So here we have an example problem that says, identify the following epithelial tissues. And so notice down below, we have these three micro graphs of epithelial tissue. And so let's start with the first one on the far left. And so when we're looking at micrograph of epithelial tissue, it can be really helpful to identify the open space because that will allow us to identify the polarity of the tissue, which side is the apical surface versus which side is the basal surface. And so if we take a look at the micrograph on the far left over here, notice that we have a lot of open space toward the top as we can see highlighted here. But you may have also noticed that there seems to be a little bit of open space toward the bottom. And so which one of these spaces is going to be considered the open space and which side of the tissue is considered the apical surface. And so in order to answer that question, we need to look really closely at this micrograph because notice that this surface of the tissue over here actually has these little tiny hair like structures that are called Celia. And recall that Celia can actually move like ores in coordination in order to move substances such as mucus, for example, through the open space. And so these CIA are only found on the apical surface of the tissue. They are not found on the basal surface. And so just based on that, of course, this means that the space up above here must be the open space. Since again, the CIA structures are going to be on the apical surface. And we know the api surface is the surface that is immediately adjacent to the open space. And so that must mean that this open space down below is not going to be the open space that we're focusing on. Maybe it's a result of the preparation of this tissue for a microscopy. And so uh what you'll notice is that this tightly packed tissue that you see here immediately adjacent to the open space that you see here, that is going to be the epithelial tissue that we're focusing on. And so notice that down below, there seems to be tissue that takes on a different organization. We can assume that that is going to be the connective tissue. And so recall that uh the basement membrane is going to separate the connective tissue that underlies from the epithelial tissue that is up above here in this micrograph. Now, in terms of the shape of the cells in this tissue, what you'll notice is that they tend to be pretty elongated, pretty columnar shape. And what you'll also notice is that the nuclei of these cells seem to be pretty scattered all throughout. We've got nuclei at the bottom, some nuclei toward the top nuclei kind of all over the place. And they're not really neatly organized into very clearly distinct roads. And so because of that, we can actually assume that this is going to be pseudostratified columnar epithelium because recall that in pseudostratified columnar epithelium, the root pseudo is a root that means false or fake. And so pseudostratified is going to be a false or a fake stratified tissue that appears to be multiple layers because the nuclei are all at different levels, but it's not actually a stratified tissue because all of the cells come into direct contact with the underlying basement membrane. And so uh we can say this is pseudo stratified columnar. I'm gonna put the columnar down below here, epithelia. And so now that we've identified this tissue in the far left micrograph, let's move on to the next tissue here. And so once again, we want to identify the open space and here it's pretty clear, this is the open space right here. And so once again, what we can see pretty clearly in this micrograph is that there are certainly multiple layers of cells. It's very, very clear that there are multiple layers of cells here. And so we know that this must be one of the four stratified tissue. Now, what you'll also notice is looking at the apical surface and looking at the cells on the apical surface that these cells are fairly pillow shaped if you will and recall that these pillow shaped cells is an indication that this is transitional epithelium. And so we can actually label this as transitional epithelium. Now recall that with transitional epithelium when it is in a relaxed state that is not stretched, the cells are going to be more cuboidal in their shape. But if you can imagine grabbing the tissue and stretching the tissue out, then these cells here are going to be elongated, they're going to widen and Latin and they're going to look more like squamous shaped cells. And so uh recall that is why it's called transitional epithelium because when it is in a relaxed state, the shapes is more cuboidal. But when the tissue is stretched, the shape transitions from cuboidal to squamous. And so that allows the tissue to stretch in order to accommodate um something like the bladder stretching when it's filled with urine. And so now that we've identified this epithelial tissue here, let's move on to the last one on the far right here. And so what you'll notice is once again, the open space can be found right here in this region, you can also see open space here uh in this area as well. And so the epithelial tissue that we're looking at that's immediately lining this open space is going to be this area right here. And so what you'll notice about the epithelial tissue here um is that these cells seem to be cube shaped or cuboidal because they are pretty much just as tall as they are wide. And notice that the nuclei are pretty round or circular and they're also centrally located. And so what we can see here is that this is going to be just one single layer of cells since the nuclei seemed to be organized into one curved layer. And also notice that the cells are forming what appears to be a ring if this were to completely round out in the micrograph. And so this is all an indication that this is going to be simple cuboidal epithelia. Again, it's simple because it's just one single layer of cells, as you can see by the nuclei being organized into one single row and it's cuboidal once again because the shape of the cells is pretty box shaped or pretty cube like. And so this year concludes this example problem 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.
