Connective Tissue Podcast | Dr Matt & Dr Mike’s Medical Podcast

Introduction: Understanding Connective Tissue

[00:00] So I think the best place to begin Dr. Matthew Barton is by talking about if I were to pluck every cell off your body one by one Offered Offered what all the bacteria just ever just I was just a pluck you apart one by one one cell at a time and Pile you up. There'd be about 30

[00:20] trillion cells that make up you Matthew. Now if what a pile it'll look like. I already get civil it's what it looks like now to be honest. Just a pile of slime. Big red slimy pile. If I were to then take those cells and then sort them according to just their function broadly I would have four piles.

Four Main Types of Body Tissues

[00:40] Okay, so these are hemorrhoids here. I'm talking about four separate piles of cells sorted by function and these are what we call tissues. Okay. And so basically you've got the cluster of cells, tried to understand what they actually do in a similar way. And then we can categorize them in four broad categories.

[01:00] Yeah, exactly what I said. Yeah. So their muscle, muscle tissue. So that's for movement. That's a huge part of the pile. Yeah. Well, for me, another really big part of the pile for you is epithelial. So just a bunch of skin. So that's to skin and barrier.

[01:20] Skin and pipes. Skin and pipes. Like the mouth to... we've covered that one. But also the lungs. Yep. So epithelia is just barriers. Then we've got nervous. So that is for communication. And then finally, the last

[01:40] tissue type is that for connective tissue, all the cells that sort of hold you together. So that's going to be the focus of today's connective tissue. Now when we think about connective tissue, they actually have, well, there's no definitive way to talk about their functions, but I like to say there's five functions.

Functions of Connective Tissue: Protection, Support, and Binding

[02:00] five categories that you've made yourself? My five categories, I think that every if not most textbooks will concur. They might only say few of them. I think I actually am more extensive. Yeah. I'm far better than most of the textbooks. Everyone says why don't you write a textbook? And my answer is because I like it.

[02:20] living a life. Yeah. No. Why would I waste my time? People think that textbooks are a lucrative deal. They ate. How would you know? We've written chapters of textbooks. It's not a financially smart idea to do. Anyway, so five functions of connective tissue. Okay. All right.

[02:40] Here we go. Okay. Any particular order? Yeah, I'll throw it at you and maybe you can think of some ways in which connective tissue does this function. Okay. All right. Protects. All right. You mean give an example of how connective tissue protects. Okay. So bone. All right. Like the thorax. You got

[03:00] rib sternum that protects your vital organs in there like your lungs and your heart or the skull. The skull is this helmet of bone protecting Matt's walnut sized brain. So okay great bone. So bone is connective tissue and that's one way that it can protect. Brilliant.

[03:20] Second function, obviously this isn't what we're going through is an exhaustive list. So that's not the only way connective tissue protects. Right. There's many ways, but these are examples. Next is connective tissue supports. So how does it support? Support, support, support. You mean like

[03:40] mechanically support? It's wild card up to you. Maybe it just kind of puts together the other three tissues that you spoke of. So you have epithelium. Let's say the skin is an example. You have the epithelium, which is the outside, the epidermis. Under

[04:00] If you go further down, you've got muscle in some cases and so you need to link them together. So you need to support the two together by having connective tissue in between them to support those other two to three tissue types. That one also sort of

[04:20] feeds into the next one I'm going to say. But you're right. Another way is bones again, they support the weight of our body. Cartilage supports the joints, forces moving through those joints. Support is also like your kidneys, so they need to be

[04:40] otherwise they're just going to be free floating throughout the body. So they need to be anchored. They get anchored to the back wall on a bed of fat. That's right. Yeah. One of the best bed types you can have. That's right. One of the best beds you'll ever sleep on. Silly posture period. But you're going to have a bed of fat. If you lose too much fat, the okay

Connective Tissue's Role in Transport and Immunity

[05:00] kidneys don't have that protection or that support and they just move up and down. That's right. They just float around. Yeah. Floating kidneys, which is actually a thing. That is a thing. So we've got protects, we've got supports. Third one is binds. Yes. It wraps stuff up, right? So maybe around organs. They put capsules on. Yeah. That's a perfect example

[05:20] Most organs have a protective capsule around it. You see it with the kidneys, the spleen, other various structures. So there's binding. But also you've got like the intestines. Yeah, they're all bound together to want, you know, it's not like the movies when somebody gets eviscerated and they're pulling their intestines out like a line of sausages. It doesn't work like that. It's just one big heap. We get the pool hard because we kind

[05:40] do that in our first AMP lab, not so much with a human, but with a catavary rodent and the students do like pulling it out and making a big long line of intestine to see how long it is, but that connective tissue puts them into a nice coordinated bun.

[06:00] Exactly right. Beautiful. Coordinated bundle is a great way of describing this podcast. Transports, connective tissue transport blood. All right. And what's what needs to be transported in blood? Let's let's yeah, I guess stuff. Yeah. Well, I was just

[06:20] trying to think of is plasma connected tissue. I guess it is. Yes. It's the fluid part. It's the ground substance. Yes. Nutrients, oxygen, cells, waste, electrolytes. Yeah, perfect. And finally, last one is immunity. Okay, well, that's the immune cells. Yeah. And that

[06:40] would be an array of leukocytes, lymphocytes or the granular sites and the ones that coordinate activities with them. And don't forget lymphatic tissues as well. They're connective. So you could also add to that

[07:00] But repair, so after you have injury, the connective tissue is part of the repair process. Right, that's good. So you're adding six to our list. Well, maybe you just put that with defence. Did you have defence? Nope. What was that last one? I guess I've got seven now. What was the last one? Immunity.

[07:20] immunity, defence, repair altogether. Okay, so you're just going to sell it as one thing? Yeah, I'm going to sell it one thing. Fair enough. That makes it easier for the students. So we've got five functions, protect, support, binds, transports and provides immunity. Now, the reason why connective tissue can do all these extensive roles is because it has three really important

Key Properties of Connective Tissue: Strength, Elasticity, and Volume

[07:40] These properties include tensile strength so it can resist like pulling and stretching and tearing. It's got elasticity so it can bounce back. So like when I throw an insult at you it just bounces straight back to me. So elasticity you can stretch it, it snaps back to its capacity.

[08:00] That's one of the things we lose over time, right? Particularly about the skin. That's right. And then finally, volume. So this is what people find to be an interesting one is that connective tissue is actually really important at filling space. So a lot of the time, the space filling material is connective tissue. So with your lips, filling that with space.

[08:20] That's the collagen that you add to it? Yes, and filling it with other things like dermal fillers and so forth, which is probably just predominantly collagen, I see. So they're the three properties that sort of allow for all these various functions, tensile strength, elasticity and volume now. Next part that we need to have a chat about is the fact that

[08:40] Some connective tissues can be really hard like bone. Some can be semi-solid. Any examples that you can think of semi-solid connective tissue? Fat. Right, fat adipose tissue. Yeah, that's, yep. Any others? Cartilage? Cartilage. Yeah, I'd say that's semi-solid because that's

[09:00] compressible, but like it takes upon the compressible forces put through our bones. So it's usually one example, high length cartilages at the end of the long bones and they kind of allow that force that goes through the bones and like a shock absorber.

[09:20] But it's semi-solid. Yeah, it's semi-solid. And then liquid. Liquid. Blood. So this is where students get confused because you know what nervous tissue is when you look at it. You know what muscle tissue is when you look at it. But connective tissue seems to be, it can be bone, it can be cartilage, it can be fat, it can be this, it can be blood, it can be that.

[09:40] can be a whole range of things. So then this question that I get asked by students is what makes a connective tissue connective tissue? And it's the fact that all connective tissue contains these three things in various quantities and various types, but they all contain these three things, cells, gels and fibers. So should we start

Cells of Connective Tissue: Blasts, Sites, and Their Roles

[10:00] look at some of the cells of connective tissues. Let's do it. Alright, that was a big thing. I'm just trying to think. Well, that'll do. Oh, that'll do. Yeah, let's just let's just cells. Alright, so I like to correct me if you like to do it a different way. But I like to think about the cells that are the immature cells of connective tissue.

[10:20] So the B for Barton, so think of the blasts and then the sites. These are the mature cells, these are the mycal cells of the connective tissue. Aren't they called the agin cells? Like the old? Let's not call them that. We'll call them the mature, highly attractive.

[10:40] which means kind of retired, not too active anymore. Yeah, sleeping, which is what I plan on doing when I retire. Okay. All right, so we've got the BLASTS, which, so this is a suffix. This is the last part of the word. They're the immature building cells. They release the fibers, the gels and fibers.

[11:00] They're doing stuff. They're the builders. And then you got the sites, they're mature, they're sitting around, they're sort of just looking around the area, seeing what needs to be fixed, what needs to be changed, what other things do I need to call upon. Or they've locked themselves into a space they can't get out of. Yes. And I think we spoke about that when we spoke about bone.

[11:20] Let's start with the blasts. Some important cell types that are blasts that you need to know for connective tissue, probably one of the most important is fibroblasts. So fibroblasts are the main immature cell type for many connective tissues. A lot of the loose – They're the real king of connective tissue. They are, aren't they? So they make a lot

[11:40] of like the what we call the loose connective tissues, areola, reticular, things like that and they can make all those fibers you spoke about they pretty much make the lot. That's right yeah well I haven't spoken about any of them but yeah. Oh you kind of did at the start when you spoke about collagen and elastin. Yeah I didn't. I think you did. I didn't. You spoke

[12:00] about collagen in the lips, but we will get there. We will get there. But they make that. Yeah, you're right. They make those fibers and the gels we're going to talk about shortly. So fiber blasts, super important. They make many types of kinetic tissues. Osteoblasts. Bone. Bone. Yeah. They're the bone builders. Conjroblasts. Cartilage. Cartilage builders.

[12:20] mastitis blasts? Our blood. What type? Do you know? bone marrow. Yeah, so both red and white. Yeah. Yep. And then you got and that's not an exhaustive list of the blasts, but they're probably the most common they they fill up most of the connective tissue types. Then you got the mature connective tissue cells, adipocytes. Yep.

[12:40] Which are? Fat. Osteocytes. So they're just blasts that are retired. So mature bone cells. Conjursites. Yeah, so they're the cartilage cells that again, retired. Erythrocytes. Red blood cells. And leukocytes. White blood cells.

[13:00] obviously others, but there we go, they're the cells. Right, so depending on the type of connective tissue depends on the cell or I should probably reword that and say the type of cell depends on the type of connective tissue. So the next thing is the gels. You must have gels. Are you going to come back to the cells? Not really, unless you want to talk more about them. I think we should do a little bit.

[13:20] Well just with the cells because that's going to kind of dictate what tissue they create. Yeah. Okay. I just said that. Yeah. But just to listen to anything I say. Another way we can kind of do an degree of categorisation with these cells is whether they are

[13:40] fixed within the tissue or they migrate into the tissue from another area. So can we really quickly go back to- All the way to the beginning Matt, to a bad embryology? Yeah, yeah. Oh, I was joking. You serious? Yeah, I'm serious. Really quickly. No, yes, please. Please. Okay.

Origins of Connective Tissue: Stem Cells and Development

[14:00] Well, we all started with a zygote. Do you agree? You had three goats, I think. So sperm, egg together, now we have a single-cell zygote. That's where we all began as an embryo.

[14:20] Then we progressively replicated so that one cell became two and so on and so on and so on. Transport, because this all began in the floping tube, transport a few weeks until we're in the uterus. Let's say at about three weeks,

[14:40] we change that cluster of cells into three broad groupings. We have the ectoderm, the endoderm and we have the mesoderm. I'm not going to go too far into this. Doesn't that just mean outer, middle and inner? Yep, that's right. Ectoderm pretty much makes your skin so your outer wrapping

[15:00] pin in your central nervous system. Okay, the endoderm is just the pipes inside, pretty much the gut and the mesoderm is everything else. So pretty much all the connective tissue that's made comes from the mesoderm. Now at this point, the cells that start to differentiate from the mesoderm is what we call mesenchymal.

[15:20] So mesenchymal. Right. Okay. So mesenchymal stem cell is pretty much all those connective tissue cells that you mentioned come from this. So like fibroblasts and osteoblasts and they're all mesenchymal cells. They come from that. Alright. Okay. And there's an important just distinction that we should make here.

[15:40] difference between a stem cell and a progenitor cell. What is it? Do you know the difference? I think a stem cell can become anything and a progenitor cell goes down one particular lineage. Or am I totally wrong? I know you're pretty much right. A stem cell though has the capacity to keep renewing itself. Right.

[16:00] Okay, so a good example was the hemopoietic stem cell. So that sits in the bone marrow, okay, but it has the capacity to regenerate itself to stay as a stem cell. But as it goes down a lineage, it becomes a pleuro or a potent cell. So now as it goes down,

[16:20] can only, so you could have a lymphoblast or a myeloid blast, they can only go down a certain line now. So lympho now can only become a lymphocyte or a naturculous cell or the myeloids can become granulocytes or red blood cells. Does that make sense? Yeah, that makes sense. But they can't renew themselves anymore.

[16:40] So they're progenitor cells. Progenitor. But the stem cell that sits back in the bone marrow, it is still a stem cell, so to speak. So at this point, the mesenchymal stem cells now. So the mesenchymal will make the majority of your connective tissue, but there's one group that, it's kind of a strange one, but as the embryos

[17:00] developing you have this kind of bulgy sac at the front, which they call the yolk sac. That is making stem cells to produce blood. So in the baby or the very early embryo that's making the blood cells. So that's where the hemopoietic stem cells are.

[17:20] Then as the embryo develops, they migrate into the liver and spleen and they take over doing the blood cells. But as we get closer to being born, they migrate further and then they go into the bones. And so they become your hemopoietic stem cells. And so now,

[17:40] As an adult, I would say a born human. You could, I mean they're both two words. Now the hemopoietic stem cells, so the ones that will make the connective tissues from all the blood driven products come from that one.

[18:00] population of cells. Okay, what's the point of this? Well it just tells you that's one where it originated from and the others, all the other ones you mentioned are from the mesenchymal stem cells. Alright, so some migrate there and some reside. So now with a

[18:20] hemipotic stem cells. They're at least the stem cells, they are fixed within bone marrow, but as soon as they start to come into a progenitor cell and then become more like their functional outcome, then they move into the blood. Okay, so now they might

[18:40] migrating in the blood, moving around the blood and then when there's potentially an issue, they will move off into the tissue. When there's an issue, they move off in the tissue. Is that only an issue to remember? Besides like red blood cells, they will stay in the blood forever, they die at least, but all the white blood cells, they will move out. Does that make sense?

[19:00] they're therefore migrating or migrant connective tissue cells. Gotcha. Cool. That's cool. But interestingly, if you took up, you know, when you did the pile of cells for me, yes. Yeah. About 40% of those cells, somewhere between 40 to 60% is only

[19:20] cell type. Red blood cells? Yeah. Isn't that amazing? So your majority of your cells are actually red blood cells. Red in there for you. Okay. I thought that was cool. No that is cool. That's the most important thing. So then. Most interesting thing you said in the past 15 minutes. Then you have the fixed cells that are actually locked in the tissue they can't really move out.

The Extracellular Matrix: Gels, Fibers, and Ground Substance

[19:40] out and around and so forth. That's going to be all the resident cells. That's going to be the ones you mentioned like the blasts. But they still come from the mesenchymal cells and that still gives them the capacity to regenerate that population. And that's where all the, I don't know if this is a safe thing to say, the quackery with stem cell therapies where they're

[20:00] injecting mesenchymal stem cells into your blood and then like it will go to the right location and regenerate your cartilage or your ligaments or whatever. Obviously there's good research being done to say if you were to take a mesenchymal stem cell and put it into say a degenerative joint whether that

[20:20] has capacity, but just to throw it into your blood and think it will go miraculously into that area to regenerate it. Yeah, it's questionable. Yeah, it is. It is. Okay, well, welcome back, everybody. I thought that was all right. It was good. Yeah, look, it's my job to hang crap on you, Matt.

[20:40] Sure do. It's harsh. Well it feels good. It feels good to do it. Alright, so done with cells? I've done. I'll just leave the room. No, no, no. I need you to be here because otherwise I'll be talking to a wall. Expand it. It's probably no different. A wall of osteoblasts. Alright, cells, gels and fibres. We just did the cells.

[21:00] So in actual fact, they're not called gels, they're called ground substance. And basically it creates the fluid rich environment that all the components of the connective tissue sit within. Yeah, that's right. So all the cells, all the fibers, all the other chemicals

[21:20] sitting within the gels or the ground substance. And in actual fact, the ground substance is made up of four major things. Water is a big one. Gags. Right? Which? Glosopharyngeal nerve? No, nor is it? Anyway, it's glycosaminoglycans. I'm glad you

[21:40] said that. Well stick with gags, I can see why you did that. Proteoglycans and glycoproteins. Now does it annoy you? Why are those two? Isn't it frustrating? Does that mean just the amount? One's got more sugar on a protein and the other one's more protein than sugar? Yeah man that's pretty much it. Thanks Dermot.

[22:00] Proteoglycan, proteins with sugars, glyco-proteins, sugars with proteins. It's stupid, but they're very similar, but I'll tell you the differences in a sec. So water

[22:20] glycosaminoglycans or GAGs, proteoglycans and glycoproteins. So let's first start where we know what water is. So we don't have to worry about that. Let's first start with the GAGs, the glycosaminoglycans. So these are these long unbranched chains of complex carbohydrates. So they're carbs and they're found in all the different. Like cartilage? Yeah. Well, they're found in

[22:40] In all the different conditions. Is this like glucosamine? Yes. So if you think about the different types of GAGs, right, you've got the chondroitin sulfate, heparin sulfate, keratin sulfate, hyaluronic acid. So they're all different types of glycosaminoglycan. They all slightly perform different functions depending on where they are.

[23:00] example, hyaluronic acid is in joints, plays a really important role as like a shock absorber and lubricant. Now I want you to have a think of the proteoglycans now. The proteoglycans are basically always attached to the gags. So the gags and proteoglycans

[23:20] together and the proteoglycan allow for the glycosaminoglycan to really absorb water, to hold onto water. So it plays a really important role in the connective tissue to bulk it up and obviously in cartilage it's very important when it comes to providing that bulk for shock absorption and so

[23:40] forth, but it also just maintains the integrity of that connective tissue. Then when you look at something like a glycoprotein, it doesn't really attach to GAGs, but it has an example of a glycoprotein is fibrinectin and laminar and they form cross-linking

[24:00] in the ground substance, also known as the extracellular matrix. Well actually the extracellular matrix is the ground substance and the fibers together are right. Yeah that's right. And so I was going to say that earlier then but I knew you'd criticize me. Because I hadn't spoken about the fibers yet. Correct. So the glycoproteins, they play an important role in cell signaling, regulating cell behavior and

[24:20] tissue repair as well. They also act as cell adhesion molecules, they promote cell to cell interaction and they maintain integrity. So at the end of the day, the way I think about it is that glycostomated glycans and proteoglycans are bound together. The different types of each is dependent on the different connective tissue type and they're all

[24:40] a slightly different role, but at the end of the day, they mostly play an important role in just pulling water in towards that tissue. That's important. They play other roles, but that's really important. Glycoproteins like the fibronectin and laminar, they play an extensive role. Like I just said, cell signaling, behavior,

Types of Connective Tissue: Dense, Loose, Supporting, and Fluid

[25:00] adhesion, things like that. And so these are the major constituents of the ground substance. Does that make sense? It does. Alright. Then finally we've got the fibres. Now like you said, the ground substance plus the fibres is the extracellular matrix. It's basically the whole thing that everything's embedded in. So when we have a look at the fibres, what are the three

[25:20] fiber types. My guess would be collagen. Yep. Do I have to say anything more? No, we'll go through them all. Collagen, elastin and reticular fibers. Perfect. Let's start with collagen fibers. Before I describe what it looks like, when you, you're a vegetarian, so you don't eat steak.

[25:40] There's different so that's just ruined my example here going I've eaten steak before you have okay, so when you eat a steak and you get that real chewy part It's real white and and glossy and you chew chew chew and you just can't break it down. That's collagen Collagen is tough collagen is strong collagen provides that tensile

[26:00] strength within connective tissue. As a fibre, it's like a metal rod that's placed within the tissue providing that strength. You compare that to like elastic fibres which is like a rubber band, you put that into tissue it just makes it stretchy so that it can snap back. Very different to the collagen. And then the reticular

[26:20] fibers. They look like feathers so they provide like networks right and so the type of tissue that they're in are tissues that require a very sort of mesh like network like structure like lymphatic tissue for example. Like the spleen. Like the spleen perfect that's filled with reticular fibers.

[26:40] So collagen for strength, elastin for stretch and reticular fibers for mesh-like networks to be able to hold and wrap things together, which sort of describes connective tissue perfectly. So depending on the connective tissue, like if you've got something like bone, you're probably going to have a lot of collagen fibers embedded within it.

[27:00] within it. If you've got something like spleen, you're going to have a lot of reticular fibers. If you've got like a stretchy artery, the wall of the artery, the connective tissue wall, is going to have huge amounts of elastic tissue embedded in it. Now you take that into consideration with the differences in extracellular matrix and ground substance and then the different cells and now you can sort of see why it's all

[27:20] so variable going from bone to cartilage to blood to whatever it may be. Does that make sense? It does. Alright. So when I put it all together, the analogy I use with my students is like making jelly. You got that airplane jelly mixed? Do they have airplane jelly in other countries? Yeah. Can you sing the song? The airplane jelly thing?

[27:40] song. I like airplane jelly, airplane jelly for me. I like it for dinner. I like if it's for tea. A little each day is a good recipe. I'm not sure that's true though. No, it sounds pretty. Is that just collagen?

[28:00] The jelly? I know what it's made out of. But let's just say it's not gelatin. So it's made out of gelatin, but we know what jelly is like. Really wobbly, really unstable. But if I were to take some metal, little metal rods and place it in the jelly, it would make it more solid.

[28:20] Or if I was to put more elastic rubber bands or whatever, what's another name for rubber bands? Elastic bands? Chuck them in the jelly. It's going to allow for it to really stretch and move and be able to snap back. Or if I would put feathers in it, again, it's creating this mesh-like network. What would the feathers do? Create a mesh-like network.

[28:40] Alright, the analogy falls short once I hit that, but you get the picture that I'm trying to make, right? Hopefully, maybe you don't. So that's how connective tissue, that's sort of like the histology of connective tissues, cells, gels, fibers. Finally, we need to talk about categorizing connective tissue.

[29:00] We've set it up now that we've first spoken about the different functions of connective tissue. Then we've said what are the components. And now by changing the components in percentage wise, it will then cause an outcome.

[29:20] that will then provide us with how we then categorize connective tissue. Yeah, so the tissue types, the connective tissue types. Do you want me to start broad and then go more specific? Yeah. There's three main types of connective tissue. You've got connective tissue proper, supporting connective tissue

[29:40] tissue and then fluid connective tissue. So connective tissue proper. The way I like to think about it is this is the proper connective tissue. When you think of connective tissue of the body, this is the connective tissue you're thinking about. The stuff that anchors the organs of the body, the stuff that sticks the skin down to more deeper layers of the body, this is the connective tissue that you think

[30:00] cough. Okay. Then there's a second one supporting connective tissue. This supports the body. So how does this not fit into the proper one then? Well, I don't think of bone and cartilage as connective tissue. Maybe we could call this special then. Yeah, or supporting like I said, I like special sounds like it sits outside. Alright, we can say that we'll say special slash

[30:20] supporting. So that's going to be bone and cartilage. And then you've got fluid, which is blood. So let's start with the connective tissue proper. So there's actually, fortunately for us, or unfortunately for the students, two subcategories here. Under connective tissue proper, you've got dense connective tissue.

Connective Tissue and Immunity: Mast Cells, Allergies, and Anaphylaxis

[30:40] and loose connective tissue. Right. That makes sense. Okay, in what way? What? That category? Yeah. Well, dense to me would kind of indicate that probably the fibers are jam-packed together in bundles. All of it really. Yeah. Or everything's jam-packed, even cells. Okay.

[31:00] Whereas loose is loosely arranged. But not to the extent where it's fluid. Yes, perfect. That's exactly right. So dense, everything's densely packed, loose, things are loosely packed. Now under dense connective tissue, you've got dense regular, dense irregular and elastic. So dense regular

[31:20] is obviously everything's densely packed, but the fibers are regularly arranged. So all parallel to one another, all facing in the one direction. What would that mean if you got connective tissue with all the fibers in the one direction? They probably provide some kind of integrity, some kind of support in the direction that they're running.

[31:40] preventing a structure getting pulled apart in that one directional manner. Yeah, perfect. So like ligaments and tendons, they will generally cross joints, for example, and they tend to be pulled in only one particular direction. And that's like the tendons in the direction of the muscles.

[32:00] fall in, if it ligaments their bone to bone, so the weak range of motion, but the way the joint moves probably in the weakest position it can be in, you put these ligaments to give it greater support. Yeah, ligaments and tendons, that's the type of dense regular connective

[32:20] Also the fascia, right? Fascia aponeurosis. Yes. Which may be not as dense as ligaments and tendons, but still. Yeah, I think fascia is loose connective tissue. Yeah, I'm quite sure fascia is loose connective tissue. Then you've got dense irregular. So this is where

[32:40] the fibers are irregularly orientated so it sort of looks like they're just arranged randomly why would that be the case? I would imagine then the mechanical depressions or the forces are going in all sorts of different ways yeah like maybe under the skin. Yeah, dermis, perfect. Yeah so obviously that's going to receive forces from multiple angles.

[33:00] So the dermis. And then finally, under dense connective, which again sits under connective tissue proper is elastic connective tissue. So these are like the walls of our arteries. So left side of the heart contracts, pushes blood out, stretches those arteries. They need to be able to snap back to give us that diastole.

[33:20] blood value and that's elastic tissue. Okay. So that's its own category. It's its own category. But it sits under dense connective tissue because it's densely packed. Then we've got loose connective tissue still under the connective tissue proper. This is three categories. Adipose, which is? Fat.

[33:40] which is sort of like the connective tissue that so would you say with adipose it's the one of the only examples where the fluid or the ground substance is actually in the cell instead of outside it because you'd say wow I've never

[34:00] even thought about that. Because you'd say, yeah, yeah, in terms of connective tissue, yeah, the ground substance. No, actually, what let's just go. Is it inside or is it outside? That's inside. So that's the never even thought about. That's the lipid droplet. Yeah. But is that the is that the ground substance? Yeah. Oh, that's amazing. I never thought about it. If you look at our

[34:20] adipocytes, it's a big round globular fat and if you looked at because it's metabolically active, if you look at it histologically, it looks like it has a ring around it. That's the cytoplasm and it will have the nucleus, which you can see histologically, but all the middle looks empty. Wow.

[34:40] So that's just the fact. Didn't even think about that. That's awesome to think about. Good point. Next is areola. So areola is the connective tissue of the deep structures of the body. It's the one that like supports and binds and holds all the mainly gastrointestinal viscera together, but obviously other structures, but it's supporting

[35:00] and binding and holding the deeper structures. Then you've got reticular and this forms remember the reticular fibers are like sort of feathers forming a mesh like network plays an important role like filtration for example think of the lymphatic tissue like the spleen that's going to be reticular. So those three adipose, areola and reticular they're loose.

[35:20] connective tissue, again sitting under connective tissue proper. Then finally, well not finally, but the second one is the special connective tissue or the support. Thank you. Bone and cartilage. Bone is bone. We know what bone is. We've done a whole episode on bone or multiple. But interestingly with bone, like you were saying earlier, when you're talking about the the rods in it and we

[35:40] I may have said this when we did the bone, but when you create cement, okay, so if you want to lay down a concrete path, if you were to just put the concrete down and nothing else, it would have strength in its compressible

[36:00] manner. But it would be very weak in, I'm not sure what that plane of movement is. It's good for a podcast. At least this is going to be up in the YouTube channel. If you were walking on it or if you put something heavy on top of the path, it would break because it's not strong in that particular. So vertical

[36:20] forces. Yeah I guess yes yes. So what they add to the concrete path is steel rods and that gives it that strength in that plane. Like putting the collagen into the bone. Right so that's kind of where I was going with it. With bone the osteoblasts lay down the collagen fibers and

[36:40] then it becomes calcified with calcium and phosphate, which what's that term called? I've got a mind blank. Calcified? Yeah, just that term though, doesn't matter. You just add in a salt to it, which then gives it a different degree of strength. Okay, and that then provides its structural

[37:00] integrity. Does that make sense? Yeah, absolutely. Whereas the other one, what was the other one? Cartilage. Cartilage. Which then is interesting because then like again, don't roll your eyes, but if you look at bones before they're made, they were cartilage before bones mostly, right? Like most. But they're like a cartilage precursor too, right?

[37:20] It's not like our current cartilage. No, but there was like the bone which was- Talking about when we were children. Yeah. So the chondrocytes and then that osteoblasts migrate and change the form, the ground substance into more bone-like. Yeah, absolutely. And that kind of allows our bones to lengthen. Yeah. Still gave the cartilage plate to stay

[37:40] open, which allows it to grow. And then eventually that ossifies itself to then close off. So it's interesting that that kind of has its own kind of differentiation or change between these two specialized groups. So with the cartilage, then we have further groups, right?

[38:00] So we've had a hyaline and that's the end of the bones. Yeah, very glossy, very shiny, very smooth, providing articulating surfaces. Friction-free movement. Yeah, knee, hip, shoulder, any joint, any like synovial joint. But then you have additional, or at least say the knee.

[38:20] then you have additional highland cartilage that's fibrocartilage. Oh the meniscus, is that? Yeah. Okay. So we'll then go to fibrous cartilage. Yeah. So fibrocartilage is like the meniscus of the neck for compressive responses. So that just increases the congruency of the joint because it's a fairly unstable

[38:40] joint until you put the meniscus in. Yes that's right and you get fibrocatilage and the vertebrae as well. Okay and between your pubis? Yes. What about your epiglottis? That's going to be elastic. Oh is it? Elastic

[39:00] elastic cartilage. That's the third time. Ear and epiclose. Yeah, a bit in the nose, but mainly epiclodosynia. That's the elastic cartilage. And then finally, fluid connective tissue. And that's blood. Which is blood. Yeah. So it obviously has very few fibers in it.

[39:20] Otherwise, the more fibers and the more glycosaminic glycines. That's a clot and then you're going to have some problems. That's true actually because obviously the types of fibers that we have in blood are going to be those that help with clotting. Which will be inactive most of the time. But it solidifies it. It solidifies it, hence the clot.

[39:40] These are all fibers that play a role in the connective tissue fibers, but they clot things up. So that's, you know, and platelets, which is an important cell for kind of modulating or initiating that clot. Yes, that's exactly right. But yes. How are we going for time? We're good. We're good. Okay.

[40:00] A cell that I briefly want to talk about, I know we're going back to cells, but I think this brings in an important clinic. Do we have to go back through sperm, meat in the air, etc. No, I will skip that. What's one of the most abundant is kind of a migrant cell, but then becomes a resident. It's found everywhere in your connection.

[40:20] into tissue by central nervous system. Close. I think they only come out when there's really some serious issues. But what's this function you're talking about here with macrophages and?

[40:40] What initiates an immune response in the connective tissue? Well, a couple of cells, mast cells. Mast cells, that's it. So the mast cell. The mast cells are the connective tissue immune cells. So they sit in the connective tissue and when there's any kind of trauma, anything from mechanical injury, physical injury, chemical

[41:00] injury, thermal injury, they will be activated and they are an immune cell that has granules inside them and they vomit them out when they get, okay, alright, technically they're degranulate.

[41:20] Pooping or vomiting everywhere. Do they pass out after that? I don't know. I think they stay alive. But good question. Oh yeah, having this go at me. Very good. So by doing so, then they bring in those other immune cells in it. But the reason why I'm bringing this up, some

[41:40] Some quite significant clinical issues go wrong when these cells are overzealous. Is this just hay fever? Could be hay fever because that's going to be, what's hay fever? Is that just a cluster of symptoms? Is that like a

[42:00] Is it a condition with multiple things happening? Yeah, I suppose it is. I always just think about it as like a hypersensitivity reaction. It is. But when you say hay fever, what are the symptoms? Every time I go to bail some hay in the back of the bank.

[42:20] So your nose runs. So your nose runs. So your nose runs or it gets inflamed. Yes. Eyes. Yeah. Watering. Anything else? Close up airways. Then it goes down to the lungs.

[42:40] hay fever? Yes, but also atopic asthma, so allergic-based asthma. Which is a hypersensitivity rate. That's right. Yep. But one or two, do you remember? It's one. But you can go further and make it whole body. Oh, boy. Okay, so the way that this works is essentially

[43:00] your. Right. So anaphylaxis is a connective tissue dysfunction. Well, yeah, it's because it's from a connective tissue cell. Interesting. Okay. So essentially what can I really just say really quickly how it happens. Thanks everyone. Yeah, go, go, go. Are we doing anaphylaxis or analogy? No, no, I want you to just say

[43:20] what you were going to say. Okay, pick an allergen that you want to get allergic to. Peanut butter protein. Okay, well just say peanuts. So you ingest it for the first time. Your body sees it as foreign. So it sees there's something going on with this we need to deal with. Well actually it's probably your

[43:40] which is also an immune cell, sorry, a connective tissue cell if we're going to be technical, right? Hence why I said macrophages earlier. So they gobble it up. They can't get rid of it in a way that a person who doesn't have an allergy to peanuts would. So they see it as, oh, there's something wrong with this peanut protein.

[44:00] I'm going to present it. I'm going to break it up, but then present it on outside of the surface. Okay. And along comes a T helper cell. Also a connective tissue cell. So this is a lymphocyte, but it's specifically a T which matured in the thymus, kind of the top of your neck, bottom of your neck.

[44:20] Communicate with your macrophage and then say, hey, we should probably build up an antibody against this foreign thing, which is the peanut. B-cell, come along please, because I needed you to make some antibodies for me. Copy itself over and over.

[44:40] over and over. So plasma cells, antibodies, clones it, makes it into a plasma cell, pumps out the antibody. This antibody is an IgE based antibody. Right, so we've got an army now trained to fight this protein. Right, but these antibodies which are IgE typed will get flooded into the body

[45:00] but they bind to mast cells. Now the mast cell is primed. The mast cells have a particular receptor for IgE antibodies, but in this case it's seen as a foreign agent that you should be. Just like a bacteria or a virus that you want to encounter later to kill off quickly.

[45:20] But in this case, it sees a peanut protein as that foreign thing. So now it's primed. So now the second exposure comes. So first exposure, you're all good. Probably. Second exposure though. Now it's going to be problematic. So now you expose. Call it the army. Now every mast cell that gets exposed to a peanut protein.

[45:40] chemicals will vomit everywhere, histamine and huge amounts of vasodilation. Now you just now basically say where all the connective tissue that mastels are located around blood vessels, around your bronchioles, around your lips and nose and around your gut and they

[46:00] all cause a response. So your bronchioles will close up, can't breathe, your blood vessels will dilate. Blood pressure drops. Blood pressure goes through the floor. None of your organs get fed because of that. Your guts feel

[46:20] like they're spasming because they're all contracting. The skin gets hives because all the blood vessels are dilating your skin so you get rashes, tongue swells up, so this is now an anaphylactic response. You can die pretty quick. Yeah and so this could be anything, it doesn't be just

[46:40] penins, it could be bee stings, it could be penicillin. So anaphylaxis is a connective tissue disease. Yeah, you like that? I like that. No, that was a good one. Was it worth the time? That's what I want to ask. That I'm yet to determine. But we do need to finish off there. That is connective tissue. I do want to read some emails though. Hi, everyone.

[47:00] I'm Dr Mike here. If you enjoyed this video, please hit like and subscribe. We've got hundreds of others just like this. If you want to contact us, please do so on social media. We are on Instagram, Twitter and TikTok at Dr Mike Todarevic at D-R-M-I-K-E-T-O-D-O-R-O-V-I-C. Speak to you soon.

[47:20] you