Transcript for:
Tissues and Tissue Systems Overview

so today we're going to talk about tissues and tissue systems and i wanted to make sure that we made the connection between cells and what happened in our embryology lecture last time and how sort of tissues come into into play here and i also want to mention that i think this is probably one of the most if not the most critical of all the lectures for for anatomy because once you understand tissues and how they're built in their various properties you can really sort of understand how we actually build a body so this is our next higher level of structural and functional organization we've talked about molecules chemicals we've talked about organelles and cells and now we're going to talk about tissues and how they sort of come into play you'll also note that there are handouts for you under the handout link in the web lecture or the web site rather for you to also examine and look at we're going to go through those today okay so let's begin with some again here's our roman numeral number one and we're going to start with basically a general set of information for what tissues are so what we can do first of course is just define what what tissues are and there are different ways of of defining this but what i like to do is to keep this as simple as possible to make it as understandable as possible so we can say then that tissues are composed of cells with similar they don't have to be exact but they can be similar structures and or functions so we can have functional definitions we can also have structural definitions for these as well and if we just look at the fundamental components of what comprises tissue so anytime you get two or more cells together we're actually creating a tissue is really what that comes down to so obviously the first main component are our cells and we'll talk about cells in depth as we go along here in a little bit so there are many different types of cells and there can be many different layers of cells anywhere from a single layer to you know thousands of layers of cells so we'll talk about cells in more detail in just a few moments but the other thing that cells do is they produce this material called extra cellular matrix or ecm so extracellular matrix now of course extracellular matrix is going to contain some extracellular fluid right that's part of the matrix itself so basically what we want to focus on here is that cells produce the ecm what they're basically doing is creating their own environment in which they exist so they're going to secrete this material around themselves right so it's the cells that are producing this this matrix and if we look at the components of the ecm and this is where it gets a little bit confusing sometimes for for individuals is we want to think about this in terms of of course our extracellular fluid and again that's mostly water right so water is going to comprise most of the extracellular fluid and then there is this material that is given the name ground substance and this is a term that comes from way way back when back in actually even in the late 1700s early 1800s where scientists were beginning to look at at and and material under microscopes they couldn't quite understand this but they figured out that it was sort of fundamental to all of these organisms and so it sort of grounded those organisms and that's where that term ground substance comes in so what is this ground substance well it is a semi-fluid semi gel so again it's this kind of weird kind of stuff that's not quite watery but it's got some substance to it obviously it has dissolved carbohydrates which are fairly complex there's lots of different kinds of these dissolved carbohydrates and these dissolved carbohydrates are really interesting because there are many many you probably have heard of things like glucosamine and stuff like that that are sold over the counter these are some of the kinds of dissolved carbohydrates that are in there and you can read about these also in your text if you if you want um but again it's very very complex but it sort of gives it some some real substance to it there's also proteins and we'll talk about those proteins here in a moment because again they provide a lot of the basic properties for for this substance and also there are some lipids so a lot of our major organic groups that are found within this and of course there's also going to be some inorganic components we talked about for example i'll put in here components we talked about sodium ions for example chloride ions calcium ions things like that that are also found within this so that sort of makes up this kind of material called ground substance and and a matrix is kind of really just a bunch of things kind of mixed up together sort of dissolved together sort of suspended together so it's not easy to exactly define what this this is now along with this i do want to talk a little bit about the protein fibers and these might be among the most critical to sort of understand and fundamentally there are three types and there's a bunch of subtypes of each of these and we're not going to worry about those sort of out of the purview of course here but the first is by far the most abundant protein in the entire body and one that you're probably familiar with it's called collagen it's found in our skin and our hair and our nails and all kinds of of things that are there and it's got some really interesting properties to it first of all it's strong these fibers are strong and there's many many different types of collagen fibers and subtypes of those collagen fibers again we don't have to worry about that but one of the other things is that although they're strong they're also very flexible so very flexible and they're also what we call inelastic i'll explain that here in just a moment as well inelastic and they tend to be sort of white to sort of yellowish in color now the term inelastic when we talk about elasticity it's about something that can actually return to its original shape after it's stretched so here this is non-stretchable stuff so i often think about these as like little strings so if you think about a string like a little piece of twine you can bend it you can twist it you can tie it up in a variety of different ways right so we can have all these little strings out here but what's interesting about them is that if you try to stretch it let's say in this direction in that direction it's not going to stretch very far in fact it's very in non-stretchable if you will and also it's not very elastic so when they're stretched out as far as they can go that's pretty much it so that provides a lot of strength for a lot of different kinds of tissues where where we have lots of collagen and collagen again is the most abundant of all the proteins is found basically in every kind of matrix that you can you can think of so it tends to dominate a lot of different kinds of of matrices okay so here we also have this we're also going to have other kinds of fibers here the the other type is called elastin so elastin as you might suspect here is a little bit weaker it's not quite as strong it's also flexible it's also elastic as the name implies which means then that it is also stretchable and sometimes we use the term extensible for stretchable so i'm going to put that in here we'll see that a little bit later on in other tissues so extensible means stretchable so we can stretch it out and it'll return to its same kind of shape that's there and these fibers tend to be very white so really kind of a bright white kind of kind of color where you see them and they often are found around various kinds of tissues that need to stretch it's found obviously in your skin uh it's found in areas of certain kinds of cartilage and also it's it's found around capsules sometimes that have to stretch various kinds of structures that have to expand themselves and again we'll have some examples of that down the line the last kind of fiber that we have here that make up this matrix is called reticular and you might recall that when we talked about the endoplasmic reticulum what reticular refers to is kind of a network so this these are very strong oh and before i forget here maybe i should use the analogy of here sort of like a rubber band right kind of like a little rubber band kind of kind of thing in here to sort of show that sort of stretches out and returns to the same shape when we let it go so reticular fibers are very strong and they're also very inelastic and they are sort of built in kind of a network way so here we can have them kind of sort of fibers that are kind of overlapping in a righty way and they sort of make like a mesh kind of network uh to this uh almost sort of like a network type stocking or something like that so they're very very strong in all directions and so when you try to stretch them in this direction or in this direction or you know some other direction like that they don't stretch very much at all and we often find these again surrounding different kinds of organs and structures that we don't want to stretch very much and we want to also you know maintain their their fundamental shape and size and dimension and so we see these reticular fibers here so again what tissues are made up of of course cells the cells produce this extracellular matrix which is again a lot of fluid to a certain degree and it has all these dissolved carbohydrates proteins lipids and inorganic components but then also these protein fibers and it's the combination of these protein fibers and i'm going to sort of slip this back here for just a moment sort of talk about these three it's the composition or the amount or concentration if you will of different groups of fibers where they occur so not all of the extracellular matrix and in different tissues are going to have all three of these components some do some don't they may have these two or these two or mostly these two and again the proportion of these different fibers gives us the properties of the tissue and so that's the important thing to sort of remember is that we're looking for how we would actually use this material to build something right and what we're going to actually end up doing is we're going to build organs right a stomach a heart a brain how do we build it right what do we use we're going to use these tissues and the kind of matrix that's around them is going to tell us a lot about the properties of that tissue okay so now if we look at um at this we can talk then about in a very general way the kinds of types of tissues that we have in terms of this so we're going to use this in terms of matrix rather excuse me so the types of matrix okay how can we classify this kind of matrix well again it's sort of a continuum but we can define sort of the extremes if you will so the first type is what we call hard matrix and hard matrix would have lots of inorganic components to it lots of collagen fibers that kind of thing probably very little elastin or reticular fibers even within this an example of this would be bone right think about your bones and how tough they are and how hard they are and that's the matrix that actually makes up these bones or at least a good proportion of the bones themselves so these cells are producing this kind of matrix that's going to be really really tough on the other extreme we have what is called liquid matrix a liquid matrix and so here very very fluidy and you might suspect then that what we would have in this case is something like blood or blood plasma that ecf that's actually that that blood plasma is actually a type of tissue or at least matrix i should say uh within that and the blood cells themselves produce that so that's what we have now kind of between all these these two extremes here and sort of running the gamut from a relatively hard to relatively liquid we have what is called gelatinous matrix like a gelatin like a gel if you will of this and again it can be relatively stiff and it can be relatively uh liquidy so we'll see a variety of tissues and most tissues are going to fall into this category to some some kind of um you know in between area here that that we have and this is really really important to understand now one of the best examples i think i can give of this is cartilage uh and if you look at like a you know chicken thigh bone or something like that that little cap on the top and we're going to talk about these structures what they actually are uh is a type of cartilage and that cartilage is kind of um a little bit elasticy in some respects but it's relatively hard in that case but it's more like a kind of a gel to it so that's how we sort of look at at all that okay so now we're going to do is we want to look at some what we call intercellular junctions so i'm going to talk a little bit about how cells are sort of held together in some cases so so remember again the prefix enter means between so intercellular these are between the cells and the meaning of these are called junctions so intercellular junctions so uh there are three basic types that we're going to to look at there are some subtypes and things and again we're not going to you know belabor this this too much here but the first type that i want to talk about are called desmosomes and again here is that suffix some which means little body here and so desmosomes are often known also as you know euphemistically anchoring junctions so sometimes books will talk about these as anchoring junctions and these are called desmosomes and these are very common in this type of tissue we're going to talk about here in just a few moments called epithelial tissue so epithelial tissue so these are very common in epithelial tissue and i always think of them sort of like little rivets i'll give you some example here of this and how they're they're sort of built okay so let's think about um how these these might actually be built in this i'm going to take a couple of cells here kind of stylized little nucleus here and do another cell that kind of looks like this of course they're not really always cubed but we're just going to look at them like like that and we're going to call this cell a and cell b over here so how are they connected so we know that around them there may be a certain amount of extracellular matrix and you know fluid within that sometimes there's a lot sometimes there's a little bit and again we'll talk about the properties of tissues that that do that the different types of tissues that we have okay so what do these things actually look like so they kind of look like little what we call plaques so i'm going to just draw a couple of these and they're going to kind of look like that these are actually made out of proteins so proteins and what they have in between them are other proteins that kind of run along through these kind of like that and so they held they're held together so if we sort of blew this up here and make this look a little bit larger just fill that in a little bit here for for that and so we can say okay here is the plasma membrane on either side this is going to be cell a cell b over here and we're going to have these proteins that kind of run through this way and kind of through this way and they have these little inner connections they're kind of weird little inner connections and i'm not going to sort of belabor this too much but basically these proteins kind of hook up with each other and by hooking up with with each other they sort of hold this together so where do we normally find a lot of these desmosomes anywhere that there is potential stress or tearing so these are to reduce what we call stress or shear forces so we find these a lot for example in the skin that's why our skin doesn't actually whoops sorry uh doesn't doesn't tear off there we go okay so these sort of stress or shear forces the example i always like to give is um a lot of you may have heard of you know levi strauss and when he um went into the gold mining camps in california back in the 1840s 1850s he basically developed these kinds of of clothes made out of denim which is a really tough kind of thing right our jeans and uh the miners love them because they were really durable and they really lasted and they were thick and heavy and and uh worked really really well the only problem they kept coming back to him was that you know when i put a lot of stuff in my pockets or whatever they would tear right they would tear out so he came up with the idea of putting these little rivets in these kind of little copper rivets at the point of stress or sheer points so if you look at a pair of jeans you'll notice there are these tiny little copper rivets that are at the places where there might be the most stressful or shearing points of that that occur in all these so came up with a very clever design to make them last a lot longer so the fabric would wear out before it would actually tear a pocket for example uh in in these all right so those are desmosomes very very common and so now we'll look at a second type of these these are called tight junctions so tight junctions now tight junctions here are generally as their name implies are going to sort of encircle the the cells themselves and so they encircle whoops let me do this sorry okay here encircle what we call the apical surface the apical means upper or more superficial surface and so these are often also occur in epithelial tissues very commonly and they form a number of different areas so uh some of you may have heard of the blood brain barrier so it's these tight junctions that that actually do this the way i like to analogize this is that it's sort of like uh when you get like a six pack of of soda cans and has that little plastic around it sort of forms a little belt around it that kind of you know holds them and it's usually up near the upper surface of these so here we're going to see these as kind of a harness so if i kind of show you where these occur we want to create barriers to transport for these okay so we can again kind of look at how these these cells would work so let's do again a little cell a and cell b and you'll notice that they're really close together and these are going to form these little sort of belt-like like structures all the way around so they're going to sort of form this little belt-like structure near the the surface of these so that brings me to talking about two different things that we want to understand about how cells are connected and how we actually define them particularly for epithelial cells or epithelial tissue that we're going to talk about so there are a couple of different kinds of surfaces that are found in these the upper surface for a number of these is what we call the apical surface so this is kind of the more superficial and again it's kind of the upper portion of this and then these two surfaces here the ones on the side and at the base these are known as basolateral surfaces i guess i should write the word surface in here and so that's this surface and this surface right in here so this is how we sort of define a lot of these kinds of cells and tissues that are there so this forms this kind of tight belt now that also tells us something in comparison to desmosomes now if we go back here for just a second here and look at our desmosomes you'll notice that there's some space in between the cells so that allows us to actually move fluid between the cells so there's often transport you know into the cell and out of the cell can be in all different kinds of directions right we can have that coming through this way coming through that way so there's a lot of what we call intercellular movement that occurs here okay in tight junctions we don't have that in fact that basically that's why i mentioned here that it creates barriers to transport what it means is that the only way that something can actually move into the cell or past that cell is through the cell itself so we can only go this way or you know this way or that way right so but we can't go in between here and so this is prevented this kind of movement is going to be prevented so we don't have that intercellular movement of fluids and that creates this really nice barrier to transport and forces things to go through cells and if cells can't actually take them in then they don't and that's the way that it that it works and that's why things like the blood-brain barrier is one of those and there are other barriers similar to that that are found also in the body okay so the third type of junction that we have are called gap junctions these are also known as connexons and these are really interesting uh kinds of of junctions that that occur uh here and here uh what we find is that there are conduits like little ducts between cells so it's like a little kind of like a little duct work that goes between them and we find these often in some nervous tissue and muscle tissue certain kinds of muscle tissue that occur particularly heart muscle tissue uh that occurs within these as well and the way that this works here is that so we'll just say they occur in some muscle and some nervous tissue like the blood-brain barrier so you know forces things to actually go through cells and that allows the cells then to be a lot more discriminating because remember that the plasma membrane is semi-permeable or selectively permeable to different kinds of substances that can be transported within the cell and between cells and outside of cells so forth so here we're looking at at these how does this sort of look and i'm going to make this a little bit larger here in terms of our cell it'll be a little easier to kind of see i'll leave some space in here because there is some inter cellular movement and the way this works is that there are these proteins the proteins themselves are called connexins so these are connexin proteins very interesting little little proteins take six of them actually to to make this and each cell makes their own connection protein so i'm going to do this in two different colors to kind of emphasize this and i'm going to do it and make these really large with the which they aren't we're going to have some proteins that kind of come down like this like that and what they're going to do here is to make a little pore in the cell so that's one side and then the other side is going to also make the same kind of thing a little pour in here let me do it this way something like that okay not the greatest picture but you can see these in your book a little bit better and what they do is they hook up with each other and what that does is that allows materials to move from the cytoplasm in here out this way or maybe that way so it actually connects them through these little little ports maybe if i kind of highlight this a little bit a little bit easier to see so there are six connects and proteins and put that here six next connects and proteins for each cell and they hook up and they form the 12 proteins that hook up here form what we call a connexon so they form a connexon so the six proteins on here and six proteins on there they hook up to form this little pore that is found around here and allows things to move through so if we look at this end on what we would see on this side over here is six of these proteins forming a pore like that and if we did a little cut through this one we would see the same kind of thing i'm just going to kind of hit 7 here so but you get the picture i guess i hope okay yeah two four six there we go so they would form this little little pore here and i'm going to emphasize that that pore that way so it's time like a tiny little duct that allows um cytoplasm to to move through here from one cell to the other so it truly connects the cells up and makes them sort of function as one and so that's something that's that's really very very clever in terms of how this this functions okay so those are the different kinds of junctions that we're going to sort of encounter here for for this okay so now [Applause] let's talk about what we call the basic tissue types okay so first of all we know that tissues are made up of cells and they are going to basically produce their own cellular environment around them right extracellular environment we call it ecm that extracellular matrix which contains mostly extracellular fluid but other things as well okay so here's the easy part is that there are only four basic tissue types now of course there's lots and lots of subtypes we're going to talk about some of those but not a huge amount again i'm going to keep it really simple for you and in fact i'm going to give you a little schema that's a little bit different than in your book to simplify all this okay so what are the four basic tissue types i've already mentioned one of those that is epithelial tissue and we will just abbreviate that as you might suspect as et and there are some sort of subtypes in here that you'll hear me mention we'll talk about epithelium mesothelium remember that word meso meaning middle and endothelium sort of with inside it's also just epithelial tissue just given different names for different reasons and when we encounter that i'll i'll remind you of that and then we have connective tissue and i mentioned we talked about embryology that in fact connective tissue is probably the most abundant by far within the body and we'll abbreviate that as ct and we have a number of subtypes within that but very very important because it connects different things up and in fact it's going to connect up most these other tissues that we have third one which i know you're very familiar with is muscle tissue and then the fourth one again you'll be familiar with is nervous tissue so we'll create this one as empty and nt so these are our four basic tissue types and they are derived they are derived as we'll see and we'll talk about this here in a little while um they are derived from the germ layers the three germ layers we talked about ectoderm mesoderm and endoderm so three germ layers give rise to the four basic tissue types now on your handouts and you can sort of follow along i'm not going to spend too much time on all these because you can read about these and and you should have them in in front of you but i do want to mention a few things about particularly epithelial and connective tissue we're not going to say very much about muscle and nervous tissue now because we get to the muscular system and the nervous system we'll talk about these in in greater depth so i want to kind of contrast these two uh here epithelial tissue and connective tissue a little bit more okay so let's start with epithelial tissue or epithelium is sometimes it is known as this et so one of the things that you want to be able to do and this is why i said this is really critical to sort of understand all this if you understand the properties right what makes these tissues different from each other and what the fundamental properties are you can actually build organs and organ systems really pretty easily here by combining different tissue types and putting them together and you'll see exactly what i mean as we do this when we do start talking about organ systems which will be in our next lecture i'll start showing you the embryological development of these and the tissues that actually make them up and you'll see that this is really what we're doing is we're sort of just building the body so we're building it up from the bottom up chemicals molecules cells organelles now tissues okay so epithelial tissue what you want to do is look at the characteristics or traits and this is really what i want you to sort of concentrate on is understanding what these fundamental traits really are because if you understand these it makes it really easy to understand what kind of tissue you would put where when you're building something in terms of what it does okay so first of all this is what we call a highly cellular tissue so what do you mean by that means that it's mostly made up of cells right lots and lots and lots of cells which then tells us that we have relatively little extracellular matrix so if you have one type a lot of cells you're not going to have very much of the the matrix itself but you do have it now a couple of things about this that are also important is that epithelial tissues are not vascularized what we mean by that is that they don't have a direct blood supply so they actually have to get their blood supply their nutrients and get rid of their waste products through that process of diffusion that we talked about that non-carrier-mediated transport that occurs so when we see the word vascular we want to think about blood supply in terms of of that and also they are not typically although there are some exceptions here okay not typically um when we talk about how the how this this works we call innervated so innervation is about nerves so this is tissue that doesn't have a lot of or doesn't have any vascularization and for the most part it isn't really innervated that is it doesn't have a nerve supply so if we took a little bit of this and we did something with it you wouldn't be able to feel it necessarily so it's a little a little bit different we'll talk about the exceptions a little bit later on uh in other lectures as we we do that but here's the other thing that is really important about this this will typically and there's only one exception in the body where this does not occur and we'll get to that again down the line typically this lies on top of a layer of ecm that ecm is known as the basement membrane so basement membrane sometimes you'll see the word basal lamina basalamine can be found within basement membranes this is the more general and broader term for for all of this okay so what we're going to do is we're going to look at how this is actually built and you'll see when we build this it actually is really pretty simple so let's take a look at at this and i'm going to again keep this relatively simple so let's say we have a bunch of cells here and i'm only going to just do one layer of cells there can be many as you'll see in a few moments so here is some epithelial tissue like that at the base of this the basal lateral membrane portion that basal lateral portion is going to start making this specialized matrix now there's matrix all around these cells in between these cells like that but there is a specialized kind of matrix at the very very bottom of this the base of this and this is going to be our basement membrane and without exception well excuse me i should say without only one exception rather we're going to have this other kind of tissue that is is found here and that is underlying this attached to that is i'm going to throw a couple little cells in here very small kind of scattered this layer right here is connective tissue and it can be lots of different kinds of connective tissue but the idea here is that with one exception only in the lymphatic system which we'll talk about it's a very specialized kind of thing we're going to have this connective tissue and so we're going to have this lots and lots of matrix here so again the way i like to think about this is that if you had an envelope and you were going to send you know a letter uh to to somebody basically what you would have is you'd have this envelope which is going to represent the connective tissue and you're going to put a stamp on it so you'll notice that the stamp is really thin compared to the envelope that's going to be our epithelial tissue and how do we stick that on there well there's going to be some sort of adhesive there and that's going to be our basement membrane so the basement membrane is going to sort of stick this stamp onto this envelope that's right there or you can say envelope envelope depending on where you come from in the country so um so this is kind of how these are always built and so we're going to have an epithelial tissue with a basement membrane and some connective tissue so et bm and ct so we can kind of do it like that if you think about it et pm and ct and that's the way this is always built and that makes it really easy so whenever you see an epithelial tissue you know how it's actually put together which is is kind of interesting and so what we want to do then is to look at some other aspects of of this okay so what we want to do is look at how we sort of classify epithelial tissue and when we look at epithelial tissue here let me do this here we are we're going to do a classification by structure now this is where it comes into play really really importantly here is sort of understanding remember that this tissue is mostly cellular and because it's mostly cellular that means then that we're going to fundamentally have this tissue set up by the kind of structures that we're going to be looking at all right so we can kind of classify these as what we call simple versus stratified simple literally means one layer of cells so one layer of cells stratified means two or more layers of cells that's it okay so again pretty simple in terms of how that that works now what we want to be able to do is to look at the different kind of types of this and again there are all kinds of subtypes i'm not going to have you get hung up on on all of that kind of stuff so we're going to talk about the fundamental five basic um cell types that we're going to encounter you know throughout the course and these are the ones that we're going to sort of look at here and there's great pictures in the web lecture there's pictures in your book again on all of these so the first one that we have here is what we call squamous or squamous some people pronounce it as squamous some people say squamous and this can be either simple or stratified okay so we can have simple squamous epithelial tissue or stratified squamous epithelial tissue and the way that this looks here is that the word squamous also means sort of like squashed so if you sort of think about it that way so we're going to have some sort of squash cells kind of flattened and if it was a single layer it would look something like this and we know that we're going to have our basal lamina here just like that our base membrane rather right there like that and we're going to have again some connective tissue and it's going to look like that if it was stratified what we're going to see is we'll have a complex of layers and again we might have two or more i'm just going to do two of these layers keep it from being too complicated again and we'll have our basement membrane at our very bottom of all this and connective tissue and there it is so simple stratified just like that so very squashed so again you'll see why the designs remember we talked about form and function this is where form and function really come into play as you'll as you'll see okay the next type we have here is called cuboidal cuboidal again simple or stratified and in this case we would have cells that are more or less cube-shaped they're not exact but kind of you know bulky kind of thing like that and this would be an example of a simple type and here's our ct with that and if this was going to be stratified we'd have you know two or more layers again i'm just going to do two layers for this and we'll talk about where we would normally find these in just a moment so here's our basement membrane again and our connective tissue here so again simple stratified just like that then we have a third type of cell move this up a little bit and this one is called columnar again simple or stratified simpler stratified so in this case we're going to have columns so we might have something that looks kind of like this and notice that these are relatively uniform and their nuclei tend to be in the same plane they can be anywhere but i'm just going to make them kind of in the middle again here would be our basement membrane and then of course some this so this would be simple in this case and then for stratified these kind of look like this and again i'm just going to do two layers something like that again the nuclei lined up more or less in the same place here's our base membrane and of course our connective tissues so you can see this is really actually pretty easy right we're going to keep this you know pretty pretty straightforward now we get into something that's a little bit a little bit different and there's some specialized type here this is called pseudo stratified so the word pseudo of course speedo here pseudo means fake not exactly a real um and so this pseudostratified and this comes in in two types so obviously it's not stratified it's actually all simple but it can be what we call ciliated or non ciliated and we didn't really talk about this up here we didn't really talk about cilia but hopefully you read a little bit about cilia in your cell chapter about that cilia are these little hair-like projections so what makes this pseudo-stratified in this case is that when you first look at it it looks like there's a whole bunch of different levels that are that are found here so you might find some tall ones short ones tall shorts like this and even if a lot of them are in the same height the nuclei are all over the place different levels so when you look at this under the microscope it appears like we have all these different kinds of levels that are that are found here but it really all the bases of them all go down and produce that extracellular matrix and here again we're going to have our connective tissue just like that now some of these are going to be non-ciliated the ones that are ciliated are going to have little tufts of hairs kind of sticking out kind of like that so this would be ciliated and these of course would be non-ciliated right there so um we'll find those in different places too as we'll as we'll talk about a little bit later on okay the the final type that we have this out and this is called transitional and transitional epithelium is really only found um in a couple of places primarily the urinary bladder and in some of the readers we'll talk about a little bit later on but what's interesting about these is that these are first of all always stratified so it's a really unusual one but very abundant in those those areas like urinary bladder sort of lining all that so what transitional does this is kind of interesting thing if you look at the way these are built is and i'm just going to draw one layer here of these each of the individual cells are going to kind of look like this so the apical portion here is going to be folded so this is the apical surface that is found here and so we're going to have that and then of course we'll have our basement membrane and connect tissue so pretend that this is actually stratified i just want to draw a bunch of different layers here for this so what happens here this is a really clever thing so you know when your bladder begins to fill up we want it to expand so it's made out of elastic muscle but it also has these cells that would actually tear they're sort of in the lining of that so what happens is that as the urinary bladder fills up water begins to move in to these cells and as water moves into the cells it changes their shape and i'm just going to draw one of these so it kind of changes its shape to kind of look something like this so these unfold and so this apical surface here becomes kind of smooth right so that it kind of balloons out so it looks sort of like looking at the end of a you know a loaf of bread or something like that so these are going to unfold to allow the urinary bladder to stretch without actually tearing these cells so each one is going to be able to to do that which i think is a pretty clever design when you think about it overall for this now if we look at the classification of epithelial tissue by function what we can now do is we can look at that sort of form and function idea right that sort of form and function idea that we've talked about before early on and so one of the really fundamental kinds of functions that are that occur in the body particularly different kinds of tissues is this idea of protection so you'll see a number of different systems organ systems are also involved in protection and so these are going to be found as either a covering around organs or the lining of organs they're going to protect the inside and the outside yeah i should maybe say and or for for these we're also going to have this function called absorption now absorption means that we actually absorb things into the cells turns out that the most common kinds of things where you're doing lots of absorbing is a columnar type of cell so when you have a columnar type of cell these are ones that have a low surface area but a very high volume so we want to absorb lots of materials so we find these in those areas where we have absorption we're going to have mostly columnar again it can be simple or stratified in that case we also have secretion and secretion and i'm going to also include here excretion again sort of a fine semantic definition or difference in in these but they both work pretty much the same way here we're going to find mostly cuboidal type cells where we actually have a more or less even surface to volume ratio so it gives us a lot of surface area but also a lot of volume for this kind of secretory or excretory kind of process as as well we also have the process as we said of diffusion so what we want to be able to do is get things across from one side to the other as quickly as possible when you diffuse things because remember that it's not an energetic type of process so here we're mostly going to use really thin squamous cell types of of materials and that allows us then to have things pass along through this in the smallest area possible so it's going to have a lot of area very low volume so different kinds of structural features these forms these morphologies are going to dictate a little bit of the function and vice versa so in terms of what we want to be able to do one other sort of interesting feature that occurs in some epithelial tissues is we call the reception of stimuli so how do we detect things like heat and cold and touch and pressure and pain and stuff like that it's using these and there are specialized cells that uh that do that um and we'll talk about a few of those to get to the integumentary system for example how we do that all right so in your handout also you'll notice that when we look at epithelium tissues we sort of want to understand like how we we find that like where do we find them in the body and so there is a particular kind of arrangement a particular kind of arrangement and distribution of these tissues so where in the body are we going to find these and how are they built excuse me so we find them in basically arranged in two different ways one as membranes so these are epithelial tissue membranes and it basically again forms outer coverings or inner linings of many organs and body cavities and as i mentioned they're built the same way we're going to have a layer of cells either simple or multiple layers of cells stratified with a basin membrane and of course our connective tissues they're all built the same way right it's just the kind of cells that are there and usually there's different kinds of cells that are found within them not just one type of cell necessarily so not always one type of of cell so turns out that there are three basic types of membranes epithelial tissue membranes that are found in the body only three so the first is one you're sure you're familiar with these are called mucous membranes so mucous membranes um have a couple of different features one is that they contain what are called goblet cells so these are sort of specialized epithelial cells as i said there's many different kinds of epithelial cells cell types but these are the main ones that we talked about goblet cells are kind of uh interesting because they kind of have this basic shape like this a big surface area here and then kind of come down and look like this nucleus in them so this is going to be the apical side here in basal lateral is kind of squished in and these produce this material called mucus now notice that we spell mucous membranes oul but the mucus or what we call mucoid material is m-u-c-u-s so it doesn't have the o in it for some some reason is the way that they have that that set up so how do we find them so we know that these exist where are they distributed well turns out that they line organs and structures that open to the outside of the body so let's think about this here what's open to your body or the outside of your of your body your mouth your nose your anus as it turns out um your urinary system so urinary digestive respiratory systems uh reproductive systems they're all open to the outside and so they're all lined with these mucous membranes and mucous membranes are highly protective and so again they form these linings that are going to be very important in terms of of that kind of the of the thing so again built the same way we're going to have a bunch of different cell types that are found in different mucous membranes some are ciliated some are non-ciliated some are pseudostratified some are columnar a whole variety of things but they're all going to have some scattered goblet cells within them so they're going to have some goblet cells scattered within them so mucous membranes we also have what are called serous membranes serous epithelial tissue membranes so cirrus is interesting these have gland cells that produce what is called serous fluid strangely enough serous fluid and this is a protective oily fluid so it's just like the oil that you put in your car whatever to protect the the metal pieces uh we have these uh the serous fluid which is a lubricating fluid if you will so maybe put that in parentheses here so it's a lubricating fluid and again we'll see that in different different areas so one of the interesting things here in terms of its distribution is that it covers typically it can be lining but it usually covers organs and structures that do not underline that do not open to the outside of the body so they're not going to open to the outside of the body and it turns out that there are basically three different kinds of these that we'll see so we look at the types or their names here they all start with the letter p i love that so pericardium so again just as a little reminder here perry is the prefix for around cardi refers to heart and again remember anything that ends in ium means tissue so around the heart tissue we've mentioned this a little bit before the pluri or plural membranes and these are around the lungs and then we have the peritoneum so the peritoneum and the peritoneum is around the various spaces within the abdominal pelvic cavity as well so all three start with a p they're all built the same way now what's interesting about these uh in this case is that if we have let's say an organ we're going to actually have three components for all of these so i'll show you how this works so we're going to have a component that comes around like this and encircles that organ completely and then i have a portion as found kind of outside so this is continuous i'm just sort of showing in different colors here so we can label these so three different components to all of these three different types so i'll put this in asterisk so the outer portion here is called the parietal parietal means wall or outside this is the parietal portion this purple one in here right around touching the organ is called the visceral portion so remember the word viscous refers to organ and so visceral is pertaining to the organ itself and in between that we're going to have a cavity so this is a serous membrane cavity that is partially fluid filled so partially fluid filled so whenever this organ moves we're going to have some lubrication around it to be able to do that okay the third type of epithelial tissue membrane that we have is called the cutaneous epithelial tissue membrane and i'm not going to say too much about this but this is the skin right this is our skin it's the outer membrane of the body um and so we're going to have the epidermis and the dermis layer here for that since we're going to be talking about the integumentary system organ next we'll talk about these but again there's going to be a layer of epithelial cells all different kinds in your skin we're going to have glands in your skin things like sweat glands and so forth that are that are there and again an underlying connective tissue layer as well so that's them now i mentioned that in terms of the arrangement and the distribution of of this we also had not just membranes but i've been talking a little bit about here also the kind of of membranes that we have whoops i just realized i sort of screwed up my outline here so serous membrane should have actually been b and this should have been c so you can adjust that i'm sorry but these are the kinds of things that i do all the time my little listexia here doing this okay so asterisks for for these these would be full circle ones here if you want to do this so um we have what is called glandular epithelium and these are embedded in the epithelial tissue membranes so embed within the epithelial tissue membranes themselves scattered throughout sometimes densely packed sometimes scattered quite a bit into that these are all types of what we call exocrine glands things like sweat glands and we'll talk more about those you'll be reading in your book about a lot of different kinds of gland types i'm not going to hold you to uh too many of these kind of gland types just sort of understand there's some simple and some complex ones take a look at the pictures understand that they're all over the place and basically what they do is they function to secrete sort of protective fluids in general protective into ducts from their ducts so as opposed to endocrine glands which don't have ducts and and then onto typically the surface of an organ or structure okay so there we are for for that okay so that's a lot i know that we've sort of covered that i'm gonna briefly go over just the classification of connective tissues so i know there's a lot and again we're gonna talk about muscle tissue and nervous tissue another time as we get to those the subject areas okay so we've been going along and looking at you know epithelial tissues so we're going to do now connective tissues i'm going to keep this a lot briefer i think thank goodness okay so but again this is so critical i really want you to understand this so this is one of those things where you can sort you know stop the video and you can come back to it and and look at the rest of this uh here but again in your handout what we want to be able to do is to contrast this and look at the differences because the differences between epithelium connective tissues are really stark and they're basically opposite of one another so in this case we have relatively so relatively few cells so relatively few cells these cells by the way uh in general are known as fibroblasts so here's that term blast again so these are fibroblasts they create fibers right and so it turns out that there is lots of extracellular matrix ah so they're going to screen lots of matrix remember one of the primary components of matrix are these proteins these fibers protein fibers that are that are found in here so that's where we're gonna this is gonna come into play these are highly vascularized they have a tremendous blood supply with one exception it's a big one except for cartilage so cartilage is one of the reasons that cartilage sometimes is difficult to heal is because of its lack of blood supply that's there some are directly innervated that is they have a nerve supply not that many as it turns out or they're associated with other connective tissues that have some innervation running through them and one thing that we definitely know is that they are not associated per se with a basement membrane they do not secrete a basement membrane that is the only thing that secretes that are epithelial tissues now they can stick together with basement membranes and when they come together with epithelial cells or epithelial tissues but they're not producing it themselves for a part of that so let's look at some of the fundamental functions because again this is all about form and function here in this we're going to have these work as binding and support so i'll tell you right up front that most of your bones in your body are made out of connective tissue so support most of the joints have connective tissues that hold them together so there's your binding part of all that again one of the really important features protection skeletons are really hard right that's highly protective cartilage is pretty tough stuff so it also is highly protective as well so a lot of things it's also involved in fighting infection and we'll talk about that in a different system that's the lymphatic system and also it's involved in fat storage so it turns out that fat is a connective tissue for all of this okay so i promised you a little bit earlier that i was going to keep this classification relatively simple and that's exactly what i'm going to do for this so i'm going to give you a classification that's different than the one in your book and this classification here we're going to make it really simple we're going to do it in groups of threes so be easy to remember one is we have what we call typical connective tissue so typical connective tissue and there are three basic types of typical connective tissue there is what we call areolar also known commonly as loose connective tissue i like that designation actually and then we also have what we call dense connective tissue and here i have to give you a couple of different classifications or subclassifications for for these because both of them are very very important to distinguish one for for this is that we're going to have and by the way this is also often known as fibrous connective tissue so it's really densely packed all that matrix is densely packed with with lots of proteins we're going to have dense what we call regular and dense irregular irregular there we are and the regular stuff is where we have lots of collagen fibers and they're all lined up kind of in a row kind of like that we see these mostly in tendons and ligaments irregular is the most common and this is where the fibers are kind of scattered in a variety of different directions and gives them a lot of toughness so we find that very very commonly throughout the body i'm not i'm and you'll hear me talk about that all the time and in fact when we talk about fibroct we're mostly talking about the irregular type so we kind of almost use those terms in similar ways and then the third type of typical is called adipose connective tissue which of course is fat so big fat cells that are there so adipose connective tissue then our second type is cartilage and it too has three basic types and those three basic types are what we call fibrocartilage and this fibrocartilage is really really dense right it's really dense so the uh lots of collagen again fibers are lined up mostly in a row in the axis of the cartilage itself uh this is often used like in shock absorption and so forth we'll talk about inner vertebral discs and also the menisci of the of the knees those that's fibrous cartilage as well fibrocartilage we also have elastic cartilage and you might suspect that elastic cartilage is going to have lots of elastin fibers and it absolutely does so things around your nose and your ears um your outer ears have that and then we have the most common of all and this is called hyaline cartilage this is found all over the place i mentioned earlier about sort of the chicken bone and the cartilage at the top of that that sort of gelatinous matrix that's hyaline cartilage that's a good example of hyaline cartilage here it's the most abundant cartilage in adults it's relatively elastic uh itself and it is really really strong and pretty tough it's you know tends towards the hard type of matrix that that we have now what's important about uh this as well and you'll see this in your outline is i want to talk a little bit about some of the features of cartilage because it is so so different as i mentioned before it is non-vascularized and anytime you see the prefix chondro or suffix chondro that means cartilage right so that means cartilage like this okay so chondro refers to to that and because it's non-vascularized it's going it would die if it didn't get nutrients and get rid of waste products so it's typically surrounded by dense irregular and sometimes loose connective tissue which is highly vascularized and this is known as the peri again around chondrium so again around conjuring referring to cartilage and again here's our tissue so around the cartilage tissue itself there are three different kinds of cells that are involved in in all of this and the first type are called general these are called chondrocytes that's a general term for that so chondrogen cartilage site meaning cell for that we also have chondroblasts this happens embryonically but also even postnatally and again this is the formation of the nate of the matrix so we're going to say that chondrocytes maintain the matrix chondroblasts actually form the matrix and we're also going to have what are called chondro oops class so we're going to introduce this new suffix here class which means the destruction of that like an iconoclast right the destruction of of this so this is a dynamic tissue that's in here and we also have in the matrix so we'll say in the ecm the chondrocytes exist within what we call lacunae and the word lacuna in latin means cave so they're sort of like in their own little little cave and so let me draw a little picture here to sort of show you uh again sort of stylistically how this this works so i'm going to do this over here okay so let's say we have fungicide here chondrocyte there chondrocyte there let's do one over here like that so these are scattered remember that this is going to be mostly matrix in between them with some scattered cells so surrounding these whoops we're going to have these little openings so think of these like little condominiums for these individual cells so here is our matrix in here and the way that these communicate and also get nutrients is that they have little conduits in here now these are not gap junctions these are not gap junctions they're literally little conduits that are going out in all directions and they're going to hook up with other ones of these lacunae in here so again the lacuna is the space the cell is existing within that space and now we have this matrix that's in here right this little little matrix i'm going to put the matrix in a slightly different color and that way hopefully it you know we'll be able to preserve the idea of these little conduits that are there i'm just going to do this like that okay so the red part here is going to be the matrix and we're going to have these little kind of canals the canals are actually given a name so these little canals are called canaliculi sounds like a little italian noodle or something like that a little catalyst so the canaliculus is singular so these are canaliculi here so those are little canals that's literally what they mean tiny little canals and they allow material then to go from one lacuna to another and that will supply the chondrocyte with nutrients uh and also get rid of waste products as as well with regard to that and that will eventually go out to the perichondrium and that allows the perichondrium then to be able to do that so you can see that there are a variety of different kinds of cartilages and but they all have the same basic feature they're non-vascularized and they're surrounded by typically a perichondrium and we have different kinds of cells that will either form the matrix destroy the matrix and re-pattern it as well in all of this okay so now we're going to get to our third type of in our classification here and this is what we call specialized it's called specialized connective tissue so three basic types in the classification of of this so specialized and this is going to be simple and again we're going to talk about these individually later on we're going to have bone almost all of your bone is made out of this well it is made out of connective tissue um and we'll talk about where it's actually derived from later on this is a type of course hard matrix that we talked about uh we talked about excuse me blood so this is our liquid matrix and then there's this material called lymph which we'll talk about later on which is also a liquid matrix so this is going to be hard matrix and liquid matrix and liquid matrix type and we're going to be describing each of these in their own time so i'm not going to really have you worry about about the various features of of these so again in this classification here we're looking at three different kinds of car of connective tissues typical cartilage and specialize again this is a different classification and there are tons of different kinds of classification so this is just as valid as any really and that pretty much covers just about everything that uh that we need to know as far as that goes okay so we'll talk about muscle and nervous uh in their own right all right