they start devouring again they're big eaters so they start devouring gobbling up all that fat so this is going to get a little bit tricky but let me try to sketch it out again up here for you they start gobbling up fat and they get loaded with this little fat these little particles of LDL so this is now LDL that's inside of the macrophage right and if you look through a microscope what this might look like is now you have to use your imagination here but is seafoam so if you actually look go out to the sea you know let's say they go to the Mediterranean Sea and you look at seafoam that's actually what it would look like potentially that's someone thought so anyway and so this because they called these cells these macrophages that have gobbled up LDL and actually died so this cell is now died I'll draw a little X's because it ate so much it died these cells they call them foam cells foam cells and I'll just write a little arrow here so you know which one I'm talking about foam cells so if you look in the Tunica intima again that's where all the action is right this is this is the important part here I'll I'll draw a box around it that's kind of the center stage the LDL that's the macrophages that chased it down and now the dead foam cells are all sitting here in this lake of fat now you got macrophages a step forward I mean just make sure I catch up with our picture macrophages and plus foam cells foam cells into Tunica intima right so now we're all on the same page and this this intima now really starts looking a lot like this let me erase this clean this up a little bit because it's getting quite messy I think you'd you'd agree it needs a little cleaning up let me erase all this stuff on the outside we know that LDL was in the blood but it went into the intima we know that so so now you have basically this LDL all these little molecules of LDL start merging into literally a lake think of like a lake of fat how disgusting a thought is that right like a lake of lard here or fat here because it's your fat or this person's fat and it's all in this layer called the Tunica intima in fact let me even draw another dead macrophage this is another foam cell and making foam cell out of this looks like sea foam maybe and so you have here a lake of LDL you have foam cells and it's all sitting in the Tunica intima and if you're actually - let's say you're to fillet this cell open or this blood vessel open let me try to show what I mean if you were let's say you have this blood vessel I'm drawing it very simply now you know that there are three layers not the one that I'm drawing there but just imagine you took a knife and you slice through it so now you're basically looking at kind of just the inside of it right just the inside of it what you would see is basically just a giant streak of fat and this is kind of that lake that I just showed you right now looking at it lengthwise so this lake of fat is called a fatty streak so if you open up a blood vessel and look at it if this process has been going on you might start seeing fatty streaks and so that's basically the first half of atherosclerosis so let's pick up there in the next video