in the previous video we looked at the introduction to the different types of blood vessels where there were five types of blood vessels that we talked about the arteries arterials capillaries venules and vein in this particular video we are going to be just focusing on the artery and arterials the artery if you remember are just blood vessels that transport blood away from the heart at high pressure and the arterials it is smaller branches of the arteries so in my diagram here as you can see I'm drawing out a heart and their Associated blood vessels I'm not growing all the blood vessels that are connected to the heart just like you know as close to as reality as possible and as you can see there is a very large blood vessel over there that is extending out and that is known as an artery which have colored in pink so as a reminder the artillery plant spots blood away from the heart at high pressure and the arrow represents the direction of the blood flow a very important thing to understand is as the artery moves away from the heart the further it goes away from the heart the size of the artery becomes smaller the artery closest to the heart is quite large as it moves further away it becomes smaller and furthest away from the heart as you can see I've labeled there it is the smallest that's just the nature of how arteries work in general now arteries are then subdivided into different types the artery closest to the heart is referred to as something known as an elastic artery slightly further away from the heart we will call the artery something known as a muscular artery and when they are much further away from the heart and their size is extremely small that's when we refer to them as something known as arterials we have divided the arteries into three groups now even though I've divided them into three groups it is important to know that they are all still arteries with very similar structures so let's look at their basic structure in detail so at the bottom over here I'm just drawing a three-dimensional version of an artery the Shaded region is the artery wall and the hole in the middle refers to the Lumen the Lumen is the hole where the blood is flowing through like a tube now if we were to draw the artery as a side view that is when we call it the longitudinal or longitudinal View and I've also labeled the artery wall and the Lumen so you can see it right there in a two-dimensional View a more important section of the artery that as a student you must be familiar with is the transverse or cross-section that is when we are looking at the artery through the highlighted region the transverse or cross-section is the easiest way to look at the artery because we can actually appreciate how thick the artery wall is and how small the Lumen uh is in relation to the artery wall so this is the more common diagram that as a student you should be familiar with the transverse of course section however sometimes they may give you the longitudinal view in the exam too okay and I've also labeled the uh Lumen and the artery wall a very important thing to know about the artery wall is the artery wall is divided into the inner wall which is nearest to the Lumen and the outer wall which is furthest away from the Lumen and in between the inner wall and outer wall is the middle section of the middle wall which I've not labeled in this diagram but not to worry I'm going to do that later now why do we have to separate the artillery wall into the inner middle and outer section the reason is because the inner middle and outer section are all made up of different composition let's look at the basic structure of the artery this applies to elastic artery muscular arteries and arterials so you don't have to worry about that so the cloud in the closed section remember it has a very narrow Lumen and the inner wall is made up of a layer which is known as a one cell thick endothelium the one Celtic endothelium's function is to minimize friction and blood flow as the blood is moving through the artery at high pressure this is uh quite important by the way because when the blood is Flowing inside the artery at very high speeds the inner wall has to be smooth so no damage happens to the blood cells within the blood vessels and slightly just below the one Celtic endothelium it has elastic fibers but that's not so important to know in detail but what we have to understand is the inner layer is made up of two things the one cell thick endothelium and also a thin layer of elastic fibers now the more important section is actually the middle section which I have highlighted in pink it's an extremely thick section the reason why it's the thickest layer is because it has a lot of structures within it now now the middle layer is made up of this purplish things that have Advantage like squiggly or loopy lines and those cells are known as smooth muscles and I'm also drawing some orange color lines I hope you can see that those orange color lines are the elastic fibers and a very thin layer of green color lines in the middle layer which are the collagen fibers I hope you can see them very clearly so the middle layer which is the thickest layer of the artery contains three things smooth muscles elastic fibers and collagen fibers the outer layer which I've highlighted in clay quite thin all right it contains two things which are elastic fibers or which I've put orange color lines and also collagen fibers which I've represented in green color so as students you have to memorize what the inner layer contains what the middle layer contains and what the outer layer contains exam questions can be as straightforward as list out two things that can be found in the outer layer of the artery then you have to say oh it contains the elastic fibers and collagen fibers if they ask you what does the middle layer contain then you have to say it contains smooth muscles elastic fiber and collagen fibers the inner layer just to repeat it again contains the one cell thick endothelium and I'm just gonna draw out the longitudinal section again just looks like a wafer sandwich all right uh it has the naval Lumen the inner layer which is made up of that green color labels called the one Celtic endothelium the pink color layer which I'm highlighting is the middle layer which contains the smooth muscle elastic fibers and collagen fibers and of course last but not least the outer layer uh where it has the elastic fibers and collagen fibers so the transverse section and the longitudinal section gives you an appreciation as to the difference of layers within the artery it Bears repeating that the Lumen of the artery is relatively narrow the reason why it has to be navel is because it wants to maintain a quite high blood pressure so that the blood can move quickly within the artery but because the blood is moving very quickly in the artery the friction is extremely high so to minimize the friction that is why it has the one Celtic endothelium if the elastic artery muscular arteries and arterials all have the same type of inner layer middle layer and outer layer then how do they differ what makes them different why do they all have slightly different names this is what we want to see in the next part so we are going to create a table and as you can see when we look at the cross section of the elastic artery muscular artery and arterials as predicted their sizes are quite different as I've told you earlier the further away the artery moves from the heart the size becomes smaller so what we're going to do is we're going to do something called a relative comparison what I mean by that is I'm going to magnify the size of the muscular arteries and I'm also going to magnify the size of the arterials so that it's similar to the size of the elastic artery by doing so we can actually have a fair comparison of the elastic artery muscular artery and arterials that's the main reason but remember in reality elastic artery is the largest muscular artery is slightly smaller and arterials are the smallest so let's talk similarities first the similarity is as follows all three of them have the same type of inner wall where they have the one Celtic endothelium they also have the same type of outer wall which contains collagen and elastic fiber what makes them actually different is the middle layer first thing that you must notice is the middle layer of all three types of arteries are the same in terms of their thickness they have the thickest layers so that's fine but the composition of the middle layer becomes different as you can see I'm going to draw out the middle layer of the elastic artery and the muscular artery do you notice any difference between them immediately you notice that in the elastic artery the purple color the purple coloring is not as much as the one in the muscular artery but the elastic artery has a lot of those orange colored thick orange color lines as compared to the muscular artery the reason is because for the muscular artery it has a higher proportion of smooth muscles but the elastic artery has a lower proportion of smooth muscles and for the elastic artery the elastic fiber is in higher proportion and muscular artery has a lower proportion that is why the arteries are named as such elastic artery is called the elastic artery because it has a higher proportion of elastic fiber muscular artery have a higher proportion of smooth muscles in their middle layer that's the difference between the two of them they also have some students who ask what about the collagen fibers both the elastic arteries and muscular arteries have collagen fibers but we don't have to care about it our main comparison between them is the smooth muscles and the elastic fiber the arterials however have the highest proportion of smooth muscles and they have very minimal elastic fibers so what we have to know about the arterials is just the fact that the middle section is made up of mostly smooth muscles it does have elastic fiber but it's extremely minimal in its propulsion so these are the difference in the elastic artery muscular artery and the arterials so of course then as a student you must be like okay why do they have different compositions of their middle layer there is a reason for that obviously looking at the elastic artery our main focus is the fact that it has a high amount of elastic fiber so the question is why do elastic arteries need a high proportion of this very elastic fiber so it lost the city before we go into that in detail is just imagine a rubber band a rubber band is elastic because when you stretch the rubber band it's able to accommodate the pull but when you let go of the rubber band it will go back to its original shape so that's what elasticity means okay so elastic arteries also have this kind of property so I'm drawing out a heart over here filled with blood now imagine if the heart is connected to an artery that is non-elastic which means to say it is not elastic why would this be a problem this would be a problem because when be heart contracts to pump the blood into the artery the pressure within the artery becomes very high because the blood is rushing into the artery okay and because there is going to be a high pressure in the artery what will happen is imagine the artery to be non-elastic like a wooden ruler if you put pressure on the wooden ruler if the pressure is sufficient the wooden ruler will not Bend because it's not elastic it will snap and break due to the high pressure the same thing will happen to the artery if it's not elastic it will just break and rupture and blood will start to leak out this is extremely dangerous because this is called an internal hemorrhage or or internal bleeding and this can be quite dangerous for the person so the solution to this problem is the artery closer to the heart is quite elastic because when the heart pumps the blood and the pressure in the artery is very high just like a plastic ruler which is quite elastic when you apply pressure on the ruler it bends but it does not break same thing happens to the artery as well the wall bends outwards or it stretches outwards to accommodate that very high pressure so that's a good thing so the artery will stretch under high pressure and that's what creates a pulse so if you touch the artery near your neck on the side of your neck or if you were to touch a specific part of your wrist you're able to feel the artery stretch and that's called the pulse that pulse is when the artery wall is stretching due to high pressure so the stretching is important because it does not it prevents the artery from breaking or rup chilling and high pressure and of course the plastic ruler when you let go when you do not apply pressure on it anymore it returns to its original shape the same thing happens to the artery wall because when the heart relaxes the artery wall does not remain bulged outwards immediately what will happen is it will recoil back to its original shape okay and The Recoil is good because when it recoils the blood that is collected in that artery will be pushed forward so this is why elastic arteries have a high proportion of elastic fibers the very important reason is to allow it to stretch under high pressure so it prevents the artery wall from bursting and it also allows the artery wall to recoil to push the blood forward and in doing so it maintains a high pressure in the artery so this elasticity of the artery is important to ensure that the artery is functioning the way it's supposed to function because the artery is supposed to push blood forward at high pressures constantly so stretching and recoil will stretching will prevent it from bursting under high pressure The Recoil allows it to maintain a high pressure within the artery this is basically what the elastic artery is all about so uh going next to the muscular artery the muscular artery as a reminder has a high proportion of smooth muscles so the question is why why does it need a high proportion of smooth muscles within the um muscular artery the reason is because it wants to control blood flow and when I say control it means increase or decrease blood flow then you might want to ask the question how is it able to increase or decrease blood flow it is able to control the blood flow due to two processes and the two processes are as follows vasoconstriction and vasodilation in vasoconstriction the smooth muscles in the artery will contract and look at the size of the Lumen the size of the Lumen is very small but in vasodilation the smooth muscles will relax I want you to see what happens to the size of the lumen it will increase so when the Lumen size decreases well obviously less blood will float and conversely when the Lumen size increases more blood flow is able to happen so as students you might be thinking okay why does the I don't I thought arteries are just these automatic tubes where blood flows through constantly no matter what see this is where we are wrong our body is constantly controlling the amount of blood going to specific parts of the body through vasoconstriction and vasodilation let's talk about a real life example now I'm drawing out an artery where it branches or uh the artery reaches a junction where it goes into two muscular arteries one muscular artery is transporting blood to the stomach and one muscular artery is transporting blood to the leg muscles this is just my example by the way so right now the amount of blood going to the stomach and leg muscles um is almost similar the stomach is getting the same amount of blood as the leg muscles now imagine you are running away because a scary monster is chasing after you I didn't have I have no idea what that wants this I want to define otter but yeah I can't I can't make otters look scary um yeah but just bear with me with that monster so the monster is chasing after you now when the monster is chasing after you your leg muscles because you are running your leg muscles need more oxygenated blood okay so when your leg muscles need more oxygenated blood our body has to go into this mode where well if one part of the body needs more blood it has to compromise another part of the body that's how our body works okay so if the leg muscles need to receive more blood the stomach has to receive less blood because it has to shunt or divert extra blood to the leg muscles how does it do so it does so by the muscular arteries at the top undergoing vasoconstriction and the muscular arteries to the leg muscles undergo vasodilation so in doing so the stomach receives less blood and more blood is then able to be shunted or diverted to the leg muscles so that you can run away from the scary monster hopefully okay hopefully so vasoconstriction and vasodilation allows the body to control which part of the which organs or which tissues need to receive less blood which tissues need to receive more blood and last but not least we also have the arterials as a reminder arterials are smaller branches of arteries they are like arteries but they are extremely small by the way in their size and they have a very very very high proportion of smooth muscles in their uh middle layer a middle section first question why are they extremely small the reason why arterials have to be very small is because in the artery blood is moving extremely fast but the moment they go into the arterial the size of the Lumen is quite small that it slows the blood down this is important to happen now I know a lot of students may think oh well if blood slows down that's not good in this case the arterial has to slow the blood down significantly the reason will be explained when we talk about capillaries in the next video and last but not least it also has a high proportion of smooth muscles so that it's able to do vasoconstriction and vasodilation just like we saw a few minutes ago these two processes help to control blood flow to specific areas in our body so in summary the elastic artery Which is closest to the heart has a high proportion of elastic fibers muscular arteries which are slightly further away from the heart as a higher proportion of smooth muscles and lower proportion of elastic fibers and arterials are just very small and they have a high proportion of smooth muscles the reason why elastic artery needs to have a high proportion of elastic fiber is so that it can stretch and recoil muscular arteries mostly do vasodilation and vasoconstriction and arterials have to be very small as a reminder to slow down blood flow and also they do vasoconstriction and vasodilation now an important question students ask me are some some students have asked me this question before they asked oh muscular arteries do not have much elastic fibers are they able to also stretch and recall the answer is yes muscular arteries can also stretch and recoil but they don't do it as well as elastic arteries right so all arteries are able to stretch and recoil all arteries are able to do a degree of vasoconstriction and vasodilation but elastic artery does stretch and recoil much better muscular arteries are way better at vasodilation and vasoconstriction right so that's the difference between all of them