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This video covers the topic “What Is Epithelial Tissue?”
Introduction
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hello and welcome to another video in this video I want to talk about the epithelial tissue so as you probably
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know the body consists of four type of tissues we have epithelial tissue nervous and muscle and connective tissue
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and each of these tissue types have under group so in this video we’re going to cover the epithelial tissue look at
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their under group and how they are divided into the body and we’re also gonna see the development of epithelial
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tissue and at the end of this video I’m gonna put some random at the feel of the tissue so you can try to pause the video
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and try to guess which cell types you’re looking at so talking about epithelial tissue you’re gonna find two main types
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we have the covering epithelia and we have glandular epithelium and then I’m gonna talk a lot about glandular fever
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as most of the times when we look at epithelial tissue you can think of covering epithelia but I’m gonna mention
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the most important structures you’ll find the glandular epithelium pourtant to know so covering epithelia is called
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covering because this covers the structures you have in the body you know the skin cells gonna composed of the
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epithelial tissue you have the outside surfaces of organs gonna be epithelial
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tissue and also going to line the internal surfaces of organs so as an example of that if you look at this
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intestines right here you can see that you can see if a fatty tissue covering the external surfaces of the the
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intestines but it’s also going to line the internal surfaces of it you can have different types of epithelial tissue
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covering and lining but they’re all gonna be a Patil tissue now when you talk about glandular epithelium you can
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you can think of glands and when you think of glands you can think I’m either exocrine or endocrine but you’re gonna
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also see them in single cells like it goblet cells so an example of an slike
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like this one this is a sweat gland consists of epithelial tissue around the
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glans right here and so and so if we would look at it in a histological perspective you would see that the
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internal structures of the intestines would look like this you can see the villa is right here and you can see
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epithelial lining the surface of the internal part of the
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intestines when we talk about the glandular epithelium see that they’re mostly gonna look like this and tissue
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slides we’re gonna have the epithelial tissue lining up in a circular motion here this is just a cross section of the
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the gland now when we look at epithelial tissue we need to know it’s a
Development of Epithelial Tissue
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development as well so it all starts when a sperm fertilizes an egg and it
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becomes a zygote and that the cycles gonna divide a lot and become a ball of cells called blastula and blaster that’s
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gonna keep dividing and dividing and dividing until it becomes something called gastrula and then gastrula is
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gonna keep dividing and it’s gonna be divided in different ways you’re gonna have something called ectoderm
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ectotherms is in the name ecto means outer layer so ectoderm mesoderm middle
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and endo terms internal so the gastrula is gonna divide into different body
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tissue types and epithelial tissues actually found within all these different terms you’re gonna have it in
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ectoderm mesoderm and endoderm you can find it in an ectotherm outer layer
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you’re gonna find it in the skin in mesoderm in the middle layer you can find it in the tubules of the cell of
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the kidneys for example and in endoderm you can find it covering the the lung
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cells the alveolar cells we’re gonna look at it later on so epithelial tissue may present
Surfaces of Epithelium
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different specialization along their various surfaces so when we’re talking about the apical pole epical is a free
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surface you can find another top of the the epithelial tissue and we’re talking
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about the lateral surface and the lateral surface you’re gonna find some other type of specialization here you’re
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gonna find what is called the terminal bars what you’re gonna find junctions junctions are going to be just two cells
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joined together junctions are really important to know because that’s what gives the epithelial tissue one of its
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major functions because as you’re studying epithelial tissue you’re gonna see that epithelia shall really really
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tight packed together now another thing we’re gonna look at is the basal part the basal part you’re
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gonna find at the bottom of the epithelial tissue because you’re gonna find at the bottom every every epipheo
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tissue no matter what type of it the epithelial tissue you’re gonna study you can always find what is called the basal
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membrane and I’m gonna talk more about the basal membrane in a bit but first let’s look at the lateral surface first
Lateral Junctions of the Epithelium
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the lateral surface you’re gonna find three types of junctions that the two
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cells are gonna connect with each other in 3 3 different ways so first you are
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what is called tight junctions and tight junctions another name for it is gonna be zoo Nuala up Lutins and if you
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imagine you have a cell here right there’s one cell and here’s another cell if you can imagine one cell here on
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another cell here and they both can have plasma membrane and inside the plasma membrane you can have transmembrane
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proteins and that is what tight junctions is it’s going to be those those transmembrane proteins that
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contact with the other cells transmembrane proteins and form those tight junctions right here and you’re
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going to have a lot of different transmembrane proteins that form these tight junctions but the most important
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transparent proteins you’re gonna find forming those tight junctions gonna be what is called the cloud in the cloud
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dense oops claudinês the cloud in some cloud is
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gonna be the biggest participant when it comes to building this physical barrier and these tight junctions gonna be so
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tight that’s not gonna be any room for water to pass through they’re just gonna bounce off and you’re gonna find most of
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the tight junctions in places like the bladder you’re gonna find a lot of them
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in the bladder you can find a lot of them also in the in the intestines the
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intestines it’s really important to have these tight junctions when it comes to the bladder for example because you
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don’t want the urine in the bladder to start leaking inside your body and so it’s called vanilla
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occlusions whenever you see the word zona that means that the it’s gonna be
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bands that completely surrounds Selman remember the cell is 3-dimensional right so these bands canis
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bands are gonna surround the whole cell making sure that there is no leakage of any type of liquid the next type of cell
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junctions are going to find is the gap junctions and these guy junctions are gonna form these membrane channels right
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here and through these membrane channel is gonna pass water and ions and you can
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afford find most of these type of gap junctions in tissues that that spread
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action potential the heart is gonna have a lot of these membrane channels because the heart needs to keep pumping all the
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time and it’s able to communicate really well through these membrane channels and these gap junctions you’re gonna find
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them under another name as well as communicating junctions now the third
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type of lateral Junction you’re gonna find in epithelial tissue is gonna be at least in junctions these have two types
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actually you can find them as vanilla adherence or macula adherence and here also gonna have you know if you imagine
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one cell here right and one cell here and they can it and they’re really close each other and what’s gonna happen here
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so you’re gonna have those tapering filaments right here that connects with these cytoplasmic plaque of a
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transmembrane proteins and then you’re gonna have what is called the cadherins that are gonna project out and then fit
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with the Catering’s of the other other other cell and here’s another picture just to show it visually how it works
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I’m gonna have the filaments of the cytoskeleton right here and here you’re gonna have the cytoplasmic plaque right
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here and then the Caterine molecules that connect with the other coloring of the other cell this way and if you
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notice the name is this one’s called the zona adherence that means that this type of adherence gonna completely surround
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the cell as well now the other type of adherence you’re gonna find is ma clad human macula means that you’re gonna
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find it on some spots and the cell again you’re not gonna find it surrounding the whole cell there’s no spots around it
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and it does that through what is called the desmosomes and to visualize this one if you look at this picture right here
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you’re gonna see that you still can have those filaments the sky cytoskeleton I still didn’t have
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those plaques right here right those plaques right here and again here we see that the molecule adhering is gonna
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connect in the same way as zonal adherence but this time we can have other proteins involved this time this
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this binding right here these are called the desmosomes right these desmosomes and the Decimus ohms in here are gonna
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be made out of the decimal Lane and this McCullen and in this movie in this meconium is going to be also gathering
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proteins these are in the carrying family of coloring proteins and to
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visualize this in histological perspective you can see really small projections out of these most small
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cells and these are gonna be desmosomes around surrounding these cells attaching them together the desmosomes are gonna
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be really strong type of cell Junction that you can find them in in places that are constantly going through stress like
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the skin for example are gonna find a lot of desmosomes in the skin and those are actually so strong bindings that if
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you were to pull the tissue really hard these Apple chunks are not gonna tear
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what its gonna tear is the cell itself so that’s just gonna be give you a little picture of how strong this these
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type of junctions are and another thing I wanted to mention when it comes to
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desmosomes is that the distance between those two cells connected together it’s gonna be a little further away than all
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the other type of junctions then and the the distance between those two cells are
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going to be roughly around 30 nanometers so it’s gonna be space for water and
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ions to go through freely go through these these type of cells all right so
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that is the three type of junctions you’re gonna find when it comes to when you’re looking at the lateral
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perspective of the epithelial tissue now if you look at the basal Pole in the
Basal Pole of Epithelium
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other hand now remember I said that the epithelial tissue are so tightly packed
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together like this actually it’s so tight back together that there’s not going to be any place for blood vessels
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or capillaries that are going to fit in between them so they’re gonna need their their nutrients in some other way
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and that nutrient they get through what is called the basal membrane right here in the basal membrane and the basal
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membranes can work in two way it’s gonna work as anchoring membrane and coring
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membrane so all those epithelial tissues are gonna be anchored to this basal
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membrane and no matter where you are in the body no matter which type of epithelial tissue you are looking at
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you’re always gonna find the basal membrane you know even though you’re
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looking at glandular epithelium or lining epithelia you’re still gonna find the basal membrane and some another
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thing you’re always gonna find is some type of connective tissue under the basal membrane or you’re nearly always
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gonna find those connective tissue under the basal membrane and the connective tissue is gonna have blood vessels
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inside it so remember I said that the epithelial tissue I’m not gonna have access to any blood vessels at all so
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they need to get their nutrients in some way how do they do that they do that through a diffusion of nutrients through
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the basal membrane you can have nutrients going out that way we’re also gonna have waste products
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from the epithelial tissue go into the bloodstream so that then they can be secreted out from the body so that’s how
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they mainly stay alive so the basal number is also gonna work as a nutrient
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provider all right nutrients and if we
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were to zoom really close into the basal membrane you’re gonna see that it considers consist of different lambdas
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it consists of lamina Lucinda and lambda densa which both may go together and
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make the basal lamina and I’ve heard a lot of people confuse the basal lamina
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with the basal membrane so don’t do that mistake the basal lamina is what the basal membrane is consists of so the
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basal membrane is consists of the basal lamina and also the reticular lamina so
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those two together is gonna form the basal membrane all right
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and so the main components of the basal lamina is gonna be the type for collagen called a gin I find a lot of that in the
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basal lamina and so the basal lamina is gonna be connected to the underlining
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connective tissue or underlying reticular lamina by the it’s going to be connected right about here by the type 7
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plugin type 7 collagen and when I said underlying connective tissue
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I meant that when you look inside the reticulum and I gonna find some connective tissue cells that’s gonna
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make I’ll make the reticular lamina cells connective cells connective tissue
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cells alright so when you’re looking at the base of Paul you’re also gonna find another structure and that’s gonna be
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what keeps the epithelial tissue connected to the basal lamina they can do that through what is called the Hemi
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desmosomes so if we remember I talked about the desmosomes to him and desmosomes going to be or we call them
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half half at this muscle and it’s half a decimal form because it’s not connected
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with another cells connect the way these type for collagen right here and if you
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remember when I talked about the desmosomes you can find the same structures here as well you’re gonna find the filaments of cytoskeleton right
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here and you’re also gonna find this plaque so just like the desmosomes Hemi
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these muscles are also gonna have plaques but these plaques are made by transmembrane proteins called integrins
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and integrins can have receptors for the type 4 collagen in lamina Lucinda and
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just like the desmosomes these bindings are really really strong that if you were to pull the epithelial tissue away
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from the basal membrane you’re most probably not gonna break the Hemi desmosomes what you’re gonna break is
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the cell itself so those Hemi desmosomes are really effective in keeping those cells
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together with the basal membrane and so if we would look at all this in a histological view the basal membrane
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right here right here’s basal membrane and here we’re gonna find those epithelial tissue
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you’re gonna find different type of epithelial tissue here I’m gonna talk more about them but what I wanted to highlight is that
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under the basement membrane you’re always gonna find those connective tissue right here and inside the
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connective tissue gonna find blood vessels
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all right so keep thinking about that when you look at epithelial tissue you know that’s one way of orientating
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yourself and you look at slides of epithelial tissue always look for the basement membrane and then under the
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basement membrane you’re gonna find connective tissue and about when you’re gonna find a different type of
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epithelial tissue all right so that is the different characteristics you’ll find a different side of epithelial
Classification of Epithelial tissue
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tissue now as we go further and look at the classification of epithelial tissue you’re gonna see that we divide them
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mainly in two types either find them as simple epithelium or stratified epithelium so what does that mean that
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means when you look at epithelial tissue you’re gonna find that basal lamina again right that’s basal lamina when it comes to simple epithelium that means
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that the type of epithelia you’re looking at only gonna have one layer
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right only gonna have one layer when it comes to stratified stratifies another word for many so when you see that
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epithelial tissue has many type of layers that’s gonna be stratified stratified are gonna be two or more more
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layers layers so one thing that is
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important to know as well is that even though these cells are far away from the basement membrane as you see here they
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can still get oxygen and nutrients through diffusion but are some stratified epithelial tissue where cells
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do get too far away from the basal membrane and will eventually die due to lack of oxygen and nutrients I will talk
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more about that in a while but you know keep that in mind during the video all right so simple means one layer and
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stratified means two or more layers but there another way to classify epithelial tissue and that is by looking at the
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shape of the cells as well so there are three common types of epithelial tissue we have squamous cuboidal and columnar
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epithelium tissue so the first one is squamous and squamous you’ll find it as simple and if you find that simple you
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will call this simple squamous epithelium tissue so for instance if you have the basal membrane here right and
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then you have these flat thin simple squamous epithelium tissue on top of that base
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membrane and then go look like fat pancakes on that based on country but if
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we would pile up those a simple squamous epithelium tissue on top of each other will get stratified called a stratified
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all right we’ll get stratified squamous epithelium tissue all right so then we have cuboidal and
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boydle these cells you’ll find them cube-shaped all right cuboid will
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typically come as simple simple you will
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rarely find them as stratified in the human body but I’m gonna show you an example of when we actually do that and
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actually find cuboidal cells stratified so then we have columnar columnar you’ll
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mostly find these as simple as well since these are these cells are really
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tall they don’t really need a lot of layers of these two for them to serve their function a wrassle I’m talking
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about cuboidal these cells you mostly find in areas with secretion like glands
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you also find these in in the renal tubules in the kidney as well and it
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comes to caboodle cuboidal you will find these in absorptive areas because these cells are really tall picking they can
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catch a lot of nutrients they want to absorb alright and then we have squamous at the feeling tissue these cells you’ll
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actually find everywhere in the body you’ll find them as covering epithelial tissue and you will find them in
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absorptive areas as well alright so another thing you will notice when you look at all these three cells is the
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nucleus you’ll see the nucleus that may be flat and elongated well then go over to the caboodle cuboidal I’m gonna have
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around the nucleus or when it comes to columnar I’m gonna have elongated nucleus and going to mostly find them at
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the lower one-third of the cell alright so that’s essentially how you classify epithelium tissue you look at how many
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layers of cells we have and you look at the shape of the cell and you also look at the shape of the nucleus as well
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alright so that is the three types of with you teacher you have in the body now if we start with simple squamous epithelium tissue before us are just
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want to mention that all these slides I used in this presentation I got from this website right here this website
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belonged to the department of histology in the university of michigan i found this website really useful when it comes
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to studying and histology because in this website i can actually search for whatever organ you want to see and it
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gives you a lot of different slides from different organs and a good thing here is that you guys search for what type of cell you want to
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look at and gives you a lot of different organs and and slides that actually shows that that specific cell you’re
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looking for so I’ll put the link in the description if you want to use that arise are now starting with simple
Simple Squamous Epithelium
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squamous epithelium so these cells as mentioned these are going to be flat cells right and since these cells are
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flat you can immediately think that protection is not their main function these type of cells you can mostly find
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them in areas where the secretion and absorption and also well for filtration
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occurs so if you use this picture as an example I know if you’re familiar with the alveolus is this is gonna be
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alveolus right here I’ll realize you’re gonna find them in the lung so if you say here are the lungs right you breathe
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in air and that air is gonna go into your lungs and then into a scald bronchial tubes and then into those air
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sacs called alveoli and this is where the exchange between oxygen and carbon dioxide is gonna happen you find a lot
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of capillaries surrounding these alveoli all right so if you look at this picture
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again you will see that the simple squamous epithelium is going to surround
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these air sacs right here this alveoli and then remember under the simple squamous epithelial tissue can have what
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is called as the basal membrane right all right since you’re also always gonna
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find epithelial tissue resting on basal membrane all right so when you breathe in air those alveoli is gonna filled
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with air right all those air sacs when were filled with air what’s gonna happen is that the good thing in having those
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thin small simple squamous epithelium tissue skeleton is that they’re gonna allow rapid exchange of oxygen and
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carbon dioxide in that way this exchange right here
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will happen really really fast and then if you would look at these cells from an apical viel I’ll tell you a little more
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about what apical means but apical means so if you have the basal membrane right here and then we have a patina tissue
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apical part is the surface of it so if you look from the top of the cell ethical view look like this right you
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can see that these cells all have different shapes right here all right and they usually really easy to spot
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because they don’t have any kaboodle shape or columnar shape like the other two types of epithelial tissue we have
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alright another thing you are known is here is that these type of cells the simple squamous epithelium is gonna
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cover the visceral organs and then you can immediately think these cells are really thin so what’s the use in having
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them cover the visceral organs if they’re not able to protect the organs all right so let’s say you have the
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heart right here right and then here we have intestines and then you have that simple squamous epithelial tissue
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covering those organs right here right and there was a good thing with that simple squamous of thin tissues that
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they’re gonna form what is called C reduce membrane membrane all right and
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the good thing about having that a serious membrane something’s gonna make sure that the surrounding area stays wet
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or also think about this a little bit what does the heart and the intestines have in common they both gonna be in
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conscious movement right so heart needs to keep beating to keep the heart circulation going and the intestines
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need to keep moving to digest that food you eat and that’s a good thing and having that white surface because it
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reduces the outside friction when these organs move all right so that’s why we have simple
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squamous epithelium tissue covering those visceral organs now another place you’re gonna find simple squamous
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epithelium is at the glomerulus of the nephron in the kidney I don’t know if
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you’re familiar with the nephron the kidney but remember the main function of the kidney is filtration of the blood
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and producing urine right and they’re able to do that by those nephron right here so this imagine this
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the head of the nephron and then you have the body of that nephron the the tubules right here right that’s gonna
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lead the newly filtrated urine down to your urinary bladder all right so one
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thing to remember here is that remember you have fifty-five percent of your blood is water right and then you have
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forty-five percent of the blood is gonna be cells but only certain five percent
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is gonna be sugar proteins and also you can have a waste products containing
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nitrogen right and eventually one gets rid of those and nitrogen what’s gonna
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happen that you have these blood vessels right here right they’ve gotten come into that head of the nephron the
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glomerulus and they’re gonna turn into capillaries and those capillaries I’m gonna be thinner right and because I’m
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gonna become thinner that blood is gonna come in to your capillaries with a high velocity right the pressure is gonna
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increase and that’s a good thing and having these simple squamous epithelium tissue lining that a gloominess right
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here is because everything that is small enough to go through those cells are gonna be filtrated into your urine all
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right so these simple squamous epithelium Teezer allow for rapid absorption of those substances right
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here and in this picture right here you’re gonna see the glomerulus right here I’m gonna also see those thin
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epithelium two shorter here those thin a simple squamous epithelia and remember
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epithelial tissue is always gonna rest on the basal membrane all right so here
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we see here we see the simple squamous tissue right here and you’re also gonna find capillaries in the middle here so
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it’s gonna happen instead is that a substance that’s gonna be filtrated through those simple screams and filled
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tissue alright so that was simple squamous epithelium tissue the next one is a simple cuboidal epithelium tissue
Simple Cuboidal Epithelium
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remember these type of cells you’ll find areas were a secretion absorption and filtration of Q so an example that has
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the renal tubules remember said that the head of the nephron can be a simple squamous at the
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feeling tissue the glomerulus and so if you look at the glomerulus right here everything after the blue matters
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it’s gonna be a simple cuboidal epithelium and everything in the cuboidal is gonna be simple squamous
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epithelium alright and these structures are here you can see that they are cube shaped these structures are going to be
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a cross-section of the renal tubules of the nephron all right so while still in the kidney remember that all right
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another thing one way to orientate yourself if you’re looking at a renal tubules is you know you have a proximal
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tubular the loop of Henle the distal tube alright so we classify the tubes
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into different types and as you see here in this picture right here you will see
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that this one is taken from the proximal convoluted tubule it’s one right here and how do you see that is that the
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simple cuboidal epithelium in the proximal 2 bar the only cells in the renal tubules that’s gonna have these
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small hair like right here you can see very small projections coming out from
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the simple cuboidal epithelium alright so let me just remove everything first
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alright so here we see the basement membrane again right remember we also was gonna see specimen membrane and he
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received the key boydle cells you can see that they had around that nucleus and you can see that their cube shaped
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right and the good thing in having those cuboidal epithelium tissue in your renal tubules is that you know when when blood
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is filtrated and comes down with that direction you know as I said everything
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that’s small enough to be filtrated are going to be filtrated but we don’t want to get rid of all the sugar we don’t
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wanna get rid of all the proteins we just want to get rid of the waste products right so what happens is that
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this pre you written we call it pre urine because it hasn’t been refill
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traited yet some of the sugar and the protein and the ions and water even are going to be reabsorbed into the
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bloodstream again and that’s a good thing and having those microbial eyes inside of proximal convoluted tubule is
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because in the proximal tubular receive newly filtrated pre-hearing and they’re most probably going to contain a lot of
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proteins and water and stuff so you need something to assist the reabsorption and
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that’s those micro is gonna do that’s why you find the microvilli together with the simple
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cuboidal epithelium tissue and you look at the proximal tube of the nephron also
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remember these are called microvilli ins these are micro villi and microvilli
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typically be about one micrometer all right so another place you’re gonna find
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simple cuboidal epithelium is usually in the ovaries he goes flying them in part of the eye we are also gonna find them
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in glance all right we’re gonna find them in endocrine and exocrine gland I’ll talk more about that later alright
Simple Columnar Epithelium
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so that is simple cuboidal now going over to simple columnar epithelium these
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cells are gonna be highly specialized cells in absorption reverse at that that’s because they’re they’re very long
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cells all right so if you look at this picture for example if you think of
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absorption as the main function of the simple columnar epithelium you will think of the intestines because you need
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to absorb the nutrients they eat right so this picture here you’ll see a cross-section of the intestines and here
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you’ll find the lumen the lumen is mainly gonna be nothing right here that’s just gonna be a hollow opening or
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space it’s gonna be space for the food you ate all right so if one thing also
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notice right here is those finger like projections you see right here now you’ll find these mostly inside the
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inside the intestines so if you go ahead and zoom in on one of them you would look like this right well see it looks
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like a finger and these finger-like projections are called the lice and remember as I said before you had a
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basal membrane right here and under the basement membrane you have a loose connective tissue and you have blood
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vessels as well so that the nutrients you eats gonna end up in the bloodstream all right and here you see the tall
30:08
columnar cells you can see that they’re tall and you can see that the nuclei are located in one third lower part of the
30:14
cell right a small part right here and again these are highly specialized cells
30:20
because they are tall and that’s a really good thing in having these tall columnar epithelium in your inside your
30:26
test because they’re tall and they can catch a lot of different nutrients right here coming coming and through another thing
30:33
that’s important to mention when coming to the villas is that you know on the surface of the villas you’re gonna also
30:39
see small hair like predictions the micro villas my crew feel lies you will
30:46
find a lot of micro villas inside your intestines lining these villas right here and they’re also going to assist
30:52
with absorption you know you have them basal membrane here right and you have
30:58
these tall columnar cells and you have these microvilli speaking out from the
31:04
apical surface of the simple columnar epithelium I remember these are gonna be
31:09
mostly one micrometer long and they assist with absorption and how do you do
31:15
that you know if you imagine this is the macro villa right and when this micro villi comes in contact with nutrients
31:21
what’s gonna happen is that the fibers inside the micro villi is kind of contract and it’s gonna lead the
31:26
nutrients to towards the simple columnar epithelium all right so it’s a really
31:32
good thing in having those micro beulas inside our intestines alright so another place you’ll find them in saying the
Pseudo-Stratified Columnar Epithelium
31:37
uterine tubes alright so that is the simple columnar the next one is sad a stratified columnar epithelial tissue
31:43
that was hard to say but if you break the word stamp Souda means false right false now remember when you see the word
31:52
stratified that means multi-layer right we call this Posada stratified because
31:57
when you look at it in the microscopes like you see right here this tissue it looks like multi-layer but they’re
32:03
really not so basically every cell right here is gonna originate from the same basement membrane but not all the cells
32:11
are gonna have the same height there are some cells some cells are gonna be shorter than the others and that’s why
32:18
it looks like multi-layer because these nucleus you’ll find them in different levels in the epithelial tissue all
32:24
right and you mostly find these ciders stratified columnar epithelium in in conducting Airways all right esophagus
32:31
would be an example of that all right and the good thing in having both sides stratified columnar epithelium
32:36
enlightening the conducting Airways is that you see those small hair like you see right here he’s hairlike
32:43
projections can be called Celia Celia are gonna be longer remember I said that microvilli is mainly gonna be one
32:49
micrometer long but these Celia this gonna be longer there’s gonna be 10 micrometer about 10 micrometer and if
32:57
you look at the structures inside the Celia you will mostly think of this equation right here 9 times 2 plus 2 and
33:04
the reason why is because you’ll find 9 pairs of microtubules located in the peripheral part of the Celia peripheral
33:11
means that they’re just gonna be located at the surrounding end of the Celia all
33:17
right so here you see 9 pairs so is a 1 2 microtubules right and these 9 pair of
33:23
microtubules are mainly found surrounding these two central located
33:29
microtubules that’s why plus 2 is because you have two microtubules in the central again
33:35
the structures of Sylvia is nine pair of microtubules surrounding two central
33:41
located microtubules alright so another structure you’re mostly gonna find inside a stratified columnar epithelium
33:47
is dogs goblet cells right here you can find something called capsules goblet cells and goblet cells gonna be simple
33:54
cell glandular epithelium I’m going to talk about more later but that’s also one thing I forgot to mention when it
34:00
comes to you know the simple columnar epithelium in the intestines it’s also
34:06
gonna have these goblet cells and good thing about these goblet cells is that they’re gonna produce what is called
34:12
mucin right and that musings gonna react with water and it’s gonna become mucus
34:20
all right they’re gonna have a layer of mucus right here as well together with the cilia and the good thing and having
34:27
those mucus and the cilia in your conducting Airways is yet when you breathe in air right what it does is
34:34
that it works as filtration as well and it’s also gonna warm up the air you
34:40
breathe in alright so in that way it’s less chance to get sick and another thing is that when we breathe in
34:46
something be Celia it’s gonna catch that right and what happens when those Celia catches something we’re gonna start
34:52
laughing a lot and when we cough though caelius gonna assist us in in removing
34:57
that thing we just breathe in we’re gonna coughing cough and it’s gonna come out as mucus you can either spit it out
35:04
or swallow it all right so that is the status stratified columnar epithelium now if you go over to something called
Stratified Squamous Epithelium
35:11
stratified squamous epithelium and remember I talked about the single scores at the thulium where it only had
35:17
one layer of cells on a basement membrane at this one is stratified those ones going to be more layers of squamous
35:24
epithelium on the basement membrane so stratified squamous are divided into two
35:29
parts to either have keratinized on non-keratinized a keratinized epithelium you’re mostly find in in dry areas while
35:38
not curtness you’re mostly find in what areas all right so what’s interesting about this stratified squamous
35:43
epithelium is that the deeper cells you’ll find closest to the basement membrane are gonna have a cuboidal or
35:50
columnar shape but as they divide a lot it’s gonna move old cells upwards and
35:55
then you’re gonna see that the outer layer are gonna be stratified epithelium right another thing when it comes to a
36:02
keratinized stratified squamous epithelium is that these cells gets reinforced when they were down here at
36:09
the basal layer and they’re gonna be reinforced with something called keratin that’s why they’re called keratinized a
36:16
carotenes can be a protein that provides a strength to the epithelia is gonna protect it from damage or stress alright
36:24
so another function keratin has is that it’s extremely insoluble in water and organic solvents and you’ll most define
36:32
these keratinized stratified squamous epithelia in the skin alright so if you
36:38
imagine this is the outer layer of the skin right and this right here is gonna be a lot of dead stratified squamous
36:44
epithelia filled with protein keratin right and keratin as I said it’s gonna
36:50
be extremely insoluble in water and an organic solvent and that’s the main reason why our skin is waterproof right
36:57
it’s because of those carotene right here alright so now if you start with non-keratinized s claims
Stratified Squamous non keratinized Epithelium
37:04
yeah so again think of these as wet areas all right think of these as when
37:09
you see a stratified squamous knock your denies think of these as lining the mouth or the esophagus or the small
37:16
intestine also the vaginas can be lined by these stratified squamous non-keratinized epithelium
37:22
alright so again we got the basal membrane right here right and we got closed connective tissue filled with
37:27
blood vessels alright so if you look at the cells closest to the basal membrane right here they’re gonna look the
37:33
healthiest and and you know knowing the function of the basement membrane it’s
37:38
gonna be logical because these cells are gonna be closest to the source of oxygen and nutrients right right and another
37:45
function epithelial tissue has I forgot to mention it earlier but they’re what we call high turnover type tissue I mean
37:51
that they’re gonna have a rapid rate of mitosis so these cells are gonna divide a lot and old cells gonna be pushed out
37:57
towards the surface all right so they divide a lot and also to push out and cells at the apical surface here I’m
38:03
mostly gonna be replaced every two to three days right this this picture is gonna be the lining of your stomach so
38:09
the surface of your stomach gonna be replaced every two to three days to do this rapid mitosis happening in the
38:16
epithelial tissue here all right so one thing you notice is that the further away these squamous epithelia gets from
38:23
the basement membrane the shape of the cells again change right you can you can see that the cells up here looks
38:29
different from the cells down here these cells up here are slowly dying that’s why the shape is different is because
38:35
they’re far away from the source of oxygen and nutrients but you know on the apical surface here these cells are
38:42
still gonna be alive and that’s the biggest difference between keratin and non curtness epithelium and keratin eyes
38:48
these cells at the apical surface are going to be dead but in non curtin eyes these cells are still alive they’re on
38:54
the last stages of their lives but they’re still alive alright so when it comes to keratinized stratified squamous
Stratified Squamous Epithelium
39:00
epithelia remember here are the basal membrane right and here you see it loose connective tissue and blood vessels
39:07
around here right so these cells are keratinized meaning that they have the keratin protein or the details are gonna
39:13
be keratinized these cells are gonna divide a lot and and old cells are gonna be pushed up to the surface like that
39:19
and when it comes to the surface these stratified squamous keratinized epithelium are going to be dead and
39:25
they’re gonna pile up with a lot of keratin in them and again that’s most of the reason why our skin is
39:31
water-resistant right and again when you think of keratinized stratified squamous
39:36
epithelia think of dry ill areas like your skin our acid is stratified squamous keratinized epithelium now the
Stratified Cuboidal Epithelium
39:43
next one is stratified cuboidal epithelium and when it comes to stratified cuboidal epithelium Ember I
39:48
said that these are gonna be rare to find you mostly gonna see a stratified cuboidal epithelium as two to three
39:54
layers maximum as you see here and these are going to be located in sweat glands and intestines of the male alright so
40:03
that is stratified cuboidal epithelial you see picture of a sweatband arrestor
40:08
that is the stratified cuboidal epithelial now going over to transitional epithelium a transitional
Transitional Epithelium
40:14
epithelium is only cool cells because these cells are gonna be are gonna change their form according to the
40:19
stress they receive so one place you’ll find these cells is in the urinary bladder are also in the unit so if you
40:27
don’t know what the unit is here you see the kidney right and here we see the bladder and the ureter is gonna be what
40:32
leads the urine from your kidney to the urinary bladder or a so that is you dated and they change it form according
40:40
to how much urine they are leading to the bladder and here we see a cross section of the you rated here you see
40:46
that this one is stretch and this one is relaxed and transitional epithelium gonna be located at the inner surface of
40:54
the ureter alright so Aiko if you go ahead and zoom in on these cells you will see that
40:59
these cells are gonna be looked like this or as a transitional epithelials not gonna be kaboodle is not gonna be columnar it’s
41:06
gonna be just transitional epithelium form right and one thing to notice here
41:12
is that that these cells right here in a relaxed form are gonna look like a peer it’s gonna have a pair shaped cells
41:18
right here alright and their nucleus are gonna be rounded and really big but as
41:24
soon as a lot of urines comes down this direction these cells are gonna stretch and when they get
41:30
stressed these cells gets flattened and also the nucleus it goes from round to flat all right and that’s a good thing
41:37
and having this transition epithelial lining those places that are receiving a lot of stresses because these can change
41:43
their form or acid that is the transitional epithelium all right and then we have glandular
Glandular Epithelium
41:49
epithelium and really that’s gonna be formed by cells special.i to produce secretion and we’re gonna mostly find
41:55
glandular epithelium as two types you can find them as multicellular when exocrine and endocrine is gonna be
42:01
example of that and you also find them as unicellular as goblet cells and remember as I talked to a goblet cells
42:06
when talk about episode a stratified epithelium and you’re also gonna find them in the intestines between the
42:12
simple columnar epithelium and so this is the goblet cells that’s how it looks like this is the structures inside it
42:18
alright so here is see the nucleus with their DNA right here alright and remember the main function of cells is
42:24
to produce proteins right you got these mitochondria’s here that fuel the process of protein synthesis alright so
42:31
you’re gonna have a lot of rough and the prismatic reticulum as well and you can have a lot of Golgi apparatus as well
42:38
which packs the proteins and and send us away all right now I got all these packed proteins ready to go out from the
42:45
cell and that proteins remember as I said that the cell produced mutant
42:52
mutant egg comes in contact with water and because mucus Rasim museum comes comes the water
42:59
becomes a kind of water and then comes a mucus alright and you will find these goblet cells between epithelial cells as
43:06
I mentioned now I’ll just give you a little challenge here can you guess what kind of epithelial cells to see right here I’ll give you three seconds think
43:13
about that one two three that’s gonna be sorry stratified epithelium because you
43:18
see that all the cells are still gonna be in contact with the base of membrane but the nucleus are gonna be found in
43:25
different levels alright so that is unicellular now going over to exocrine
43:30
and endocrine the multicellular glandular epithelium awright so we
43:36
classify glands based on their secretion right is either gonna have endocrine or
Endocrine vs Exocrine Glands
43:41
exocrine glands and endo means within so the products of endocrine is gonna go
43:47
within the body in their bloodstream and the products of exocrine scale go outside right or any surface where these
43:54
glands are located all right so imagine endocrine our glands that produce hormones right you
44:00
can have this cell right here but these cells are gonna be ductless they’re not gonna have any doubts so what happens is
44:06
that when they be cells going to produce hormones right and then these hormones are going to diffuse out to the body
44:13
tissue fluid where you’re gonna have blood vessels that eventually gonna catch those hormones and then send them
44:19
away over a long distance all right so that’s another thing to think of when you think of endocrine is that they’re
44:26
secretions going to travel a really long distance to another part of the body but
44:31
when it comes to exocrine other hand exocrine is gonna have ducts right these ducts right here it’s gonna have a duct
44:37
and also gonna have a secretion part and I just want to mention that remember I said that cuboidal cells are mostly
44:43
confound in gland role as epithelial you see those a cube-shaped epithelia right
44:48
here all right they’re gonna lie on both exocrine and endocrine glands all right
44:54
so these cells can synthesize their secretion all right so this interesting you’ll find another type of epithelial
45:00
surrounding these glands and these type of epithelia is called mayo epithelia I
45:06
said it’s called my yo epithelia aiolia it’s called Maya epithelium you see the
45:14
word Maya you will think of muscles right so these epithelial cells there are specialized cells that can contract
45:20
and when they contract they’re going to squeeze this duct and lead their secretion up to the surface all right so
45:28
that is mainly a two type of multicellular glandular epithelium in the body and a very known example these
45:35
two glands is the pancreas which is a mixed gland and the mixed gland means that it contains both endocrine and
45:41
exocrine glands really epithelia so i don’t know if you’re familiar with the functions of a pancreas but about
45:46
98% of the function of the pancreas is gonna be exocrine right exocrine and
45:54
that’s because you’ll have a lot of exocrine glands leading to the intestines assisting the digestion of
46:00
the food you eat or so that’s 98% of the function that pantry has now the rest of
46:05
the 2% of the function in the pancreas isn’t gonna be endocrine right I want to
46:12
think of endocrine in the in the pancreas that’s gonna produce what we call insulin and glucagon look around
46:23
these two hormones can be found in the beta cells in the pancreas so all right so that is the different glands we have
46:29
in the body when you think of X occurring and C it looks to me just to remove that you have the gastric glands
46:34
we’re gonna find those straight tubules you can see you’re going to find the secretion part here and the duct part here and you can also find these tubules
46:41
as branch you’re gonna find this equation part branch right here and a duct and it’s really important to have
46:47
these branch when you need rapid a production of this equation they produce and in the tank place you’re gonna find
46:54
the s in your glance these glands or you have or the secretion part of those glands are gonna be bigger and fatter
47:01
and if you think of the pancreas you’ll think of 98 as I said 98% of the pancreas is to assist the digestion of
47:08
the food you eat so we need to produce a lot of this secretion right here you’re also going to find in a Salvatore a
47:14
glance and if you think it’s self with your glance you need to produce a lot of saliva that’s why it is a good thing to
47:19
have a branched type of a scene or a secretion part right so that’s mostly
47:25
how we classify those a glance right here and another way to classify it is that you see that duct right here if
47:32
that thought would be shorter we’ll call this alveolar a duct alveolar duct it
47:37
would look like an LV lie in the in the lung and if this gland has a long duct it will be tubular all right um another
47:45
thing I wanted to mention is that when you look at a histological slide of endocrine you will see that these cells
47:50
are pretty light compared to the surroundings so these cells are quite easy to spot if you ever see
Neuroepithelium
47:57
two green glands alright so that is the glandular epithelium one more thing I wanted to talk about really quick is a
48:04
narrow epithelium and nary epithelium is in the naming their rule that means they are with the nerve cells and here they
48:12
serve as supporting cells or the nerves passing through you can most define them in the roof of the nose right here you
48:19
see the Alumni clear blows off the ethmoid bone and the olfactory bulb with their nerve cell that sense smell you
48:26
can see those neuro apathy Liam in between those nerve cells I know even though you look at neuropathy Liam we’re
48:32
still gonna find that a basal membrane right here with the basal cells now another place you’ll find in your
48:37
epithelium is in the tongue you’ll find them protecting the taste receptors right here you know you still have base
48:43
membrane and you gonna have these their epithelium protecting these taste receptor cells right here all right so
QUIZ Yourself!
48:50
that is all the epithelium I wanted to talk about now here is c3 histological
48:56
slides of epithelial tissue now can you pass the video and guess which type of epithelial cells you looking at all
49:03
right so I will reveal the answer in three two one there we go so if you got this correct
49:09
you I shall learn something all right so that was the video about the epithelial tissue and I hope this was helpful
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