In this video, we're going to talk about the 1st epidermal cell type in our lesson which are the keratinocytes. And so keratinocytes are actually the most abundant cell type in the epidermis by far. In fact, these keratinocytes can make up over 90% of the cells in the epidermis. And as their name implies, the keratinocytes are responsible for keratin production. Now, these keratinocytes are actually specialized epithelial tissue cells.
And because they are considered epithelial tissue, it's no surprise that they are going to be connected by tight junctions, which hold the keratinocytes really tightly together, creating a leak-proof barrier. And they're also held firmly together by desmosomes, which allows for mechanical resilience. Now, the keratin that these keratinocytes produce is tough, fibrous, and water-resistant proteins that give the epidermis its protective properties. Providing both mechanical and tensile strength to the epidermis, allowing the epidermis to resist forces in many different directions while still remaining flexible at the same time.
Now, it's also worthy of noting that keratin is also one of the main components of both hair and nails. And later in our course when we're talking about accessory structures of the integumentary system, we will talk more details about the structure and function of hair and nails. But for now, let's take a look at this image that we have down below. And notice on the left-hand side, we're showing you the diagram of the integumentary system. And notice that only the epidermis is being colored here in this image.
Since that's what we're focusing on here in this video. And notice that zooming into the epidermis here, we have these cells of the epidermis. And notice that the vast majority of the cells, again over 90% of the cells in the epidermis, are going to be these keratinocytes. And so, the keratinocytes, as their name implies, are going to be producing the protein keratin, which is being represented as this blue squiggly line that you see here.
And the keratin is going to fill up the cytoplasm of these keratinocytes. And one thing that's important to note is that the superficial cells of the epidermis, or the cells of the epidermis that are closest to the surface, are actually going to be older cells than the cells that lie deeper in the epidermis. And so, because that's the case, the cells that are more superficial and are older have had more time to produce more keratin. And so, the superficial cells of the epidermis are going to have more keratin. And so that's one thing that you can notice here in this image.
Notice that the cells that are more superficial, that are higher up here in our image, they are actually packed with a lot more keratin. Whereas the cells that are deeper and lie below, they actually are newer cells. And because they are newer, they have not quite had enough time to produce as much keratin. And so they have less keratin in them. However, as cells divide in the epidermis, these newer cells are pushed up into more superficial layers, and they have more time to produce more and more keratin.
And so, the cells become more and more keratinized, filled with keratin, as they move up into more superficial layers. And so, we'll get to talk more about this idea here later in our course as well when we're talking about the layers of the epidermis. But for now, this here concludes our brief lesson on keratinocytes, and we'll be able to get some practice applying these concepts and learn about the other types of cells in the epidermis as we move forward in our course. So, I'll see you all in our next video.