hi everyone and welcome to loan a of apology for free with mr. ik this video is going to go through the blood vessels comparing the different types so first of all just an overview we'll be looking at arteries arterioles capillaries and veins and this diagram is just showing you how they all link together so just a reminder from GCSE arteries are carrying blood away from the heart so a away the arteries then branch into arterioles which are smaller than the arteries Bigler the capillaries and they connect the two together the capillaries connects the arterioles to the veins and the veins carry blood black back into the hearts so veins have the word in inside of it carrying the blood back in so again we can see here the network and what you need to know for a level the difference is a comparison of the composition of the wall of all three of those and actually all forks we look at the arterioles as well and not just what it's made of but also the different thicknesses of the different tissue layers so if we start with the arteries and veins we'll compare those two here we have a micrograph showing the cross-section through an artery compared to a vein and straight away you can see some clear differences so the veins lumen is there in a regular shape and it's much bigger the arteries and lumen and lumen means a space in the middle that the blood would flow through that is much much smaller and this is due to the differences in the thickness of the wall so an artery wall is much much much thicker than a vein and again you can see that up here they both contain the same three tissue types but different thicknesses so an artery the muscular layer which we can see here that's our muscular layer and again you can see here that is the muscular layer there as much thicker in arteries compared to in veins and in arteries it has that thicker layer so it can constrict and dilate to help control the volume of blood that is being pumped out of the heart veins are relatively thin so they don't actually have any control over that blood flow the elastic layers they are both elastic but the arteries have much much thicker elastic layers and that's to help to maintain the blood pressure but also so that they can stretch and then recoil back to their original shape in response to the heartbeats so instead of the blood vessel tearing under high pressure instead it's really elastic so it can stretch out instead because veins are carrying blood at a much much lower pressure they don't need that thick elastic layer so they have a relatively thin elastic layer and that's what we can see here that white part is the elastic layer and here we've got a much much thicker elastic layer so overall then the thickness of that wall is much much thicker in an artery much much thinner in a vein the final tissues I did say three tissue types is referring to the valves now arteries do not have valves but the veins do we don't actually see a valve in this image but valves are these flattened flaps which help prevent the backflow of blood so that's all comparison of the arteries and the veins next and if we have a look at the capillaries so capillary is one cell thick which we can see here is only made up of one cell where blood cells can only just fit through the diameter of the lumen and that is an advantage because it means the blood flow slows down significantly when it gets to the capillaries and we want the blood to flow slower so that there's more time for diffusion and if we think about the locations of capillaries we learn about capillaries in the villi in the alveoli in the nephron and all of these play is where diffusion occurs so it's an advantage at the blood flow slowly you do all such you have capillary beds we are only looking at one single capillary here but in this diagram we can see the capillary bed or network of capillaries so you don't actually just have one you have a whole brand gene Network so just to compare all four then we've already go through the arteries in the veins but the arterioles then in comparison and this is what connects the arteries to the capillaries and that has a much thicker muscular layer compared to arteries which actually people often wouldn't expect the reason for that is it helps to restrict the blood flow before I get into the capillaries because if too much blood is flowing into the capillaries that have been very very high pressure and it could damage the capillaries the elastic layer is much much thinner because the pressure has already started to drop by the time it gets the arterioles and overall the thickness is much thinner because it's got a significantly thinner elastic layer and the pressure is lower no valves so capillaries they do not have any muscular tissues they don't have any elastic tissues either they are just simply one cell thick just one layer of cells and the function is to provide a short diffusion distance and also slow the blood so there's more time for diffusion to occur so that is it for the blood vessels I hope you found it helpful please get a thumbs up if you have and click click subscribe to keep up to date with more the latest videos [Music] [Music]