 All right, so I don't know how you feel right now. I know that I've been recording this lecture and prepping for this lecture for what feels like 100 days and I'm ready to get moving. One of the reasons why this video took me so long to prep is because I actually put together a key for our list of required histology for today. And I don't know if this is going to work or not, but what I have is basically all the tissues you have to know down the right hand side of this key. And my intention is that you will be able to use this thing to help you sort of target the significant features of the 20 different tissues that we're going to be looking at. It is not complete, it's not comprehensive, it's sort of windy-ish because look, most of the cells look like pinkish concave donuts lacking nuclei. That doesn't sound super scientific, maybe a little rigged-ified. Yeah, this whole thing has been rigged-ified. And maybe you'll be like, ah, that's not going to work for me. I don't know, we'll try it out. If it does help, let me know. If you are not in my class and you're interested in this thing, I'm going to try to link on the YouTube video, I actually posted it to a Google Sheet that anybody can have access to. So if anybody else wants to try it out, my only condition of you trying it out is that you tell me how it worked for you and what would make it better. So we'll try to do a little research on this thing. But the reason why I'm showing it to you is because I'm not going to go back and forth on this thing. Like I'm really not even going to look at this anymore. I'm going to let you look at it as you're sort of studying and preparing. In fact, probably a great thing for my students. This is in Canvas. Print this thing out as you are watching this lecture or watch the lecture and then print it out. And see if you can identify, see if you can see how it's kind of organized and the things to look for that help you define the tissues and distinguish. You tell me, does the tissue line a space? If it lines a space, like if it's right next to a space, what kind of tissue is it 100% of the time guaranteed? Well, it's going to be some kind of epithelium. So it's going to say, yeah, lines of space, go to number two. Well, number two, we're definitely going to start getting in epithelial tissues. And look, all of these are epithelial tissues. So the strategy is set up to try and help you identify the significant characteristics. What I'm going to do now is show you pictures of these things. I'm going to show you the pictures in the order of the dichotomous key. So while I'm not going to come back to this thing, if you do, you can actually see how I described it on the key and compare that to what you're seeing in the slide, the image that I'm going to show you. Okay? So you tell me which tissue are we going to look at first? The composed tissue. Okay. So this is actually in a histology lab, which over half of our labs have some histology component to them, not all of them, but over half of them. So when we do histology on a quiz or an exam, I usually do the questions like this on a PowerPoint slide. In fact, I stole these from an existing quiz and just basically made it look exactly like your quizzes are going to look. Even down to the question, we have 20 slides to look at right now and every single one of them has the exact same question on it, which is name this tissue. The first tissue that we're going to look at is this tissue with these big open spaces. And I'm going to tell you right now inside those spaces is actually lipid or fat. Those are fat vacuoles. These cells store fat. It's a kind of connective tissue. I wish I could write on this thing, but I can't. My technology won't let me do that. So you take notes, take notes. And then your vacuole found inside what kind of tissue? Adipose tissue. So this first tissue, there's six, I think, tissues at the beginning of my key and all six of them are like, dude, these are... Okay, there's five, I mean. These are the easiest tissue. You hope that these are questions on the quiz or exam because they're really, really straightforward and really, really easy to see. Adipose tissue, super straightforward. Looks like a whole bunch of open spaces. Look, donuts. Concave pink donuts. These are red blood cells. This is blood tissue. These are white blood cells. White blood cells are larger than red blood cells. The space here is just blood plasma. Obviously, it's a slide, so the plasma's all dried up. It's blood tissue. It's super obvious. If you see it, you're going to be really happy. This one, this might be my favorite slide of all. It's compact bone tissue. It's shockingly cool in these concentric circles of hard tissue. These little dark spaces are actually... They're actually spaces where the bone cell or osteocyte lives. So the osteocyte lives inside that space. One of the characteristics of structural connective tissue is that there are spaces. The spaces are called lacuna, and the space is where the cell lives. So you can't really tell that this is lacuna, but it is. The big central thing in the middle is where blood vessels travel because bones do have bloods and nerves going to the bone. That's why if you break your bone, it hurts. And there's something else I was going to tell you about this. Super obvious. It's really pretty, isn't it? Okay, compact bone. Look at the stripes on this one. This one's really cool, too. This tissue right here, this thing right here, that's one cell. Here's another cell and another cell. And do you notice the stripes? The stripes are the significant piece. This is actually striated skeletal muscle tissue. And each one of these tube things is one cell. You'll notice these, this is possibly a confusing bit. They're actually nuclei, and I don't know if you can tell, but the nuclei are on the edges of the skeletal muscle cell. So this long cell has nuclei squished around the edges, and that's because the rest of the entire cell is full of proteins that enable contraction. Awesome. So if you see something that looks like this, super striated nuclei on the edges, that's going to be skeletal muscle tissue. The last super easy one is our lone ranger. This right here, look at the size of this cell. These are all little cells, too, in this pink crazy land. But look at that big, huge cell. This is a neuron. This is a neuron cell body. So what kind of tissue is this? This is an example of our neural tissue. There's all different kinds of neural tissue. This is a smear, and this is the, in fact, this is our, one of our slides that I believe I took a picture of. And so this is almost exactly what you will see in lab on whatever day you come to lab. All right, so this one, I wanted you to see the tissue, and I also wanted you to identify the structure indicated by this arrow right here. The structure will help you identify the tissue itself. First of all, what do you notice up here? It's a space. And if this is a space, what kind of tissue do you think this is? Epithelial tissue. And if this is epithelial tissue, what do you think this structure is? Connecting the epithelium to the underlying tissue. What is your basement membrane? I wish I could draw on it to show it to you. It is, you can see it, like right there, you can actually see the line. It's epithelial tissue. What kind of epithelial tissue is it? Well, my friendlies, how do we decide? If we look down here, you might be like, dude, it looks kind of bubbly. Must be like transitional epithelium. You will be in trouble if you answer that. So, how do we decide on the shape? It's definitely got multiple layers, but this right here, what is the shape of those luminal cells? Those things are definitely flat. This is stratified, squamous epithelium. It's actually found in your eyeball. It's super cool. Who's this? Look, again, what's this right here? Space. What means what's this right here? Basement membrane. Which means, what do you think, stratified or simple? Hopefully, you definitely are like, dude, it's stratified. Except, go look at the luminal layer. What is the shape of those cells? This is transitional. This is actually quintessential, beautiful transitional epithelium. Notice those bubbly luminal cells. They look sort of cuboidal, but they almost don't even look cuboidal. They look balloony, bubbly. Balloony is not a word. Okay, what do you notice up here? Space. What do you notice right here? Sometimes, it's super clean and clear, and other times, you kind of have to know that it's there, here it's nice and clean. What's my basement membrane? Which means, what kind of tissue is this? Connective tissue. Looks like a mess. It's totally connective tissue. What kind of cells do you think these are? What kind of, what's the shape of these cells? This is my basement membrane down here, and here's my lumen. How many layers do we have? One layer, long, tall cells. This is simple columnar epithelium. Notice up at the top, it looks like there's some furriness at the luminal edge of these cells. Maybe cilia, I actually don't know where this is. Oh, it's in the gallbladder. That does not help me. I don't know if there are, I guess there would be cilia in the gallbladder and not microvilli, but there are definitely extensions on the luminal end of the cells. All right, who's this? What's this structure down here? Basement membrane. What's that up there? Space. What do you notice about these cells? What do you notice about the number of nuclei? We definitely don't have a single layer of nuclei, do we? And in fact, like, whoa, there's lots and lots of layers of nuclei. Do you think that this is a stratified tissue? No, this is actually pseudostratified columnar epithelium. And this stuff up at the top, those are cilia. So this is ciliated pseudostratified columnar epithelium, because these are all individual cells. Check out this one. This is actually, nobody cares where it is. The two arrows are sandwiching the tissue. So the tissue is found in between those two arrows. Do you see any spaces? Space. What kind of tissue are we talking about? Epithelium. What's the shape? How many layers do we have? Dude, do you even see one layer? Like, that's a thin layer. If that's a layer, it's a layer. It's one layer. It's a simple, what's the shape? Squamous epithelium. On a quiz, this, in fact, was taken directly from a quiz. On a quiz, I would sandwich the tissue just like this if I was trying to grab the simple squamous epithelium, because it's hard to visualize halfway through. That was pretty easy, wasn't it? What's next? What about these guys? Do you see a space? Totally. Look, this is a tube. This is the lumen of a tube, which means over here on the basal side is my basement membrane, and you can really see it. I almost wish I could zoom in a little bit more on this one, because that basement membrane just sort of pops. Histo's so fun when it pops. This is the shape of my cells. Those are like the best example ever of cuboidal epithelium, simple or stratified. One layer, simple, cuboidal epithelium. How do I know that these aren't all layers? Well, you just get a sense of where the basement membrane is. This is actually like jillions and jillions of tubes. Here's an interesting place. It's a tube that actually got cut the long way, which is how the lumen of the tube looks really, really long, but it's because we cut the tube in the long way, which is why it looks long. Look at this tube. This is a tube as well. It's simple cuboidal epithelium, but do you see a space right there? No, that's because the tube got cut on the edge of the tube, so you didn't catch the lumen in this part of the tube. One of the most challenging things about anatomy in general and histo in particular is you have to visualize the slice. There's this spatial magic that has to happen where you can visualize a tube that gets cut and then or any body part, a brain or whatever, that gets cut and then you have to imagine what that looks like on the cut edge. Okay, simple cuboidal epithelium. All right, we are out of epithelial land. There's a couple of clues here that are interesting. First of all, does it look tidy and organized to you? Honestly, to me this looks like somebody finger painted with pink pudding, which I actually right now at this moment would be kind of fun to do. The pink pudding like smear things, collagen fibers, big, thick collagen fibers. That's hint number one. Hit number two, these big circles. See how huge they are? They're big circle spaces. They're houses for cells. I already told you about one kind of tissue that had a little home for a cell called a lacuna. Remember compact bone? What do you think this stuff is? It isn't bone. This isn't an example of spongy bone. This is actually big, thick collagen fibers. This is fibrocartilage. The space, the big lacuna, the cell inside it, and those giant fibers. That is an example of fibrocartilage. There's nothing that you will mix that up with. You got to see the lacuna in order for it to be structural connective tissue. All right, lacuna are also in this one. Do you see them? The foliage and spongy bone actually look, it's almost like bubbles coming through fluid. Doesn't it kind of look like soda pop or bubbly carbon dioxide, whatever? This is a lacuna. This is where a cell would live. Now, if it has a lacuna with a cell living inside it, what kind of tissue do you think it is? It's going to be a structural connective tissue. And I'll tell you again, it's cartilage. And here's your clue. If you look at this stuff, do you see how it kind of looks spiderwebby? Doesn't that look spiderwebby right there? Those are elastic fibers in this cartilage tissue. What kind of tissue is it? Elastic cartilage. Look for your lacuna. Look for your elastic fibers. Are there collagen fibers in this tissue? Totally, it's connective tissue. All my connective tissues have collagen fibers in them with possibly the exception of blood. I don't know. What was I saying? I was saying something elastic. I can't see the collagen fibers in cartilage. I remembered. Oh my gosh, I'm on number 13 of 20. I'm not counting. Structural connective tissue. What's left? Oh, there are two left of our structural connective tissues. This one, do you see my lacuna? My spaces, look, those are the spaces that are found in the structural connective tissue. So there's cells living inside there. You know what, the shape of this thing, this thing that has lacuna in it, that's your giveaway. This shape is what you see in spongy bone. If you see lacuna in weird island shapes, you're in spongy bone land. It's easy to get spongy bone mixed up with this next one. It's our last structural tissue, but this next one does not get shapes like this. This next one is just regular cartilage and that's called hyaline cartilage. Hyaline cartilage also has collagen fibers, but it's a really clear cartilage. Fibro cartilage had those big, huge collagen fibers that you could see, elastic cartilage had those elastic fibers. Hyaline cartilage almost looks like there are no fibers in there. There are, but you just can't see them. Process of elimination, do you see my lacuna? Look at all those lacuni, they're everywhere. Real cartilage cells or chondrocytes living inside them. Ah, what's that? Looks like a mess. It's connective tissue. Do you see fibers? Look at these fibers. What do you think the big pink fibers are? Collagen fibers. What do you think the little, thin spider web-looking fibers are? Elastic fibers. What do you think the dots are? Fibro blasts. They're blasting out fibers everywhere that they are. They're barfing out all these fibers right here. This tissue looks like a bunch of tinny winks got thrown up in the air with some M&Ms in the mix and ended up with just like pure madness. It's loose connective tissue or a realer connective tissue and it's a type of connective tissue proper. So we are no longer in connective tissue land with all of our structural stuff. We are still in connective tissue land. We are, I'm telling you, these pink lines, what are these things? Connective tissue, big pink things are fibers. What kind of fibers are big and pink? These are giant collagen fibers. They're giant collagen fibers. Do they look like they're organized or unorganized? Well, you might think that's unorganized, but I'll tell you right now. Dude, if my kids' rooms looked that clean and organized, they would have a little party right now, right about now. This is dense, regular connective tissue and these little dots right here, these are your fibroblasts. Dense, regular connective tissue kind of looks like skeletal muscle tissue. No striations and the cells are outside of the fibers. They're not like in muscle tissue, the cells, those circles look like nuclei. They are nuclei in muscle tissue and they're found inside the cells. These cells are all over the place. They're found in between the fibers. They're not actually in the fiber, which means they're not actually in nucleus because they're not, they're cells. All right, does it look dense? Do you see any lacuna? No lacuna, no lacuna for you. Do you see cells? Yeah, holy cells, like these are my fibroblasts. They're definitely blasting some fibers. Where are the fibers? Dude, that pink vomit. Those are collagen fibers. Does it look dense? Does it look regular? This is dense, irregular connective tissue. Okay, look really closely. These are nuclei. Do you see any striations on here? You do because they're there. You kind of have to look really closely, but it's true, they're there. They're striated tissue doggies. These things right here, those are actually the structures. They're called intercalated discs. Certainly not going to test you on them, but those distinctive vertical lines in this mess. It looks like collagen, doesn't it? Flamingo vomit, no. These lines are actually characteristics of cardiac muscle tissue. Cardiac muscle tissue is striated. Cardiac muscle tissue has these connectors between the cells, and they're super significant. We're going to look at all this stuff again. At this stage in the game, all you're doing is going, ah, I see those lines. I see striations. I'm going cardiac muscle tissue. Striations mean it's either skeletal or cardiac. These lines mean it's cardiac. This is our last one. It's so pretty. First of all, okay, this is the tissue. I probably should have thrown an arrow on this one because that's actually, those are neurons cell bodies. That's super cool too, but these, this is what we're looking at right now. What, doesn't it look smooth? Doesn't it look smooth? Look at the shape of the nuclei in this tissue. These are the nuclei of individual cells. This is smooth muscle tissue. And we're going to see lots of smooth muscle tissue in lecture number five when we do digestive histology. So there you have it. I can't believe this crazy scene. All of that prep work prepped you for your lab. You know what we're going to get to do in lab? Not this. I do not have to talk to you during lab. You get to have your face in a microscope, looking at tissues and practicing, identifying these things. By the end of lab, you will be feeling very comfortable and ready to go. All right, holy cow. I have no idea how long that thing was and I can't figure out how to turn it off. I guess that means I just don't want to go yet. Do you want to keep going? I bet I could think of something else to tell you. Just kidding. All right, see y'all in class. Bye, bye.