The Epidermis: Cells - Video Tutorials & Practice Problems
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1
concept
Introduction to Cells of the Epidermis
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1m
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In this video, we're going to focus in on the epidermis, specifically the cells of the epidermis. Now recall from our previous lesson videos that the epidermis is the outermost layer of the skin and is composed of stratified squamous epithelial tissue or many layers of these flat or squished cells. Now notice over here on the right, we have a diagram of the integumentary system and notice that the only layer that is colored is the epidermis, which you can see is the outermost layer of the skin. Now, there are actually four main types of cells in the epidermis that we have numbered down below. And they are carotenoids, melanocytes, dendritic cells and tactile epithelial cells. And moving forward in our course, we're going to talk more details about each of these four types of cells starting with the Carroo sites in our next lesson video. So I'll see you all there.
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concept
Keratinocytes
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4m
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In this video, we're going to talk about the first epidermal cell type in our lesson, which are the Carroo sites. And so Carroo sites are actually the most abundant cell type in the epidermis. By far. In fact, these Carroo sites can make up over 90% of the cells in the epidermis. And as their name implies, the Caratti sites are responsible for carrot production. Now, these Carroo sites 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 Carroo sites really really tightly together, creating a leakproof barrier and they're also held really firmly together by desma zones which allows for mechanical resilience. Now, the Carotin that these Carroo sites produce are 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 Carin 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 carno sites. And so uh the carno sites are of course, as their name implies, going to be producing the protein Carotin, which is being represented as this blue squiggly line that you see here. And the Carotin is going to fill up the cytoplasm of these Carroo sites. 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 Carotin. And so the superficial cells of the epidermis are going to have more Carotin. 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 Carotin. Whereas the cells that are deeper and lie uh below, they actually are newer cells. And because they are newer, they have not quite had enough time to produce as much Carotin. And so they have less Carotin 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 Carotin. And so the cells become more and more carin uh filled with carrot 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 year concludes our brief lesson on Carroo sites 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.
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example
The Epidermis: Cells Example 1
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3m
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So here we have an example problem that says use the words in the word bank that you can see down below right here to fill in the blanks and complete the sentences that you can see down below here. And so notice that the words in the word bank are desmosome proteins, tight junctions, water and barrier. And so this first sentence says that Carin is one of the most abundant and important blank in the human body. Now, this first blank here has to be filled with one of these words in the word bank. And so we know that Carotin is not going to be a desmosome nor is it a tight junction? And of course, Carin is not water. And so we're between either proteins or barrier here for this first blank. Now let's stick with proteins for now and we can always make a change later if we need to. So it is the case that Carotin is one of the most abundant and important proteins in the human body. And so because we've used this word in the word bank, we can go ahead and cross it off the list. Now, the second sentence says that one of its primary roles is forming the skin blank. Now, we know that one of its primary roles is not forming desmosome, nor is it forming tight junctions? Nor is it forming water. And so we know that Carton's primary role is to form the skin barrier. And so that's going to be this next blank here and we can cross it off our list. Now, here, the third sentence says the blank between Caratti sites and the epidermis, protect the body from blank loss pathogens and other harmful substances. Now, in terms of something, this this blank here, it's actually uh going to be water loss since it doesn't make sense to have desmosome loss or tight junction loss, but it is going to prevent water loss. And so water is going to be this, this uh fourth blank here. And so we can cross it off our list. And so now that we know that this is going to prevent water loss. This blank right here must either be desma zones or tight junctions. And of course, recall that tight junctions are going to hold the cell so tightly together that it creates a leakproof barrier, preventing water loss. And so this blank here is going to be tight junctions. So the tight junctions are going to help uh are going to fall between Carroo sites, holding the Carroo sites really, really closely together in the epidermis and protect the body from water loss pathogens. And other harmful substances. And so, of course, this means that the final blank here must be desmosome. And so desmosome are also going to be important connection. Uh And these desmosome are going to connect to Caro sites very, very firmly together uh and hold them to each other, very firmly providing mechanical strength to the skin. And so this here concludes this example problem and I'll see you all in our next video.
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Problem
Problem
Would you expect to find more keratin in keratinocytes closer to the external surface of the skin (more superficial) or further from the external surface of the skin (deeper)?
A
Deeper, because it's more important that the skin is water-resistant in deeper areas.
B
More superficial because skin on the external surface needs to be tougher and more resistant.
C
Neither, all keratinocytes have approximately the same amount of keratin.
5
concept
Other Epidermal Cells
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7m
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In 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 carno sites. And so in addition to those Carroo sites, there are also three other main types of cells found in the epidermis. And those are melanocytes, dendritic cells, more specifically longer han 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 bali, 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 Carroo sites so that those Caro sites carry melanin as well. Uh 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 long han cells. And so not all dendritic cells are longer han cells, but the dendritic cells found in the epidermis are longer han cells. And that's named after a specific scientist. Now, these dendritic cells or longer han 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, uh again, really, all you should know is that these dendritic cells or longer hunt 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 intent 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 Carroo sites. And so again, the Carroo sites 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 uh what you'll notice is that the melanin that's produced here can be transferred to neighboring carno sites. Now, uh notice that the next cell that we have up above here in green is actually the dendritic cell, more specifically, the longer han 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 uh 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 year 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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example
The Epidermis: Cells Example 2
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2m
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So here we have an example problem that asks which cell types in the epidermis are responsible for preventing a pathogen from entering the body and causing infection. And we've got these four potential answer options down below. And so, recall from our previous lesson, videos that there are four main types of cells found in the epidermis or the outermost layers of our skin. And those four main types of cells are carno sites, melanocytes, dendritic cells, specifically Lohan cells and tactile epithelial cells or merkel cells. And so what you'll notice is that three of these options mention tactile epithelial cells and recall that these tactile epithelial cells, their main function is to work with nerves to allow for touch sensations and they're found toward the bottom of the epidermis in the deepest layer of the epidermis. And so these tactile epithelial cells, their main function is not to protect and prevent a pathogen from entering the body and uh causing infection. And so for that reason, we can actually eliminate options, BC and D. And of course, this leaves us with answer option. A which says Carroo sites and dendritic cells. Now recall that Carroo sites are going to make up about 90% of all of the epidermal cells. And so they make up the vast majority of the epidermis and these Carroo sites, as their name implies, they create carat 10, which recall is a tough fibrous water resistant protein that gives the epidermis protected properties and allows it to serve as a very good barrier to things in the environment such as microbes, for example, and recall that the dendritic cells specifically longer han cells are immune cells that actually help to activate the immune system. And so together these carotenoids and dendritic cells can help to prevent a pathogen from entering the body and causing infection. And so option A here is the correct answer to this example that concludes this example and I'll see you all in our next video.
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Problem
Problem
Which type of cells play the most important role in preventing skin cancer?
A
Keratinocytes
B
Melanocytes
C
Dendritic cells
D
Tactile epithelial cells
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Problem
Problem
Which epidermal cell can roam in and out of the epidermis?
A
Keratinocytes.
B
Melanocytes.
C
Dendritic cells.
D
Tactile epithelial cells.
9
Problem
Problem
Imagine you're a doctor, and a patient comes to you with a rare medical condition. It seems that their epidermal cells are not producing keratin. Which of the following symptoms are they most likely to experience?
A
They will have reduced sensitivity to touch.
B
They're much more prone to sunburn.
C
Their skin will tear easily upon exposure to mechanical stress.
D
Their skin will harden significantly.
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