Anatomy and Physiology Help: Chapter 4 Tissues

chapter four the tissue level of organization now as we started the chapter in Chapter one we talked about the definition of anatomy physiology we looked at some anatomical terms and some of the basic points of cells in Chapter two we went up to atoms and molecules and bonds and chapter three we then went up to cells and cell parts and when we combined cells together we get tissues so chapter four is going to cover the tissues so we’re working our way up through the hierarchy of life that we talked about in Chapter one tissues are collections of specialized cells that are organized to perform a limited number of functions this means that the cells become really good at specific tasks for example cardiac muscle cells become specialized for contraction to help the heart beat and so those particular cells become really great at that function and focus on it more than anything else histology is the study of tissues so a histology would be a scientist that works in studying the tissues and what’s going on inside those tissues there are four main tissue types and every tissue in the human body can fit into at least one of these types we first have epithelial then connective muscular and nervous we’re going to spend spend the majority of this chapter talking about the epithelial and connective tissues muscular will cover the majority of that in chapter 10 and 11 of anatomy one and we’ll discuss more muscle as far as cardiac and smooth muscle in anatomy to the nervous system will also be covered in late chapters so for chapter four we’ll focus again mainly on epithelial and connective and we’ll give a little intro to the muscular so epithelial tissue is our first type of tissue and the best way to remember epithelial tissue is that it’s always going to be found covering or lining all body surfaces whether that is internal or external that means that every visible part of your body is covered with epithelium and all the internal parts of your body from the lining of your heart cavities the outside of the heart the covering of the intestines and inside lining of the intestines the skin all epithelial tissue so mainly epithelial tissues job is going to be protection because we find it covering and lining all organs and tissues of the body epithelial tissue specifically has glands that are secretory which means there are many glands in the epithelial tissue that are secreting products and those products are going to differ depending on what organ we’re talking about epithelial tissue is also a vascular which means it has no direct blood supply there are no blood vessels in epithelial tissue which is sort of weird when we think about a living tissue not having any blood vessels in it it doesn’t seem like it would be possible for it to survive the epithelial tissue actually receives all nutrients and oxygen through the process of diffusion which takes place in the lower layers of tissue below the epithelium it’s also going to form a protective barrier to regulate permeability in other words whatever organ or tissue it’s covering is going to protect that particular organ or tissue and keep what should be out out and what should be in in epithelial tissue also exhibits polarity and polarity we’re going to kind of hold that thought a minute there’s a slide coming up that will show polarity give you a visual which is much easier to understand than me just telling you about it so we’ll finish up the polarity point in just a few minutes the main functions of epithelia are again physical protection whether the epithelial tissue is found inside the body or outside the body it’s going to physically protect that organ or tissue from abrasion dehydration or destruction it’s also going to control permeability again it’s going to keep what’s out out and what’s in in it’s also going to provide sensation if we use the skin is our main epithelial example if a bug lands on our arm or the wind blows or

it’s warm or cool outside we feel it through our epithelial tissue and it also produces specialized secretions for the skin example that would be things like sweat or oil or if we looked at the lining of the intestines it would be mucus as one of the examples so depending on what area of the body we’re referring to those secretions are going to change some epithelia can become specialized to perform secretory functions and we’ll give some examples of that a little bit later it also performs transport functions we’ll give some examples of that later as well it maintains the physical integrity of the underlying tissues and organs and some epithelia develops cilia which help them to move materials across their surfaces an example of this would be the epithelia found the respiratory tract the cilia lining the respiratory tract will help move mucus and other materials around and through the respiratory tract so that we don’t get too many particles of bacteria dirt or dust down into the deeper portions of the respiratory tract so in this picture here we can see a clump of epithelial tissue and in the picture we can see one cell here another cell here another one here and they continue on towards the back a couple of key words for us to notice about this is the top surface this is called the apical surface the apical surface the bottom surface is called the basal surface basal not not in the herb it’s a completely different spelling bas al basal basement or bottom surface of the epithelial tissue we can tell that each one of these is a cell because we can see some of the familiar organ organelles that we talked about in chapter 3 here is a nucleus below that the mitochondria and above the nucleus we can see the golgi apparatus now a little bit earlier I mentioned polarity that epithelial tissue exhibits polarity and the definition of polarity in this instance is an uneven distribution of organelles an uneven distribution of organelles so if you notice a lot of cells that we look at and we’ll look at each cell is crammed from one corner to the other with organelles but an epithelial tissue is a common characteristic for the organelles to be crammed into one side of the settle and as you can see here about two-thirds of the cell has organelles in it and this top portion is just empty okay so it’s an uneven distribution of organelles they do not stretch from one end to the next of the cell they’re only in one portion of the cell so it’s a polar or unequal distribution this is characteristic of epithelium so when we look at a tissue under a microscope one of the ways we can tell we’re looking at epithelia is if we do see this polarity now we know the definition of a tissue is when the cells stick together to form a sheet or a barrier and the weight of those cells stick together to form a tissue is by what are called cell adhesion molecules or cams the cells attach its specialized cell junctions and there are four types there are three you can see here and we’re going to add one to this list the first type is the type Junction tight junctions are a fusion of membranes this is where the two neighboring cells actually fuse part of their membranes together and form what is called a tight Junction so if you look at the board we’ll draw an example of this so I’m drawing for you here a clump of epithelial cells each one has a nucleus I won’t bother drawing in the other organelles just to keep things simple but I think you get the idea we’ll make it ciliated so a tight Junction again is a fusion of membranes and it might look something like this so the tight Junction is where the two

membranes between neighboring cells fuse together and this is good because it makes sort of a leak-proof seal so that it protects the lower layers of tissue from things seeping down in between the cells so it acts as a barrier keeps things from seeping down into underlying tissues but any good epithelial tissue will always be a good barrier to protect the lower tissues from damage or bacterial toxins infections the next type of cell adhesion is called a dead zone desmosomes attach one cell to another via the cell adhesion molecules attach one cell to another through the cell adhesion molecules whenever we get sunburned and we toast our skin pretty good where the skin actually begins to peel it’s not very attractive but you know when you peel a piece of skin off you actually peel it off in sheets and those sheets are caused by desmosomes desmosomes and again desmosomes are going to keep the cells connected to each other via cams and I’ll show you a picture from your book that exhibits those cams in just a second but that these desmosomes attach one cell to another and helps the cells to peel off in sheets when we have sunburn okay and our next one is a gap junction gap junctions permit the flow of ions they permit the flow of ions back and forth so a gap junction is almost like a little portal between cells it allows one cell to communicate with the neighboring cell sending messages or ions back and forth so if this cell had a little extra sodium it could send it to its neighbor and vice versa this allows the cells to communicate and act as a team instead of acting as individuals and finally we have the Hemi desmosomes which we’re going to add to the list here Hemme desmosomes are almost like little root systems in a way you can sort of imagine it like that Hemi dozens ohms anchor the epithelial tissue into the underlying tissues anger the epithelial tissue until an unfit to the underlying tissues so it almost looks a little bit like a root system Hemi does his own okay so we’re going to look back at the PowerPoint just for a second to see some examples of these from your book all right so in this picture which is from your textbook it should show some of those structures that I just went over this is that same clump of epithelial tissue and they’ve done is scooped out the cytoplasm so that we could see the inside of the cell membrane and starting up here towards the top this is the type Junction which is a fusion of cell membranes and if we blow that up a little larger this is what a tight Junction would look like up close on the Left we can see one cell membrane and on the right we can see another and see how they’re fused together it almost looks like they’re stapled together or bolted together this makes a nice tight fusion up towards the apical surface here we have the gap junctions which are the portals that lead from one cell to the next and if we blow the gap junctions up a little bit here’s a cell membrane on this side and here’s one on this side and in between we can see the little portals or hallways almost that lead from one cell to its neighbor down here at the bottom is the Desna zone and if we blow that up a little bit here’s one cell membrane here’s the next in between the cells we can see the cams they almost look like little boat bores or it sort of looks too like the two cells were zipped up together with a zipper each one of these little boat oars clicks together and makes the desmosomes or this this lower sail attachment and finally at the bottom we have the hynny desin zone and the heavy dozen zone if we blow it up looks like a root system in a way that

helps attach the tissue to underlying layers so what does the other thelia actually stick to it sticks to what’s called the basal lamina or what could also be called the basement membrane basal lamina or basement membrane the basal lamina is made up of two layers the lamina lucida and the lamina densa the lamina lucida acts as a barrier that restricts the movement of proteins and other large molecules from underlying connective tissue acts as a barrier that restricts the movement of proteins and other large molecules from underlying connective tissue the lamina densa gives the basement membrane or basal lamina it’s strength gives the basement membrane or basal lamina its strength Dermott of cells at any time we see a word with German it we should not think of bacteria but we should think of reproductive derivatives cells are reproductive epithelial cells that replace short-lived epithelial cells so there are reproduction cells for the epithelial layer alright so if you look back at the board we’re going to draw out the basal lamina so the basal lamina has two layers the top layer is the lamina least it up and the bottom layer is the lamina densa okay and together they’re known as the basal lamina or basement membrane you can call it either one and that’s what the epithelial tissue sticks to so what the epithelial tissue sticks to now epithelial tissue can be found in layers some epithelial tissue is thick and some is thin and there are some terms we need to learn to allow us to determine whether we’re looking at thin or thick epithelia all right so we’ll clean up our drawing a little bit and give us a little bit more room to look at this next part so the theme it can be classified in two ways it can be classified as either simple or stratified simple epithelia is epithelia that is one cell layer thick one cell layer thick this would be example an example of simple epithelia because it’s only one cell layer thick only one cell makes up the later simple again only one cell layer thick stratified is two or more cell layers thick so if we erase the cilia here we can make this stratified so stratified would be two or more cell layers thick so because we see at least two layers of epithelia here we would classify this as stratified epithelia or multiple layers of cells thick stratified epithelia could be ten layers thick 50 layers thick it doesn’t just have to be two but for simplicity got two here’s our first example and we’ll look at some examples of these from your book as well so simple is one cell layer thick and stratified is two or more we can also determine the shape of the epithelia that we’re looking at and there are three main shapes the first shape is squamous or squamous squamous or squamous actually stands for irregular so the cells are all different they’re all irregular shaped they don’t really look like a square or a rectangle or a circle they’re just irregular some books compare them to a fried egg they’ll call them a fried egg sale because they’re nice and thin with a little yolk in the middle this is squamous or squamous and then we have cuboidal and cuboidal is what it sounds like a cube nice and square the nucleus right in the middle cuboidal like a cube and then we have

columnar cells which look like a column or rectangle so these are pretty easy to identify and we’re going to use we’re going to look at a couple of examples back on the PowerPoint to see some different types of epithelial tissue now one key thing to note before we start looking at different types is that whenever we determine shape of epithelial tissue we only look at the apical surface and if you remember apical surface is the top surface of the epithelial tissue so that’s why it says there on your notes we have to look at the shape of the apical surface cells in order to determine the shape overall for the epithelial tissue in question so we’re going to look at a sample here all right another key thing to note is that epithelial tissue can be simple or stratified just like we can see here and after we look at this I’ll give you some examples of where we would find simple epithelia and where we would find stratified epithelia so we’ll first look at this example and notice we’re looking at a cross-section okay this epithelial tissue is only one cell layer thick here we can see the basal lamina which is what the epithelial tissue sticks to and this yellow area is the underlying connective tissue which we have not yet talked about so right here we can see just one cell layer thick so this is definitely simple epithelia now that we’ve determined that it’s simple we need to figure out the shape so if we look at the top surface notice that there’s they’re not really cubes and they’re not really rectangles so they must be squamous or irregular and it is if you look over here this is simple squamous epithelia one cell layer thick irregular shaped so simple epithelium is epithelia that is very thin this is not epithelial that you would find close to the surface of the body imagine if your skin was only one cell layer thick every time you bumped into a wall or even something as gentle as a pillow you could potentially bleed to death places that might come up against abrasion or scratching of any sort need to be thick and well protected so anytime we see simple epithelium we’re always going to expect to find it somewhere deeper inside the body that’s very well protected and this epithelium is taken from the lining of the abdominal pelvic cavity which is quite deep so we would expect that simple would be okay in this instance because it’s deep it’s not close to the surface let’s look at our second example so here’s the basal lamina and this is all epithelial tissue now right away it should be quite obvious to you that this is stratified there are definitely more than one layer of cells in the thickness of this tissue we’ve got multiple layers there so this is stratified and now to determine shape remember we always look at the apical surface apical surface here and notice it’s not a cube it’s not a rectangle it has to be squamous irregular so this is stratified squamous epithelia and we would expect to find this somewhere that’s probably close to the surface of the body because stratified squamous or anything stratified can take destruction and if we look at where this was taken from it was actually taken from the surface of the tongue and we certainly do have a possibility of biting our tongue or eating something sharp that could potentially scratch us so it makes sense because it’s close to the surface that we would have lots of protective layers so here’s another example and we try to figure out what this one is as well there’s the basal and there’s the epithelia it’s definitely only one cell layer thick and the shape is a cube a square okay so we’ve got simple because it’s one cell layer thick cuboidal because it’s shaped

like a cube so this epithelia is simple cuboidal epithelium and because it’s simple we would expect to find it somewhere deep inside the body where it doesn’t have a lot of chance to be under any type of abrasion or destruction and this in fact was actually taken from the inside of the kidney which is certainly well protected so that makes sense that it would be simple so this one we’re looking at is a little harder to see but we definitely have more than one layer of cells there so that’s going to definitely be stratified and then if we look around the perimeter there we can see that the shape is cubed so this is stratified cuboidal epithelium now because it’s stratified even a little we would expect to find it a little closer to the surface of the body and it was in fact taken from a sweat gland in the skin which certainly would be close to the surface of body all right now this is kind of a weird one it doesn’t really fit into any of the other categories it’s its own special type called transitional epithelium transitional epithelium and transitional epithelium is epithelial tissue that is found in an area where stretching needs to occur and this was actually taken from the inside lining of the bladder if you notice this is the epithelial tissue in an empty bladder and this is the epithelial tissue from a full bladder you see how much the tissue that’s stretched without tearing so transitional epithelium is a special type of epithelia that’s found in organs that need to expand things again like the inside of the bladder other parts of the urinary system like the ureters which drain bladder or drain the urine into the bladder this is columnar on we can definitely tell that right away because it looks like a rectangle now is it simple or stratified well we can only see one cell layer thick only one cell so that’s simple and then the shape is columnar because it looks like a rectangle so that simple columnar epithelia and because it’s simple we would of course again expect it to be found somewhere deep inside the body and this in fact is taken from the lining of the intestine now another reason that simple epithelia is useful is because it permits diffusion and absorption if you think about it in your small intestine this is where 90% of all nutrients are absorbed from your diet so we don’t have time to wait for nutrients to absorb through 56 layers of cells we need the absorb absorption process to be fast so this simple epithelia will allow nutrients and ions and vitamins and water to absorb almost instantaneously the same thing applies for the lining of the alveolar sacs in the lungs they too are simple only one cell layer thick so that oxygen can diffuse into the bloodstream almost instantly if the epithelia of the alveolar sacs were 40 or 50 cell layers thick could make it almost impossible for epithelial or for oxygen to get through the epithelial tissue which would not be beneficial to maintain life so anywhere we see simple epithelium is usually a place where we’re going to have diffusion and absorption this is another special type of epithelia that does not fit into any of the other categories when you look at it initially it appears to be columnar and it also appears to be maybe stratified because if we take a look at it we can see some little cells down here at the bottom and some bigger cells on top so initially it looks stratified but it isn’t if we get a little closer you’ll notice that every one of these cells even the small ones are in touch with the basement membrane that means they’re not layered and because they’re not layered then it’s not truly stratified this particular weird-looking type of tissue is called pseudo stratified epithelia pseudo stratified means not true stratification looks try find initially but it isn’t

pseudo stratified not true stratification and this is found one of the places we find it is the lining of the nasal cavity and finally we have our last example of epithelium here which is definitely at this point we should recognize stratified right away we can see at least two layers of cells here so that’s stratified and we look at the top cell which is columnar so this is stratified columnar epithelia and because it’s stratified again we would expect to find it somewhere closer to the outside of the body because it’s well protected and that’s actually taken from the salivary gland duct which is certainly close to the surface of the inside lining of your mouth all right so epithelial tissue we mentioned already that it is full of glands and depending on where the epithelial tissue is found the glands are going to change there are two major kinds of glands in the body into crin glands and exocrine glands endocrine glands are glands that release hormones into surrounding fluid we’ll talk about those more in chapter 18 of anatomy to exocrine glands secrete through a duct onto the surface of the gland and there are many types of exocrine glands found in epithelial tissue glandular secretions can be one of three types we have merocrine glands these are glands that release a product through the process of exocytosis which we covered in chapter 3 this is when we release the product by little secretory vesicles that are produced by the golgi an example of America England would be saliva sweat and mucus saliva sweat and mucus are merocrine glands apocrine involves the loss of a product that is produced and also some cytoplasm okay an example of this is a mammary gland and a holocrine gland is a gland that when the product is produced the cell bursts open to spill the product which will destroy or kill the cell an example of this is an oil gland so we’ll take a look at these in this picture which can also be found in your book three examples of glands so I’m here at the top we have the merocrine glands and example again would be the salivary gland sweat or mucus any of those and inside this gland we have cells epithelial cells like you see here each one of these represents a cell we can see a nucleus and a Golgi in each one and little secretory vesicles that are filled with saliva the saliva will then be released by exocytosis which will be projected of course into the mouth so merocrine releases a product through exocytosis apocrine an example is a mammary gland the apocrine cells the cells that line the African apocrine gland instead of just releasing milk through exocytosis the top part of the cell is filled with secretory vesicles and instead of those being released by exocytosis the cell pinches off its top and the product milk is released mixed with cytoplasm so yes that does mean when you drink milk you’re drinking a little cow cytoplasm as well it’s completely normal it’s exactly how those cells release as soon as this part of the cell actually breaks off the cell will regenerate itself and continue same process on and on and on again releasing the product mixed with cytoplasm finally we have the holocrine glands down here like the oil glands and you can see the bottom layer of cells in the gland are going through mitosis they appear to be dividing pretty pretty quickly which makes sense because the top layer of cells are releasing oil but when they release the oil the whole cell bursts open and spills out the contents of the cell along with oil so it kills the cell so if these cells are releasing oil and dying at the same time we need to be replacing them as quickly as they

are dying which is why the bottom level here is going through mitosis this again is the hologram type of bland alright so that ends the epithelial tissue section and will now begin with the connective tissue so connective tissue establishes a structural framework for the body by transporting fluids and dissolved materials protecting delicate organs surrounding supporting and connecting tissues storing energy in the form of lipids and defending the body from micro organisms like bacteria so if you’re looking at the board we will now draw an example of some connective tissue or we’ll draw an example of a little chart that will help keep us organized with connective tissue now I left the epithelial tissue layer up here just to let you know when we talk about connective tissue where we’re talking about connective tissue is actually found below the epithelial tissue and the basal lamina so this is our connective tissue down below so connective tissue is what it sounds like it connects the epithelial tissue to the rest of the body and connective tissue is highly highly vascular it has lots and lots of blood supply we talked about how the epithelial tissue does not have any blood vessels but this makes sense because if we our skin which is a type of epithelial tissue and every time we bumped into anything we begin to bleed profusely this would be a very dangerous way of life so the epithelial tissue because it is not vascular can be bumped and nicked without bleeding the connective tissue on the other hand very vascular very much full of blood vessels and very sensitive lots of pain and pressure receptors down in that connective tissue level so connective tissue can actually be broken up into some categories so I’m going to give you a little chart here to help keep that organized and then we’ll start going through each type of connective tissue so we’ll use some abbreviation to to give us enough room so the different types of connective tissues are one we have connective tissue proper which has two types loose and dense we then have fluid connective tissue which also has two types blood and lymph and our third type is supporting connective tissue which also includes bone and cartilage okay now I would suggest that you pause the video so that you can have a chance to write this down all right so hopefully you got that down by pausing those different types of connective tissues we’ll cover each one by the end of the section but one thing that we do need to keep in mind something that I would suggest also that you write somewhere nearby so that you can refer to it multiple times throughout this section is that all connective tissues must have specialized

cells and a matrix matrix includes ground substance and fibers okay so I would again suggest that you pause the video and copy this down somewhere that you can see it throughout the next several slides all connective tissues must have specialized cells and a matrix specialized cells if we’re talking about a tissue we would expect to see cells in a tissue that’s natural but what the matrix is the matrix is made up of fibers and we’ll talk about some examples of those fibers and also a ground substance matrix is what the cells are suspended in I like epithelial tissue we looked it up a few little tissue it was just a bunch of cells in a sheet with connective tissue it typically can be more sloppy looking it’s got a lot of different cells kind of thrown in to this matrix substance which suspends the cell the matrix can be runny it can be thick it can be hard it can be gelatinous and we’ll mention which type they are as we go through each one of those connective tissues that you wrote down in the previous chart so if you’ll look back at the PowerPoint connective tissues contain specialized cells this is what you just wrote down and the matrix which is what the cells are suspended in the matrix is made up of ground substance and fibers the first type of connective tissue that you wrote down in your chart was connective tissue proper connective tissue proper contains a varied cell population and I’ll give you the names of those cells in just a minute various fiber types and a syrupy ground substance fluid connective tissue contains a more distinct cell population a watery ground substance with protein and there are two types blood and lymph supporting connective tissue has a less diverse cell population Dent’s ground substance closely packed fibers and there are two types cartilage and bone so we’ll start a connective tissue proper and we’ll go through it first then fluid and finally supporting connective tissue proper contains fibers a viscous ground substance viscous means syrupy serve be kind of like the texture of honey in a very cell population first we have first type of cell in our population is a fibroblast and you may want to pause between each cell as each cell has a definition fibroblasts are the most abundant always present and secrete proteins to keep the ground substance syrupy macrophages are large phagocytic cells if you remember phagocytic means eating cells they eat other things like bacteria or food particles viruses macro thaj is a large phagocytic cell that engulfs pathogens or damaged cells adipocytes are fat cells fat cells that contain a lipid droplet fat cells that contain a lipid droplet mesenchymal cells divide to produce daughter cells divide to produce daughter cells in response to injury or infection in response to injury or

infection miletto sites store the brown pigment melanin store the brown pigment melanin mask cells are found near blood vessels and contain histamine which causes inflammation contain histamine which causes inflammation and inflammation is just an increased blood flow to an area an increased blood flow to an area lymphocytes are defenders of cells defenders of cells and macrophages are blood cells that are phagocytic blood cells that are Faygo siddik so we’ve just listed the first thing we need in every connective tissue which are the specialized cells the specialized cells are suspended in a matrix the matrix is made up of fiber and ground substance here are the three types of fibers that we could find in the matrix the first is collagen collagen is long straight and unbranched long straight and unbranched very very flexible very flexible reticular fibers are thinner than collagen and can withstand forces from all directions thinner than collagen and can withstand forces from all directions elastic fibers contain the protein elastin and are very stretchy contain the protein elastin and are very stretchy so connective tissue proper as we wrote in our chart can be grouped as loose or dense some loose examples start with the embryonic mesenchyme embryonic buzzing time is the first tissue to appear in the embryo first tissue to appear in the embryo mucous connective tissue is found in the umbilical cord mucous connective tissue is found in the umbilical cord areolar tissue absorbs shock and separates the skin from deeper tissues absorb shock and separates the skin from deeper tissues adipose tissue is fat too soon of course we know it is very loose and squishing unfortunately reticular tissue surrounds organs surrounds and protects organs so we’ll look at some examples of loose connective tissue this is our first type and just like when we were looking at the epithelial tissue before epithelial tissue is again just a sheet of tissue a sheet of cells that make a great barrier but connective tissue is nothing like that it’s a bunch of cells kind of mixed together within this matrix or ground substance that they’re suspended in so in this picture remember that connective tissue must have specialized cells specialized cells are all here these are the ones that you just defined a second ago millena site plasma cell adipocyte lymphocyte mesenchymal macrophage mast cell fibroblast all those cells you define are they’re just kind of scattered amongst some fibers and ground substance the three fibers we have collagen this black one is an elastic fiber and up here at the top the brown one is reticular fiber the pink substance in the background that’s the ground substance that the cells are suspended in so this is loose connective tissue proper this is also loose connective tissue gave an example of one type of loose connective tissue being embryonic mesenchyme and it does look

very soft and squishy and loose you can see the individual nezam Kimmel cells these dark pink areas and in the background all this light pink is the matrix on the right we have the mucous connected tissue which is what’s found in the umbilical cord and it too is a collection of mesenchymal cells suspended in matrix very loose and soft the top we have adipose tissue or fat and it is made up of a collection of fat cells suspended in a soft squishy viscous matrix at the bottom reticular tissue which surrounds and protects the organs it’s made up of cells reticular fibers and the soft squashing viscous matrix as well so loose connective tissue again very soft not very organized and next we have dense connective tissue and dense connective tissue is what it sounds like it’s a lot more dense and a little more organized than the loose connective tissue dibbs connective tissue is mostly made of fibers and there’s two types dense regular and dense irregular dips regular is called regular because all of the fibers run in a nice neat parallel pattern its unidirectional one direction of collagen fibers nice and neat and regular an example of where you would find this is in a tendon very stretchy and tough dense irregular connective tissue is a tissue where there are also a lot of fibers but the fibers run in multiple directions it’s a lot more disorganized as you can see here all the fibers are running in different directions this is exceptionally strong because of all the different directions of fibers this makes the tissue very very tough we find this in our dermis which is part of the skin this makes the skin very stretchy you can pull on it and let it go and it bounces back would be very challenging to care with the bare hands so that’s connective tissue proper and we can move now to fluid connective tissue which either includes blood or lymph now if you’re anything like me the first time I’ve heard this I didn’t really understand how a liquid could actually be a tissue most of the time when we’re starting out we think of tissues being nice pink sheets of cells but blood is actually considered a tissue type so just because it’s liquid doesn’t mean that it can’t be considered a tissue fluid connective tissues contain distinct collections of cells this means that there’s not all kinds of different cells mixed together like we saw in loose connective tissue there’s just a few types makes it a little bit more simple to learn about a distinct collection of cells in a fluid liquidy matrix so we know who has we’ve seen blood and lymphatic fluid before we know that they are very liquidy so we would expect the matrix to be fluid and not viscous so this matrix is notably different from the lip from the connective tissue proper category blood is our first example of a fluid connective tissue and it’s made up of formed elements which are the cells there are three types of cells red blood cells white blood cells and platelets red blood cells are also known as erythrocytes erythrocytes er Y th ro SI y te erythrocyte which are red blood cells and make up half the volume of blood they’re actually what makes blood look red white blood cells and platelets white blood cells are great for fighting infection and platelets are great for clotting so if you’ve ever seen a vial of blood that is left to sit for a period of time you may notice that it kind of separates into two layers the bottom layer is a clump of red cells and the top layer is kind of a clearish

yellow plasma the plasma is the ground substance this is the fluid part that the cells are suspended in the three cell types float in the plasma and we mix together makes mixed blood actually look red arteries carry blood away from the heart artery starts with a away starts with a arteries away veins carry blood to the heart capillaries are tiny thin walled blood vessels that allow for diffusion into the tissue fluid we’ll talk more about blood vessels when we get to chapter 20 which is over the heart lymph is the interstitial or tissue fluid that enters the lymphatic vessels so in the lymphatic system we have a lymph fluid that contains white blood cells that help fight infection it’s another type again a fluid connective tissue supporting connective tissue is our third type supporting connective tissue includes cartilage and bone and they’re called supporting because they support and protect the rest of the body cartilage and we’ll talk by the way we’ll talk about cartilage and bone very lightly because we have two chapters coming up later chapter 9 and chapter 6 where we will discuss each one of those in great detail so we’ll just mention some intro things for right now cartilage grows via interstitial and appositional growth interstitial means length and a positional means width length and width the matrix is a firm gel that contains chondroitin sulfate which is a mineral firm gel containing chondroitin sulfate the cells are called chondrocytes anytime we see anything with a Kandra in it it should always make us think of cartilage there are three types of cartilage hyaline elastic and fibrocartilage hyaline cartilage is the most common type of cartilage the most common type of cartilage it’s found in the joint cavities it’s found in the joint cavities and contains lots of collagen found in the joint cavities and contains lots of collagen elastic cartilage contains elastic fibers which make it very flexible contains elastic fibers which make it very flexible you can find elastic cartilage in the ears and the tip of the nose fiber cartilage has densely interwoven collagen fibers densely interwoven collagen fibers in the matrix and is extremely tough extremely tough phone or osseous tissue contains osteocytes and very little ground substance what there is is dense and mineralized which if we felt before a femur or a humerus we know how incredibly hard it is so we would expect the matrix to not be soft viscous fluid we would expect it to be very dense very hard and very calcified so that’s all I’ll say about bone for now because we have a chapter chapter 6 7 & 8 will cover bone in much greater detail so that’s the supporting connective tissues and that wraps up connective tissue in general so now we’ll talk about membranes membranes are simple organs that form barriers and they’re great at lining or covering body surfaces lining or covering body surfaces and they’re actually made up of epithelial and connective tissue epithelial and connective tissue combined there are four types of membranes cutaneous synovial serous and mucous cutaneous synovial serous and mucous so the four types are shown here in this picture which are also in your book and we’ll

start up at the top this is the mucous membrane and we can see some familiar things here first of all the epithelial tissue and that certainly looks like simple columnar then we have the basal lamina underneath that and below that is the connective tissue mucous membranes are found lining cavities that communicate with the exterior of the body like the mouth and the intestine the mucous membranes are lined with special cell like you can see right here called goblet cells they’re called goblet cells because they look very much like the Goblet the drinking glass but instead of being filled with a nice drink it’s filled with a lot of mucous these goblet cells expel mucus constantly to lubricate and moisturize that particular tissue in question which in this example would be the large intestine next we have the serous membrane serous membranes line sealed internal body cavities and this one is very thin you can see it’s simple squamous epithelia and where this one was taken from was lining the abdominal pelvic cavity and it keeps the organs nice and moist cutaneous membranes a fancy name for skin and if we look at it blown up a little bit it’s definitely stratified squamous if we look at that top layer thick which makes sense because skin certainly comes into contact with abrasion destruction and dehydration here we have the synovial membrane which lines the joint cavities synovial membranes produce synovial fluid which lubricates the joints so summing that up mucous membranes live cavities that communicate with the exterior of the body like the intestines or the oral cavity serous membranes form sealed line sealed internal cavities and form a watery solution called transudate cutaneous membrane is the skin covers the body surface and synovial membranes are an incomplete lining within the joint cavity and produce synovial fluid for lubrication Tasha Tasha is made up of a network of connective tissue proper and there are three types superficial deep and sub serous superficial deep and sub-series fashio are connective tissue layers connective tissue layers that support and surround the organs support and surround the organs superficial Asha is also known as the hypodermis also known as the hypodermis it’s a layer of areolar tissue and fat a layer of areolar tissue and fat that separates the skin from underlying tissues separates the skin from underlying tissues deep fascia is made up of dense irregular connective tissue dense irregular connective tissue and can resist forces from all directions can resist forces from all directions it surrounds the organs sub serous is a layer of areolar tissue that lies between the deep fascia and serous membranes layer areolar tissue that lies between the deep fascia and serous membranes finally muscle tissue which again we will cover in great detail in chapter 10 and 11 so we’re just mentioning very lightly a few points about muscle tissue so if you would look at the board there are three types of muscle tissue skeletal cardiac and smooth skeletal

muscle is found around the skeleton and it is what we call spindle shaped the individual muscle cells are spindle shaped long and thin like a fiber spindle shaped skeletal muscle is multinucleate which means it has more than one nucleus multinucleate striated which means it has a striped appearance and voluntary we control our skeletal muscles cardiac muscle is found in the heart it’s what makes up the heart we don’t find it anywhere else it’s what’s called branched the individual cells kind of look sort of like X’s branched contains one nucleus is striated because I striped the parents and is definitely involuntary we have no control over our heart which is wonderful if we had to control our heartbeat imagine how easily we would be distracted and not remember to tell it to beat so that’s a responsibility we don’t want involuntary smooth muscle is found lying hollow organs this is things like the uterus the bladder the intestines the cells are spindle shaped but they’re kind of short and fat little spindles they also contain typically one nucleus Arnon striated that’s why we call them smooth because they don’t look striking and then involuntary you do not have control over your uterus intestines bladder none of that involuntary so if you need to pause this for a second and get this down and after you do that let’s take a look back at the PowerPoint skeletal muscle again just reviewing the cells are multinucleate which means more than one nucleus striated and voluntary and divides via satellite cells which means it can repair itself if it needs to cardiac muscle is made up of cardio sites which our heart cells occur only in heart their striated involuntary and rely on a pacemaker for regular contraction again we have a natural pacemaker we don’t have to control our heartbeat we don’t have to think about it smooth muscle tissue is non striated involuntary found lining hollow organs and can divide and regenerate if it needs repair so whenever our tissues are injured they can respond in a coordinated fashion by inflammation which is increase blood flow to the area which would not only bring in nutrients and oxygen but also repairing cells that can help restore and regenerate homeostasis to the area when we age one of the things to note that does occur in the epithelial or connective muscle or nervous tissue is repair and maintenance is less efficient because of the chemical composition being different the structure being different repair in aging is much much slower this concludes chapter 4 you