Cytoskeleton: Structure and Function

foreign engineers in this video today we're going to be talking about the structure and function of the cytoskeleton that includes microtubules that includes the intermediate filaments and the microfilaments which will go into each one individually going over the instruction and then subsequently their function before we get started if you guys like this video it helps you it makes sense please support us and the best way you can do that is by hitting that like button commenting down the comment section and please subscribe you guys already know that also if you guys really want to follow along with some great notes illustrations check that out on our website we'll have a link down in the description box below to take you there and check that out all right let's get started so cytoskeleton there's three primary components okay that's what I want you to remember microfilaments intermediate filaments and microtubules we're going to go through each one of these talking about their structure and subsequently their function so the first one being microfilaments the biggest thing to know about these is that these are going to be the smallest of all of the cytoskeletal elements so this is definitely going to be the smallest we should know what it's made up of so another name for a microfilament is actually known as actin this is another name for a microfilament and again I think the big thing to remember is it's going to be the smallest of the cytoskeletal elements but it's also going to be the most flexible which is a really cool kind of attribute to this so we have actin which is the primary microfilament now when we talk about this it's actually made up of these cool like little monomers so you have like these little monomers here and these are called G actin and what happens is if we take these G actin molecules together and we fuse them together we actually polymerize them and form something called a polymer in this case so we're going to form a polymer this is one of the polymers this is going to be called f actin so F actin so this is the polymer form so we take the G actin the individual monomers link them together like Legos and then eventually form F actin which is our polymer then what we're going to do is we're going to take two of these polymers and we're going to form this like double helix if you will of actin so this will be a f actin here and this will be an F actin here isn't that pretty cool so that's your actual structure of the microfilament actin and the question has to come from this which is what in the heck does actin do we know it's the smallest and we know it's the most flexible but it's obviously the key function of the cytoskeleton is to perform a in a job of being able to maintain the shape of the cell it's allowing for the the cell to be able to allow for particular movements and allowing for the cell to adapt to compressive forces and we'll go into that a little bit more detail so specifically with the microfilaments one of the cool things about this is that it can actually form like these it can little polymerize and cause a cell to be able to squeeze and change its morphology to fit through tiny spaces that's because of the flexibility Factor so one of the greatest examples of this is a process called diapedesis so there is a process called a diaphodesis I really want you guys to remember this and it's basically here you have your white blood cell so this is a white blood cell here and this is a white blood cell here what I can do is is I can literally through the actin molecules have it change the cell shape and if I have it change the cell shape it now may be able to squeeze itself through these tiny little capillary components here you see how now this poppy is squeezing through these actual spaces the intracellular clefs between these capillaries so this will allow for white blood cells to be able to squeeze and move out of the blood vessel and into the tissue spaces which is really important right because white blood cells are in the blood but then if there is a nasty pathogen let's say that's out here in the extracellular fluid here so it's actually sitting out in here into the interstitial spaces I want these white blood cells to be able to move out of the blood and into the interstitial spaces to go and fight these particular bacteria so they can you know phagocytize them and kill them right so that's really one of these cool processes is that actin molecules they will allow for the movement so they'll depolymerize and polymerize the different places and allow for the cell to change its shape and squeeze through tiny spaces tell me that's not cool the second thing that it can also do is something called cell division so there's different phases right of mitosis so we're not going to go through each one of these but there's prophase there's also something called metaphase then you have something called anaphase and then you have something called telophase and then technically there's this like little subsection here called cytokinesis and this is really a phase that's kind of like very Dynamic and pretty much an action and then here you get your two daughter cells this is the process of mitosis right so you start off with one cell and then at the end of this you form one one your two daughter cells now what actin does is it really kind of comes in here at this point and it forms like this constriction ring so imagine it forming kind of this like little squeezing ring that's going to kind of like pinch if you will these two cells apart it's going to create a little constriction ring I'm going to call this a constrictive ring a constriction ring if you will and it's going to pinch these two cells apart that's a really cool concept of the microfilaments or the actin function so one of the particular functions in cell division is it allows for it helps in stimulating the cyto Kinesis by separating using that acted constriction ring to separate one cell into two cells so that's a really cool function as well all right so so far we've covered cell migration allowing for it to change its shape to squeeze through small spaces and on top of that allows for it to form a constriction ring during cell division to separate one cell into two cells during the mitotic process okay let's come down a couple more functions of these microfilaments or actin is they can form cell extensions and this is really really cool so when we talk about these imagine here you have these like little extensions you see these kind of coming off of the cell so naturally you would have two parts of a cell membrane you would have this apical portion which we call like the top of the cell and then you would have this basal portion which we would call kind of like the bottom of the cell well on the apical surface the actin filaments can literally kind of form like the core of these like little projections so imagine here's your actin filaments and they're literally forming like the core of these like finger like projections or extensions that are coming off the apical surface they're pretty cool right and so what this allows for is these allow them to kind of have a little bit of movement and so it forms two particular things one as it forms something called the micro Villi and the microvilli are going to be the smallest cellular extension on the apical surface the other one is going to be What's called the stereocilia and they're going to be just a little bit bigger than the microvilli that are present on the apical surface so when you talk about these in comparison to size this one is small extension this one is larger extension that is actually formed by the actin filaments projecting out of the apical membrane giving these kind of like finger like projections Isn't that cool now you ask the question okay what do these finger like projections do I got you one of these is that they are super super prominent in the gastrointestinal tract so as food or fluids are running through your git they come into contact with these microvilli and what these do is they increase the surface area for digestion and absorption that's the primary function of microvilli so one of the big things to remember is they increase surface area for what in this case for digestion and absorption in the git that's pretty cool the stereocilia they actually beat and when they move they depending upon their movement it opens up little channels that are present on those actual little finger-like projections that are super involved in your inner ear and what they do is so they're involved in your inner ear your what's particularly there's different parts of your hearing so there's the vestibular function which is involved in your balance and then there's the cochlear function which is actually involved in hearing this is involved in both so it's involved in both balance and it's also involved in hearing and that's a really really important function so I want you to remember that microvilli are you know very very important cellular extensions formed by actin that are involved in increasing the surface area of the git and the stereocilia are going to be these actin extensions that are super involved in the inner ear which helps to play a role in balance and hearing okay the next component here my friends is the cell Junctions so this is basically helping the cells to stick to one another so here I have cell one here I have cell two I want these cells to stick to one another and not separate how do I do that I use these particular actin filaments they're a component of these cell Junctions we will talk about these a little bit more when we get into the video on Cell Junctions but in this concept here academic filaments are key in the formation of two particular types of cell Junctions which helps to keep cells tight together so it helps to be able to keep these cells it prevents the cells from prevents cells from separating which is a really cool thing and there's two particular types one is there's called tight junctions and we'll talk about these a little bit later and the other one is called adherence Junctions adherence Junctions and these are ones that are very very heavily involved with again utilizing actin as their primary one of their big components in these cell Junctions so so far we have cell migration allowing for the cell to kind of change its shape and squeeze through tiny little spaces in the blood vessels by blood cells this is called diapedesis we said cell division it's important that the last part of mitosis called cytokinesis where it forms a constriction ring to pop one cell into two cells we said it's involved particularly as well as in cellular extension so it's a core and the finger-like extensions that come off of the apical surface of the cell called small ones microvilli big ones stereocilia which one's in the inner ear stereo cilia which one's in the git for increasing surface area that's microvilli and then we also talked about cell Junctions how they're an integral and component into tight junctions and adherent Junctions preventing the cells from separating from one another and preventing things from being able to move in between these cells and we'll talk about that more in the cell Junction video another really cool thing is okay here these blue strands are actin here's my actin in the blue strands in these red strands here with these like spokes coming off here this is a motor protein which is associated called myosin and then here in the blue is called actin these make up something in our muscles called myofilaments so this one and this one with a combination of a couple other proteins make up the primary components of your myofilament and this is important being able to Aid in contraction so what happens is the myosin clicks on with the actin so it clicks on with the actin and once it clicks on I want you to imagine the myosin pulling the actin strands closer to one another and it'll basically cause these filaments to slide and to shorten this entire myofilament which shortens the muscle and that's critical in being able to allow for muscle contraction and relaxation so it's super super critical in muscle contraction heavily involved in ATP production as well heavily involved in ATP reduction all right the last one that's also really cool is it's involved in a process called endocytosis where we take things that are outside of the cell and bring them into the cell right and the way that we do that is that we may use these actin proteins to help to be able to create this like little invagination into the cell and suck the actual contents into the cell the other one is we may have what's called exocytosis and exocytosis may be taking these substances that are in the cell and pushing them out of the cell and again in order to be able to elicit this process we may need some of these actin molecules to fuse here with the cell membrane to engage it and then have fuse with the cell membrane to release the contents out so these are the things that the actin filaments or the microfilaments are involved in again Smalls most flexible made up of g-actin forming F actin that makes a polymer two polymers make a double helix of your microfilament it's involved in cell migration diapedesis it's involved in division cytokinesis it's involved in cellular extensions making microvilli and stereocilia it's involved in cell Junctions particularly tight junctions and adherence Junctions it's involved in muscle contractions associated with the motor protein myosin and whenever myosin binds to actin it shortens the filaments and has it shorten the muscle which which is involved in muscle contraction and finally it's important in being able to allow for things that are outside of the cell to come into the cell making a endosome or an endosome that's inside of the cell being secreted and pushed out of the cell this is endocytosis and exocytosis respectively okay my friends let's move on to the next cytoskeletal element which is your intermediate filaments all right my friends so now intermediate filaments are the next one so there's actually no like specific kind of monomer polymer type of thing or any specific thing that we actually when we compare to microfilaments how it was G actins to F actins to making two of those and making the entire double helix this one it's just this like you know decent sized it's actually you know I'd say again if based upon the name it's the middle child I'm literally going to write it down it's the middle child okay so it's not the smallest it's not the biggest but I will say it's probably the most resilient okay it's probably the most resilient or the most tough out of all of these types of uh cytoskeletal elements so it's a super strong tough resilient type of protein now one of the really cool things about intermediate filaments is that they can be used clinically and I find this like super interesting because when you think about it let's say that you have a tumor cell like you have melanoma right there's a particular intermediate filament that is present in the cells of your epithelium so let's say you're you know you have melanoma that spreads so you get into your bloodstream spreads and let's say it goes to your brain when they go and they actually resect the tumor out and they look at it and they do what's called immunohistochemistry they can use stains to find the intermediate filaments and depending upon which one it is well to determine where the actual tumor came from and so that's really cool because intermediate filaments can be used as what's called an immunohistochemical marker so it can be used kind of if you want to think about it it actually can be used as it was called a tumor marker and I think that'll make a little bit more sense after I explain something so different cells there's at least five different types main types of intermediate filaments that are actually very important the first one is the particular type of intermediate filaments that's super heavily coated with inside this is a maroonish color here heavily coated with inside the nucleus of almost every single cell in our entire body these are called lamins so lamins is heavily involved in the cellular nucleus and the epidermis so the actual epidermal cells there's a very specific type of intermediate filament that is specifically kind of coated within these ones you guys know what this one is this is called keratin this is called keratin there's another one I want you to dependent upon the connective tissue so it's found in different connective tissues right specifically if you were to use this cells that actually make connective tissue this is called fibroblasts so they're called fibroblasts there is a specific type of intermediate filament that's actually very heavily coated within these fibroblast cells that may connect to tissue you guys know what this one is this one is called a vimentin vimentin there's another one which is located in your muscle cells just going back here for keratin which is found in the epithelial cells just to remind yourself of that this is found within the EPA filial cells and then over here we have muscle cells so this is going to be your muscle cell so this can be your skeletal muscle cells this could be the smooth muscle cells the cardiac muscle cells but in these there's a very specific type of intermediate filament and this is called Desmond so it's called Desmond so so far we have lamins and the nucleus it's found in the nucleus of almost every single cell keratin and epithelial cells by mentin and fibroblaster connective tissue Desmond and muscle cells and the last one here is going to be found within neurons So within neurons there's actually going to be the easiest one to remember here thank goodness so here we have the intermediate filaments of muscle cells here in this one you're going to have neurofilaments oh thank goodness it's an easy one so neurofilaments so these are the different types of intermediate filaments that can be found in these primary tissues so what I was saying is let's say that you have a tumor here a melanoma right so for example what's really cool about this is let's say that someone has a tumor okay so here they have melanoma from their epithelium and then what happens is some of these cells break off get into your bloodstream and they spread and they go to the brain tissue so here's some of your neurons okay and then here you're going to have some of these cancerous epidermal cells that move through the blood and they get over here well when you go and you actually take and look at the intermediate filaments that are present in this brain tissue when you go and you actually maybe resect a piece of that tissue what you're going to find is different intermediate filaments so here you should have what neurofilaments that'll tell you okay that's brain tissue that's there but this one will tell you have keratin and what we can do is when we take this tissue we put it under a microscope and we actually stain it we'll be able to find keratin and say oh this was probably a melanoma that spread to the brain so that's a really cool kind of thing that we can utilize to our advantage all right intermediate filaments middle child meaning is the the middle in size it's bigger than the microfilaments smaller than the microtubules the most tough most resilient these are the five primary types that I want you to remember importance of this is understanding can be used as a tumor marker but what are some other functions to talk about with this one honestly it's really easy it's probably the easiest out of all of the actual cytoskeleton because this is definitely the most tough out of all of them so really I want you to think that it's going to resist compressive Force but resist compressive forces so that's really one of the biggest things so that whenever there's a lot of compression that's placed onto these cells these have the ability to keep and maintain the cell shape despite a lot of compressive forces so that's a really really cool thing so that they can maintain shape despite any type of compressive forces that's a really important thing my friends okay so that's really kind of highlights how powerful and how tough and how resilient these are the other thing is that they help to be able to keep cells together so here's cell one here's cell two and then here's what's called your basal lamina this is basically your connective tissue lining so you know epithelial cells they sit on a bed of connective tissue because generally the blood supplies within the basal lamina that supplies these epithelial cells well if I want to keep these two cells stuck together we already said actin was one actin helps to form cell Junctions by forming tight junctions and adherence Junctions well these are even tougher so these will really prevent cells from ripping apart and so because of that because these are super super intense types of cytoskeletal elements these will be the toughest of all of the of the actual cell Junctions you know what these are called these are called desmosomes so this one here this one here is called desmosomes and they are going to be the toughest of all of the cell Junctions it's really going to prevent cells from ripping apart very very common to have these particularly in cardiac tissue very common to have these in cardiac tissue because cardiac tissue has to be able to again sometimes they're having a lot of like stretching that's going on from filling with blood and Contracting and you can also find this in the epithelium so you can also find this in the epithelium as well the next one is we have to be able to Anchor the epithelial cells on a bed of connective tissue so we want to connect the epidermis to the dermis and so we have a very strong fiber here that's also kind of present that's very very critical and what is this that's the intermediate films that help to be able to link the cell to the connective tissue bed what is this one here this one is called hemidasmosomes so this is called Hemi desmosomes and this is basically helping to Anchor the cell this is cell to The extracellular Matrix desmosomes is between cell to cell that's important to remember but I think the big thing to take away from intermediate filaments is that they are the middle size but the most tough and resilient and so because of that they can maintain the shape of the cell the spike compressive forces and they can really prevent cells like cardiac tissue and epithelial tissue from separating apart via desmosomes and they can prevent the separation of the epithelium from the dermis via hemidezmosomes all right my friends that covers the intermediate filaments now move on to the next and the last and the biggest of all of them the microtubules all right my friends off to the last one the microtubules the biggest and the baddest of them this one's actually a really cool one it has a lot of cool functions and a lot of different structures that we have to talk about but when we talk about microtubes so we talked about how microfilaments are made up of G act and they forms f-actin which forms polymers and then we take two of those and make a double helix right then we talked about intermediate filaments it wasn't anything special there wasn't any particular things that we needed to know for the synthesis of it you just need to know the five types lamins keratin vimentin Desmond and neurofilaments because those were the big big types of intermediate filaments that cover the main tissue types and we talked about how you know the microfilaments are involved in cell migration cytokinesis they're also involved in cell extensions cell to cell Junctions and they're also involved in muscle contraction and membrane transport endo and exocytosis whereas intermediate filaments are involved primarily in really maintaining cell shape despite compressive forces and really sticking cell to cell together desmosomes cell the connective tissue together hemidesmosomes microtubules are a little bit more uh Suave right they get a little more kind of finesse to it so they're a little bit cooler so here we have these particular proteins that make them up so we have something called a alpha tubulin and a beta tubulin okay so this these proteins here are called turbulence how ironic right then we're going to do is we're going to take these tubulins together we're going to fuse them together and then we get a dimer so we literally get a tubulin dimer and generally in order for these diameters to be able to kind of get added on and to make these generally it requires some degree of GTP to be added into this process what we do is we take the tubulin dimers and we just kind of click and click and click and click and we make this long chain and we actually call this a Proto filament not even kidding we call it a protofilament this is just basically a bunch of tubulin dimers strung up together into a bead and then what we do is we take 13 of these protofilaments together and make them into this hollow tube so we take 13 of these poppies and we make this hollow tube and this is your micro tubule so you see how there's a lot of things that go into this one another thing is there's a degree of kind of anatomy um with respect to the ends of the microtubules which I'll discuss a little bit later but there is what's called a positive end of the microtubule and a minus end of the microtubule what I like to use to remember this is that the minus n or the negative in points towards the nucleus of a cell and the positive n usually points towards the periphery of this cell and we'll go over this when we talk about the next component which is axonal transporter intracellular transport because that's one of the really great things that these microtubules can do they're basically the railroads of the cell but the big thing for microtubules is that these are really the largest of all of the cytoskeletal elements they have some degree of flexibility into them as well they're not as tough and resilient as intermediate filaments they're not as flexible as the actin or microfilaments so they're kind of in between so what are some of the functions of the microtubules if you will one of the really really cool ones is that they play a role in what's called intracellular transport another way that we like to design this one is it's very the best example of this is what's called axonal transport this is literally the most perfect example of how the microtubules play a role in transporting things across the cell like the railroads of the cell if you will so here in the center so this is what's called your Axon right this is the axon terminal this is where basically neurotransmitters are being released and then here we have the body of the axon or I'm sorry I have the neuron I apologize now when things are being transported up and down this neuron in other words from the body to the axon terminal axon terminal to the body we depend upon these microtubules here and then how would I tell you again if I said this is the end of the microtubule pointing towards the nucleus this would be the minus end or the negative end negative n points towards the nucleus the positive end would be the end pointing towards the periphery of the cell or the end that's not pointing towards the nucleus okay so this is our microtubule what's really cool is that there is little cute little motor proteins here and what these motor proteins do is they use this microtubule as their railroad system and what they can do is they can carry things in different directions so in other words I could use this protein to travel from the positive end to the minus end and I could use this protein to travel from the minus end to the positive end in order to understand this transport which is moving from the minus end to the positive and for the positive n to the minus n we have to talk about these enzymes and then talk about the name of that transport so the first one here this enzyme we're going to put a K on him a K on his chest this is called kinesin this is called kinesin and kinesin does something called Antero grade transport and this is important right and we also can say that if it's anterior grade transport it's moving things from the minus end to the positive end you guys have to remember that so the minus into the positive end kinesin is really good because if we think about integrated transport it's taking things like vesicles you know what this vesicle may contain neurotransmitters so make carry vesicles containing neurotransmitters from where from the body to the axon terminal because now these will fuse at here and then release those neurotransmitters out Isn't that cool so they contain things like neurotransmitters or other proteins that we have to move from the body to the axon terminal and the other way and we use this microtubules of the way of being able to transport these things down but the proteins are what help us to be able to carry those things down all right what's the name of this other motor protein so this other motor protein we're going to put a you know Put Some D's on that chest it's a little odd gotta be careful there this is called dynein so Dyne is important for the opposite it's carrying things from the axon terminal towards the cell body so this will be called retrograde retrograde transport and again important to remember that we can also say that this is going from the positive n to the minus end of the microtubule so it's using the microtubule as of the railroad to carry particular things from the positive n to the minus n towards the nucleus important maybe I need to carry something from like an old organelle that needs to go up to the cell body to get destroyed for a particular reason like the lysosomes it's you know he's lived his life good you know goodbye I'm carrying old organelles back it's just an example right and that's a really really important thing to be able to understand so again when we talk about axonal transport the microtubes can be used as the railroad to carry things up and down the actual neuron from axon terminal to the body this is retrograde utilizing or it could be going from the cell body towards the axon terminal this is going to be anterior grade transport utilizing kinesin these are going to be your motor proteins that are utilizing the microtubule as their railroad to carry things up and down the cell that's important okay next thing that we're going to talk about besides this aspect is cell movement so cell movement's really really cool so you know these microtubules they can actually help in making something on sperm cells so here we have a sperm cell and on the sperm cell there is this little thing here called the flagella and the flagella is important for being able to give the sperm cell a degree of motility so whips back and forth back and forth and helping the sperm to be able to propel through the actual female uterus up to find that ovum and the same concept here we have let's say this is an epithelium of some type this is an epithelium of some type and this epithelium has these like little extensions coming off their membrane so there was microvilli there was stereocilia guess what the last one is just Celia this one is called cilia and Cilia are also important because if you think about this one of the best examples of epithelium you can think about this as the respiratory tract Pretend This is mucus that's present within the airway and you need to be able to propel that mucus out of your actual respiratory tract to spit it out or cough it out the Cilia will beat they'll create like a propulsive action to move this mucus in the proper direction so that's the two things that microtubules help with is sperm motility and ciliary function to beat things like mucus out of the airway you can also find this in the Fallopian tubes as well if you think about that the Fallopian tubes if there was the egg Pretend This Is The Egg and you want to move it after you've actually fertilized it so the sperm cell found the egg fertilized it and you want to move this from the actual fallopian tube towards the actual uterine lining the Cilia and the Fallopian tubes will beat it towards the actual uterus that's cool right the cell maintains its shape through a cytoskeleton the cytoskeleton includes the thread-like microfilaments which are made of protein and microtubules which are thin hollow tubes the respiratory tract is lined with cells that have cilia these are microscopic hair-like projections that can move in waves this feature helps trap inhaled particles in the air and expels them when you cough another unique feature in some cells is flagella some bacteria have flagella a flagellum is like a little tail that can help a cell move or Propel itself the only human cell that has a flagellum is a sperm cell now what we have to do is is we have to take a second though because this is sometimes questioned in your actual exams when you take and look at the structure because you're like you're like wait a second microtubules I can get how they can be involved in axonal transport but how are they involved in making flagella and Cilia they're like cellular extensions if you will yeah let's talk about that so I want to look at the flagella and I want to look at the Cilia at two levels so what I want to do is I actually want to come a little bit different here I want to look at the base so we're going to start off here right here right here and I'm going to chop this cilia and I'm going to chop the actual flagella right at the base so we're going to start at the base of the flagella in the base of the Cilia when you cut it and you create a transverse section this is what it looks like and it's actually really really cool because what you're going to notice here as you're going to notice these triplets so you notice this triplet here how many are there three four five six seven eight nine nine triplets you know what that actually is interesting we call this nine times three orientation so that means that there is nine groups here and each one of these groups contains three microtubules so how many microtubules make up the base of this cilia and flagella 27 microtubules so that means that I can have upwards of 27 microtubules that can make up the base of this cilia and flagella so again this is for the flagella this is also for the Cilia we give this a particular name we don't like to call it the base so we just add a little bit to it we call it two names so we actually call it the centriole but the preferred name when it's applied to the flagella and the Cilia is actually called the basal body it's actually called the basal body so it's easy to remember because it's at the base of the Cilia and the flagella now as we go upwards so imagine that this actual kind of silly or flagella is continuing upwards and I'm just taking another section of it so as I continue to go upwards here I cut a little bit farther down so then I go all the way out maybe to this point or this point of the Cilia and the flagella so now I'm getting towards the top of the Cilia and the flagella it takes a tiny bit of a difference in anatomy and structure so again this is for the flagella and this is for the Cilia at this point here what do we notice okay let's count how many of these we have we have doublets here one two three four five six seven eight nine nine doublets plus two in the center of that actual flagella and Cilia so two in the center you know we say this one is this is nine times two plus two so that means that there's doublets so there's two microtubules here and then nine groups of them plus two in the center so that means that there's 18 microtubules in the periphery and then two microtubules in the center for a total of 20 microtubules that make up these dang cilia and flagella this is also known as the axoneme so they call it this part the axo neem so we have the two components of the silly and the flagella one is we can call it two names we can call it the centriole technically though it should be called the basal body for flagella and Cilia that's the nine times three Arrangement nothing in the center as we go further up the Cilia and the flagella we come to the axonine which is towards the top of the psyllium flagella that loses that triplet and now it becomes doublets and you have the doublet in the center there okay this is the big structural thing that you have to understand for the components of the flagella and the cilio so we know what they do and we know what the makeup of it is the last component of the microtubules is that they're also involved in cell division which one of them uh cytoskeletal elements was also involved in cell division you guys remember the microfilaments particularly actin was involved in cytokinesis well this one can do a couple different things so here we start off our mitosis with prophase then we go into something called metaphase right so we have prophase interface and then you have metaphase then you have what's called anaphase I'm just hitting the big ones that are relevant and pertinent to this case the microtubules telophase and then we come to the last one which is basically you undergo cytokinesis and you separate and you make one cell two cells now prophase interphase not too worried about that we kind of condense down the actual DNA into chromosomes and then what we do is we line the chromosomes up along the center axis of the actual cell and then at the ends at the ends if you will I'm going to kind of do this in this color here we have these things here that will actually I'm sorry that we're going to form at the opposite pole so they have to form the opposite poles so they'll form down here the opposite ends so we have the actual chromosomes that'll line up along this axis here and then we'll have these things which are part of microtubules lining at these ends and we're going to do the same thing here so what these are which are really interesting here we're going to kind of make like a cross this is microtubules but they're conformed into two things so you know how we have a microtubule and a 9 times 3 Arrangement what was that called when you take a 9 times 3 arrangement of a microtubule that was called a centriole right we said if it was particular for the flagella or the Cilia it was called a basal body but for right now we're going to call this a centriole if we take two centrioles this makes something called a Centro Zone that is what's right there at these ends so the centrosomes which are made up of two centrioles which is made above 27 microtubules so in this case it'd be 27 times two these are going to form at the ends so there's one Central there's a second centriole second centriole second Central these are making your centrosomes these will form at the ends here and what they'll do is they'll give off these things called mitotic spindles and these mitotic spindles will extend all the way from the centrosome and connect all the way to the chromosomes so if you imagine here here is a centrosome here here is a centrosome here and I'm just going to draw one of these chromosomes I'm going to zoom in on one of them here's your centromere of the chromosome right around the edge there's this protein component called the kinetochore it's called the kinetochore these centrosomes will create these things called mitotic spindles that'll click and connect with the kineto core of this chromosome and then what they'll do is is they'll start to kind of pull and separate these the chromosome this is a sister chromatid this is a sister chromatid we're going to separate these apart so this is metaphase right here then what I'm going to do is I'm gonna start pulling the sister chromatids apart so what would that look like that would look like this where now I've separated the sister chromatids and I get this so you see how now what I did is I just separated these poppies so what I would do is I would literally kind of disintegrate this kind of bond here and then what you would get as a result out of this is you would get the separation of the sister chromatids and then they would start going to opposite ends of the cell so here they were in the middle at this point they'll start moving towards the opposite ends towards the center Zone then at the end of it we'll have them start to kind of like create like this little divot in the cell so that we can start beginning to separate the genetic material between these two cells because we want to be able to create two cells out of this and this is going to be the telophase and then eventually the whole goal would be to take this genetic material and to put this into these two cells and have an equal amount of that material there Isn't that cool so that's what the microtubes are involved in they're helping to make something called a centrosome the centrosome from it extends all the way out to the chromosomes via these structures here what are these called mitotic spindles which connect to the chromosomes at the kinetochore and separate them during the cell division process that's the microtubules so my friends in this video we covered all these things about the cytoskeleton we cover their structure we cover their function in great detail I hope it made sense and I hope that you guys enjoyed it love you thank you and as always until next time [Music]

foreign engineers in this video today we&#39;re going to be talking about the structure and function of the cytoskeleton that includes microtubules that includes the intermediate filaments and the microfilaments which will go into each one individually going over the instruction and then subsequently their function before we get started if you guys like this video it helps you it makes sense please support us and the best way you can do that is by hitting that like button commenting down the comment section and please subscribe you guys already know that also if you guys really want to follow along with some great notes illustrations check that out on our website we&#39;ll have a link down in the description box below to take you there and check that out all right let&#39;s get started so cytoskeleton there&#39;s three primary components okay that&#39;s what I want you to remember microfilaments intermediate filaments and microtubules we&#39;re going to go through each one of these talking about their structure and subsequently their function so the first one being microfilaments the biggest thing to know about these is that these are going to be the smallest of all of the cytoskeletal elements so this is definitely going to be the smallest we should know what it&#39;s made up of so another name for a microfilament is actually known as actin this is another name for a microfilament and again I think the big thing to remember is it&#39;s going to be the smallest of the cytoskeletal elements but it&#39;s also going to be the most flexible which is a really cool kind of attribute to this so we have actin which is the primary microfilament now when we talk about this it&#39;s actually made up of these cool like little monomers so you have like these little monomers here and these are called G actin and what happens is if we take these G actin molecules together and we fuse them together we actually polymerize them and form something called a polymer in this case so we&#39;re going to form a polymer this is one of the polymers this is going to be called f actin so F actin so this is the polymer form so we take the G actin the individual monomers link them together like Legos and then eventually form F actin which is our polymer then what we&#39;re going to do is we&#39;re going to take two of these polymers and we&#39;re going to form this like double helix if you will of actin so this will be a f actin here and this will be an F actin here isn&#39;t that pretty cool so that&#39;s your actual structure of the microfilament actin and the question has to come from this which is what in the heck does actin do we know it&#39;s the smallest and we know it&#39;s the most flexible but it&#39;s obviously the key function of the cytoskeleton is to perform a in a job of being able to maintain the shape of the cell it&#39;s allowing for the the cell to be able to allow for particular movements and allowing for the cell to adapt to compressive forces and we&#39;ll go into that a little bit more detail so specifically with the microfilaments one of the cool things about this is that it can actually form like these it can little polymerize and cause a cell to be able to squeeze and change its morphology to fit through tiny spaces that&#39;s because of the flexibility Factor so one of the greatest examples of this is a process called diapedesis so there is a process called a diaphodesis I really want you guys to remember this and it&#39;s basically here you have your white blood cell so this is a white blood cell here and this is a white blood cell here what I can do is is I can literally through the actin molecules have it change the cell shape and if I have it change the cell shape it now may be able to squeeze itself through these tiny little capillary components here you see how now this poppy is squeezing through these actual spaces the intracellular clefs between these capillaries so this will allow for white blood cells to be able to squeeze and move out of the blood vessel and into the tissue spaces which is really important right because white blood cells are in the blood but then if there is a nasty pathogen let&#39;s say that&#39;s out here in the extracellular fluid here so it&#39;s actually sitting out in here into the interstitial spaces I want these white blood cells to be able to move out of the blood and into the interstitial spaces to go and fight these particular bacteria so they can you know phagocytize them and kill them right so that&#39;s really one of these cool processes is that actin molecules they will allow for the movement so they&#39;ll depolymerize and polymerize the different places and allow for the cell to change its shape and squeeze through tiny spaces tell me that&#39;s not cool the second thing that it can also do is something called cell division so there&#39;s different phases right of mitosis so we&#39;re not going to go through each one of these but there&#39;s prophase there&#39;s also something called metaphase then you have something called anaphase and then you have something called telophase and then technically there&#39;s this like little subsection here called cytokinesis and this is really a phase that&#39;s kind of like very Dynamic and pretty much an action and then here you get your two daughter cells this is the process of mitosis right so you start off with one cell and then at the end of this you form one one your two daughter cells now what actin does is it really kind of comes in here at this point and it forms like this constriction ring so imagine it forming kind of this like little squeezing ring that&#39;s going to kind of like pinch if you will these two cells apart it&#39;s going to create a little constriction ring I&#39;m going to call this a constrictive ring a constriction ring if you will and it&#39;s going to pinch these two cells apart that&#39;s a really cool concept of the microfilaments or the actin function so one of the particular functions in cell division is it allows for it helps in stimulating the cyto Kinesis by separating using that acted constriction ring to separate one cell into two cells so that&#39;s a really cool function as well all right so so far we&#39;ve covered cell migration allowing for it to change its shape to squeeze through small spaces and on top of that allows for it to form a constriction ring during cell division to separate one cell into two cells during the mitotic process okay let&#39;s come down a couple more functions of these microfilaments or actin is they can form cell extensions and this is really really cool so when we talk about these imagine here you have these like little extensions you see these kind of coming off of the cell so naturally you would have two parts of a cell membrane you would have this apical portion which we call like the top of the cell and then you would have this basal portion which we would call kind of like the bottom of the cell well on the apical surface the actin filaments can literally kind of form like the core of these like little projections so imagine here&#39;s your actin filaments and they&#39;re literally forming like the core of these like finger like projections or extensions that are coming off the apical surface they&#39;re pretty cool right and so what this allows for is these allow them to kind of have a little bit of movement and so it forms two particular things one as it forms something called the micro Villi and the microvilli are going to be the smallest cellular extension on the apical surface the other one is going to be What&#39;s called the stereocilia and they&#39;re going to be just a little bit bigger than the microvilli that are present on the apical surface so when you talk about these in comparison to size this one is small extension this one is larger extension that is actually formed by the actin filaments projecting out of the apical membrane giving these kind of like finger like projections Isn&#39;t that cool now you ask the question okay what do these finger like projections do I got you one of these is that they are super super prominent in the gastrointestinal tract so as food or fluids are running through your git they come into contact with these microvilli and what these do is they increase the surface area for digestion and absorption that&#39;s the primary function of microvilli so one of the big things to remember is they increase surface area for what in this case for digestion and absorption in the git that&#39;s pretty cool the stereocilia they actually beat and when they move they depending upon their movement it opens up little channels that are present on those actual little finger-like projections that are super involved in your inner ear and what they do is so they&#39;re involved in your inner ear your what&#39;s particularly there&#39;s different parts of your hearing so there&#39;s the vestibular function which is involved in your balance and then there&#39;s the cochlear function which is actually involved in hearing this is involved in both so it&#39;s involved in both balance and it&#39;s also involved in hearing and that&#39;s a really really important function so I want you to remember that microvilli are you know very very important cellular extensions formed by actin that are involved in increasing the surface area of the git and the stereocilia are going to be these actin extensions that are super involved in the inner ear which helps to play a role in balance and hearing okay the next component here my friends is the cell Junctions so this is basically helping the cells to stick to one another so here I have cell one here I have cell two I want these cells to stick to one another and not separate how do I do that I use these particular actin filaments they&#39;re a component of these cell Junctions we will talk about these a little bit more when we get into the video on Cell Junctions but in this concept here academic filaments are key in the formation of two particular types of cell Junctions which helps to keep cells tight together so it helps to be able to keep these cells it prevents the cells from prevents cells from separating which is a really cool thing and there&#39;s two particular types one is there&#39;s called tight junctions and we&#39;ll talk about these a little bit later and the other one is called adherence Junctions adherence Junctions and these are ones that are very very heavily involved with again utilizing actin as their primary one of their big components in these cell Junctions so so far we have cell migration allowing for the cell to kind of change its shape and squeeze through tiny little spaces in the blood vessels by blood cells this is called diapedesis we said cell division it&#39;s important that the last part of mitosis called cytokinesis where it forms a constriction ring to pop one cell into two cells we said it&#39;s involved particularly as well as in cellular extension so it&#39;s a core and the finger-like extensions that come off of the apical surface of the cell called small ones microvilli big ones stereocilia which one&#39;s in the inner ear stereo cilia which one&#39;s in the git for increasing surface area that&#39;s microvilli and then we also talked about cell Junctions how they&#39;re an integral and component into tight junctions and adherent Junctions preventing the cells from separating from one another and preventing things from being able to move in between these cells and we&#39;ll talk about that more in the cell Junction video another really cool thing is okay here these blue strands are actin here&#39;s my actin in the blue strands in these red strands here with these like spokes coming off here this is a motor protein which is associated called myosin and then here in the blue is called actin these make up something in our muscles called myofilaments so this one and this one with a combination of a couple other proteins make up the primary components of your myofilament and this is important being able to Aid in contraction so what happens is the myosin clicks on with the actin so it clicks on with the actin and once it clicks on I want you to imagine the myosin pulling the actin strands closer to one another and it&#39;ll basically cause these filaments to slide and to shorten this entire myofilament which shortens the muscle and that&#39;s critical in being able to allow for muscle contraction and relaxation so it&#39;s super super critical in muscle contraction heavily involved in ATP production as well heavily involved in ATP reduction all right the last one that&#39;s also really cool is it&#39;s involved in a process called endocytosis where we take things that are outside of the cell and bring them into the cell right and the way that we do that is that we may use these actin proteins to help to be able to create this like little invagination into the cell and suck the actual contents into the cell the other one is we may have what&#39;s called exocytosis and exocytosis may be taking these substances that are in the cell and pushing them out of the cell and again in order to be able to elicit this process we may need some of these actin molecules to fuse here with the cell membrane to engage it and then have fuse with the cell membrane to release the contents out so these are the things that the actin filaments or the microfilaments are involved in again Smalls most flexible made up of g-actin forming F actin that makes a polymer two polymers make a double helix of your microfilament it&#39;s involved in cell migration diapedesis it&#39;s involved in division cytokinesis it&#39;s involved in cellular extensions making microvilli and stereocilia it&#39;s involved in cell Junctions particularly tight junctions and adherence Junctions it&#39;s involved in muscle contractions associated with the motor protein myosin and whenever myosin binds to actin it shortens the filaments and has it shorten the muscle which which is involved in muscle contraction and finally it&#39;s important in being able to allow for things that are outside of the cell to come into the cell making a endosome or an endosome that&#39;s inside of the cell being secreted and pushed out of the cell this is endocytosis and exocytosis respectively okay my friends let&#39;s move on to the next cytoskeletal element which is your intermediate filaments all right my friends so now intermediate filaments are the next one so there&#39;s actually no like specific kind of monomer polymer type of thing or any specific thing that we actually when we compare to microfilaments how it was G actins to F actins to making two of those and making the entire double helix this one it&#39;s just this like you know decent sized it&#39;s actually you know I&#39;d say again if based upon the name it&#39;s the middle child I&#39;m literally going to write it down it&#39;s the middle child okay so it&#39;s not the smallest it&#39;s not the biggest but I will say it&#39;s probably the most resilient okay it&#39;s probably the most resilient or the most tough out of all of these types of uh cytoskeletal elements so it&#39;s a super strong tough resilient type of protein now one of the really cool things about intermediate filaments is that they can be used clinically and I find this like super interesting because when you think about it let&#39;s say that you have a tumor cell like you have melanoma right there&#39;s a particular intermediate filament that is present in the cells of your epithelium so let&#39;s say you&#39;re you know you have melanoma that spreads so you get into your bloodstream spreads and let&#39;s say it goes to your brain when they go and they actually resect the tumor out and they look at it and they do what&#39;s called immunohistochemistry they can use stains to find the intermediate filaments and depending upon which one it is well to determine where the actual tumor came from and so that&#39;s really cool because intermediate filaments can be used as what&#39;s called an immunohistochemical marker so it can be used kind of if you want to think about it it actually can be used as it was called a tumor marker and I think that&#39;ll make a little bit more sense after I explain something so different cells there&#39;s at least five different types main types of intermediate filaments that are actually very important the first one is the particular type of intermediate filaments that&#39;s super heavily coated with inside this is a maroonish color here heavily coated with inside the nucleus of almost every single cell in our entire body these are called lamins so lamins is heavily involved in the cellular nucleus and the epidermis so the actual epidermal cells there&#39;s a very specific type of intermediate filament that is specifically kind of coated within these ones you guys know what this one is this is called keratin this is called keratin there&#39;s another one I want you to dependent upon the connective tissue so it&#39;s found in different connective tissues right specifically if you were to use this cells that actually make connective tissue this is called fibroblasts so they&#39;re called fibroblasts there is a specific type of intermediate filament that&#39;s actually very heavily coated within these fibroblast cells that may connect to tissue you guys know what this one is this one is called a vimentin vimentin there&#39;s another one which is located in your muscle cells just going back here for keratin which is found in the epithelial cells just to remind yourself of that this is found within the EPA filial cells and then over here we have muscle cells so this is going to be your muscle cell so this can be your skeletal muscle cells this could be the smooth muscle cells the cardiac muscle cells but in these there&#39;s a very specific type of intermediate filament and this is called Desmond so it&#39;s called Desmond so so far we have lamins and the nucleus it&#39;s found in the nucleus of almost every single cell keratin and epithelial cells by mentin and fibroblaster connective tissue Desmond and muscle cells and the last one here is going to be found within neurons So within neurons there&#39;s actually going to be the easiest one to remember here thank goodness so here we have the intermediate filaments of muscle cells here in this one you&#39;re going to have neurofilaments oh thank goodness it&#39;s an easy one so neurofilaments so these are the different types of intermediate filaments that can be found in these primary tissues so what I was saying is let&#39;s say that you have a tumor here a melanoma right so for example what&#39;s really cool about this is let&#39;s say that someone has a tumor okay so here they have melanoma from their epithelium and then what happens is some of these cells break off get into your bloodstream and they spread and they go to the brain tissue so here&#39;s some of your neurons okay and then here you&#39;re going to have some of these cancerous epidermal cells that move through the blood and they get over here well when you go and you actually take and look at the intermediate filaments that are present in this brain tissue when you go and you actually maybe resect a piece of that tissue what you&#39;re going to find is different intermediate filaments so here you should have what neurofilaments that&#39;ll tell you okay that&#39;s brain tissue that&#39;s there but this one will tell you have keratin and what we can do is when we take this tissue we put it under a microscope and we actually stain it we&#39;ll be able to find keratin and say oh this was probably a melanoma that spread to the brain so that&#39;s a really cool kind of thing that we can utilize to our advantage all right intermediate filaments middle child meaning is the the middle in size it&#39;s bigger than the microfilaments smaller than the microtubules the most tough most resilient these are the five primary types that I want you to remember importance of this is understanding can be used as a tumor marker but what are some other functions to talk about with this one honestly it&#39;s really easy it&#39;s probably the easiest out of all of the actual cytoskeleton because this is definitely the most tough out of all of them so really I want you to think that it&#39;s going to resist compressive Force but resist compressive forces so that&#39;s really one of the biggest things so that whenever there&#39;s a lot of compression that&#39;s placed onto these cells these have the ability to keep and maintain the cell shape despite a lot of compressive forces so that&#39;s a really really cool thing so that they can maintain shape despite any type of compressive forces that&#39;s a really important thing my friends okay so that&#39;s really kind of highlights how powerful and how tough and how resilient these are the other thing is that they help to be able to keep cells together so here&#39;s cell one here&#39;s cell two and then here&#39;s what&#39;s called your basal lamina this is basically your connective tissue lining so you know epithelial cells they sit on a bed of connective tissue because generally the blood supplies within the basal lamina that supplies these epithelial cells well if I want to keep these two cells stuck together we already said actin was one actin helps to form cell Junctions by forming tight junctions and adherence Junctions well these are even tougher so these will really prevent cells from ripping apart and so because of that because these are super super intense types of cytoskeletal elements these will be the toughest of all of the of the actual cell Junctions you know what these are called these are called desmosomes so this one here this one here is called desmosomes and they are going to be the toughest of all of the cell Junctions it&#39;s really going to prevent cells from ripping apart very very common to have these particularly in cardiac tissue very common to have these in cardiac tissue because cardiac tissue has to be able to again sometimes they&#39;re having a lot of like stretching that&#39;s going on from filling with blood and Contracting and you can also find this in the epithelium so you can also find this in the epithelium as well the next one is we have to be able to Anchor the epithelial cells on a bed of connective tissue so we want to connect the epidermis to the dermis and so we have a very strong fiber here that&#39;s also kind of present that&#39;s very very critical and what is this that&#39;s the intermediate films that help to be able to link the cell to the connective tissue bed what is this one here this one is called hemidasmosomes so this is called Hemi desmosomes and this is basically helping to Anchor the cell this is cell to The extracellular Matrix desmosomes is between cell to cell that&#39;s important to remember but I think the big thing to take away from intermediate filaments is that they are the middle size but the most tough and resilient and so because of that they can maintain the shape of the cell the spike compressive forces and they can really prevent cells like cardiac tissue and epithelial tissue from separating apart via desmosomes and they can prevent the separation of the epithelium from the dermis via hemidezmosomes all right my friends that covers the intermediate filaments now move on to the next and the last and the biggest of all of them the microtubules all right my friends off to the last one the microtubules the biggest and the baddest of them this one&#39;s actually a really cool one it has a lot of cool functions and a lot of different structures that we have to talk about but when we talk about microtubes so we talked about how microfilaments are made up of G act and they forms f-actin which forms polymers and then we take two of those and make a double helix right then we talked about intermediate filaments it wasn&#39;t anything special there wasn&#39;t any particular things that we needed to know for the synthesis of it you just need to know the five types lamins keratin vimentin Desmond and neurofilaments because those were the big big types of intermediate filaments that cover the main tissue types and we talked about how you know the microfilaments are involved in cell migration cytokinesis they&#39;re also involved in cell extensions cell to cell Junctions and they&#39;re also involved in muscle contraction and membrane transport endo and exocytosis whereas intermediate filaments are involved primarily in really maintaining cell shape despite compressive forces and really sticking cell to cell together desmosomes cell the connective tissue together hemidesmosomes microtubules are a little bit more uh Suave right they get a little more kind of finesse to it so they&#39;re a little bit cooler so here we have these particular proteins that make them up so we have something called a alpha tubulin and a beta tubulin okay so this these proteins here are called turbulence how ironic right then we&#39;re going to do is we&#39;re going to take these tubulins together we&#39;re going to fuse them together and then we get a dimer so we literally get a tubulin dimer and generally in order for these diameters to be able to kind of get added on and to make these generally it requires some degree of GTP to be added into this process what we do is we take the tubulin dimers and we just kind of click and click and click and click and we make this long chain and we actually call this a Proto filament not even kidding we call it a protofilament this is just basically a bunch of tubulin dimers strung up together into a bead and then what we do is we take 13 of these protofilaments together and make them into this hollow tube so we take 13 of these poppies and we make this hollow tube and this is your micro tubule so you see how there&#39;s a lot of things that go into this one another thing is there&#39;s a degree of kind of anatomy um with respect to the ends of the microtubules which I&#39;ll discuss a little bit later but there is what&#39;s called a positive end of the microtubule and a minus end of the microtubule what I like to use to remember this is that the minus n or the negative in points towards the nucleus of a cell and the positive n usually points towards the periphery of this cell and we&#39;ll go over this when we talk about the next component which is axonal transporter intracellular transport because that&#39;s one of the really great things that these microtubules can do they&#39;re basically the railroads of the cell but the big thing for microtubules is that these are really the largest of all of the cytoskeletal elements they have some degree of flexibility into them as well they&#39;re not as tough and resilient as intermediate filaments they&#39;re not as flexible as the actin or microfilaments so they&#39;re kind of in between so what are some of the functions of the microtubules if you will one of the really really cool ones is that they play a role in what&#39;s called intracellular transport another way that we like to design this one is it&#39;s very the best example of this is what&#39;s called axonal transport this is literally the most perfect example of how the microtubules play a role in transporting things across the cell like the railroads of the cell if you will so here in the center so this is what&#39;s called your Axon right this is the axon terminal this is where basically neurotransmitters are being released and then here we have the body of the axon or I&#39;m sorry I have the neuron I apologize now when things are being transported up and down this neuron in other words from the body to the axon terminal axon terminal to the body we depend upon these microtubules here and then how would I tell you again if I said this is the end of the microtubule pointing towards the nucleus this would be the minus end or the negative end negative n points towards the nucleus the positive end would be the end pointing towards the periphery of the cell or the end that&#39;s not pointing towards the nucleus okay so this is our microtubule what&#39;s really cool is that there is little cute little motor proteins here and what these motor proteins do is they use this microtubule as their railroad system and what they can do is they can carry things in different directions so in other words I could use this protein to travel from the positive end to the minus end and I could use this protein to travel from the minus end to the positive end in order to understand this transport which is moving from the minus end to the positive and for the positive n to the minus n we have to talk about these enzymes and then talk about the name of that transport so the first one here this enzyme we&#39;re going to put a K on him a K on his chest this is called kinesin this is called kinesin and kinesin does something called Antero grade transport and this is important right and we also can say that if it&#39;s anterior grade transport it&#39;s moving things from the minus end to the positive end you guys have to remember that so the minus into the positive end kinesin is really good because if we think about integrated transport it&#39;s taking things like vesicles you know what this vesicle may contain neurotransmitters so make carry vesicles containing neurotransmitters from where from the body to the axon terminal because now these will fuse at here and then release those neurotransmitters out Isn&#39;t that cool so they contain things like neurotransmitters or other proteins that we have to move from the body to the axon terminal and the other way and we use this microtubules of the way of being able to transport these things down but the proteins are what help us to be able to carry those things down all right what&#39;s the name of this other motor protein so this other motor protein we&#39;re going to put a you know Put Some D&#39;s on that chest it&#39;s a little odd gotta be careful there this is called dynein so Dyne is important for the opposite it&#39;s carrying things from the axon terminal towards the cell body so this will be called retrograde retrograde transport and again important to remember that we can also say that this is going from the positive n to the minus end of the microtubule so it&#39;s using the microtubule as of the railroad to carry particular things from the positive n to the minus n towards the nucleus important maybe I need to carry something from like an old organelle that needs to go up to the cell body to get destroyed for a particular reason like the lysosomes it&#39;s you know he&#39;s lived his life good you know goodbye I&#39;m carrying old organelles back it&#39;s just an example right and that&#39;s a really really important thing to be able to understand so again when we talk about axonal transport the microtubes can be used as the railroad to carry things up and down the actual neuron from axon terminal to the body this is retrograde utilizing or it could be going from the cell body towards the axon terminal this is going to be anterior grade transport utilizing kinesin these are going to be your motor proteins that are utilizing the microtubule as their railroad to carry things up and down the cell that&#39;s important okay next thing that we&#39;re going to talk about besides this aspect is cell movement so cell movement&#39;s really really cool so you know these microtubules they can actually help in making something on sperm cells so here we have a sperm cell and on the sperm cell there is this little thing here called the flagella and the flagella is important for being able to give the sperm cell a degree of motility so whips back and forth back and forth and helping the sperm to be able to propel through the actual female uterus up to find that ovum and the same concept here we have let&#39;s say this is an epithelium of some type this is an epithelium of some type and this epithelium has these like little extensions coming off their membrane so there was microvilli there was stereocilia guess what the last one is just Celia this one is called cilia and Cilia are also important because if you think about this one of the best examples of epithelium you can think about this as the respiratory tract Pretend This is mucus that&#39;s present within the airway and you need to be able to propel that mucus out of your actual respiratory tract to spit it out or cough it out the Cilia will beat they&#39;ll create like a propulsive action to move this mucus in the proper direction so that&#39;s the two things that microtubules help with is sperm motility and ciliary function to beat things like mucus out of the airway you can also find this in the Fallopian tubes as well if you think about that the Fallopian tubes if there was the egg Pretend This Is The Egg and you want to move it after you&#39;ve actually fertilized it so the sperm cell found the egg fertilized it and you want to move this from the actual fallopian tube towards the actual uterine lining the Cilia and the Fallopian tubes will beat it towards the actual uterus that&#39;s cool right the cell maintains its shape through a cytoskeleton the cytoskeleton includes the thread-like microfilaments which are made of protein and microtubules which are thin hollow tubes the respiratory tract is lined with cells that have cilia these are microscopic hair-like projections that can move in waves this feature helps trap inhaled particles in the air and expels them when you cough another unique feature in some cells is flagella some bacteria have flagella a flagellum is like a little tail that can help a cell move or Propel itself the only human cell that has a flagellum is a sperm cell now what we have to do is is we have to take a second though because this is sometimes questioned in your actual exams when you take and look at the structure because you&#39;re like you&#39;re like wait a second microtubules I can get how they can be involved in axonal transport but how are they involved in making flagella and Cilia they&#39;re like cellular extensions if you will yeah let&#39;s talk about that so I want to look at the flagella and I want to look at the Cilia at two levels so what I want to do is I actually want to come a little bit different here I want to look at the base so we&#39;re going to start off here right here right here and I&#39;m going to chop this cilia and I&#39;m going to chop the actual flagella right at the base so we&#39;re going to start at the base of the flagella in the base of the Cilia when you cut it and you create a transverse section this is what it looks like and it&#39;s actually really really cool because what you&#39;re going to notice here as you&#39;re going to notice these triplets so you notice this triplet here how many are there three four five six seven eight nine nine triplets you know what that actually is interesting we call this nine times three orientation so that means that there is nine groups here and each one of these groups contains three microtubules so how many microtubules make up the base of this cilia and flagella 27 microtubules so that means that I can have upwards of 27 microtubules that can make up the base of this cilia and flagella so again this is for the flagella this is also for the Cilia we give this a particular name we don&#39;t like to call it the base so we just add a little bit to it we call it two names so we actually call it the centriole but the preferred name when it&#39;s applied to the flagella and the Cilia is actually called the basal body it&#39;s actually called the basal body so it&#39;s easy to remember because it&#39;s at the base of the Cilia and the flagella now as we go upwards so imagine that this actual kind of silly or flagella is continuing upwards and I&#39;m just taking another section of it so as I continue to go upwards here I cut a little bit farther down so then I go all the way out maybe to this point or this point of the Cilia and the flagella so now I&#39;m getting towards the top of the Cilia and the flagella it takes a tiny bit of a difference in anatomy and structure so again this is for the flagella and this is for the Cilia at this point here what do we notice okay let&#39;s count how many of these we have we have doublets here one two three four five six seven eight nine nine doublets plus two in the center of that actual flagella and Cilia so two in the center you know we say this one is this is nine times two plus two so that means that there&#39;s doublets so there&#39;s two microtubules here and then nine groups of them plus two in the center so that means that there&#39;s 18 microtubules in the periphery and then two microtubules in the center for a total of 20 microtubules that make up these dang cilia and flagella this is also known as the axoneme so they call it this part the axo neem so we have the two components of the silly and the flagella one is we can call it two names we can call it the centriole technically though it should be called the basal body for flagella and Cilia that&#39;s the nine times three Arrangement nothing in the center as we go further up the Cilia and the flagella we come to the axonine which is towards the top of the psyllium flagella that loses that triplet and now it becomes doublets and you have the doublet in the center there okay this is the big structural thing that you have to understand for the components of the flagella and the cilio so we know what they do and we know what the makeup of it is the last component of the microtubules is that they&#39;re also involved in cell division which one of them uh cytoskeletal elements was also involved in cell division you guys remember the microfilaments particularly actin was involved in cytokinesis well this one can do a couple different things so here we start off our mitosis with prophase then we go into something called metaphase right so we have prophase interface and then you have metaphase then you have what&#39;s called anaphase I&#39;m just hitting the big ones that are relevant and pertinent to this case the microtubules telophase and then we come to the last one which is basically you undergo cytokinesis and you separate and you make one cell two cells now prophase interphase not too worried about that we kind of condense down the actual DNA into chromosomes and then what we do is we line the chromosomes up along the center axis of the actual cell and then at the ends at the ends if you will I&#39;m going to kind of do this in this color here we have these things here that will actually I&#39;m sorry that we&#39;re going to form at the opposite pole so they have to form the opposite poles so they&#39;ll form down here the opposite ends so we have the actual chromosomes that&#39;ll line up along this axis here and then we&#39;ll have these things which are part of microtubules lining at these ends and we&#39;re going to do the same thing here so what these are which are really interesting here we&#39;re going to kind of make like a cross this is microtubules but they&#39;re conformed into two things so you know how we have a microtubule and a 9 times 3 Arrangement what was that called when you take a 9 times 3 arrangement of a microtubule that was called a centriole right we said if it was particular for the flagella or the Cilia it was called a basal body but for right now we&#39;re going to call this a centriole if we take two centrioles this makes something called a Centro Zone that is what&#39;s right there at these ends so the centrosomes which are made up of two centrioles which is made above 27 microtubules so in this case it&#39;d be 27 times two these are going to form at the ends so there&#39;s one Central there&#39;s a second centriole second centriole second Central these are making your centrosomes these will form at the ends here and what they&#39;ll do is they&#39;ll give off these things called mitotic spindles and these mitotic spindles will extend all the way from the centrosome and connect all the way to the chromosomes so if you imagine here here is a centrosome here here is a centrosome here and I&#39;m just going to draw one of these chromosomes I&#39;m going to zoom in on one of them here&#39;s your centromere of the chromosome right around the edge there&#39;s this protein component called the kinetochore it&#39;s called the kinetochore these centrosomes will create these things called mitotic spindles that&#39;ll click and connect with the kineto core of this chromosome and then what they&#39;ll do is is they&#39;ll start to kind of pull and separate these the chromosome this is a sister chromatid this is a sister chromatid we&#39;re going to separate these apart so this is metaphase right here then what I&#39;m going to do is I&#39;m gonna start pulling the sister chromatids apart so what would that look like that would look like this where now I&#39;ve separated the sister chromatids and I get this so you see how now what I did is I just separated these poppies so what I would do is I would literally kind of disintegrate this kind of bond here and then what you would get as a result out of this is you would get the separation of the sister chromatids and then they would start going to opposite ends of the cell so here they were in the middle at this point they&#39;ll start moving towards the opposite ends towards the center Zone then at the end of it we&#39;ll have them start to kind of like create like this little divot in the cell so that we can start beginning to separate the genetic material between these two cells because we want to be able to create two cells out of this and this is going to be the telophase and then eventually the whole goal would be to take this genetic material and to put this into these two cells and have an equal amount of that material there Isn&#39;t that cool so that&#39;s what the microtubes are involved in they&#39;re helping to make something called a centrosome the centrosome from it extends all the way out to the chromosomes via these structures here what are these called mitotic spindles which connect to the chromosomes at the kinetochore and separate them during the cell division process that&#39;s the microtubules so my friends in this video we covered all these things about the cytoskeleton we cover their structure we cover their function in great detail I hope it made sense and I hope that you guys enjoyed it love you thank you and as always until next time [Music]

Transcript for:Cytoskeleton: Structure and Function

Transcript for:
Cytoskeleton: Structure and Function