Cardiovascular Tunic Layers & Types of Capillaries

The layers of our blood vessels or our 

tunic layers so what I have over here I pre drew two distinct blood vessels so I have over here on the left I have an artery and I have over there on the right I have a vein and what I want to do is now they're layering is pretty much gonna have all the same things it's just gonna be about which one's thicker.

which one's gonna be a little a 

bit thinner and then we might talk about just a couple abnormalities within this and then I want to go over here and talk about capillaries the three different types of capillaries all right so first things first if we look here this inner lining of the blood vessel the Tunica internal are the Tunica intima it actually the area is two distinct like layers of it so if you look here there's an endothelial lining so as these little black cells here these little black cells are simple squamous epithelial cells and then right underneath it there' that's called the subendothelial layer so it prevents the blowout right of the blood vessels it's made up of collagen and some other types of proteoglycans and proteins so it's kind of like a loose areolar connective tissue so this right there is called our sub.

endothelial layer and these cells 

here these black cells are called our endothelial cells and it makes up the combined two those two is the Tunica intima so I'm gonna write that here in black for those cells the Tunica interna of the intima all right so you can put one of the two there again so Tunica Interna or Tunica intima and again it consists of these simple squamous epithelial cells with the subendothelial layer under it all right so this next brown layer right there that's the internal elastic lamina so let's write that there internal elastic lamina, okay and again it's made up of you're gonna have some collagen some fibrin and other types of proteins that are present within this layer this is actually since we're talking about I'm gonna mention a quick thing there is two different types of congenital disorders.

where you don't make febrile in or you 

don't make a specific type of collagen and it can affect the internal elastic lamina and these two conditions I'm just going to write them down here briefly for you it's called Marfan syndrome and another one is called Ehlers-danlos syndrome and these are both connective tissue disorders Marfan is usually lack of fibrin Ehlers-danlos syndrome is the lack of a specific type of collagen but it affects this internal elastic lamina and other types of connective tissues and can obviously increase the risk of aortic dissections and then aneurysms so I just thought I'd mention that real quick all right so that's the internal elastic lamina that's the second layer that we'll talk about next one is we have a whole bunch of smooth muscle cells all the way around you really really really thick smooth muscle layer right here this thick smooth muscular.

the layer is kind of actually but the main 

three layers are this one out here and then this middle one so it kind of gives it the name the media or the one in between right so I'm gonna write it here in red and this thick smooth muscle layer is called the tunica media and the tunica media again is made up of smooth muscle and that's really important because obviously, it's involuntary and so we need our sympathetic nervous system to come in and actually innervate this tunica media so I wanted to write that there this is an important note to have here is that this is under sympathetic innervation, in other words, it has a vasomotor tone that's extremely important because without the lack of that motor tone our blood vessels would dilate and we would have neurogenic shock so the tunica media is under sympathetic innervation. which means the sympathetic nerves it has scepters adrenergic receptors present on them so again that's our tunica media and it's important for contracting so it's important.

what's called 

vasoconstriction constricting the blood

vessel and increasing pressure or 

dilating the blood vessel and actually decreasing the blood pressure all right next one again we have another brown squiggly layer that brown squiggly layer it's not the internal now it's the external elastic lamina so that the last one is called dead seconds the last one's called external elastic lamina and again it's composed of certain types of proteins proteoglycans again collagen fiber Lynn and again it's a very important type of structure that allows basically the purpose of the elastic lamina is to allow for the blood vessel to stretch and to be able to Requip without that ability it's not going to be as a kind of elastic and then it can obviously lead to rigidity or maybe some thickening and hardening to be able to expand those arteries if you don't have these elastic laminas all right so they're very important for being able to be stretchable you know distensible or compliant and then also recoil last one that I wanted to talk about here is this green layer this green layer is actually gonna be called the Tunica externa or the tunica adventitia I prefer Tunica externa cuz.

it's easier to spell so we'll put two in 

a car externa but again there is another name for it and you can call the tunica adventitia also now the Tunica external is made up of a specific type of connective tissue and I'm gonna write that down here it's dense irregular I'm just gonna put I am irregular connective tissue so it's made up of dense irregular connective tissue so it's out as that neural arrangement the important thing about the Tunica external is it's not super vascular so it needs a few blood vessels to provide some blood supply to it and maybe to the deeper parts of the tunica media so if you look here I drew these small little tiny system of blood vessels right there.

So these tiny little system of blood 

vessels are here really important and these are called the vasa vasorum so there are a tiny system of blood vessels that nourish the Tunica external visa fficer means vessels on vessels so it provides nourishment to the Tunica externa and some of these actual outer layers of the tunica media so that it gets some oxygen supply this is actually important because then a disease of tertiary syphilis actually destroys these blood vessels and if it destroys these blood vessels it leads to the decreased blood supply to the Tunica externa or tunica adventitia and they may be damage to the tunica media and then it can actually lead to thickening of the blood vessel and then actually weakening of the blood vessel and increased chances of aortic aneurysm alright so this can actually be is is affected by tertiary syphilis which is caused by a spirochete also known as chip animo pull item alright so it can actually damage this phase of a storm here and it can cause decreased oxygen supply to the Tunica externa and again that could weaken the walls of the blood vessel and then lead to dissections and aneurysms and emergency situations right all right.

So everything we went over here and all of 

these different tunics are exactly the same in this and this vessel in that vessel so again remember this is the artery right and this one over here is the vein so now what's the difference then what's the difference we already know that this is going to have all the same layers the only difference is in the thickness of those layers so in a vein it's still gonna have a Tunica interna consisting of the sub endothelial layer and the endothelial lining that's still there the big difference is and I could have shown it I could have not shown it but the internal elastic lamina is not very abundant inside of the veins because the veins aren't high-pressure systems veins if you remember our video on blood vessel characteristics we said that the pressure of veins is like five to ten millimeters of mercury so they don't really have to be distensible and stretch so but they do have a tiny little bit of that internal and external elastic lamina but in some veins it might not have any of it so again very very little if not if any internal and external elastic lamina in veins but very very little again it can't have some usually in the larger vessels.

And then if you look here has a tunica media just like the artery 

does but what's the difference the tunica media for a vein is a lot thinner because if you remember and I'll say it again veins are not meant to be very very high power high-pressure systems and contract to expel blood they're meant to be capacitance vessels to be reservoirs to hold 70% of our blood volume so it's not going to have a very thick tunica media it does have sympathetic innervation so it can contract but not very much the most important one right here is the Tunica externa the Tunica externa is extremely extremely thick in a vein extremely thick so it is a very very thick Tunica externa in the vein and on top of that if you notice the lumens here the artery lumen versus the vein lumen when you look at these histologically one of the things identified is that a vein actually when you look at it on a histological or you look at it on a microscope it's actually going to have a collapsed lumen so that's another thing when you're looking on the slides so you put this light under you look in the microscope you notice that a vein has to collapse lumen also so that's really important also that covers the histology of arteries and veins alright guys let's move over here for a quick recap all right.

We look over here again remember artery 

and veins they both have a Tunica interna or Tunica intima it's an endothelial lining with the sub endothelial layer they both have an internal and external elastic lamina it's just going to be more prominent and more abundant in the artery than it is in the veins, some veins are not going to have it more the larger veins will right and then the tunica media is the smooth muscle layer and that's obviously going to be more it's gonna be thicker in the artery than it is in the vein and then the Tunica externa which is the dense fibrous irregular connective tissue is more abundant and thicker with the inside of the vein than it is in the artery and again they both have innervation by the Vaes of a Sorum now let's come over here and let's take a look at three different types of capillaries so if we look over here we have three different types of capillaries each one of these has some type of morphological difference and that's what helps us to distinguish them so if you look here I'm gonna kind of give you the name of each one of these capillaries and we're gonna discuss each one in detail and the difference is within them and where you can find them so the first one here I'm gonna right up here this is going to be called a sinusoidal capillary all right the one beneath it here which is kind of going to be a giveaway when we see these parasites here this is going to be called continuous capillaries.

So this is called continuous capillary that's the 

continuous capillary all right the last one here is gonna be called a finish treated capillary so this is called a finished rate of capillary okay so now that we have all of these capillaries let's go ahead and discuss each one why they're specifically given these names and then on top of that let's go ahead and talk about where you can find these guys all right so the first one sign is sort of capillary what really makes this one different well if you notice here I'll get the endothelial cells that we talked about the artery in the vein right so these are endothelial cells you're going to notice that they have huge huge gaps or clefts in between the cells so these huge gaps are here called intercellular cleft so again what do they have that really makes them distinguishable one big thing is intercellular clefts and they are huge okay so large ones will put large okay so that's one big big thing they're so big that you know that you have white blood cells and red blood cells specifically red blood cells red blood cells can literally leak out of this is okay so red blood cells can literally leak out of this blood vessel okay so that's one thing so if we look here we can have red blood cells and these red blood cells can leak out of the capillaries you can also have plasma plasma can also leak out of these capillaries okay so when we can even have large molecular weight proteins .here in a molecular way a large molecular protein here like albumin, this can even leak out to okay so this air these are very very permeable capillaries and kind of what makes them specific is these extremely large intercellular cleft okay that can allow for blood cells to leak out it can allow us for plasma solutes to leak out and it can even allow for large molecular weight proteins to leak out.

Where you're going to find this is where 

you want a lot of cells to be able to move in and out so this is going to be more commonly found in your bone marrow okay specifically the red bone marrow I'll write that there at the end specifically red the spleen is a really good one-two really important ones to remember this one I'm gonna exclamation point that one spleen is extremely important for this one and then the last one can be the liver okay all right so these are gonna be the common locations of where you would find these capillaries again you can find them within the bread bone marrow, you can find them in the spleen and you can find them in the liver and again what really makes them important large intercellular cleft one last note these are the most permeable capillaries okay so the leakiest if you will that's one important thing I want to mention right there continuous capillaries if you look here they don't really have very large intercellular cleft kind of small intercellular cleft alright and in certain places like in the blood-brain barrier they don't even have intercellular cleft because in the blood-brain barrier the endothelial cells are joined together by tight junctions.

But we're gonna mention here 

that there is a small intercellular cleft and we'll put an exception in the blood-brain barrier so let's write that down here so let's put here and this one let's say has a small intercellular cleft the smallest clefts all right and then another thing let's put a little note here there's actually going to be tight junctions tight junctions between these endothelial cells between endothelial lining in and I'm gonna put here BBB blood-brain barrier this is important so I want to mention continuous capillaries are found in the blood-brain barrier but the only difference is they don't have small intercellular cleft they have tight junctions that leak link those actual endothelial cells together it's important ok another thing that they had that none of these other ones have is these really cool cells here and I'm gonna just write them next to them it's actually called peri sites and peri sites are believed to control endothelial cell growth they're believed to be able to cause maybe some vaso Jenica ability so basal constriction and they've also been found actors like phagocytes for things leaking out of the cells so for this one small solutes and plasma can leak out through this and also another cool thing and we'll talk about this when we get into cellular 

physiology is that these guys have the

ability to take in little like solutes let me actually kind of show you what happens I'm going to take one endothelial cell here that endothelial cell can literally form a little vesicle and endo CITIC vesicle and it can actually take in small molecular weight proteins and it can actually allow for it to cross.

What's  called transcytosis throughout the other side here 

and then leak those things out this is called pinocytosis it's called pinocytosis so continuous capillaries can actually do that they have the ability to do what's called pinocytosis and just passive diffusion ok that's important where would you find continuous capillaries you would find continuous capillaries where that's got to be very very controlled so the main areas you would find this one is action gonna be present within the muscles the skin we already said it but on mission again blood-brain barrier and even the lungs so these are some main areas that you would find the continuous capillaries again what is important about these guys small intercellular cleft but they have tight junctions between the endothelial cells in the blood-brain barrier they have parasites and they have the ability to do what's called pinocytosis and they can also allow for passive transport between the clefts alright let's go into the last one now so this last one is called finished rate of capillaries what makes these guys are so crazy important or specific if you look here they still have intercellular cleft small intercellular cleft all right a little bit bigger than the I'm gonna put here medium-sized intercellular cleft.

let's write that down there 

let's put medium intercellular cleft okay that's one big thing medium intercellular cleft and they're also gonna have these little CC the endothelial cells there's a little pore between them there's a tiny little pore running right between them this little pore and I'm gonna draw it here and Brown here I'm gonna imagine like it's a little tube there so imagine that's like a little tube these little tubes right here running between those endothelial cells are called finish station pores okay so they're called fenestration pores let's write that down these are called finish traction pores and this allows for actually some decent sized molecules to be able to leave the actual plasma so we can allow for some larger molecular weight proteins some solutes some plasma to leak out but no blood cells okay and again you had these intercellular cleft which will allow for passed the diffusion of solutes and plasma and stuff like that and it can also do what this guy can do so he can also do pinocytosis so he also has cells that can actually do pinocytosis okay that's important now where would you find this so you want to find this in areas where there's a good exchange occurring so this is actually going to be more common in the kidneys so common min the kidneys and it's very common in glands okay it's common in the glands and there are two types of glands.

That we could really describe them we could say 

exocrine which means that they have ducts endocrine which means that it is having no ducts so extra Karina's duct glands and endocrine are going to be ductless glands and these are some areas that you would find that the kidneys the glands and stuff like that okay so real quick recap of everything again let's start at the top sinusoidal capillary largest intercellular cleft okay most permeable you're gonna find them in the red bone marrow the spleen the liver right and they can allow for blood cells plasma and large molecular weight proteins to leave the continuous capillary it's the lead permeable let's write that down let's write that here right here let's put this is the least permeable that's an extremely important so least permeable here and again what's makes him different he's gonna have tiny little intercellular cleft but in the blood-brain barrier he doesn't have those classiest tight junctions and again it has the ability to do pinocytosis okay through the Calvillo lait and on top of that has parasites that can control what leaves the actual blood tissue also controls endothelial cell growth and it can control vasoconstriction and you'd find these within the muscles the skin the blood-brain barrier and even in the lungs and the last one is these finished rate of capillaries they have medium-sized intercellular cleft they have these little fenestration pores between the endothelial cells and it can allow for plasma solutes and then through these fenestration pores and can allow for some larger molecules to leak out through that also and it also has the capability of doing pinocytosis through that caviola again and where would you find this one you find in the kidneys the kidneys specifically that's the best one and then evening plans like exocrine glands and endocrine glands alright guys so that pretty much gives us everything we need to know about capillaries and layers of our blood vessels.