The lab list for unit number two I have available in the front of the room. We only do the first page today, these skin models, but you can see what we're going to have to do for Thursday and Tuesday in finding the axial and appendicular bones. Also available in the front of the room we've got the class handout and a concept map for the integument system.
Both of those things are where the questions come from for quiz number three. If you were to go to D2L into the quizzes you should be able to see quiz three now. I don't know if anybody's seen that yet, but it's after today. You should be able to log on to that and answer those questions. Feel free to grab anything you need.
We've got, that is the class handout, and then this is the concept map that we'll draw. I would, I would get either one of these, or both of these actually, for, did you get these? Does anybody need a concept map or a class handout for?
Did you get this? No, thank you. Yeah, no problem. You get this?
Octavia, did you get these? Okay. Are they on the same? They are on D2O. They are?
They're on D2O? Okay. Okay. Is everybody ready to switch gears to unit number two? Yeah.
All right. A little hesitant, but it gets easier from here. Rama, did you get the class handouts for today?
Well, I just went ahead and grabbed the lab handout. Yep, that's right. That's one of them. We'll start with that concept map, and then we'll kind of get into the lecture handout. In fact, when I start with these PowerPoint slides, we really kind of start on the first page and start working our way down.
I'm going to grab a blank copy of this lecture handout for the integument system, and I've got a blank copy of my review sheet. So if you're following along with me, you'll be right where we need to be. And the top of our integument. hand out, I guess the first page, it's going to have us list the layers of the integument system and then down at the bottom there are those five key functions of the skin. And I guess we could do this in any order.
I'm just going to start with those five key functions of the skin and then I'm going to go back to questions number one and two and draw those on the board. And there isn't a whole lot that I have to draw today. Maybe I'll be able to fit the concept map in just this one little space. We'll erase it and then draw the two layers of the skin, the epidermis and the dermis.
But on question number three, the bottom of this first page, it wants you to list the five key functions of the skin. So we'll start at the top by listing the first function as protection. And if you want to elaborate on that, you can say that it provides protection from slight abrasions.
If I were to fall down and scuff my knee or my elbow or something like that, I've got multiple layers of stratified squamous epithelium that will help me from, you know, protect me from slight abrasions. Sometimes I'm cutting down brush and ripping down these green briars and I get scratched a bunch and I've got multiple layers of squamous there to protect me from those slight abrasions. So protection from scrapes but also protection from dehydration is another main component there in terms of the protection that it provides. people that come into the ER that have severe burns over, you know, more than half of their body, that one of the major threats there is to prevent them from dehydrating more than they would normally do because the skin, if it's intact, protects you from that dehydration. So protection from slight abrasion and protection from dehydration.
The second thing that we're going to list there is thermoregulation. We talked a little bit about that before with the... The fact that the skin can regulate how much blood is in the skin, in the surface of the body, versus forcing that blood out of the skin and keeping it in towards the core of the body, around those internal organs.
And we'll see that when the skin is regulating body temperature, it's going to run through lots of water to do that. We're thinking of that second function. Thermoregulation and the fact that the skin can do things like sweat to cool the body off.
And if you're sweating to cool the body off, it costs lots of water to do that. The third function that we can list is sensation and we'll elaborate on that when we start to draw some of the layers of the skin. We're going to see there are nerve endings in the skin that allow for touch perception.
So feeling and touching. These sensory reception is also found in the skin. So protection, thermoregulation, sensation like touching and feeling. The fourth function we can just say is a metabolic function and in this reaction that we're seeing here is an example of the metabolic function of the skin. We won't have to know the sequence of events here but what it's trying to show you is that when exposed to UV rays the skin is capable of manufacturing its own vitamin D.
So the main takeaway from here is again sun exposed, say that again, the skin exposed to the sun is capable of manufacturing its own vitamin D. Now we're going to get into the skeletal system next but in thinking about how the the vitamin D production in the integument system goes hand in hand with the skeletal system, we're going to see that there are bone building cells and we're going to grab some of these models to see how these these bone building cells are going to build bone and they obviously have to use lots of calcium to lay down this bony matrix and build bone. And it turns out cells can't can't actually use calcium unless there's proper amounts of vitamin D present.
It's going to be one of these cofactors that's necessary for building bone, for depositing bone tissue. So in order for your cells to use calcium there has to be sufficient levels of vitamin D present and that's why you see in the grocery store now just about any milk that you pick up it'll say vitamin D is in this milk. So that ensures that when you drink the milk your cells also have the vitamin D that they need to use that calcium. Well okay.
We'll leave that with vitamin D production and then we'll list the fifth function of the skin which is excretion. So we can see that the skin is going to get rid of things like certain ions and waste like urea just through the process of sweating. I'll elaborate on those just a little bit further. We said the first function there was protection, and if you look closely, there's actually three different layers, three types of protection that the skin is going to give us. There is on the surface of the skin, and we'll see this when we get into the immune part of the system next semester, we're going to see that there are secretions in the oral cavity, in the reproductive tract, in the digestive tract, and even on the surface of the skin where these secretions are going to be slightly acidic.
And that slightly acidic secretions again on the surface of the body, on the surface of your mucus membranes is going to help prevent bacterial growth from occurring there. So you have what's called this acid mantle that's there for protection against bacteria. I mentioned the physical barrier that you've got multiple layers of these waterproofed cells that provide protection from dehydration. So that physical barrier of multiple layers of waterproof cells like we said provides protection from dehydration and also those multiple layers of cells give us protection from slight abrasion or scrapes. So there's the physical barrier, there's the chemical barrier, and then we will also see, we'll introduce it today and it comes back in the immune system, there are going to be some cells in the epidermis whose job it is to function as part of the immune system.
These dendritic cells are going to be like that. They Well, to use an analogy, what these dendritic cells do, they're on the surface of the skin, and they're constantly catching any bacteria or foreign cells that don't belong. And they basically take a picture of them. They take some of their surface proteins, and they remember it.
It's like a mug shot. And then they will actually go back to the other immune cells, these T cells and B cells, and show these immune cells what types of threats are out there in the body. It's a way of training the immune system.
So these cells are going to be part of the immune system. They help show other immune cells what threats. are out there.
So we'll see individual cells that are functioning as part of the immune system on the surface of the skin. So physical protection, chemical protection, and then biological protection by those cells. The second one we listed there was temperature regulation. And I talked before about the fact that the skin can regulate how much blood is flowing to the surface of the skin.
If you're really hot, we can see that blood is forced out towards the shell of the body. And so your face is red, your ears are red. That's an attempt to cool off.
And even if you're not running around, if you're just sitting there writing notes. The activity of just breathing is something that is also causing you to lose water. It's just evaporation through respiration. If you are doing exercise or having to sweat in order to cool your body off, that's also going to eat into how much water the body is using in order to cool off.
So the second point, like we said, the skin is capable of regulating the body temperature. One way that it does that is producing sweat. And in order to produce that sweat, it uses large amounts of water.
About a half a liter of water per day. if you're not exercising, you were just sitting there watching TV and breathing, but that's going to be significantly ramped up if you start to again push your body to where you're having to sweat excessively to cool off. So temperature regulation was number two. The third thing we said was sensation, just like touch, feeling around.
We're going to mention a couple of different types of sensory receptors in these models, either for light touch or or for deep touch. Fourth thing we said was a metabolic function. The main thing that we mentioned in terms of metabolic function was the fact that the skin is able to synthesize its own vitamin D. As long as it has access to sunlight, your skin can manufacture its own vitamin D. If you had a job like I had a few years ago where you're just in an office all day and you never get to see any sun, then your skin might not be manufacturing enough vitamin D.
Luckily, like I said, the milk in most of the grocery stores now already comes with vitamin D mixed in it, so that even if you don't get normal amounts of vitamin D just from your own skin making it, you can still use that calcium from the milk when you drink it. The fifth thing there we said was excretion of nitrogenous waste like urea is something that can be sweated out. also water and other ions, salt ions. If we've significantly filled out number three there, those five functions, we're then going to get into the concept map. You have a single page that's got some terms on one side.
Well that happened and on the back side you've got these series of boxes that I'm going to do my best to try and fit on this part of the board. I may have to make my own little Weird version of it, but let's try. So you have on there at the very top there is a box.
Sorry, I did, but I'm doing terrible in terms of trying to remember everything, but I'll give you an own personal little, it's five minutes. In fact, all we did was go through the five functions, so you're actually right in time. You feeling alright though? I'm feeling like crap. I just put the test down there in the testing center.
You got all week to take it so don't worry about that. Sorry for the stress though. You're good. What's up? Oh, okay.
Yep, so I kept you out there and all we did was just go through the first five functions of the integument system. So let me make sure that you've got these handouts. We're about to start with question number one and number two here. All we did was list those things down. The other handout which we haven't gotten to yet, this is going to be our lab list of things that we'll talk about.
And I'm about to write on the board that thing right there. While I'm writing those things down real quick, I'll just go back. This is the very first slide that we saw, so we're only three slides deep into this, and those are those five functions.
If you want to list them, I'll elaborate on those whenever we get into lab. By the time you get those down, I'll still be slowly writing over here, but I'm going to start with our concept. ...map on the board that I believe starts with just the integument system at the very top. So we're going to take this entire integumentary system and we're going to separate it into two branches here. There's only two components of this integument system.
One we consider the cutaneous membrane. This cutaneous membrane we can think of as the skin, and then the other part are just the accessory structures. So we've got the skin and all of those accessory structures. In fact, if I can just briefly list these accessory structures, it might tell me how much room I have on the board to write the rest of these things.
The three accessory structures that we need to list on here, the first one is just hair. So we'll see hair, we'll see nails, and then the third thing are going to be glands. Hair, nails, and glands are going to make up the accessory structures of the integument system.
And then we've got the actual skin part. So the skin is going to be separated into just two layers. There is this layer technically above the skin that we call epidermis.
So dermis just means skin. Epi is above the skin. We'll see five layers of epidermis that we'll need to know.
And then the other part of the cutaneous membrane is just the dermis. And we're going to see two layers of dermis that we need to know. And also to kind of show me how much room I'm going to have, I'm just going to go over here to the two layers of dermis.
Just to describe the two layers of dermis that we have, the top layer of dermis is called the papillary layer. And then the other part of the dermis, kind of the deeper layer to the dermis, is the reticular layer. Let's list, if you have that concept map out, let's just list something about the papillary layer real quick. If we're thinking about the papillary layer of the dermis, this is going to be the upper 20% of the dermis. I don't know if that's obvious.
Upper 20%, while the reticular layer is going to be the lower... 80% of that dermis. So most of its reticular layer there is this upper papillary layer.
Maybe what's what's noticeable about this papillary layer is that we're going to see these dermal ridges. Dermal ridges are going to be the the structures that are responsible for our unique fingerprints. Maybe the other thing, and I'm going to have to erase this in a second because I already see that I'm taking up too much space. Somewhere on your concept map, write that in this papillary layer is where we find abundant areolar tissue. So areolar connective tissue is all found in the upper layer of the dermis.
But as we get deeper down into the dermis, down into this reticular layer, what we start to see, instead of areolar connective tissue, we see this dense irregular connective tissue. In addition to this dense irregular connective tissue, when we start to get deep down into this reticular layer, we're going to see things like the roots of hairs. I'll also put glands.
When we get deeper down in that reticular layer, which Did you get those five functions down? So all I did was kind of I elaborated on those five functions which is what I will do whenever we break into lab and this was the slide that was on there when you walked in. So we can kind of see when we're looking at this cross section through the skin.
I like this slide because it does a pretty decent job of showing us all of the things that we're going to see on our two skin models. Notice we have two skin models Models that look like this and then there's one skin model that is slightly different looking and they have each their own advantages that I'll talk about and then I was able to find these three smaller skin models that I'm not as excited about but they do have some good things to them that we'll point out. To our concept map, if we're thinking about this dermis layer, we can see that is separated into this upper papillary layer and this lower reticular layer.
And when we get down into this lower reticular layer, that's when we see things like the roots of these hairs, and we also see glands down here in this reticular layer. The papillary layer we can see is just those series of little projections, those dermal papillae that are really just that upper surface of the dermis. We can see above the dermis, just as its name is suggesting, there is a layer of skin above that called the epidermis. And this is what I like using the picture for. Whenever I write this down on a concept map, there's five layers of the epidermis that we need to know.
So I have to take up a lot of board space to write the five layers of epidermis. But comparing the five layers of epidermis to the dermis itself, you can see the skin is mostly dermis. with this very thin layer of epidermis on top. And that thin layer of epidermis is going to be separated into five layers. Here's where I'm going to erase a little bit of that to make some Make some more room to write.
But just with my tips about what we see in the dermis once we get that out of the way. We still have this papillary layer that's the upper 20%. We've got that lower reticular layer that's the lower 80% of the dermis. So maybe that gives me just enough room to come down here and list these layers of epidermis. There are going to be five and...
I'll just come over here and do it like this. I'm going to let this space on the board, I'll just let the top part over here represent superficial. And then down here at the bottom of the board, this is going to represent deep, deep layers of the epidermis.
And there are going to be five layers of epidermis that we're just going to list. in order from superficial to deep. So the most superficial layer of epidermis at the very top is going to be what we call the stratum corneum.
So, stratum corneum is at the very top. The second layer is what we're going to call the stratum lucidum. And this second layer, if you want to note, it's only going to be found in thick skin, which is the palms of the hands and the pads of the feet.
Stratum lucidum. So, maybe a little asterisk because that's in thick skin only. The third layer is what we call the stratum granulosum. It has a grainy appearance, hence the name granulosum. We'll start to see grains of keratin start to form in this layer.
Before the stratum granulosum, there isn't actual keratin proteins. it's all pre-keratin before the stratum granulosum. The last two superficial, there I go using the word superficial in the wrong spot, the last two deep layers here we have the stratum spinosum, stratum spinosum, and then the very bottom layer is the stratum bacelli.
Now I'll show this a couple of different ways, but I'll just say it with words real quick because I was starting to hint at it. There's something that happens right here at this stratum granulosum layer that I'll mark with a little asterisk. I'll just say keratin forms right here in this stratum granulosum layer.
What's unique about this keratin is it's a waterproofing protein. It's a watertight protein. I liken it to a Ziploc bag.
Your cells have to be able to get in nutrients and get waste away from the cell. And if they're coated in a Ziploc bag, then they can't get nutrients in and they can't get waste out. So when cells start to become waterproofed, they also start to die off. Basically what I'm saying is as the cells start to accumulate keratin here, In this granulosum layer, this is where the layer where the cells start to die off. And everything above this is all dead cells.
Stratum lucidum, stratum corneum, they're all dead cells. The only living layers of cells, I'm trying to find a different color here. I'll go get it.
Stratum corneum, we'll say these are dead cells. These are dead cells. And even right here in the stratum granulosum layer is when the cells are starting to die off.
But before that, in the stratum spinosum and stratum bacelli, we're going to have cells that are alive. These two living layers of cells you can collectively refer to as the stratum germinativum. I think that's a term that's in your class handout. These two living layers of cells can be described as the stratum germinativum. A term that just collectively refers to the living layers of epidermis.
I know your boxes are kind of stretched along the bottom of the page so maybe you can just write superficial next to the side where you've got stratum corneum and then the deepest layer down there is at the stratum bacellae layer. Is everybody okay with that concept map? I realized the only thing that we didn't finish there were these types of glands. So let me hold off on, I'm going to hold off on those types of glands real quick and we'll come back to this. Hang on to that.
That's right. In the granulosome layer, some of those cells are alive, but also some of those cells are starting to die off. It's kind of, and what's causing those cells to die off is when this keratin protein finally forms. It's like this long chain of amino acids.
And so the first two layers is when this protein is in its non-functional form. It's still being kind of built. But when this protein finally gets built, it starts to waterproof these cells. And so as it is finalized... we start to see the cells in this layer die off.
So at the early stratum granulosum, you still have some cells that are still alive. By the time we get out of it, you've got cells that are all waterproofed and dead. Okay, I got most of the way through that concept map. Let me look at my class notes.
We've got, you should have underneath number one, we've got the epidermis and you've got the five layers of epidermis underneath that. For number two, we've got the dermis and then those two layers of dermis, the outermost papillary layer and the innermost reticular layer. And then underneath that, you can see kind of underlaying the cutaneous membrane, you have what's called the hypodermis.
And we'll see... the next slide that by definition hypodermis is telling us the layer that's just underneath the skin so it's not technically part of the skin rather it's the layer that we find just underneath the skin and you know that whenever you find the hypodermis layer because you start to see abundant adipose tissue and you also see abundant blood vessels now this model it shows plenty of adipose tissue but you have to look close to find the blood vessels because they've cut them in kind of a transverse way where you're just seeing the openings of those arteries and veins. But if I set that one down and grab this other model, one of the benefits of this model is that you can see adipose tissue down here in the hypodermis and they show those larger blood vessels, the arteries and veins that run through this hypodermis.
Just think if you're drawing blood from somebody, you use a hypodermic needle because you're trying to get to those blood vessels down there in the hypodermis. Before I erase this completely, let's review a little bit from what we talked about last time. Epidermis, this is all going to be made out of primarily epithelial tissue.
We know epithelial tissue doesn't have any direct blood supply and when we look closely at this slide you can see how these blood vessels they get really close to the epidermis but they stop in these dermal layers. They don't ever cross out into the epidermis. They don't ever cross that into epithelial tissue.
We will see some nerves actually cross that layer of connective tissue and end up in this epithelial tissue but we know epithelial tissue is innervated with nerves even though it doesn't have direct blood supply. And I had that listed below. When we get into the dermal layer, we're going to start to see this. areolar connective tissue and this papillary layer.
That's the basement membrane we said is made out of mostly areolar tissue. But when we get down deeper into this reticular layer of the dermis, this is when we find a lot of abundant collagen fibers kind of interwoven with one another. So you find dense, irregular connective tissue all in this reticular layer of the dermis.
When we're no longer in that reticular layer of the dermis and we're down here in the hypodermis, we can easily identify that because for the first time we start to see abundant adipose tissue. Okay, so we put this on the board. We know the epidermis is superficial to the dermis. Just underneath the dermis is our hypodermis, which we said is technically not part of the skin. It's mostly adipose tissue and blood vessels.
So let's start by looking a little bit more closely at the epidermis and here is where I'll attempt to to give you some type of visual connection between these layers. So I'm about to erase this if anybody needs to get a picture of it or ask any questions about it real quick let me know. If not I will slowly make my way over here to erase it. You got it.
We're going to start with the epidermis and I'm going to try and draw this for us. So I'll grab a couple of different colors and let's look at this dermis and epidermis connection. I'll come back and finish our glands concept map in just a second.
Okay, stop me if there's any questions about this, but what we're looking at on the screen here is kind of a sketch of the layers of epidermis. And that little pink structure that we see popping in here, that's one dermal papillae, one little papillary projection of the dermis. So we're seeing epidermis and then there's a little bit of the dermis.
I'm going to expand on that picture. Let's see how we do. I'll just start right here.
I'll stop right about there. And what this little red line is representing, it's representing the basement membrane. This basement membrane is just made out of connective tissue.
It's really where epithelial tissue stops and connective tissue begins. We said epithelial tissue is always anchored to some type of connective tissue. And just underneath this basement membrane is where we would find a lot of that areolar tissue.
Okay, but... not to get too caught up with what's going on below this basement membrane just yet let's think about the layers of cells that are above that so I'll try and get hopefully we've got some juice into this this one maybe a little bit of juice So what I'm drawing here just on top of our basement membrane is a single layer of cells that are more or less kind of cube shaped. But this first layer of cells that we see right on top of the basement membrane, this is our stratum basale. And we can see nuclei in each of those cells that tells us that's a living cell.
And above the stratum basale, we're going to see several layers of cells that kind of take on this rounded shape. And each one of these cells has a nucleus in it as well. So we can see these are living cells. They've got a nucleus. This is our stratum spinosum.
But above that, we start to see the cells take on kind of a thinned shape. There's only a few layers there and these cells not only do they thin out but we start to see the accumulation of these little granules in here. Those granules are made out of keratin.
So maybe let me list that little orange structure as a keratin protein. That keratin protein starts to accumulate in this granulosum layer. So stratum granulosum is what we're looking at with this grainy appearance of keratin proteins.
On top of this stratum granulosum, not really pictured in this sketch because this is thin skin. This would be on the surface of your forearm or the surface of your earlobe. Thin skin is not going to have this next layer that I'm about to draw. Thick skin, however, will. So the palm of the hand and the pad of the feet are going to have an additional layer of cells that don't have any nucleus.
Anything above this stratum granulosum is all dead keratinized cells. But this layer just above the stratum granulosum, now that we know those are keratin proteins, I'm just going to get that little reminder out of the way. And we're going to put the layer above the stratum granulosum in thick skin. This is what we call the stratum lucidum. So we'll say thick skin only.
Really, it's within this stratum lucidum. That is the layer in which you are able to develop calluses. So, if you've got calluses on your feet or your hands, it's within that.
Thick calluses are indicative of a thick stratum lucidum. So, if you don't have well-developed calluses, then you will have a relatively thin stratum lucidum. Anytime in between gigs, if I don't play a lot of guitar, I will lose my calluses on my fingers, and I'll have to build those back up.
And sometimes it's painful if I don't have enough time. So anyway, stratum lucidum, that's where the calluses come from. Above the stratum lucidum, we're going to have multiple layers of these flat, squamous-shaped cells. And this is the most superficial layer. It's also the thickest layer.
So our outermost layer of skin is this stratified squamous epithelial tissue. If we're going to be specific, we would make sure to call this keratinized stratified squamous epithelial tissue. We don't see any nuclei in these cells because again, they're dead waterproofed cells.
This outermost protective layer, again, protecting us from slight abrasions and protecting us from dehydration is our stratum corneum. All this is epidermis. We doing good so far?
I'm going to come over here real quick. Yep, let's do that. I'm going to come over here and just erase this for a second because I want to I want to put some questions up that that I want to make sure that we answer before we get out of here. And I'm not yet going to put them on the drawing. I'm just going to set them over here.
When we're thinking about all of these cells out here in the epidermis, there should be four different cell types. Four cell types in the epidermis. So what are those four cell types in the epidermis? Right now I've drawn all of those cell types just in a brown color. So all of my epidermal cells are these brown color cells.
We'll learn and we're going to come back in here and change the color of a few of them to give them a certain names and we'll see there are four different names of different cells that are out there in the epidermis. I'm going to set that right there for now and we're just going to finish labeling this reticular layer, sorry, we'll finish layering up labeling the dermis papillary and reticular layer and then we'll draw the hypodermis. Then we can come back and answer these questions about the cells in the epidermis. You can see a few of them right here.
Notice how there are a couple of these different types of cells. There are four of them in all. Let's just label, like we said, the dermis down here. Even though I haven't left myself any room over here to write epidermis, but now that we're crossing below this basement membrane, we're getting down into the layers of the dermis. So I'll just list this.
This superficial layer of the dermis as the papillary layer, I guess, and the deeper layer down here as the dermis. Jeez. Even though I'm saying dermis, I'm meaning to say reticular layer of the dermis.
So we know this dermis is split into an upper papillary layer. It's about the upper 20% of this dermis, and then the lower roughly 80% of the dermis is this reticular layer. And then if we get below the dermis altogether, let me just, I'll use this color to represent our hypodermis.
Maybe I'll just put a dotted line right here. and anything below this can represent hypodermis. Because there's some structures down here in the hypodermis that we should see that tell us we're obviously down here in the hypodermis. One of the main things that we're going to see is all of this abundant adipose tissue. So adipose tissue is found down here in the hypodermis.
The other things that we see down here in the hypodermis, see if we've got juice in these things, you see major blood vessels down here in the hypodermis. So we'll say veins and arteries. And these veins and arteries, we're going to see that they have branches that will allow these arteries to leave the hypodermis. They make their way up into the dermis, all the way into these little dermal papillae.
Each one of these little nipple-like projections is a dermal papillae. And we'll see these capillaries, they make their way right up into these dermal papillae. I'll draw another one over here. So we'll see an artery kind of branch and deliver blood right into this dermal papillae.
And what I'm drawing there that kind of looks like a letter E, that's the start of my capillary bed. You've got an artery feeding blood into this capillary bed, and then we're going to have veins that basically pick up that blood. and distribute it right back down there towards the hypodermis. So we have fresh blood coming up to the surface into this little capillary bed into this in the dermal papillae and then we have veins that will take that blood right back down to the hypodermis.
So what we're drawing here is that the dermis has direct blood supply but again the epithelial cells out on the epidermis don't have any direct blood supply. That's as close as the blood vessels get to them. The other thing, I'll switch colors here and I'll put in a green color.
The other thing that you see down here running through the hypodermis are also nerves. And we can see branches of some of these nerves. In fact, some of these nerve branches are going to have branches that come all the way out once again to these little dermal papillae. And we're going to see these little egg looking structures that that nerve dead ends into.
I'll draw another branch to one of these things that comes up right into that dermal papillae. Other nerve endings are not going to make it into the papillary layer of the dermis, but they're going to stay down here closer to the reticular layer. They're going to end up kind of looking like a fingerprint or a little bullseye. On your lab list, make sure those things are on there, yes, this nerve ending that we have down here in the reticular layer, on your lab list, this structure is called a pacinian corpuscle. So, Pacinian corpuscle is this, it's a nerve that's found deep in the reticular layer of the dermis.
And what it is, it's there, it's picking up sensation for deep touch. So, Pacinian corpuscles, think deep touch. The other nerve ending that we've drawn are the ones that make their way way up into the surface of the papillary layer.
Those are on the lab list as the Meissner corpuscles. Maybe I'll just sneak it in right here. The Meissner corpuscle is that one right in the dermal papillae.
There's another Meissner corpuscle right there in the dermal papillae. There is one more nerve ending that you have that we can mention that gets close to the the epidermis end. There's my green color.
Your lab list has these mentioned as free nerve endings. We're going to notice that these free nerve endings are ones that actually make their way. Let's draw a free nerve ending here. I'm just going to peel one off of the hypodermis and this free nerve ending is actually going to go across the basement membrane out into one of these cells that I'm going to now draw in a green color. Because this is going to be a special, a unique type of cell out there in the epidermis.
I'm going to go to our list over here, and we're going to list this one as our third type of cell. This is called a Merkel cell. It's also called a tactile cell. So Merkel cells or tactile cells, these are cells that are found out on the epidermis and they're unique because they have a sensory neuron attached to them.
So these are for light touch. I'll just call this our Merkel cell. I'll say light touch.
Meissner corpuscle, I'm just going to jump in here and also say light touch. Because those are close to the surface. My example is if you're feeling in your pocket and you're trying to feel, do I got keys? Is that chapstick in my pocket?
Is that a money clip? What am I feeling? You're feeling around with light touch sensory. So Merkel cells and Meissner corpuscles to feel what's your pocket.
Pacinian corpuscles, the deep touch sensor, if you've ever been sitting in like a red light and a car pulls up next to you and they've got that low like bassy music playing and you can feel the car vibrating, that feeling of the vibrations that's being picked up by pacinian corpuscles. Well, it depends on how bad the burn is. You know, superficial burns, we're just talking about Merkel cells and light touch. But if it's a third degree burn, you could get down into that reticular layer and it might be those placinian corpuscles.
Yes? What cells are associated with the placinia? So those are going to be nerve cells. They're also called laminated corpuscles or pacinian corpuscles.
This is a specialized receptor when we get into nerve endings. We'll talk about receptors. And this is a special type of receptor that's found for vibrations down in the reticular layer of the dermis. So if we're thinking nervous tissue, so this is a nerve cell.
This is the receptor end of a nerve cell. In Unit 4, we talk about a bunch of different neurons, and we'll see that neurons have their dendritic ends at one side, and some of these dendrites are specialized for picking up vibrations or touches. Other receptors are going to be specialized for picking up chemical levels, like blood calcium levels or blood glucose levels. Some of them are going to be sensitive to temperature, like if you're walking across a cold surface of the floor. We'll see there are at least five different nerve endings, and some of them are...
Like I said, chemoreceptors, mechanical receptors, some of them are pain receptors. I don't know if I'm getting further away from your question or not. But this would be qualified as a type of touch receptor, particularly deep touch, those vibrations. And it would be a type of nervous tissue rather than epithelial tissue or connective tissue. I'm doing a couple of things here.
Now that we've kind of listed at least our hypodermis, our dermis, and then I'll just for completing the thing, let's list everything above our basement membrane as the epidermis. So we've got dermis and epidermis. Before I get this thing any more confusing than it already is, there's one thing that I want to point out, and that is about this basement membrane kind of having this wavy structure.
There's... There's two key things I want you to remember about that. I'm going to give you three, but I just want you to remember two of these key functions.
The thing that I don't really want you to remember about or that you don't need to remember about these things, I'll just go ahead and say you might need to remember it a little bit. I don't think it's a major part, but everybody has their own unique fingerprints and those fingerprints are due to these unique dermal ridges. These collection of dermal papillae are unique in every individual. So they give you unique fingerprints. That's interesting, but the real function there is that these ridges are increasing the amount of surface area between the dermis and the epidermis.
So again, the things to remember here, this increased surface area due to the wavy line of this basement membrane, it's going to provide two key functions that we need to remember. One key function of this increased surface area, kind of this wavy line of basement membrane, it provides more points of attachment between the epidermis and the dermis. It reminds me of kind of like two good pieces of Velcro.
Like if you get two good pieces of velcro together and if they make contact there's enough of those little loops that are hooked around one another that provides a an effective connection between those two pieces of fabric. So by giving their by increasing the amount of surface area between the epidermis and dermis it allows for a more effective connection between the epidermis and the dermis. That's one thing that this increased surface area does. It, like I said, helps ensure that the connection is tight between dermis and epidermis.
But the other key function that we need to at least draw here before I get too crowded with this diagram. Remember when we were thinking about the cells of the epidermis. The only two living layers of cells in the epidermis are these first two layers of cells, the stratum bacelli and the stratum spinosum.
Anything above that we start to see cells that are dying off and and there's really two reasons why these cells start to die off. The only one that I've given you so far is the fact that at some point in the maturation of these cells, they start to produce the keratin proteins. So keratin granules start to form and accumulate in this stratum granulosum layer. So the only reason that I gave you before for these cells dying off is because they're now becoming waterproofed, like they're put in a Ziploc bag. The second reason that I'll give now that is also why these cells, the top three layers of cells, are dead is because they don't have access to any nutrients.
Remember there's no direct blood supply to the the cells of the epidermis. The blood supply stops right here in these dermal papillae. So nutrients like glucose and ions, they can diffuse out of these capillary beds and they can actually deliver nutrients to the first few layers of cells that are close to this basement membrane. So the stratum bacelli, these are cells that get nutrients and can get their waste washed away. The same thing for the stratum spinosum.
These cells are close enough to the nutrients where they can still have access to food and get their waste washed away. So again, stratum spinosum. stratum bacelli, all living layers of cells, but past that stratum granulosum, stratum lucidum, and stratum corneum, they're going to be too far away from any nutrients.
So anyway, to talk about this wavy line of the basement membrane, it increases surface area to make a more effective seal between epidermis and dermis, and then the second thing that that increased surface area does is it makes it easier for nutrients to diffuse from the dermis. out here into the two layers of cells of the epidermis. Nutrients to go from the dermis to epidermis. The more surface area there is, the more nutrients can make their way out there to the epidermis.
Okay. What I'm not able to draw in here, in the dermis, we'll see this with a couple of pictures. When we get to the reticular layer, we're going to see some, the roots of hairs down here, and we'll also have to separate different types of glands. But since I didn't fill in that part of the concept map just yet.
I'm going to stick to epidermis and dermis for just a second longer, and I think we're now to the point where we can actually list these four different types of cells of the epidermis. Right now, the majority of the cells that we've drawn in the epidermis, they're all of these brown cells, and I'm going to just write these as the first type of cell in the epidermis. They're called keratinocytes. So keratinocytes, these are the most common cell of the epidermis, and what they do is they produce keratin.
Keratin, that's that waterproofing protein I was drawing. an orange dot over there. We'll just say most common.
By far, those keratinocytes are the most common. The second that we're going to list... Dr. Looking at this sketch, all of these orange cells that we can see, these are all keratinocytes.
By far the most common cell are these orange keratinocytes. But if you look closely, there are some other cells like this one right here that we're about to draw. This is a melanocyte.
This melanocyte is going to produce melanin. And these are not very numerous cells. They're going to be found down there in the stratum bacelli and stratum spinosum. So I know I'm already using purple as a color in here, so I don't want it to get super confusing, but I'm just going to put one of these.
I'm going to change one of these. epidermal cells to a purple cell. And you'll notice that this cell actually has these little arms that kind of stretch out and they're kind of reaching in between some of these other keratinocytes. I'm not a great artist but I'm just going to draw some of those arms reaching in there. I'm just going to bring this over and label this a melanocyte.
So this melanocyte, it's producing melanin, and what we can see, if I can flip ahead to a couple of slides, these melanocytes, as they produce melanin, I'll go back to there. Here's the list that we are working on. Keratinocytes, we've got melanocytes that we are just about to mention. They produce melanin. We've got on our list these Merkel cells or tactile cells.
So I will just grab the last different color and let's list the fourth cell type which are these Langerhans cells. Langerhans cells are sometimes just referred to as dendritic cells. Dendritic cells are going to be part of the immune system and I'll just switch one of these cells out here, maybe this one, let's switch it to an orange cell.
I'll put some little arms on it. That orange cell can represent our Langerhans cell. So we've got melanocytes, we've got Merkel cells, we've got Langerhans cells, and then the most common cell here are these keratinocytes. I just wanted to show the picture of that melanocyte doing its job. Which is right here.
This green colored cell is the melanocyte. And you can see one of the things that it's producing are these little melanin granules that are in a red color. And then what it's doing with those melanin granules is it's actually passing those melanin granules off to the surrounding keratinocytes.
See there's a keratinocyte that's taking on some of these melanin granules and it didn't produce those melanin granules. Here's the melanocyte producing all of those melanin granules and then passing them out to the surrounding keratinocytes. What's unique about those melanin granules is that they are going to act as a protective shield against UV rays. You know skin cancer rates go up with exposure to UV rays. And what UV rays will do, if they can hit the nucleus of the cells, they can cause damage to the DNA.
And one of the things these melanocytes do to minimize the damage to that nuclear DNA is the melanin granules, once they get inside those keratinocytes, you can see they form these little protective shields around the nucleus of those cells. Again, the goal there is to prevent any damage to the nuclear DNA by UV rays. Okay, melanocytes, keratinocytes, we talked about those. I skipped over a couple of slides here.
I want to point out tactile cells and these Langer hand cells. In this sketch that we were just looking at right here, notice how this little blue cell has a sensory neuron attached to it. That tells us that this blue cell is trying to indicate one of these tactile cells. or these Markle cells.
It's for touch reception. Then this purple cell that we can kind of see with arms that are stretched out, this is representing our Langerhans cell or these dendritic cells. I mentioned these are cells that are out in the surface of the body and they're kind of like the hall monitors.
They're trying to see what other cells or substances are present on the surface of the skin. And they're capable of taking surface proteins off of cells or bacteria and then displaying those surface proteins to other immune cells. It's like taking a mug shot of potential threats and then relaying those messages to other immune cells so they can prepare for those threats.
These are the cells, like we said, that train the other immune cells. Okay, so we've got four cells in the epidermis. I feel like we're now ready to jump down into these dermal layers.
Are we doing okay so far with the class handout stuff? You said that melanin is the pigment that responds to oxygen? Correct. That's right. And here's one that's labeled like I was just trying to point to.
We've got a sensory neuron that's touching this Merkel cell or this tactile cell. You've got this melanocyte that is producing melanin and sharing those melanin granules with all of those surrounding keratinocytes. All those orange cells are keratinocytes.
And then that darker purple cell we said was representing our Langerhans cell or dendritic cell, part of the immune system. I guess still in the epidermis, this is just an actual picture of real cells that were, we can see the stratum bacelli. If you look close, you can still make out some of the nuclei in those cells. Above that, this is all stratum spinosum. We can see kind of not perfectly round cells, but they're not, they're not flat squamous shaped cells just yet.
And if you look closely in the center of each of those cells, you can still see a dark staining nucleus. We leave this stratum spinosum layer and can tell we're in the stratum granulosum layer when you see those dark keratin granules start to accumulate. So stratum granulosum here, and then above that stratum granulosum layer, this is all just stratum corneum.
You can see a bunch of layers of cells there. You no longer can make out the dark staining nucleus. And if I show the sketch of this, so this previous picture. It's exactly the same thing that we're looking at.
This first layer of cells is the stratum bacelli. We can see living layers of cells. This is the stratum spinosum. Then we can see the little granules of keratin start to accumulate.
This would be our stratum spite. We try that again. Stratum granulosum with the grainy appearance.
And then above that, you kind of lose the grainy appearance. This would all be stratum corneum. So once again, thin skin. I did have a slide of Well, this is also thin skin over here on this side. Closer to me, we have an example of thick skin.
So this would be in the palm of the hand. You can see stratum bacelli, that first layer of cells. But then on top of the stratum bacelli, everything in here is stratum spinosum because we can see living cells.
Then the stratum granulosum is easy to recognize because you get that dark accumulation of keratin granules. And then just on top of that stratum granulosum, we have a layer of stratum lucidum. So again, thick skin you'd find the stratum lucidum. On top of that is just multiple layers of that stratum corneum. Four cells in the epidermis, we've seen the labeled sketch.
Some things we mentioned just with words about melanin, we said melanin, its job is to get inside those other keratinocytes and protect the nucleus of those cells from Damage to their DNA by too many UV rays hitting them. So they provide those little pigment shields for nuclei. Also the the other thing I think this is something in the class handout.
There are three things that are responsible for skin pigments and one of those three things is melanocytes. I don't know if this is on here or if this is... Last page. Yeah.
So I guess that's one of the true-false questions thinking about the pigment melanin. It is true that melanin, like you can see, is going to be responsible for red or brown or blackish skin tones, but melanin is not the only thing responsible for skin tones. there are we'll see that carotene this is like the carotene that you would get from eating a bunch of carrots so from your diet if you have a bunch of carrots in your diet it is one of the things that can cause kind of this orange color a colorization to the skin it's it's more prominent in the hands or in the feet or even like a newborn Children, you can notice the skin pigmentation due to high levels of keratin a little bit easier. In adults it tends to show up more in the hands and the feet like you can see between these two individuals. But in terms of things responsible for skin colors, you've got melanin like we said, there is keratin which depends on the diet, how much carotene you're eating.
And then the third thing is hemoglobin. This is responsible for the skin either having kind of a pinkish colorization, or if you have lack of hemoglobin, you'll have kind of a pale colorization to the skin. You know if somebody's not feeling good and they've got lack of blood flow to the surface of the face, they're going to look pale. Or if somebody comes in here and they've been running up and down stairs, their face is going to be red because they're trying to cool off.
So you can sometimes tell if I'm really hot when I walk in here because it's the summertime versus if I were just to come out of a deep freeze or something like that I'd probably not nearly would have as much hemoglobin on the surface of my skin I might have kind of a pale or even bluish color to me. One thing I can say about melanin is that it We know that it's protecting our cells against UV rays. So in the summertime, when we are under more intense UV ray bombardment, our cells will produce more melanin in the summer than we will in the wintertime. So if you were to take this class in the fall, I wouldn't have as much melanin production as I would in the summertime. So melanin, carotene, and hemoglobin are all responsible for skin pigmentation.
we saw this picture of how the melanocyte was passing on those melanin granules to the other surrounding keratinocytes. And that ramps up in the summertime here and will slow down in the wintertime. Now that we've introduced those four cells of the epidermis, it looks like we're finally ready to drop down below this basement membrane and compare these two layers of dermis. We can start with this upper papillary layer and then we'll talk about that lower reticular layer. Here is this papillary layer, that little series of dermal papillae or dermal ridges like we said are responsible for giving us our unique fingerprints.
That increased surface area also makes for a more effective connection between epidermis and dermis. you And the third thing that increased surface area does is it makes it easier for nutrients to diffuse from this dermal papillae out to those living layers of cells in the epidermis. And that papillary layer, like I said, was only maybe the top 20% of the dermis because as we drop down deeper into this dermis layer, we get into the roots of hairs.
We start to see some of these glands like sweat glands or sebaceous glands. So let's look more closely. I'd mentioned the upper papillary layer is where those collection of dermal ridges give us our unique fingerprints.
So here's a close-up picture of those dermal ridges. You can also see the openings to sweat glands on the surface of those dermal ridges. We'll talk about sweat glands in just a second. I know we haven't filled out our glands portion of the concept map.
But in thinking about those dermal ridges and thinking about this papillary layer, now that we're down in the dermis, we know just underneath this papillary layer, as we start to get down in the reticular layer, there's going to be abundant collagen fibers. And knowing the direction that those collagen fibers run is going to be important if you're ever doing any kind of incisions. If you're going to do surgery where you have to cut through layers of the skin, giving stitches or any things like that. You'll want to pay attention to these cleavage lines, which are just the lines, going this way, the lines in which those collagen fibers will follow. And it's kind of unique per individual, but there are some similarities.
So these two slides here are showing us the direction that collagen fibers typically run in the dermis. The dermis of the skin basically. And the thing that we want to remember is if you're ever in a situation where you're giving stitches or you're having to cut through layers of the dermis, you'll want to go parallel or follow those cleavage lines if possible.
You don't want to go across those cleavage lines like you can see here. If we go across those cleavage lines, this type of cut is not going to be easy to sew up because stitches are not going to want to hold those collagen fibers together. If you make an incision kind of going with the lines, with those cleavage lines, then you're just kind of pushing those two collagen fibers apart, not really severing those collagen fibers.
And this type of incision is much easier to connect with stitches. Just know that when we get down into the papillary layer and we start to make it into the abundant levels of collagen fibers, that those collagen fibers run in a certain direction. Those lines in which those collagen fibers run are called cleavage lines.
And you'll want to pay attention to that if you're ever cutting through the layers of the dermis. I'm going to go parallel to the cleavage lines. Okay, now if we go through all those cleavage lines, if we're through all the collagen fiber, then we've gotten all the way through the dermis and we're down here in the hypodermis. And we know hypodermis is not technically part of the skin, and we know that we've made it to the hypodermis because we can see abundant adipose tissue.
Here is where we're at down here in the slide. We've got big blood vessels. We've got adipose tissue.
And, well, since we can't go any further down past hypodermis, I'll turn around and we'll make our way back into this reticular layer of the dermis and we'll start to point out the different types of glands. We'll separate glands and then the types of nerve endings. The glands that we need to know, I guess I'm going to erase our four cells of the epidermis.
Is everybody okay with that? All right, let's get this out of the way and let's finish that concept map of the glands. We had it almost done, but since we're about to list glands and most, well, all of these glands are going to end up on the lab list. So let's make a distinction.
So far we had our accessory structures. I can spell it. Accessory structures included the hair, which we'll look at.
Structures of the hair, we'll look briefly at structures of the nails. But then most of the attention that we spend on accessory structures are classifying these different types of glands. So we're thinking of glands of the epidermis. We can separate these two types of glands into one type of gland that I'll try and stick to the right order that you have.
So in your box of glands, the ones that goes to the left, these are called pseudoriferous glands. So pseudoriferous glands. You can think of pseudoriferous glands.
These are just a type of sweat gland. I'll say sweat glands are these pseudoriferous glands. The other glands are called sebaceous glands. Sebaceous glands we can think of as oily glands. We've got sweat glands and we've got oily glands.
There's only one type of oily gland that we have on our lab list and that's just those sebaceous glands. But the other box of pseudoriferous glands takes us to two other possible glands. One type of gland is called an eccrine gland. And the other gland is called an apocrine gland.
Both of them are sweat glands, but one of them is going to produce a watery sweat. Ecrin glands, they produce this watery sweat, and we can also notice that eccrine glands are all over the body. So they're found on the forehead, the palms of the hands, you know, in anywhere they produce this watery sweat.
So they're all, they're body wide basically. Versus the other type of sweat gland that we'll talk about, these apocrine glands. Maybe that word apocrine, think armpit or groin because apocrine is the part that's going to make you sweat.
glands are only in the armpits and the groin regions and they produce a sweat that has a musky odor to it. And I'll have to explain that in just a second but apocrine glands we can think of they are a type of sweat gland it produces a musky sweat. And we said these are not body wide, they're only located in the armpits and the groin regions.
In the armpits and in the groin regions, you've got more body hair. And I'll just say here's where I'll describe the muskiness of those apocrine glands versus an eccrine gland. The only job of the eccrine gland is to produce this watery sweat in order to cool us off.
So evaporative cooling is what this... eccrine gland is all about. The apocrine gland, however, it produces a substance that has, and just to be clear, there's some protein substances that are produced by this apocrine gland. And when those protein substances hit the surface of your skin, you have bacteria on the surface of your skin that will break down the products of this apocrine gland and the result of your unique skin bacteria breaking down the products of these apocrine glands it produces body odor, this musky smell. Now I guess the side note about that is that there's something in your lab notes that mentions that these apocrine glands are actually an example of the fact that humans have instincts and they are sometimes described as a gland that will help you tell the compatibility of a potential mate.
This is a little side story that we'll talk about, but it's interesting because I remember remember growing up in a small town like my aunt told me as a kid like you know hey Chad humans are different from animals because humans have reasons for doing things and animals have instincts and humans don't have any instincts I remember thinking that's probably BS but as a kid I didn't have any examples so here's one for you that shows how humans have instincts In addition to reasons for why we do things, an example of this instinct is the musk that's produced by this sweat gland. It's not that the gland itself is producing an odor, but the gland is producing a protein. And depending on your unique surface bacteria, that surface bacteria on your body as it breaks down this protein is going to produce an odor. Now, some individuals might think that is a smelly odor, while other individuals might really like the way that odor smells.
And here's the study that has been replicated many times in different parts of the world. The different versions of the study, they all go something like this, where they have, you know, the more individuals in the study, the better the results are going to be. But one recent study, they took 50 males and they took 50 females, and the males and the females never met each other in this study. They gave each of the males a white t-shirt, and in one study, the males slept in these t-shirts for like a couple of weeks. Every night they would go to bed, they would put on these t-shirts, they would sleep in the t-shirts, and when they would get out of bed they would put the t-shirts back into this little ziplock bag.
And all they were doing is trying to infuse the shirts with their own body odor. In another study they had those 50 males play basketball in these shirts and sweat in the shirts a bunch. So in all of these studies you've got males that will infuse these t-shirts with their body odor and then They put those t-shirts in a ziplock bag that's numbered like 1 through 50. And the females, once the males are gone, the females then come into the room and they each get their turn going through each of the 50 bags. And they open the bag and they smell it, and they rank that smell in terms of most appealing smell to least appealing smell. And surprisingly, what they found out, every time they run this study, what they find...
And I guess I should also have preference this study that that all of the males and all of the females in this study they had their immune genes sequenced before this study and what they found is that females are consistently ranking males the males that they think are the most pleasing in terms of smell they're finding that those females have a completely different set of immune genes. Let's see if I can explain this the right way. What we're trying to show here is that there's an evolutionary selection for trying to ensure that your offspring have the greatest variety of immune genes.
So, I mean, it's tricky now that, you know, you might just think that you like the way somebody smells or that you don't like the way that somebody smells. And it's weird now because we put on all this cologne and... And, you know, artificial odors, so you don't really know if you like the way somebody smells because you like the whatever cologne they're using, or is it their actual body odor that you are finding appealing.
That sounds weird, but they find that, again, members of the opposite sex that find the body odor of the other individual pleasing, they found out that those individuals have completely different sets of immune genes. Whereas individuals that have relatively similar sets of immune genes, they don't find that they like the other's body odor as much. And what you're doing there is you're basically, you have this instinct that you're telling quality of a potential mate.
You want to make sure that your offspring are going to have the greatest variety of immune genes. You don't want to give them the same set of immune genes that you have because we don't know what the conditions are going to be like in the future. So anyway. What's that? Well, who you would think smelled the best would be somebody that had a different set of immune genes than you.
And Evelyn might think that she might find somebody else that you thought smelled horrible, she might think that they smell the best. So it's relative based on the immune genes that you have. And again, you can throw most of that out of the water when you start putting on cologne and all these other things like that. But apocrine glands are there to tell you something about genetic compatibility in a potential mate.
Armpits and groins, it's different than watery sweat that's just for evaporative cooling. You don't have to know all the compatibility of mate stuff. I just was trying to make a distinction between those two glands.
Good with glands so far? Are you thinking about something back there? So sebaceous glands, these are going to be the oily glands.
They really become active during puberty and they're always going to be associated with some type of hair follicle. So the first thing that we see up here, sebaceous glands, these oily glands are associated with some type of hair follicle. What is a hair follicle?
Might be a good question. Let me show you what a hair follicle is. Here is our picture. I'll go back to this picture because it's a little bit bigger and I'm going to kill one of these lights just for a second. I'll just dim it.
Maybe that's a little bit better. When we're looking at this hair itself, you can see, let me get this pointer. We've got the actual structure of the hair, which is kind of this lighter tan. thing that sticks off the surface of the hair. So you got the shaft of the hair.
If I can use a plant analogy, the stem of a plant or the trunk of a tree and all the branches of the tree, these are considered, they're similar to the hair shaft. They're above the surface of the epidermis. But if we go down into the epidermis and into the dermal layers, this is the root of the hair.
And if you follow the root of the hair down into the dermal layer, you'll notice that down here in the dermal layer that root starts to expand into this swollen bulb. But Again, instead of thinking of the hair itself, the root of the hair or the shaft of the hair, look at how this hair is surrounded by layers of epithelial cells. These layers of epithelial cells that sometimes are described as, to use another analogy, if the hair itself is kind of like a big sword, think of if I were to carry around a big sword, the swords are typically held in like a...
Whatever a sword case is, sheath, I didn't know if there was a proper, maybe that is the only term for a case. Yeah, sheath is the term that I'm really looking for. So you can imagine if I'm putting this sword into a sheath that is going to hold the sword and keep it from cutting into my leg, the hair follicle, all of these cells that surround the perimeter of the cell, that hair follicle is like the sheath that would house a sword.
And what's unique about those hair follicles, you can see some of those hair follicles right there. They're forming these little glands that we call sebaceous glands. So this, we're looking at the outside of a hair follicle, and we can see the outside of these sebaceous glands. Just notice how sebaceous glands are always found in the...
the epithelial cells that surround a hair. So the hair follicle is the same place that you find these sebaceous glands. There are other glands that are not associated with a hair follicle whatsoever. These eccrine glands over here, we said they produce that watery sweat. They are not associated with a hair follicle at all.
They're just like a coiled garden hose. This little coiled series of tubes sits right there in that dermal layer. Watery sweat goes up to the surface of the epidermis. Again, if we're thinking of the hair follicle, those glands that you always find in hair follicles, those are the oily sebaceous glands.
Here's the smaller picture that I was just trying to show. So this one is a sebaceous gland. Always associated with that hair follicle.
If we look at the actual tissue, this is some of the cells of the hair itself. And you can see kind of some of the cells that make up the sheath around that hair. Some of those sheath cells have formed a sebaceous gland.
So sebaceous glands always, again, form from the hair follicle. Those are the oily glands. The other pseudoriferous glands, or the sweat glands, can be broken into two varieties.
The first one, the most common one that we see, are these eccrine glands. We said this produces a watery sweat whose main function is temperature regulation, evaporative cooling. These are located all over the body. They're the most abundant glands.
So, eccrine glands everywhere, watery sweat, evaporative cooling. Here is a picture of one of those eccrine glands. In fact, to grab our models, these skin models, let me explain these skin models to everybody real quick.
They're the only models that we see in lab today and we have a very short lab. If you read on here, there's an A, a B, and a C. The A is representing the scalp. So, this is The first part of this model is supposed to represent the scalp. So on the scalp of the head you can see these hair follicles.
There are sebaceous glands, these oily glands, and there's also the eccrine glands, those watery glands. The middle part of this model, letter B, is representing the armpit or the groin region. So you'll notice in this middle part of the model this is the only place where you find the sebaceous gland that's associated with the hair follicle. Again, sebaceous gland and the hair follicle go hand in hand. We see an eccrine gland out there all by itself.
So these white glands on this model, these are eccrine glands. Two of them have been cut open, so you can see the hollow tubes. The other two eccrine glands, you can see just the outside of the tube. Nobody's cut into it. Again, first part of the model represents the scalp of the head.
The second part of the model represents the armpit or the groin region. In all of those regions we can see eccrine glands, but if you look close there's kind of this tan colored gland and it's kind of a loosely woven gland. It's only found in the middle part of this model that represents the armpit or the groin.
This tan colored gland is our apocrine gland. Can you see those blood vessels, those kind of cut blood vessels, the little blue and red dots around this gland? That's where it gets those protein secretions that end up producing the musky. odor. Apocrine glands again they're a little bit more loosely woven here if I can catch up with my slides there it is we're thinking of this apocrine gland here that if we compare it it's a little bit more loosely woven than one of these eccrine glands.
Here is an eccrine gland, a little bit more tightly packed together. Again, the main difference is not in the structure, but in what they produce. Watery sweat for the eccrine gland. These are more numerous.
They're located all over the body versus the apocrine gland, which are only located in the armpits and the groins. They produce that musky odor. And we said sebaceous glands are associated with the hair follicles, the oily glands. So that leaves only a couple of other, I think your lecture handout wants you to know that there are some other glands that we will mention that are specialized apocrine glands.
These are specialized sweat glands. One of them is called a ceruminous gland. See if I have a picture. Here are the modified sweat glands. This is that ceruminous gland that I just mentioned.
Ceruminous glands are located in the ear and they produce a substance called cerumen which is earwax. That's a fancy word for earwax. Ceruminous glands are found in the ear then mammary glands are obviously found in the breast and they are going to produce milk. Mammary glands and ceruminous glands are modified apocrine glands, modified sweat glands.
So before I switch to the hair, let me make sure that we've seen each of these things on the model. The only part of this model that I didn't point out is the far part of this model that has a really Really thick stratum corneum. This part of the model that's showing you a really thick stratum corneum, you'll also notice, can you see just underneath this thick stratum corneum, that little white layer of right there, that little white layer just underneath that thick stratum corneum is trying to represent our stratum lucidum. This stratum lucidum is in thick skin only, and it's only this distant part of the model right here that is representing the palm of the hand or the pad of the foot.
So only in the palm of the hand or in the pad of the foot do we have thick skin and only in that thick skin do we find that that additional layer of the stratum luceum. So you only see that white layer in this part of the model that represents the palm of the hand. Also in the palm of the hand we don't have any hair so you don't see any sebaceous glands. There's no hair follicles there. You don't see any apocrine glands because those would only be in the armpits or the groin.
But what you do see on the palm of the hand are abundant eccrine glands, that watery sweat. Okay, I'll set that down. I was just talking about some of the hair structures and then the last few slides we go through some of these structures of the hair and in your lecture handout towards the back I feel like there are some diagrams.
This starts on page three where we're going to start to look at some of the structures of the hair and if we're thinking about that diagram this is on page three you can see that number one I'm going to go back to this picture I don't know where, well here, where you can see the part of the hair that's sticking off, you know, kind of above the surface of the skin, that's the shaft of the hair. That would be number one in your diagram. Then as we get kind of deeper down into this reticular layer, it looks like number five on your, if you go to page three, number five is pointing to the root of the hair. So one is the hair shaft and number five is the hair root.
Can you see that number four is pointing to the hair follicle, those cells that surround the hair itself? So number four on your diagram there on page three, that little number four is pointing to the hair follicle itself, this thing, hair follicle. And then can you see that number six on your diagram there is trying to point to one of those glands that's made out of the same cells that you find in the hair follicle? So number six would be your sebaceous gland. Let's see what else we can fit on there.
I'm going to jump to Here we are back at this picture. You have a structure on your diagram here, number three, that is pointing to this little muscle right here. This little muscle is called the erector pili muscle, and each one of your hairs has an erector pili muscle.
pili muscle that goes to it and you know when you get like a cold chill or something like that and the hairs kind of stand up on the back of your neck what's causing those hairs to stand up on the back of your neck is is the contraction of that erector pili muscle stands the hairs up That's probably the best example to use for humans now, but the erector pili muscle is something that all mammals have. Even dogs and cats still have it. And my dog, if you were to come spook my dog, when they get spooked, they involuntarily flex those erector pili muscles, and it causes the hair to stand up on their back. And that's something that's like a defense mechanism that makes them look bigger. Anyway, Erectopillae muscles, they stand the hair shafts up.
Let's see. As we get down into the base of that hair, let's zoom into the base of that hair. So you saw number five represents the hair root itself.
But as we get down towards the root, you'll notice that when we get all the way down to the bottom of that root, the root starts to expand into what we call a bulb. So this hair bulb is number seven in your diagram. it's kind of a dark, kind of the arrow blended in with the image there. So I just wanted to point that out.
Number seven is the hair bulb. But if we look in the center of that hair bulb, there's this lighter staining patch of tissue. That light staining patch of tissue in the middle of that hair bulb is what we call the hair papillae.
So you've got this structure right here, hair papillae, that you should be able to see right there at the Kind of in the middle of that hair bulb. I'm going to go over here just to make a connection real quick. In these dermal papillae, those dermal papillae are where the blood vessels stopped. And we said all of those cells in the epidermis didn't have any nutrients that went directly to them. The nutrients had to diffuse from this dermal papillae out to these epidermal cells.
The hair is the same way. All of these hair cells, these are going to end up being keratinized dead cells. And they get their nutrients. From the capillary beds in this hair papillae. Just like these cells got their nutrients from the capillary beds in the dermal papillae.
So the only living layers of cells are these cells that are part of what we call the hair matrix. This would be analogous to the stratum bacelli on the skin. The hair matrix is the first layer of cells that surrounds this hair papillae.
So they get fresh nutrients. They're still living, dividing cells. You can see some of those cells are melanocytes that produce pigment. This would be responsible for dark hair or light hair. At some point, your melanocytes will stop producing pigments, and then your hairs will become white.
But anyway, I just want to make a distinction between the hair papillae, which is connective tissue, blood vessels feeding nutrients to all of these epithelial cells. So you've got the hair matrix and then everything above that is just going to be other. cells of the hair. So you've got a couple of other diagrams.
If I look to the next page, this is page four, you've got a cross section through the hair. So let's maybe take this the structure of the hair and do that. Let's take a cross section through it just like we've done here and now we're looking kind of from above, we're looking right back down onto the transverse cut through this hair.
And what you can really see, so the hair is right there that kind of yellow structure. in the middle, the hair is surrounded by this sheath. So to use our analogy again, if this hair was the sword, you can see the sword is sitting in its little protective sheath made out of epithelial cells.
And on your diagram, it looks like letter A is pointing to this sheath that's made out of epithelial cells. So it's called the epithelial root sheath. So A is the epithelial root sheath. And look at how those epithelial cells are surrounded by a layer of connective tissue.
So this outermost layer, this would be letter E on your diagram, this is the sheath that's made out of connective tissue. So you've got a connective tissue root sheath, and then inside of that you've got an epithelial tissue root sheath. What was that?
Yeah, connective tissue root, yeah, that would be E. Yeah, so connective tissue to the outside, that outermost root sheath, and then as we get closer to the hair, we get the epithelial root sheath made out of these epithelial cells. And then as we get even closer to the hair there, so letter B on your diagram is pointing to this little white layer that we see. It's just to the outside of the hair.
It's what we call the cuticle. So cuticle of the hair you have as letter B on your diagram. And then inside that cuticle, you have the actual hair itself. So letter C on your diagram is the outer part of the hair, what we call the hair cortex. And then the middle part of that hair, think medulla is always in the middle.
So the middle part of that hair... In this picture, it looks like the ones that have the little dots in the middle. So the medulla is in the middle.
The cortex is around the outside. So letter D on your diagram is the hair medulla. Did we get all of those from that diagram?
Did I skip anything from the one before that? Page 3, what did we miss? I heard number six that would be that sebaceous gland and that sebaceous gland is made out of the same cells that you find in number four. Number four is just the hair follicle. Number two, it looks like number two is pointing to that first layer of living cells in the epidermis.
So that would be pointing to that stratum bacelli. Did we miss any other ones in there? We feel good about that? Number eight, if we go to this picture, number eight is representing that hair papillae, that little light staining patch in the middle of that hair bulb. So number seven would be that hair bulb, the part of that hair root that kind of swells and expands.
It accommodates that hair papillae. Let's look at page 2, number 3. So the diagram, that's good. So there is a diagram on page 2 and I'm just going to go back to this thing. So number 1 on the diagram that looks like this on page 2. This is not super detailed, but number one is just representing the epidermis, kind of all of those layers on top.
Number two and number three are both pointing to parts of the dermis. So number two would be the papillary layer of the dermis. and number three would be the reticular layer of the dermis. And number four would be the hypodermis down there with the adipose tissue.
That would leave number five as a sebaceous gland and number six as an eccrine gland. No problem. If we were to go through number four there, that's when we were talking about specific tissue. So we said the epidermis was mostly epithelial tissue.
We can say predominantly epithelial tissue. There are some free nerve endings that go there, so if you put nervous tissue, that's okay too, because we know if we paper cut ourselves, there can be some nerve endings that get damaged. So epidermis is mostly epithelial tissue. For the papillary layer, that's the top part of the dermis we said, the papillary layer, that's mostly areolar connective tissue.
That areolar connective tissue that had collagen, elastic fibers, and reticular fibers in it. So areolar connective tissue for the papillary layer. And then when you get down into this reticular layer, that's when you find those abundant collagen fibers running in opposite directions. So the reticular layer is when you find dense, irregular connective tissue.
And then the tissue that you know that you're in the adipose, let me say that again, the tissue that allows you to know that you're in the hypodermis is the adipose tissue that you see. All right, so does that catch us up on page two and three? Looks like we've gotten past four as well.
So I'm going to look at some of these questions on page five. And the first one at the top of page five, the true-false questions, the first one it says keratin is found in all layers of the epidermis. True-false questions can be kind of confusing. So it is false.
This says keratin is found in all layers of the epidermis. And what I was trying to stress in our first diagram here is that you don't actually see true keratin show up until you hit the stratum granulosum layer. Before that, it's all what's called pre-keratin, not true keratin yet. It's not capable of waterproofing the cells. So keratin is not found in all layers of the epidermis.
Keratin is found in the stratum granulosum and above. So stratum granulosum, stratum lucidum, stratum corneum would all have abundant keratin. Number nine, the pigment melanin is responsible for for brown skin tones only well it is I guess it is responsible for brown skin tones but we said there were also other skin tones right so brown skin tones only is kind of what makes that false Then number 10, all of these glands are derived from sweat glands, apocrine glands, ceruminous glands, eccrine glands, and mammary glands.
That one is true. And now, well, this is the last page, so let's see how far we can get through those. Number 11, it says variation in skin color is due to difference in the amount and type of...
That would be melanin produced in the skin, that's right. And melanin is produced by those melanocytes. Pinkish colorization in skin or pale colored skin, that pinkish color in skin is due to hemoglobin. So melanin is one thing that colors skin tones.
Hemoglobin is another one. And then once again, in number 13, the answer is melanin. That is the pigment that responds to UV radiation. So melanin, that produces those little UV ray shields. You said 11 was melanin.
11 was also melanin, that's right. Number 14, we're looking for, well, I had erased them. We had them listed over here.
That's right. Langerhan cells are those dendritic cells that are part of the immune system. Number 14, it was Langerhan cells.
I'll go back to this. We were looking at those four cells of the epidermis right here and it was Langerhans cells that were those dendritic cells that are part of the immune system and are trying to look for cells that don't belong. Number 15 we're thinking of, that would be the tactile cell or the Merkel cell.
Those are the ones that are associated with sensory nerve endings and allow something allow you to detect light touch. So 15, that's Merkel cell or tactile cell. Number 16, this is, these are sensory structures found in the dermal papillae and associated with light touch.
So the fact that we're not out in the epidermis but we're down in these dermal papillae, the only sensory receptor found in the dermal papillae for light touch are these Meissner corpuscles. Then number 17, it's another sensory structure, but this one is found deep in the dermis and the hypodermis, and they monitor vibrations. So down there, we're thinking of Pacinian corpuscles. That's right.
17 is Pacinian corpuscles because those are the ones that are for deep touch or feeling those vibrations. I'll catch back up with, because we were just talking about our glands, in number 18 and number 19, we know that sebaceous glands, let me get out of the way there, sebaceous glands are going to be the oily glands, and pseudoriferous glands are the sweat glands. That's basically everything except the types of burns. I feel like we are...
Almost to the end of this. Where did we leave off? We were going through the parts of the hair.
So we saw the transverse cut, we saw the connective and epithelial root sheets, we saw the hair cortex and the hair medulla. So here we are, the last thing that just introduces us to the different types of burns. Burns can be due to heat, they can be due to electricity, radiation if you're exposed to the sun for too long, or even chemical burns if you're in a lab. We don't use chemicals in here, but sometimes chemicals can have the same effect as heat, electricity, or radiation. and doing a bunch of damage to tissues.
Now, how deep down that damage occurs is what's going to allow us to classify burns as first-degree, second-degree, or third-degree burns. Here is what we call a first-degree burn. This only hurts the epidermis. It never gets down into the dermis.
So, there's no blood vessels that are ever damaged because you're not down into the connective tissue. You're not down where there's blood vessels. So first degree burns are just superficial. There's nothing that damages any layers of the dermis.
So like a bad sunburn or something like that would be first degree. Second degree burns, they're... Let's see, we've got what's called a superficial second degree burn compared to a deep second degree burn.
Second degree burns, whether it's superficial or deep, is going to get down into the dermal layer. So a superficial second degree burn only affects the papillary layer of the dermis, kind of that top 20 percent. But if the burn happens to get down into that reticular layer, this is going to be a deep second degree burn.
It has not yet got down into the hypodermis, so it's not yet a third degree burn. But a third degree burn goes all the way down into the hypodermis and has damaged adipose tissue and blood vessels. And, you know, at that point, you're. Well, a lot of damage has been done, but even first-degree burns can be problematic because you've lost the waterproofing layers of cells. So you're at risk for dehydration.
But again, first-degree burn doesn't hurt the dermis. Second-degree burns involve the dermis. And if the hypodermis is involved, it's a third.
Yeah, bad sunburns can get into second degree burns. Let's see. I'll be glad to pull any of these slides back up if I went too fast through any of those parts.
I'm looking at our class handout and our concept map. If you've got the concept map filled out. Did everybody get that?
Did I miss anything from our... Integument system. I keep going back here like I still have the to-do list on the board, but this stuff is where the questions for quiz 3 comes from. So if you have this filled out, you can use this to go ahead and click on those quiz 3 questions and navigate them just to ensure that you got it all.
I'm going to set over here on the side I've actually got a key to the concept map and I've got a key to the integument system class handout so if you just want to take a picture of these lecture handout keys you're welcome to do that too. I always recommend like towards the end of the semester people will say what can I do to practice for the comprehensive exam and really the best thing to do is just to practice filling out these class handouts just blank copies of the class handout. If you ever get stuck in a spot, you can either bring it to class and talk about it, but I just want to make sure that you have my class note keys that you can also refer to.