Structural Naming of Epithelial Tissue - Video Tutorials & Practice Problems

Structural Naming of Epithelia

So now that we've covered the characteristics and functions of epithelial tissue, in this video, we're going to begin our lesson on the structural naming of epithelial tissue. And so, structurally, humans have 8 main types of epithelial tissue. And most of them, in fact, 6 out of 8 of them are named using a two-word naming system, where both the first word and the second word of this two-word naming system will reveal structural characteristics of the tissue. And so the first word of this two-word naming system will tell us the number of cell layers in the tissue. More specifically, the first word of this two-word naming system will indicate whether the tissue has just one layer of cells or if the tissue has multiple layers of cells. And the second word of this two-word naming system is going to indicate the cell shape. And so let's take a look at our image down below where we can start to piece things together here. And so, just to orient you on this diagram, notice that across the top here, what we have is the first word of our two-word naming system. And across the side, what we have is the second word of our two-word naming system. And then notice that down below what we have are the 2 naming exceptions to this two-word naming system. But we'll talk about the exceptions to the two-word naming system a little bit later toward the end of this video. For now, let's focus on these two words of this two-word naming system. And so once again, the first word of this two-word naming system will tell us the number of cell layers. More specifically, it will tell us whether there is just one layer of cells in the tissue or if there are multiple layers of cells in the tissue. And so the first word of this two-word naming system can either be the word simple or the word stratified. Now, the word simple will indicate that the tissue has just one cell layer, as you can see right here. And so, in this little diagram right here, notice that the cell layer is this layer at the top here, and the purple thing at the bottom here is supposed to represent the basement membrane. Now, if the first word is stratified, that would indicate that there are multiple layers of cells in the tissue, as you can see here in this diagram. Now, in terms of the second word, recall that the second word will reveal the cell shape of the tissue cells. And so there are three possibilities for the second word. It can either be squamous, cuboidal, or columnar. Now, the term squamous literally means scales in Latin. And scales are pretty flat. And so, the word squamous will indicate that the shapes of the cells are flat or squished, if you will. And so, you can think squamous is for squished. And so if we take a look at the shape of the cells here in this diagram, notice that they are pretty flattened or squished. And in fact, they remind me a little bit of fried eggs, if you will. Now, the term cuboidal, as its name implies, is going to reveal that the cell shape is cube-like or box-like, if you will. And so notice looking at the diagram here, the cell shape is cube-like or box-like. And then, of course, the term columnar is going to reveal that the shape of the cells is tall and narrow, like a column. And so, you can think columnar cells are going to be shaped like a column. And so notice that the diagram here shows these elongated tall and narrow column-shaped cells. And so what we can start to do is pair first words with second words to reveal the epithelial tissues. And so for example, if we take this first word simple, as we have right here, and we pair this first word simple with the second word over here squamous as we have right here, then we should expect to have one cell layer of flat or squished cells. And so take a moment to imagine what this tissue might look like. Well, it should look something like this right here. One layer of these flat or squished cells. And so simple squamous epithelial tissue is going to look something like this. Now, this time, imagine using the first word stratified and pairing it with the second word squamous. So that we have stratified squamous, like what we see over here. Well, in this case, we would expect to see multiple layers of these flat or squished cells. And so take a moment to imagine what this tissue might look like. Well, it should look something like this right here. And so notice that we have lots and lots and lots of cell layers here, and these cells are going to be flat or squished. Now, one thing to keep in mind about these stratified tissue is that usually the naming system is going to be looking at the shape of the cells that are on the apical surface of the tissue. And so, the shapes of the cells that are deeper in the tissue can actually change and be different. And so really, when you're focusing on stratified tissue that has multiple layers of cells, you want to be focusing on the shapes of the cells that are on the apical surface, which again are the cells that are facing toward the open space. And so keeping that in mind, we can continuously pair these first words with second words to reveal these epithelial tissues. And so, for example, if we take the first word simple and we pair it with the second word cuboidal, then we should expect to see one layer of cube-shaped cells. And so it should look something like this right here. And then if you take the first word stratified and pair it with the second word cuboidal, then you should expect to see multiple layers of cube-shaped cells, which would look something like this right here. And then if you take the first word simple and pair it with the second word columnar, then you should expect to see one layer of these tall and narrow column-shaped cells. And so it should look something like this right here. And then if you take the first word stratified and pair it with the second word columnar, then you should expect to see multiple layers of column-shaped cells. And so that would look something like this right here. And so what you'll notice is that from pairing the first word with the second words, we were able to get these 6 different epithelial tissues. Simple squamous, simple cuboidal, simple columnar, and stratified squamous, stratified cuboidal, and stratified columnar. And so, really, there are only two exceptions to this naming system, and that's what we have down below right here. The two exceptions are going to be pseudostratified columnar, which is actually a type of simple epithelial tissue, meaning that it's going to have just one layer of cells. And then the other exception is transitional epithelial tissue, which is a type of stratified epithelial tissue, meaning that it has multiple layers of cells. And so moving forward in our course, we're going to talk about each of these 8 epithelial tissues in their own separate videos, covering a lot more of their characteristics and features. But one thing that you should note here is that although pseudostratified has the word stratified in it, it is categorized as a simple epithelial tissue, meaning that it has one cell layer. And so what can help you remember this is that the root pseudo is actually a root that means false or fake. And so, really, this is just saying a fake stratified or a false stratified columnar epithelial tissue. And so, although it may appear to be multiple layers of cells, it's actually just one layer of cells. So pseudostratified is still a type of simple epithelial tissue. And then once again, transitional is a type of stratified epithelial tissue because it has multiple layers of cells. And so this here concludes our brief lesson on the structural naming of 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.

Structural Naming of Epithelial Tissue Example 1

So here we have an example problem that's asking what are the names of the following tissues? And notice down below we have tissue A over here and tissue B over here. Recall from our last lesson video that most epithelial tissue is going to be named using a two-word naming system. The first word will indicate whether there's just one or multiple layers of cells, and the second word will indicate the cell shape. Looking at this tissue A on the left, we can clearly see that there are multiple layers of cells. In fact, it looks like there are 3 layers of cells. We know that there are multiple layers of cells because not all of the cells are touching the basement membrane, which is at the bottom. Because there are multiple layers of cells here, we know that the first word must be stratified, which indicates that there are multiple layers of cells. Now, the second word we know is going to indicate the cell shape. When we're looking at stratified tissue that has multiple layers, it's best to look at the shape of the cells that are closest to the apical surface. Recall that the apical surface of the tissue is going to be facing the open space. That would be the open spaces up above here because the basement membrane is down below. The cells closest to the apical surface would be up here. Notice that they take this box-like or cube-like shape, which tells us that the second word is going to be cuboidal. So, what we have here is stratified cuboidal tissue. Now, moving on to tissue B over here, notice that we have just a single layer of cells. We can tell that because all of these cells appear to be touching the basement membrane we see down below. Because all of the cells are touching that basement membrane, we know that we have one layer of cells, and so the first word must be simple, indicating that there's just one layer of cells. Now we want to focus on the second word, which is going to indicate the cell shape. Notice looking at the shape of these cells that they are very long and narrow, and they look column-like. That means that the second word here is going to be columnar. So this tissue B here is going to be simple columnar tissue. This concludes this example and we'll be able to get some practice applying these concepts moving forward. So I'll see you all in our next video.

You look at a slide under the microscope & the tissue has a single layer of cells next to an open surface. The indicated cells are roughly as tall as they are wide. How would you identify these cells?

• A. Simple cuboidal epithelium. 
• B. Simple squamous epithelium.
• C. Stratified cuboidal epithelium.
• D. Stratified squamous epithelium.

Of the following tissue types, which is likely to be the thinnest overall? 

• A. Stratified cuboidal epithelium. 
• B. Simple columnar epithelium.
• C. Stratified columnar epithelium.
• D. Simple cuboidal epithelium.

True or false: stratified squamous epithelium is thicker than simple squamous epithelium. 

• A. True.
• B. False.

You look at a slide under the microscope & the tissue has a double layer of cells next to an open surface. The indicated cells are tall and narrow. How would you identify these cells? 

• A. Stratified columnar epithelium.
• B. Stratified cuboidal epithelium.
• C. Simple columnar epithelium.
• D. Stratified squamous epithelium.