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Current time:0:00Total duration:6:54

Video transcript

we've given a lot of importance to individual cells and that's for good reason cells are the basic unit of life and they are fascinating in their own right as we've seen in other videos there's a whole universes in inside of cells there's a lot more complexity than many of us might have guessed before really studying cells but how do we go from cells to tissues so when you know if you look at your even if you look at your skin how do you go to that tissue of your skin or the your tendons or if you think about the you know your your heart's tissues or the different organs tissues how do you go from a tissue which of course eventually will then get you to a full multicellular organism so all the tissues and organs together you're going to get the whole organism how do the cells get together coordinate structure themselves to form me or you and the answer is in or at least it involves something called the extracellular matrix extra cellular cellular matrix and just as we talked about the insides of a cell not just being a bunch of organelles floating around that we have a cytoskeleton that gives the inside of a cell structure and allows it to even potentially move and divide and transport things so if you assume that this this blob right over here is a cell what I just drew in yellow that would be its cytoskeleton on the inside but there's also an analogous thing on the outside that helps coordinate how does how the cells all relate to each other and that's what we're talking about when we talk about the extracellular the extracellular matrix and it's made up of a bunch of different types of fibers and proteins and glycoproteins and probably the most notable of these is collagen so I'll do collagen and yellow right over here so these could be collagen strands of collagen right over here and collagen is actually the most common protein in mammals it makes up it makes up approximately so this is collagen in the yellow right over there and it makes up approximately I've seen estimates of 25 to 35 percent but I'll just go it it makes up approximately 30 percent of the proteins in mammals 30% of mammalian I'll say mammal mammal protein so 30 roughly 30% of the protein in your body is collagen and a lot of it is making up these strands that make up that help make up it's not the only protein found that help make up the extra cellular matrix and you see these cells here these these things that I've drawn they are kind of embedded in this and they're the way I've drawn it there can be fixed they look like they're a little bit you know they're attached to this matrix and it helps position them and it is true that the extracellular matrix the collagen of fibers and other things that we find there help attach the stress cells and structure the cells into tissues but they also help inform the cell let the cell know when to grow when to divide even potentially when to die or when to produce different types of molecules and to get a little bit deeper to understand what's actually going on how the cell actually attaches if we were to zoom in let's say we were to zoom in right over there on that square so I'm zooming in on the cellular membrane we could get to this bigger picture that is taking up that is taking up most of the screen right over here so view this is like a zoomed in representation so right over here this is inside the cell inside this is inside the cell here and we can see that we even have we have some we have an actin microfilament right over here and that helps form this is part of the cytoskeleton and then you have the collagen fibers which is making up which is making up part of the extracellular matrix and then we see that we get it all gets attached with these proteins and these proteins they're class of proteins called integrins integrins and they are embedded in the membranes of cells and through other fibers it's something like a fibronectin they can be attached to the broader the true to the broader extracellular matrix and this is fascinating because it obviously structurally connects this extracellular I guess you could say structure this extracellular matrix to the inside of the cell to the cytoskeleton through these proteins and as I mentioned these proteins help kind of lodge things together lock them in place but they can also be used to signal they can sense tension depending on what type of cells you have they can signal for for the cell itself to to get active or deactivate in some interesting way so it's a it's a fascinating thing and I want to make it very clear to you a lot of times when you're studying biology even an introductory biology class you'll see things in like this in textbooks it's like oh of course we have integrand proteins that are you know going across our cellular membrane and they're attached to things like fibronectin and they're attached to the cytoskeleton and the and and and they get attached to the you know the collagen fibers throughout the extracellular matrix and it seems like all of the biology has already figured out but the real answer is how all of these things actually work together and how they signal to each other and how cells know what to do based on how much stress or tension or how crowded a certain area is these are areas of open research in fact everything that I'm talking about if you were to delve a little bit deeper and I encourage you to do web searches on these you'll find current research papers where people are saying well how exactly does an integral know what to do or how does it exactly signal to the cell or how does it exactly form a bind itself to the either the cytoskeleton or the extracellular matrix these are all interesting areas of research and people going to be researching them for some times because there's always more questions or how these incredibly complex proteins and glycoproteins like a fibronectin is a glycoprotein it's it's proteins where the side chains have have have have have have carbohydrate chains brands sakurai chains branching off of them and so how do all of these things interact and how do they kind of quote unquote know what to do and how do all these complex signaling mechanisms work so it's a fascinating area of research but hopefully this gives you an appreciation for even a further appreciation for the complexity that makes you you we've already talked about cells themselves being complex but now they are lodged in this extracellular matrix which helps us better define tissues and helps to let the cells live in this community and know how to relate to each other and know a little and have a little bit of signaling from their outside environment and you know I've just drawn one one kind of integrating complex right over here but you would have many along cell and these aren't the membrane and these aren't the only proteins the fascinating things about cellular membranes you'll often just see them drawn as this lipid bilayer they have all sorts of protein that are lodged inside of them that are used as receptors allow certain molecules in and certain molecules out so they really are almost you know cities unto themselves and then they interact with their with their broader environment as well
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