In this video, we're going to talk about the 3rd type of stratified epithelial tissue in our lesson, which is stratified cuboidal epithelium, which is actually a relatively rare or uncommon tissue in the human body, which is why we have the word "rare" in parentheses right after it. This is why this is the 3rd stratified tissue in our lesson instead of being the 1st stratified tissue in our lesson, for example. Recall that the term stratified indicates this tissue has multiple layers of cells or more than one layer of cells where all of the cells do not come into direct contact with the underlying basement membrane. The term cuboidal indicates that the cells on the apical surface of this stratified tissue are going to be cube-shaped or box-shaped, and stratified cuboidal epithelium is going to consist of more than one layer of these cube-shaped cells, just like what we can see over here in our diagram.
Notice that we have these multiple layers of cells where all of the cells are not going to come into direct contact with the underlying basement membrane, which is really what makes this a stratified tissue with multiple layers of cells. Also, notice that the cells on the apical surface of this stratified tissue are going to be cuboidal in shape or cube or box shaped. When it comes to stratified tissues that have multiple layers of cells, the term that indicates the shape of the cells is only going to apply to the cells that are closest to the apical surface. The cells that are deeper in the tissue may not necessarily take on that same cuboidal shape. In comparison to stratified squamous epithelia, which can have dozens of layers of cells, and transitional epithelia, which can also have several layers of cells, stratified cuboidal epithelium usually has just 2 to 3 layers of cells instead of dozens. This can be a really helpful identification tip when it comes to stratified cuboidal epithelium. Notice over here, we're only showing you 2 layers of cells.
Of course, the structure of the tissue and the cells within determine the function. This is a stratified tissue with multiple layers of cells, and because it has multiple layers of cells, it is going to be a thicker tissue, especially in comparison to its single-layered cell counterpart, the simple cuboidal epithelia, which consists of just one single layer of these cube-shaped cells. Because stratified cuboidal epithelia is a thicker tissue than simple cuboidal epithelia, it's no surprise that it functions in protection and support. And because the cells on the apical surface of the tissue are cube-shaped, in comparison to squamous cells which are squished and flat, these cuboidal shaped cells are going to have more cytoplasm and more room for organelles, allowing for the function of secretion, an important function for glands and the ducts of glands. When it comes to simple cuboidal epithelia, one of their functions was absorption.
In tissues that have one single layer of cells, it's much easier for substances to be absorbed through the tissue because the substances only need to be absorbed through just one single layer of cells. However, in stratified tissues that have multiple layers of cells, they do not function as well in absorption because the substances that need to be absorbed must go through multiple layers of cells, making it less efficient. Stratified cuboidal epithelium consists of just 2 to 3 layers of cells, so although it has some limited functions in absorption, it's not going to have a primary function in absorption like simple cuboidal epithelium might have. Keeping in mind the locations where we can expect to find stratified cuboidal epithelia, they are going to be found in the larger parts of the ducts of sweat glands and mammary glands, where they handle larger volumes of secretions and more pressure.
Stratified cuboidal epithelia are going to be found in ducts for example, usually arranged in a ring. Again, they form the larger parts of the ducts. You can see these big drops of sweat and we're actually zooming in on one of the sweat glands. What you should notice is that right here in the middle, we have this open space, and immediately, we can determine the polarity of the surrounding tissue. We know that the tissue that is immediately around the open space here is the epithelial tissue, the stratified cuboidal epithelia, because the cells that are on the apical surface here are cube-shaped or box-shaped. You can see a ring of cells here and a second layer of a ring of cells right there.
On the right, what we have is a sketch of the same exact micrograph just to make it a little bit easier for you to see. And once again, you can see that right in the middle here we have the open space or the lumen, which is the open space in the duct of the sweat gland. Notice that the cells that are on the apical surface are going to be cuboidal. And again, we have multiple layers of cells.
This concludes our lesson on stratified cuboidal epithelium, and we'll be able to get some practice applying these concepts and talk about the last type of stratified epithelia as we move forward in our course. So I'll see you all in our next video.