In this video, we're going to talk about the 4th type of simple epithelial tissue in our lesson, which is pseudostratified columnar epithelium. And so immediately, you'll notice that this tissue is an exception to the structural naming system that we covered earlier in our lesson. And 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 again, this is not going to be the case.
Pseudostratified columnar epithelium is a type of simple epithelial tissue despite the fact that it does not have "simple" in its name. And so, this means that it's going to consist of just one single layer of cells where all the cells come into direct contact with the underlying basement membrane. And so what can be really helpful to note here is that the root "pseudo" in pseudostratified is actually a root that means false or fake. And so, 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 actually not the case. The tissue is going to be a simple epithelial tissue with just one single layer of cells where all the cells come into direct contact with the underlying basement membrane.
And so 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. And so we can say that pseudostratified columnar epithelium is going to consist of just a single layer of cells that are tall and narrow and shaped like a column for the most part. And so notice over here on the right, we have a diagram of this pseudostratified columnar epithelium. And notice that 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. And what you'll notice is that most of these cells are going to be tall and narrow like a column, which is where it gets the columnar term from.
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. And so, really, 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 as tall and narrow as each other, and they're all going to reach the apical surface. Whereas this is not going to be the case with pseudostratified columnar epithelium.
And so because some of these cells are going to be shorter than others and other cells are taller than others, this is what's going to make the tissue appear to be stratified and appear to be multiple layers of cells. But again, all of these cells come into direct contact with the underlying basement membrane, and that's what makes it one single layer of cells in a simple epithelial tissue. And so notice over here, we're saying that pseudostratified columnar epithelial tissue is going to look like more than just one layer of nuclei or look like more than one layer of cells. But again, this is not going to be the case because all of the cells touch the basement membrane. And so a really helpful analogy for this is a forest.
And so notice that in a forest, we know that the trees are going to be of different heights. Some of the trees are going to be shorter trees whereas other trees we know are going to be taller trees. And so, although there are trees of different heights, we don't consider there to be multiple layers of trees in a forest. And this is because we know that all of the trees, despite the fact that they are of different heights, they're all going to be touching the ground and branching from the ground. And so the ground here is going to represent the basement membrane.
And so notice that these little holes in the trees represent the nuclei of the cells. And so, again, notice that these nuclei may appear to be in multiple layers. But, again, this is a false impression, a fake impression of stratified tissue because all of these cells come into contact with the basement membrane. And in 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.
And again, this is not the case with pseudostratified columnar tissue. Now in terms of the function, again, it's going to be the structure of the tissue and the structure of the cells that make up the tissue that determine the function of the tissue. And so it turns out that the arrangement of the cells in pseudostratified columnar epithelium, because there are some cells that are shorter, other cells that are taller, and it appears to be multiple layers of cells, this arrangement of the cells actually makes this tissue a little bit thicker, a little bit more robust, and it makes it have a little bit greater stability than the simple columnar epithelial tissue that we covered in our previous lesson video. And because this is the case, pseudostratified columnar epithelium is going to have a greater role in protection, which is why we have it listed here as protective. Now, because pseudostratified columnar epithelial cells, many of them are going to be tall and narrow, this means that there's going to be plenty of cytoplasmic space for plenty of organelles and that is going to allow this tissue to function in both secretion and absorption.
And so when it comes to secretion, just like simple columnar epithelial cells, or a simple columnar epithelial ti...