In this video, we're going to begin our lesson on simple epithelial tissues. And so recall from our last lesson video, we said that structurally, humans have 8 types of epithelial tissues. And half of those or 4 of those tissues are going to be structurally categorized as simple epithelial tissues. And the other half are going to be categorized as stratified epithelial tissues. But we'll talk about the stratified epithelial tissues later in our course. For now, we're focusing on simple epithelial tissues. And so recall that the term simple indicates that these four tissues are going to have just one single layer of cells, where all of the cells are going to come into direct contact with the basement membrane. Now, moving forward in our course, we're going to talk about each of these four simple epithelial tissues in their own separate videos. And so I'll see you all in our next video where we'll get to talk about the very first type of simple epithelial tissue in our lesson which is simple squamous epithelial tissue. So, I'll see you all there.
Simple Epithelial Tissues - Online Tutor, Practice Problems & Exam Prep
Simple epithelial tissues consist of a single layer of cells in direct contact with the basement membrane. The four types include simple squamous, cuboidal, columnar, and pseudostratified columnar epithelium. Simple squamous epithelium facilitates rapid diffusion, found in areas like the lungs and capillaries. Simple cuboidal epithelium, with its cube-like cells, is involved in absorption and secretion, located in kidney tubules and glands. Simple columnar epithelium, characterized by tall cells, aids in absorption and secretion, often featuring microvilli or goblet cells. Pseudostratified columnar epithelium appears layered but is a single layer, primarily found in the respiratory tract.
Four Simple Epithelial Tissues
Video transcript
Simple Squamous Epithelia
Video transcript
In this video, we're going to talk about the first type of simple epithelial tissue in our lesson, which is simple squamous epithelium. And so before we get started, I want to draw your attention to the numbering and lettering system that we're using for these tissues. Here, it's 1a. And so what I really want you to notice is that we're using the number 1 for all of the simple epithelial tissue. And so recall the term simple indicates the tissue has just one single layer of cells where all of the cells come into contact with the basement membrane. And so we can use the number 1 in our numbering system as a memory tool to remind us that once again, all of the simple epithelial tissues have just one single cell layer where all of the cells are going to come into contact with the basement membrane. And so the letter a here is indicating that this is the first type of simple epithelial tissue that we're covering in our lesson. Here, it's simple squamous epithelium. And so moving forward, when we cover the other three types of simple epithelial tissues, you'll notice that they're going to be numbered and lettered as 1b, 1c, and 1d. Where again, the one is indicating this is a simple epithelial tissue with just one layer of cells. And then after we cover all 4 of the simple epithelial tissues, we'll then transition to talking about the 4 stratified epithelial tissue. And those will be numbered and lettered as 2a, 2b, 2c, and 2d. Where again, the number 2 is indicating that these stratified tissues are made of 2 or more layers of cells. But again, we'll cover these stratified epithelial tissues later in our course in different videos. And for now, we're focused on simple epithelial tissues, more specifically, simple squamous epithelium. So notice that on the left, we have some text that's showing you some of the most important characteristics, functions, and body locations of where this tissue can be found. And we also include a helpful ID tip just in case you need to identify this tissue under the microscope. And so with each tissue, we're going to include an image to help support your understanding. And so once again, when it comes to simple squamous epithelial tissue, we know that the term simple implies that the tissue has just one single layer of cells. And so recall that the term squamous implies that the shape of the cells is going to appear squished or flat. And so simple squamous epithelium is going to consist of just one single layer of squished or flat cells, just like what you can see over here in our diagram. Notice that we have just one single layer of cells where all of the cells are in direct contact with the underlying basement membrane that we briefly talked about in our previous lesson videos, and you can see as indicated here in our diagram. And really, that's the defining feature that makes it one layer of cells is when all of the cells come into contact with that basement membrane. And notice that we have these flattened cells here. Again, the term squamous is Latin for scales, which are flat as well. And so these cells are so flat or squished that they're actually going to have less cytoplasm than other tissues that have cells with different and bigger shapes. And also, these cells are so flat that they actually create a pretty flat surface that makes it really easy and smooth for liquids to be able to flow on top of this tissue. And so we tend to find simple squamous epithelial tissue in areas of the body where liquids need to be able to flow smoothly. Like for example, simple squamous epithelial tissue is found lining all of the hollow organs of the cardiovascular system, such as the capillaries and the larger blood vessels and the heart as well. Now what you'll notice is that the nuclei of these cells is pretty centrally located, And this is really what makes the simple squamous epithelial cells look like fried eggs. And so you can think that the flat nature of the fried egg is just like the flat nature of the simple squamous cell. And notice that the yolk of the egg, which is pretty centrally located, can represent the centrally located nucleus of the simple squamous cells. And so hopefully thinking of fried eggs can remind you of the structure of the cells within simple squamous epithelial tissue. Now, when it comes to the functions, it's actually the structure of the tissue in the cells that's going to dictate the function. And so once again, simple squamous epithelial tissue consists of a single layer of these flat cells, and that's going to make the thinnest possible epithelial tissue. And because it's so thin, it's not going to serve a primary protection role. Because when you think about protection, it's going to be the thicker tissues that have multiple layers of cells that are going to be better suited for protection. And so protection will be a bigger function in stratified tissue. But again, with simple squamous epithelial tissue, protection is not going to be the primary role for this tissue. And so, again, the function is going to be dictated by the structure. And once again, simple squamous epithelial tissue is going to be the thinnest epithelial tissue. And because it's so thin, it's actually going to allow for the rapid diffusion of molecules across this thin tissue. And so it's going to allow for the quick exchange of substances across the tissue. And so again, one of the primary functions here is going to be rapid diffusion. And so we can actually expect to find simple squamous epithelial tissue in body locations that require rapid diffusion. For example, we can find simple squamous epithelial tissue lining the air sacs of the lungs. And of course, in the air sacs of the lungs, gas exchange or the diffusion of gases is going to be critical. Oxygen gas needs to be able to diffuse rapidly from the lungs into the bloodstream and carbon dioxide gas from the blood needs to diffuse rapidly into the lungs, the air sacs of the lungs, so that we can exhale that carbon dioxide gas. Also, simple squamous epithelial tissue is found lining capillaries and forming capillaries, which are the thinnest or smallest blood vessels. And so this is also going to allow for the exchange of nutrients, allowing nutrients such as glucose to diffuse out of the capillaries and into the neighboring tissues, and it also allows for the quick and efficient exchange of gases between the bloodstream and the tissue. And, also, simple squamous epithelial tissue is found forming the filtration membranes found in the kidneys that are called the Bowman's capsule of the kidney. And so this is going to allow for the filtration of blood to create urine. And this is a process that we'll get to talk more about later in our course in a different video. Now, in terms of the function, simple squamous epithelia is also important for covering and lining. In fact, we'll see that simple squamous epithelial tissue, makes up the epithelial tissue that lines the body cavities. For example, the serous forming the serous membranes of the ventral body cavities that we talked about back in chapter 1. And this simple squamous epithelial tissue is going to be important for producing that serous fluid, which is the fluid inside of the serous cavity. And that's going to be important for lubrication and again helping to reduce friction between these organs. Now, in terms of an ID tip, what you'll notice is that most of the time, the images of the simple squamous epithelia are often going to be from the lungs, the air sacs of the lungs. And this is simply because the other locations where simple squamous epithelial tissue is found, those simple squamous epithelial tissue cells are a little bit harder to see, the cells in those other locations. And so again, usually it's going to be from the air sacs of the lungs. And so notice here, in our image, we're showing you the lungs and we're showing you a micrograph of the air sacs of the lungs. And you can see all of the open space here being highlighted and the epithelial tissue, the simple squamous epithelial tissue is lining these open spaces as you see here. And so notice that over here what we have is just a zoom in of this particular region and it is a sketched diagram so that you can see the cells a little bit easier. Now, what you'll notice is that we are looking at kind of a bird's eye view of the tissue and so it may appear to be multiple cell layers, but again, we're looking at it straight on from the top. And so, it is creating just one single layer of cells. And again, the basement membrane is going to be so thin that in typical light micrographs like the ones that you see here and here, the basement membrane is going to be almost impossible to see without the proper staining techniques or without a more advanced microscope like an electron microscope. But the basement membrane is still there. And so, one other helpful ID tip here is that when you're looking at simple squamous epithelia from the air sacs of the lungs, it kind of looks like ribbons in open space. And so notice down below, we've got these ribbons to remind you that these ribbons that are going through open space like this kind of look like these simple squamous epithelial tissue going through the open space here creating the air sacs of the lung. And so this here concludes our lesson on simple squamous epithelial tissue. And as we move forward, we'll be able to talk about the other types of simple epithelial tissues and we'll be able to get some practice applying these concepts as well. So, I'll see you all in our next video.
Simple Cuboidal Epithelia
Video transcript
In this video, we're going to talk about the second type of simple epithelial tissues which is simple cuboidal epithelium. And so we already know that the term simple indicates that this tissue has just one single layer of cells. And so recall that the term cuboidal indicates that the cell shape is going to be cube-like or box-like. And so we can say that simple cuboidal epithelium is going to consist of just one single layer of these cube-shaped cells or box-shaped cells, just like what we see over here in our diagram. And so notice that we have just one single layer of cells where all of the cells come into direct contact with the underlying basement membrane. Again, this is the defining feature that makes it one single layer of cells. And notice that the cell shape is box-like or cube-like. Now, in comparison to simple squamous epithelium that we covered in our last lesson video, simple cuboidal epithelium is going to have significantly more cytoplasm. Because again, the simple squamous and because they're so flat, they don't have much cytoplasm, and that leaves very little room for organelles. But with these cuboidal cells, they are more box-shaped and so they have more volume and more spacious cytoplasm and that makes more space for organelles. And so those organelles are going to be important for the functions of simple cuboidal epithelium, which are for absorption and secretion. And so, absorption again, indicates the uptake of nutrients and secretion refers to the release of products. And so, this is also going to help with the locations that simple cuboidal epithelium can be found. And so, because again, it's associated with secretion and absorption, it's going to be important for areas such as the kidney, and it forms the tubules of the kidney, which are important for filtration. Again, absorbing substances and excreting other substances. And, also, it's going to be important for secretion as well. And so we know that it can be making up the ducts of many different glands. For example, simple cuboidal epithelium makes up the ducts of salivary glands and mammary glands, and it also forms the secreting portions of the thyroid gland, and it makes up the ducts of the pancreas as well, which is another type of gland. And so, down below what we have is an ID tip to help you identify this tissue under a microscope. And so, usually, the micrograph that's going to be shown is going to show the simple cuboidal epithelium as part of a duct or a tubule. And so what this means is that the simple cuboidal epithelial cells will usually be in a ring shape. Or if they're not in a ring shape, they're going to have an open space between the two layers of cuboidal cells. And so notice up above here, we're showing you an image of one of the kidneys. And here, what we're showing you is a micrograph. And notice that the micrograph here is a little bit difficult to see. But when we draw a sketch of the same micrograph, it makes it much easier to see the simple cuboidal epithelial tissue cells. And so notice that these simple cuboidal epithelial tissue cells are forming a ring here because they're forming the tubules of the kidney. And again, those tubules are going to form a basically a tube. And so notice here that we have this ring of simple cuboidal epithelial tissue cells and you can see the open space here, which is also referred to as the lumen of the tubule. And notice that the surrounding tissue here is most likely going to be connective tissue. Now, what you'll notice is that because these simple cuboidal epithelial tissues form tubules and ducts, they are going to resemble the structure of a hose, if you will, a water hose. And so, just like you can see the simple cuboidal epithelial tissue forming a ring here, you can think that that's just the ring of the hose. And if you continuously stack and layer these simple cuboidal epithelial tissue rings, you can form a hose, which is going to allow for the transport of liquids, just like a hose allows for the transport of liquids. And again, this is how liquid products can be secreted into these ducts and tubules and things of that nature. And so this here concludes our brief lesson on simple cuboidal epithelial tissue, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
Simple Epithelial Tissues Example 1
Video transcript
So, here we have an example problem that says, the drawing shows a gas and nutrient exchange in a capillary. The missing label indicates the cells of the capillary wall. Fill in the missing label with the correct tissue type and explain how you knew the correct label. And so, notice over here we have the diagram or the drawing showing a gas and nutrient exchange in the capillary. And notice down below what we have is that missing interactive blank that we need to fill in for this problem, that again is indicating the cells of the capillary wall. And so, you can see that we have these arrows pointing from the interactive blank to the cells of the capillary wall. And so, our job is to again, identify the correct tissue type of the cells that are forming that capillary wall and then to fill in that tissue type here in this blank. And so before we do that, let's first orient you on this entire diagram. And so again, it is showing you a capillary here going through the middle of this tissue, and so you can see the body cells or the tissue cells surrounding the capillary here.
And so, what you'll notice is that the blood within the capillary is coming from the heart. The blood that comes from the heart is going to contain nutrients and be filled with oxygen. And so, notice that the oxygen gas from the blood is going to diffuse into the surrounding tissues because those tissues need the oxygen in order to generate energy to drive their cellular processes. Also notice that food substances, such as the sugar glucose for example, can diffuse from the blood and into the surrounding tissue. Because again, the surrounding tissues are going to need the nutrients like glucose in order to drive their cellular processes. And then notice that the actively working tissues are going to generate the waste product, carbon dioxide gas, which can diffuse from the tissues and into the blood where the blood can transport the carbon dioxide gas to our lungs, and we can exhale that carbon dioxide waste product into the surrounding environment.
And so what you'll notice is that in this capillary, there's quite a lot of diffusion and exchange occurring between the blood and the surrounding tissues. Again, we have oxygen gas diffusing from the blood into the tissues. We have food substance diffusing from the blood into the tissues. And we have carbon dioxide gas diffusing from the tissues into the blood. And so because we have so much diffusion occurring between the tissues and the blood, this means that the cells that are forming the capillary wall are going to need to be really thin tissue. And so, that is going to allow for rapid diffusion and rapid exchange between the blood and the surrounding tissue. And so recall from our previous lesson videos that the thinnest epithelial tissue is going to be simple squamous epithelial tissue because it consists of just one single layer of these squished or flat cells. And so, that is going to be the correct tissue type that forms the capillary wall. And so that means that the interactive blank here for this problem is going to be simple squamous epithelia. And so that here concludes this example problem and we'll be able to get some practice applying these concepts moving forward. So, I'll see you all in our next video.
Which features of simple squamous epithelium makes it ideal for rapid diffusion?
Tight junctions usually hold the cells together.
It lines body cavites.
It is attached to a basement membrane.
It is very thin.
What type of cell is most often found in the ducts of glands?
Simple squamous epithelium.
Simple cuboidal epithelium.
Stratified columnar epithelium.
Pseudostratified columnar epithelium.
In the image to the right, what feature is the yellow arrow pointing to?
Basement membrane.
Cilia.
Microvilli.
Apical surface.
Simple Columnar Epithelia
Video transcript
In this video, we're going to talk about the third type of simple epithelial tissue in our lesson which is simple columnar epithelium. And so we already know that the term "simple" indicates this tissue has just one single layer of cells. And so recall that the term "columnar" indicates that the cell shape is going to be tall and narrow like a column. And so we could say that simple columnar epithelium consists of just one single layer of these tall and narrow cells that are shaped like a column. And so notice that's exactly what we can see over here in our diagram. And so, notice that we've got just one single layer of cells where all of the cells come into direct contact with the underlying basement membrane. And once again, notice that the shape of the cells is going to be tall and narrow like a column.
Now unlike simple squamous and simple cuboidal epithelia from our previous lesson videos, which have nuclei that are round and circular and centrally located in the middle of the cell, here with simple columnar epithelia, notice that the nuclei are oval shaped instead of being round or circular. And notice that the nuclei are not centrally located in the middle of the cell but instead are slightly shifted downward toward the basal surface or the basement membrane. And so this can actually be a really helpful ID tip, which is why we note that the nuclei of simple columnar epithelia are often in a neat row along the basement membrane, which you can clearly see over here in our diagram.
Now in terms of the function, of course, it's going to be the structure of the tissue cells that are going to determine the function. And because simple columnar epithelia consist of tall and narrow cells, these cells are going to have sufficient cytoplasm to host a bunch of organelles, and that's going to be important for its functions in absorption and secretion. Now, also because this is a simple epithelial tissue with just one single layer of cells, that's also going to be really important for its function in absorption because the nutrients that are being absorbed into the body only need to go through just one single layer of cells before they're absorbed into our bodies, and that's going to make it more efficient than if the tissue needed the nutrients to be absorbed through multiple layers of cells. Now, what you'll notice is that simple columnar epithelia is going to be similar to simple cuboidal epithelia in that they both function in absorption and secretion. However, the simple cuboidal cells, because they are shorter in nature, they can actually fit into these tighter spaces that form the ducts of glands and the tubules. Whereas simple columnar epithelia tend to line cavities that are much larger.
Now, in terms of absorption, it's important to note that some simple columnar epithelial tissue cells can have structures known as microvilli on the surface, on the apical surface of the tissue. And these microvilli help to increase surface area, ultimately helping to maximize the absorption capability. And so whenever you see microvilli on the apical surface, that's an indication that absorption is going to be essential. And again, not all simple columnar epithelia have microvilli, but the ones that do are critical for absorption. And so absorption is going to be essential in our digestive tract, especially in the linings of our intestines, such as the small intestine. And so, notice over here on the right-hand side, we're actually showing you the image of our intestines and zooming into the small intestine here, notice that the small intestine lining is going to have these structures called villi, which are these folds that again help to increase surface area.
And if we zoom into the villi here, the epithelial tissue that forms the villi, that's exactly what this micrograph is showing us down below. And so you can see that this little open space here is actually the lumen or the open space inside the intestine of the small intestine. And so, notice you can see that open space over here, and that helps orient us with the tissue to identify the apical surface. We can see there's an apical surface over here and another apical surface over here. And notice over here in this diagram, this is just a sketch of the same exact micrograph. And what you'll notice is that we have the microvilli labeled. Again, these structures on the apical surface are going to help increase surface area and maximize absorption.
Now, in terms of the secretion function, it's important to note that simple columnar epithelia can be sprinkled with these unicellular glands called goblet cells. And so again, these goblet cells are going to be unicellular in nature and they're called goblet cells because their shape resembles that of a goblet or a wine glass, if you will. And later in our course, we'll talk more details about goblet cells. Now these goblet cells are going to be important for secreting components that lead to mucus formation. And so the mucus is important for lubricating the tissues and also protecting the tissues as well. Now, what you'll notice is that in our diagram over here, we're indicating where the goblet cells can be found. And so you can see the goblet cell is over here and notice again, it does take on this goblet shape or this wine glass shape if you will. And you can see that over here as well. Again, it takes this wine glass shape and again, it's going to be secreting components that end up leading to mucus formation.
And so that mucus formation can be found lining the digestive tract and the respiratory tract, for example. Now, these simple columnar epithelial tissue cells can also be found lining the uterine tubes. And in the uterine tubes, these simple columnar epithelia, instead of having microvilli on the apical surface, they actually have cilia. And those cilia are tiny hair-like structures that move like oars and help to move substances through the open space. And so the uterine tubes are going to have cilia which help to move the oocyte or the egg that's released by the ovary through the uterine tubes or the fallopian tubes into the uterus. Now, simple columnar epithelia is also going to be found in the gallbladder, which is an organ important for storing bile. And bile is going to be important for digesting fats. And so, the simple columnar epithelia that is found in the gallbladder is going to help with absorbing water and ions to help concentrate the bile to make the bile more effective at digesting fats. And so, notice that the last ID tip that we have here for you is that the microvilli may appear as a border along the apical surface. And so, you can tend to see these microvilli again on the apical surface as you see here. Again, not all of the simple columnar epithelial tissue is going to have microvilli. Sometimes they have cilia instead of microvilli, and other times they may not have either. And so, this here concludes our brief lesson on simple columnar epithelium. And we'll be able to get some practice and learn more about other types of simple epithelial tissue as we move forward. So I'll see you all in our next video.
Pseudostratified Columnar Epithelia
Video transcript
In this video, we're going to talk about the 4th type of simple epithelial tissue in our lesson, which is pseudostratified columnar epithelium. You'll notice immediately that this tissue is an exception to the structural naming system we covered earlier. This is because, although pseudostratified columnar epithelium is a type of simple epithelial tissue, it's the only simple epithelial tissue that does not have the term "simple" in its name. In fact, you may have realized that it actually has the term "stratified" embedded in its name, which can be really misleading because you may incorrectly think that pseudostratified columnar epithelium is a type of stratified tissue with multiple layers of cells. But this is not the case. Pseudostratified columnar epithelium is a type of simple epithelial tissue despite the fact that it doesn't have "simple" in its name. It consists of just one single layer of cells where all of the cells come into direct contact with the underlying basement membrane. What can be helpful to note here is that the root "pseudo" in pseudostratified means false or fake. Once you know this, you realize that pseudostratified is really just a false stratified tissue or a fake stratified tissue, where the tissue appears to be stratified with multiple layers of cells, but this is not the case. The tissue is a simple epithelial tissue with just one single layer of cells where all of the cells come into direct contact with the underlying basement membrane. Recall that the term "columnar" indicates that the cell shape for most of these cells is going to be tall and narrow like a column. Notice over here on the right, we have a diagram of this pseudo stratified columnar epithelium. All of these cells are going to be coming into direct contact with the underlying basement membrane, which is again, what makes this tissue a simple epithelial tissue with just one single layer of cells. But you'll also notice that not all of the cells are tall and narrow. Some of these cells are going to be shorter and are not going to reach the apical surface. This is what makes pseudostratified columnar epithelium different from simple columnar epithelium. Because in simple columnar epithelium, all of the cells are going to be pretty much equally tall and narrow, whereas this is not the case with pseudostratified columnar epithelium. Some cells are shorter than others, and this makes the tissue appear to be stratified and appear to be multiple layers of cells. However, all of these cells come into direct contact with the underlying basement membrane. A helpful analogy for this is a forest. In a forest, the trees are going to be of different heights. Some of the trees are going to be shorter whereas other trees are going to be taller. Although there are trees of different heights, we don't consider there to be multiple layers of trees in a forest. This is because all of the trees, despite their different heights, are all going to be touching the ground and branching from the ground. The ground here represents the basement membrane. Notice that these little holes in the trees represent the nuclei of the cells. These nuclei may appear to be in multiple layers, but this is a false impression, a fake impression of stratified tissue because all of these cells come into contact with the basement membrane. In an actual stratified tissue, that's not going to be the case. Some cells will touch the basement membrane and other cells that are in a different layer will not touch the basement membrane.
Now, in terms of function, it's the structure of the tissue and the structure of the cells that make up the tissue that determine the function of the tissue. It turns out that the arrangement of the cells in pseudostratified columnar epithelium, some being shorter and some being taller, makes this tissue a little bit thicker, more robust, and gives it greater stability than the simple columnar epithelial tissue that we covered in our previous lesson video. Because of this, pseudostratified columnar epithelium has a greater role in protection, which is why we have it listed here as protective. Pseudostratified columnar epithelial cells, many of which are tall and narrow. This means that there's going to be plenty of cytoplasmic space for plenty of organelles, allowing this tissue to function in both secretion and absorption. When it comes to secretion, just like simple columnar epithelial cells, or a simple columnar epithelial tissue, it's going to be sprinkled with these goblet cells, which recall are unicellular glands that secrete a product that ends up forming mucus. These goblet cells end up releasing a product that forms mucus. We know that the mucus can help to lubricate the lining of the tissue, and it can also help to protect the tissue because dust particles and pathogens can actually get trapped in the mucus. Once it's trapped in the mucus, the tissue can move the mucus using cilia. These cilia recall are little tiny hair-like structures that move like oars and can actually move substances through the open space that it's lining. These cilia can move the mucus along the surface and move the pathogens and the dust particles that are trapped into the mucus into areas of our body where we can eliminate the mucus, for example, into areas of our body that we can cough it up, spit it up or swallow it into our digestive system where it can be eliminated through our digestive system. It's important to note that these cilia are often going to be present, but they are not always going to be present. In terms of locations or some example locations of where you can find pseudostratified columnar epithelia, it is actually going to be lining most of the upper respiratory passages, including our trachea, and it can also be found in portions of the male reproductive tracts. In the upper respiratory tracts, those pseudostratified columnar epithelia are going to be ciliated because they're going to be moving the mucus through our respiratory passages again to help eliminate microbes and pathogens and things of that nature. But in the portions of the reproductive tracts, the pseudostratified columnar epithelia is not necessarily going to be ciliated and it's going to function more in absorption and secretion to help with activating and maturing the sperm cells in the male reproductive tract. Down below, we do have an ID tip for you here, and it says that often pseudostratified columnar epithelia is going to have cilia, but again this is not always going to be the case. And although pseudostratified columnar epithelia may look like a stratified tissue, it is not a stratified tissue. And so you may think, oh, wait a second, this could look like stratified columnar epithelia because you have these columnar cells and it appears to be multiple layers. But, what we'll find out moving forward in our course
Simple Epithelial Tissues Example 2
Video transcript
So here we have an example problem that says, this tissue is from the lining of the stomach. What type of tissue is it and what makes it unique? And so really, we need to fill in these blanks that you can see down below. Now, when I take a look at this micrograph of the tissue, which again is showing the lining of the stomach, the first thing that stands out to me is actually all of this open space that you can see highlighted here in this region. And so identifying the open space is going to be really helpful to identify the polarity of the tissue. And so notice that we have immediately adjacent to the open space, a sheet of tightly packed cells that are forming a boundary immediately adjacent to the open space. And so this layer here is actually going to be the epithelial tissue layer, and notice it's forming a curved boundary here. And what you'll notice is that the tissue that is underneath is changing its arrangement totally, so it's likely to be connective tissue, the underlying connective tissue. And that means that the basement membrane is going to be separating the two. And again, the basement membrane is really difficult to see under the light microscope without the proper staining. So you won't be able to see it very clearly, but we know that it's going to be present separating the epithelial tissue from the underlying connective tissue. And so over here on this side, we could see something similar. Again, the connective tissue is here and you can see the epithelial tissue again is curved. And again, the basement membrane is going to be separating the epithelial from connective tissues. And so now that we've identified those features, it's going to be really helpful to solving this problem. And what you'll notice is that in the epithelial tissue layer here, that the nuclei of the epithelial tissue appear to be all aligned in a single row here. Again, the tissue is curved, but these nuclei are all in a single row, and that implies that this is going to be a single layer of cells. And so because it's a single layer of cells, we know that this is going to be simple epithelial tissue. And what you'll also notice is that the shape of these cells is pretty long and narrow. They're much taller than they are wide. And so because that's the case, we know that the shape is going to be columnar. And so in terms of the type of tissue, we can identify this as simple columnar epithelial tissue. And so you might recall from our previous lesson videos that simple columnar epithelial tissue actually lines the digestive system from the stomach all the way through the anus. And so here we're showing the lining of the stomach. So of course, it's going to be simple columnar epithelial tissue. And so we can actually add the word epithelia here to remind us that this is epithelial tissue. Now, what's unique about the tissue in the stomach here is that it's actually not going to have goblet cells. So there are no goblet cells in the stomach. And so recall that these goblet cells are going to be unicellular glands that actually secrete a product that ends up forming mucus. But again, those goblet cells are not going to be present in the stomach, and they're more so going to be present in other areas of the digestive tract. And also, they're present in the pseudostratified columnar epithelia that lines the upper respiratory tract. And so, this here concludes our example problem and we'll be able to get some practice moving forward. So, I'll see you all in our next video.
Which characteristic is true of columnar cells, but not other epithelial tissues?
Columnar epithelial tissue contains the protein keratin.
Columnar epithelial tissue is found in the lungs.
Columnar epithelial tissue may contain goblet cells.
Columnar epithelial tissue functions in secretion.
Both the small intestine & the trachea are lined with columnar cells. Based on their location, what do you expect would be different about these cells?
Cells in the intestine will have cilia to aid in absorption. Cells in the trachea will have microvilli to move mucus.
Cells in the intestine will have cilia to move mucus. Cells in the trachea have microvilli to aid in absorption.
Cells in the intestine will have microvilli to move mucus. Cells in the trachea have cilia to aid in absorption.
Cells in the intestine will have microvilli to aid in absorption. Cells in the trachea will have cilia to move mucus.
Imagine that you are a histologist looking at a sample of cells from the lining of the human intestine. What tissue type do you expect to see?
Pseudostratified columnar epithelium.
Simple columnar epithelium.
Simple cuboidal epithelium.
Stratified cuboidal epithelium.
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- Mark the following statements as true or false. If a statement is false, correct it to make a true statement.e...
- Each of the following statements is false. Correct each to make a true statement.b. Mesothelial cells secrete ...