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Current time:0:00Total duration:19:54

Embryonic stem cells

Video transcript

where we left off after the mitosis videos is that we had two gametes we had a sperm and an egg let me draw the sperm so you had the sperm and then you had an egg I mean we'll do an egg in a different color that's the egg and we all know how this story goes the sperm fertilizes the egg and all a whole cascade of events start occurring the the walls of the egg then become impervious to other sperm so that only one sperm can get in but that's not the focus of this video the focus of this video is how this fertilized egg develops once it has become a zygote so after its fertilized you're now so we remember from the meiosis videos that each of these were haploid haploid or that they had I added an extra I there or that or that they had half the contingency of the DNA haploid as soon as the sperm fertilizes this egg now all of a sudden you have a diploid zygote let me do that so now let me pick a nice color so now you're going to have a diploid zygote that's going to have 2n a 2n complement of the DNA material or you can or kind of the full complement of what a normal cell in our human body would have so this is diploid and it's a zygote which is just enough fancy way of saying the fertilized egg and it's now ready to essentially turn into an organism so immediately after fertilization the zygote starts experiencing cleavage and that's well it's experiencing mitosis that's the mechanism but it doesn't increase a lot in size so just you know this one right here will then turn into it'll just split up via mitosis into two like that and of course these are each 2n and then those are going to split into four like that and each of these are all have the the same exact genetic complement as that first zygote and it keeps splitting and this this this mass of cells we can start calling it this right here this is referred to as the more EULA more EULA and it actually comes from the word for mulberry because it looks like a mulberry selection let me just kind of simplify things a little bit because we have to start here so we start with a zygote so I go this is a fertilized egg it just starts duplicating via mitosis and you end up with a with a ball of cells it's often not going to be a power of two because these cells at least in the initial stages are all duplicating it all at once and then you have this more ela more ela now once the more ela gets to about 16 cells or so and we're talking about four or five days this isn't an exact process they start differentiating differentiating a little bit where the outer cells and this kind of turns into a sphere let me make it a little bit more sphere like so you had it starts differentiating between let me make some outer cells and this would be a cross-section of it it's really going to be look more like a sphere that's the outer cells and then you have your inner cells on the inside these outer cells these outer cells are going to be called or are called the trophoblast different color tro fo trophoblast let me scroll over now I go there and then the inner cells and this is kind of the crux of what this video is all about let me scroll down a little bit the inner cells look at suitable color the inner cells right there are called the embryo blast embryo blast and then what's going to happen is some fluid is going to start filling in some of this gap between the embryo blast and the trophoblast so you're going to start having some fluid that comes in there and so this the Moorilla will eventually look like this where the trophoblast or the outer membrane is kind of this huge sphere of cells and this is all happening as keep replicating mitosis is the mechanism so now my trophoblast is going to look like that and then my embryo blast is going to look like this sometimes the embryo blasts oh let me so this is the embryo blast embryo blast sometimes it's also called the inner cell mass so let me write that inner inner cell mass and this is what's going to turn into the organism and so just just so you know a couple of the labels that are involved here if we're dealing with a mammalian organism and we are mammals we call this thing that the Moorilla turned into as a zygote then amarilla then the cells of the maurella started to differentiate into the trophoblast we're kind of the outside cells and then the embryo blasts and then you have this the space that forms here and this is just fluid fluid it's called the Blastoise seal blasto seal a very non-intuitive spelling of the seal part of blasto seal but once this is formed this is called a blastocyst that's the entire thing right here let me scroll down a little bit this whole thing is called the blastocyst and this is the case in humans in humans now it can be a very confusing topic because a lot of times in a lot of books on biology you'll say hey you go from the Moorilla to the blast chiller the blast o spear stage let me write those words down so you know sometimes we'll say maurella and you go to blastula blastula and sometimes it's called blast o fear blast o spear and I want to make it very clear that these are essentially the same stages in development these are just four but you know in a lot of books they'll start talking about you know frogs or tadpoles or things like that and this applies to them while we're talking about mammals especially the ones that are closely related the stage is the blastocyst stage and the real differentiator is when people talk about just blastula and blast those fears there isn't necessarily this differentiation between this these outermost cells and these these embryonic or this embryo blast or this inner inner cell mass here but since this the focus of this video is humans and really that's where I wanted to start from because that's what we are and that's what's interesting we're going to focus on the blastocyst now everything I've talked about in this video it was really to get to this point because what we have here these little green cells that I drew right here in the blastocyst this inner cell mass this is what will turn into the organism and you say okay Sal if that's the organism what's all of this what's all of this these purple cells out here this this trophoblast out there that is going to turn into the placenta and I'll do a future video where in a human it'll turn into a placenta so let me write that down it'll turn into the placenta I'll do a whole future video about I guess how babies are born and I could learn a ton about that this past year because I a baby was born in our house but the placenta is really kind of what the what the embryo develops inside of and it's it's the interface between especially in humans and in mammals between the developing fetus and its mother so it kind of is the exchange mechanism that that separates their two systems but allows the necessary functions to go on between them but that's not the focus of this video the focus of this video is the fact that these cells which at this point are they've differentiated themselves away from the placenta cells but they still haven't decided what they're going to become you know maybe this cell and it's it's descendants may eventually start becoming part of the nervous system while these cells right here might become muscle tissue while these cells right here might I don't know might become might become the liver these cells right here are called embryonic stem cells and probably the first time in this video you're hearing a term that you might recognize so if I were to just take one of these cells and actually just to introduce you another as soon as as soon as we you know we have this zygote here as soon as it starts dividing each of these cells are called a blast omere and you're probably wondering Sal why does this word blast keep appearing in this in this kind of embryology videos this you know these development videos and that comes from it comes from the Greek for Spore Blastoise so you know it's just as the organism is beginning to Spore or out or grow but I won't go into the the word origins of it but that's where it comes from and that's why everything has this blast in it so these are blastomeres so when I talk about embryonic stem cells I'm talking about the individual blastomeres inside of this embryo blast or inside of this inner cell mass these words are actually unusually fun to say so each of these is an embryonic stem cell let me write this down and in a vibrant color because this is a so each of these right here our embryonic stem cells and I wanted to get to this in embryonic stem cells and the reason why these are interesting and I think you already know is that there's a huge debate around these one these have the potential to turn into anything that they have this this plasticity that's another word that you might hear let me write that down to plasticity and the word essentially comes from you know like a plastic can turn into anything else when some when we sit when we say that something has plasticity we're talking about its potential to turn into a lot of different things so the theory is and there's already some trials that seem to substantiate this especially in some lower organisms that look if you have some damage at some point in your body if you have some damage let's let me draw a nerve cell let me say I have a you know I won't go into the the actual mechanics of a nerve cell but let's say that we have some damage at some point on a nerve cell right there and because of that you know someone is paralyzed or there's some nerve too strong function we're dealing with multiple sclerosis or who knows what the idea is is look we have these cells here that could turn into anything we could that could turn to anything as you know and we're just really understanding how it knows what to turn into it really has to look at its environment say hey what's what are the guys around me doing and maybe that's what helps dictate what it does but the idea is you take these things that could turn into anything and you put them where the damage is so you start you layer and where the damage is and then they can turn into the cell that they need to turn into so they were in this case they would turn into nerve cells they would turn into nerve cells and repair the damage and you know maybe a cure the paralysis for that individual so there's it's a huge exciting area of research and you could even in theory grow new organs if someone needs a kidney transplant or a heart transplant maybe in the future we could take a colony of these embryonic stem cells maybe we can put them in some type of other creature or who knows what and we can turn it into a replacement heart or replacement kidney so there's a huge a huge amount of excitement about what these can do I mean they could cure a lot of formerly uncurable diseases or provide you know hope for a lot of patients who might otherwise die but obviously there's a debate here and the debate all revolves around the issue of when if you were to go in here and try to extract one of these cells you're going to kill this embryo you're going to kill this developing embryo and that developing embryo had the potential to become a human being so you know and I'll put it it it's it's a potential it obviously has to be in the right environment and it has to you know have a willing mother and and and all of the rest but it does have the potential and so for if you if for those especially I think in the pro-life camp who say hey you know this is this anything that has a potential be a human being that's that's that is life and it should not be killed so people on the on that side of the camp they they're against you know the destroying of this embryo and and I'm not making this video to takes either sides of that argument but you know it's a potential to turn into a human being it's a potential right so obviously there's a huge amount of debate but now now you know in this video what people are talking about when they say embryonic stem cells well and obviously the next question is say hey well why don't they just call them stem cells as opposed to end Briona stem cells and that's because in in all of our bodies you do have what are called somatic stem cells let me write that down so matic or adult stem cells and we all have them there in our bone marrow to help produce red blood cells other parts of our body but the problem with somatic stem cells is they're not as plastic so not as plastic which means that they can't form any type of cell in the human body there's an area of research where people actually may be trying to make them more plastic and if they are they are able to take these somatic stem cells and make them more plastic it might might maybe kill the need to have these embryonic stem cells although if they may be if they do this too good maybe these will have the potential to turn into human beings as well so that could become a debatable issue but right now this isn't an area of debate because left to their own devices a somatic stem cell or a adult stem cell won't turn into a human being while an embryonic one if it is implanted in a in a willing mother then of course it will turn into a human being and I want to make one side note here because I don't want to take any sides on the debate of you know of well I mean the facts are facts this does have the potential to turn to a human being but it also has the potential to save millions of lives those both of those statements are facts and then you can decide on your own which side of that argument you'd like to or what side of that balance you would like to kind of put your own opinion on but there's one thing I want to talk about that's that in the public debate is never brought up so you know you have this notion of when you want to get an embryonic stem cell line and when when I say a stem cell line I mean you take a couple of stem cells or let's say you take one stem cell and then you put it in a petri dish and then you allow it to just duplicate so this one turns into two those two turn into four then someone could take one of these and then put it in their own petri dish these are a stem cell line they all came from one unique embryonic stem cell or what what initially was a blastomeres so that's what they call about a stem cell line so the debate obviously is when you start a embryonic stem cell line you are destroying an embryo but I want to make the point here that their embryos are being destroyed and in other processes and namely in vitro fertilization in vitro fertilization and maybe this will be my next video fertilization and this is just the notion that they take a set of eggs out of a mother is usually a couple that's having trouble having a child and they take a bunch of eggs out of the mother so let's say they take maybe ten to thirty eggs out of out of the mother they actually perform a surgery take them take them out of the ovaries of the mother and then they fertilize them with with with semen either it might come from the father or a sperm donor so then all of these become zygotes once they're fertilized with semen so these all become zygotes and then they allow them to develop and they usually allow them to develop to the blastocyst stage so eventually these all of these turn into blastocyst they have a blasto seal in the center which is that which is that this area of fluid they have of course they have of course the embryo the inner cell mass in them and what they do is they look at the ones that they deem or healthier or maybe you know the ones that are at least just not unhealthy and they'll take a couple of these and they'll implant these into the mother so all of this is occurring in a petri dish so maybe these before look good so they're going to take these four and they're going to implant these into a mother and if all goes well maybe one of these will turn into will give the couple a child so this one will develop and maybe the other ones won't but you know if you've seen John and eight John and Kate Plus eight you know that many times they implant a lot of them in there just to increase the probability that you get at least one child but every now and then they implant seven or eight and then you end up with eight kids and that's why in vitro fertilization often results in kind of these you know multiple births and or reality television shows on cable but what do they do with all of these other perfectly well I won't say perfectly viable but these are embryos they may or may not be perfectly viable but you know you have the embryos that have the potential just like just like this one right here these all have the potential to turn into a human being but most fertility clinics they roughly half of them they either throw these away they destroy them they allow them to die a lot of these are frozen but just the process of freezing them kills them and then bonding them kills them again so most of these most of these the process of in vitro fertilization for every one child that has a potential to develop into a full-fledged human being you're actually destroying tens of very viable embryos so at least my take on it is if you're against and I generally don't want to take a side on this but if you are against in if you are against and you know research that involves embryonic stem cells embryonic stem cells because of the destruction of embryos on that same I guess philosophical ground you should also be against in vitro fertilization in vitro fertilization because both of these are involved the destruction of zygotes I think no i won't i won't talk more about this because i really don't want to take sides but i want to show that there is kind of a an equivalence here that's completely lost in this debate on whether embryonic stem cells should be used because they have a destruction of embryos because you're destroying just as many embryos in this well I won't say just as many but you are destroying embryos there's hundreds of thousands of embryos that get destroyed and get frozen and obviously destroyed in that process as well through this in vitro fertilization process so anyway now hopefully you have the tools to kind of engage in the debate around stem cells and you see that it all comes from what we learned about you know meiosis they provoke paper they produce these these these gametes the one the male gamete fertilizes a female gamete the zygote happens or gets created and start splitting up the more eula and then it turns in and then it keeps splitting and it differentiates into the blastocyst and then this is where the stem cells are so you already know enough science to engage in kind of a ver a heated debate