So here we have an example problem that says to students stratified squamous epithelium and transitional epithelium tissues often look similar. Identify each tissue below and highlight the difference or the differences between the tissues that help you tell them apart. And so notice that we have this micrograph on the left and another micrograph on the right, and our job is to fill in these interactive blanks with the appropriate tissue type, either stratified squamous epithelium or transitional epithelium.

When I look at these micrographs, the first thing that stands out to me is actually all of this open space that you can see highlighted in these regions of the image. Notice that identifying the open space when we are looking at micrographs of epithelial tissue is going to be key because it is going to help us identify the polarity of the tissue, which side of the tissue is the apical surface versus which side of the tissue is the basal surface.

Of course, the apical surface is going to be the surface that is closer to the open space. In this tissue, it is going to be up here that will be the apical surface. In this tissue over here, the apical surface is actually curving, but it is going to be that surface right there of the tissue. What we can clearly see in both of these micrographs is that clearly, they are stratified tissues. You can tell that there are multiple layers of cells because of all of the nuclei that you can see, and you can see those multiple layers again in both of these tissues.

Not all of these tissue cells are going to be in direct contact with the underlying basement membrane. The real part that is going to help us tell these two tissues apart is focusing on the apical surface. Recall from our previous lesson videos that when it comes to stratified epithelial tissues that have multiple layers of cells, like both of these micrographs, the term that indicates the shape of the cells is only going to apply to the cells that are on the apical surface. In stratified squamous epithelium, the term squamous indicates that the shape of the cells on the apical surface is going to be squamous or squished or flat-shaped cells. When we closely analyze the shape of the cells in the left diagram that are closest to the apical surface, what you will notice is that these cells are pretty flat in their shape and so they do have this flat squamous-shaped cells on the apical surface.

Whereas when we closely analyze the shape of the cells on the apical surface in the micrograph on the right, notice that these cells on the apical surface are more cuboidal in shape. Already just by looking at that feature right there, we can clearly see that the stratified squamous epithelium is going to be the micrograph on the left. So for that reason, we can actually write in stratified squamous on this micrograph. Therefore, the right tissue must be the transitional epithelium. Another key feature that we could have looked at is that in the stratified squamous epithelia, the apical surface has cells that are flaking off. The cells flaking off on the apical surface are very characteristic of stratified squamous epithelium, for example, the stratified squamous epithelium that makes up our skin, which is constantly flaking off. This is a good indication of stratified squamous epithelium.

This here concludes this particular example. Again, the micrograph on the right is transitional. The micrograph on the left is stratified squamous. We will be able to get some practice applying these concepts moving forward. I'll see you all in our next video.