5. Integumentary System
The Epidermis: Cells
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this video we're going to continue to talk about the cells of the epidermis. And so notice in the top right we have the diagram of the integumentary system with only the epidermis or the outermost layer of the skin colored since that's the main focus of this video. Now, recall from our previous lesson videos that we've already covered the most abundant cell type in the epidermis, which are the keratinocytes. And so, in addition to those keratinocytes, there are also 3 other main types of cells found in the epidermis. And those are melanocytes, dendritic cells, more specifically Langerhans cells, and tactile epithelial cells or Merkel cells. Now the melanocytes as their name implies are specialized epithelial tissue cells that produce melanin. And melanin is a specialized pigment or a molecular complex that interacts with light. And so the melanin pigment is actually going to protect our skin from UV light or ultraviolet light from the sun, which can actually cause UV damage. And so the melanin pigment protects our skin from UV damage. Now, these melanocytes are actually found in the deepest layer of the epidermis called the stratum basale, which we'll get to talk more about later in our course when we're focusing on the layers of the epidermis. And these melanocytes are essentially factories of melanin production. They produce melanin. And as we'll learn later in our course, the melanin plays a major role in skin pigmentation or skin coloration. And also, the melanin that is produced by these melanocytes can be transferred to neighboring keratinocytes. So that those keratinocytes carry melanin as well, they carry the melanin that's produced by these melanocytes. Now again, later in our course we'll get to talk more about these melanocytes. Now, the next type of epidermal cell here in our lesson are the dendritic cells, which are really a type of immune cell. And these dendritic cells are actually found in many different regions of our body. And so the dendritic cells that are specifically found in the epidermis are called Langerhans cells. And so not all dendritic cells are Langerhans cells, but the dendritic cells found in the epidermis are Langerhans cells. And that's named after a specific scientist. Now these dendritic cells or Langerhans cells, again, are immune cells and so they help initiate immune responses. And later in our course, when we focus on the immune system, we'll get to learn more about their exact role. But essentially, what they do is they scout the epidermis looking for signs of invasion or infection. And when they do find a sign of invasion or infection, they can actually migrate out of the epidermis into the lymphatic system to travel to nearby lymph nodes where they can activate these immune cells. And those immune cells can help to eliminate the invader or the pathogen. And so, again, really all you should know is that these dendritic cells or Langerhans cells help initiate immune responses to protect our skin. Now, the last type of epidermal cell in this lesson are the tactile epithelial cells, which are also called Merkel cells, named after a specific scientist. Now, it's helpful to note that this term tactile here is associated with the term touch. And so, this is helpful because these tactile epithelial cells, or Merkel cells, are actually specialized epithelial cells that work with nerves in order to detect touch and allow for sensations of touch. Now, these tactile epithelial cells or Merkel cells are also found in the deepest layer of the epidermis. Just like the melanocytes are. And again, we'll get to talk more about that later in our course, focusing on the layers of the epidermis. And it's also worthy of noting that these tactile epithelial cells, or Merkel cells, are not the only cell structures of the integumentary system that are involved with sensations of touch. And so later in our course when we're focusing on the dermis, we will see that there are also other structures involved with sensations of touch in addition to these tactile epithelial cells or Merkel cells. And so if we take a look at our image down below, what you'll notice is that this whole middle part here is really just a zoom in of the epidermis. And so, you can begin to see the layers of the epidermis, which again, we'll get to focus more on later in our course. But notice that zooming into the epidermis here, we are highlighting these three main types of cells that we've talked about. Notice that the vast majority of the cells that are outside of these dotted circles are keratinocytes. And so again, the keratinocytes that we covered in our last lesson video are the most abundant cell type and make up about 90% of the cells in the epidermis. But what you'll notice is that in the deepest layer of the epidermis, you can find these melanocytes. And so this purple cell that you see over here is zoomed in over here, that is the melanocyte. And the melanocyte again is going to produce melanin. And so you can see that these little dots that you can see throughout represent the melanin that is being produced by the melanocytes. And again, that melanin plays a major role in skin pigmentation. And also plays a role in the the color of our hair and also the color of our eyes as well. And, what you'll notice is that the melanin that's produced here can be transferred to neighboring keratinocytes. Now, notice that the next cell that we have up above here in green is actually the dendritic cell. More specifically, the Langerhans cell. Which recall is going to help initiate immune responses. And then in the bottom right over here, what we have in blue is the tactile epithelial cell, also known as a Merkel cell. And notice that this tactile epithelial cell is actually in close connection with nervous tissue. And so you can see in yellow, we have the nervous tissue, that lies beneath. That is closely associated with the tactile epithelial cell, which allows for the sensations of touch together. They allow for some some sensations of touch. And so this here concludes our brief lesson on the other epidermal cells, and we'll be able to get some practice applying these concepts and learn more about the epidermis as we move forward in our course. So, I'll see you all in our next video.
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