Development of Animal Gametes

Hello everyone in this lesson. We are going to be talking about the development of animal gametes. So we're talking about gammy to genesis and specifically we're going to be talking about the creation of sperm sperm A genesis and the create of eggs. Oh A genesis. First off we're going to start with the production of sperm sperm A genesis but I want you guys to know that in animals there are very specific developmental systems that create sperm and egg and it's actually a pretty complex process. So let's start off with sperm A. To genesis which is going to be the process that creates the male gametes. So creates the male gametes and we all know that the male gametes are going to be sperm And how does this all begin? Well I have bowled id the cells that I want you guys to know. The first cell that becomes important in this step is going to be the the deployed primordial germ cells. The deployed primordial germ cells, you can pretty much think of these as like stem cells that are able to continuously divide to give cells to the process of sperm A genesis and they are going to be found in the Seminole forest tubules of the testes. In fact this entire process is going to happen in the seminal tubules of the testes and the epidemics of the testes. Okay, so the deployed primordial germ cells is going to be the beginning of this entire process and it is going to undergo mitosis to create the sperm ago. Nia. Now the deployed primordial germ cells have the two employee because they are deployed, they have two sets of chromosomes. And if they create these sperm Atago nia via mitosis, that means that the sperm ago nia are also deployed because mitosis makes cells that are exactly the same as the parent cell. So sperm ago niA are formed via the mitosis division of these primordial germ cells. Now these sperm Atago nia are then going to go on to create these primary spermatozoa sites. And these primary spermatozoa sites are also going to be made from the sperm ago niA via the process of mitosis. So since they are made via the process of mitosis, primary sperm sites are also going to be deployed cells. Now this is where the process of mitosis is going to begin. The primary spermatozoa sites are going to undergo one round of mitosis. So they're going to go through mitosis one to create these secondary spermatozoa sites. So since the primary spermatozoa sites underwent mitosis one to create secondary spermatozoa sites, what's going to be the employee of the secondary Permata sites, they are going to be hap Lloyd because all of the cells that are products of mitosis one only have one set of chromosomes. So they are going to be hap Lloyd cells. Okay, all right. So the secondary spur metis ites are to hap Lloyd cells formed via mitosis one and then the secondary spermatozoa sites are going to undergo mitosis too. And they are going to create these cells called sperm motives. Now now these sperm it'd cells are also going to be hap Lloyd because they are a product of my Asus. Now each of those two secondary spermatozoa sites are going to make two sperm. It'd now you may be thinking, okay, we've gotten to sperm it'd is that another word for sperm? Actually, no it's not. These are going to be immature sperm. So they are non motile, they cannot swim yet and they have no acro zone. So these are the immature sperm, they're not ready to be utilized to fertilize an egg quite yet. There's actually another step that they have to go through. So these sperm, it'd are non motile, they don't have their tails, they cannot swim and they don't have an acro zone which is, it's gonna be the cap on the head of the sperm. And this cap on the head of the sperm is utilized to actually penetrate into the egg. So those are very important qualifications and they are going to get these qualifications. Once they go through the process of sperm eo genesis, sperm mia genesis is basically like a maturation stage. The sperm kids are going to undergo maturation and they're going to turn into sperm cells and these are going to be fully developed sperm cells and that means that they are going to be motile and have an acro zone. So once the sperm have reached this point they are completely ready to go and they can now fertilize an egg if need be. And that is going to be the process of sperm a genesis. It's not as simple as we may think and remember guys that sperm is hap Lloyd. Okay, Alright, so now let's go down to a figure that might be helpful. Might be easier to understand than all of those words that I said right there. Okay, so let's just start again and then we'll go through this diagram. So it may help you guys remember this information. Okay, so you're going to have the sperm a Tego nie. Um and the sperm a Tego nie um is going to be a deployed cell that was created from the primordial germ cells. We're going to have the primordial germ cell and the primordial germ cell is going to create the sperm ago nia via the process of mitosis. And remember the primordial germ cell is deployed. Okay, so the sperm a Tego nie um is going to be created via the process of mitosis. And the sperm a Tego nie um is going to divide and it's going to create the primary sperm a to cite the primary sperm attack sites are going to be deployed as well because they are also made via the process of mitosis. From the sperm a Tego nie. Um and since the process of mitosis creates genetically identical daughter cells, the sperm a to sites are also deployed. Now this is where it gets interesting. The spermatozoa sites, the primary spermatozoa sites or spermatozoa site number one are going to undergo mitosis won the first stage in mitosis. So these primary spermatozoa sites are going to then go through mitosis. One to create these cells called secondary spermatozoa sites that are half Lloyd because the price this one are hap Lloyd. So now they only put this section because it's going to get repetitive basically. All of the or the secondary spermatozoa sites are going to divide like this. So the secondary spermatozoa are then going to undergo mitosis too. And they are going to create just you guys know this is sperm a toyed sperm a tides means the same exact thing. So they are going to create these sperm a tides which are also half Lloyd's. These are sperm it ids now remember that technically we're done with the cell divisions, but we're not done with the creation of sperm itself. And in fact, you're going to have to go through the maturation stage to generate the sperm that are motile and actually able to fertilize an egg. So these guys right here are going to be our fully mature sperm and they are going to be created via the process of sperm eo genesis. And this is going to happen. And this is going to give the ark a zonal cap to the end of the head of the sperm and it's going to create the tail of the sperm so that the sperm aren't able to move and swim around and they are able to fertilize the egg. So this is just a diagram of what I said above. Hopefully this is helpful. I like visual representations, they make it easier for me to understand what's going on. Okay guys, so now let's go down and let's talk about oo genesis. So 00 genesis is going to be the process of the creation of the female gametes and those are going to be eggs. Now. Oh genesis is very similar to sperm. A genesis in the different cell types that it has and the names of the cells that we have given them. But it is far far far more complicated and it is a little confusing I think. And oo genesis is going to be different from sperm. A genesis in one it's pretty complicated to it is going to have periods of rest or halt. The process stalls a lot. And this is going to be dealing with the coming to age of puberty, this is going to be dealing with ovulation, This is going to be dealing with pregnant, this is going to be dealing with menstruation. You're going to see that the creation of these eggs and the development of these eggs is going to start and stop, Start and stop, start, then stop. And guys, oh genesis is going to be really interesting because all of the oocytes, the primary oocytes that we will talk about in a second for a female are going to be created even before she is born but they don't finish developing until they are fertilized by a sperm which is really crazy. So and then females don't continue to make more eggs. Once they're done with the amount of eggs that they have once, they've used them all up, they will no longer create gametes. This is different than male's sperm A to genesis after puberty begins is going to continue for the rest of his life. So there are some major differences between these two forms of media genesis. But guys, let's get into talking about oh genesis and I will try to make this as easy as I can but don't feel bad, it can be kind of confusing. Okay, so again, we're going to start off with a deployed primordial germ cell just as we did in sperm a genesis and these are going to be deployed so they're going to be two in, they're going to have two sets of chromosomes. Again, guys think of these kind of stem cells that are able to divide to create the cells for this process and these are going to be found in the ovaries which are the female gonads. Now the deployed primordial germ cells are going to undergo mitosis to create the oh ago Nia, the ogoni A are going to be important cells that are going to then create the primary oocytes But because the ogoni A are made via mitosis, they are also deployed cells Okay now the Oh ago Nia are then going to create the primary oocytes also via the process of mitosis. So the primary oocytes are going to be deployed as well. Now these are going to be the cells that begin the process of mitosis. These cells, the primary oocytes are going to undergo the first round of mitosis. Now just you guys know all of the primary oocytes for a female have been made before she is born. So every single one of her egg cells that every single one of these cells that will become an egg has been turned into a primary oocyte at this time before she is born which is pretty crazy. And then it is going to go into pro phase one. So the primary oocyte is going to begin mitosis one but it is not going to finish my This one until the day of ovulation which can be years after the female is born. I believe the first age of menstruation in the first age of ovulation for most females is between the ages of 12 and 14. So those primary oocytes are waiting in the process of mitosis one for years at a time. So the primary oocytes are going to go through mitosis one. Now they are going to halt in mitosis one until ovulation and then the secondary oocyte and the first polar body are going to be made via mitosis one from the primary oocyte. Okay and this is going to happen at ovulation. Let me write this down for you guys. So this happens at ovulation and let me write this down for you guys. This happens the creation of primary oocytes happens before birth generally or very very soon after birth. Okay, so now that the follicle has decided that this particular egg or this particular cell is going to develop and be ovulating that primary oocyte when it is going to be ovulating it we'll finish my Asus one and it's going to create this secondary oocyte and this first polar body. Now because they are made via mitosis one the secondary oocyte and the first polar body are going to be hap Lloyd because they are the products of mitosis one. Now this is where it becomes kind of interesting in spermatozoa genesis. The cells are evenly made but in o genesis they're going to be unevenly made Whenever the primary oocyte divides into the secondary oocyte and the first polar body the secondary oocyte is going to be so much larger than the first polar body and that is going to be because the first polar body is going to be discarded. It is not going to be used, it will be recycled inside of the female. And the only usable cell is going to be the secondary oocyte the secondary oocyte is going to go through mitosis too. So the secondary oocyte is going to be ovulating. Okay, secondary oocyte is going to be ovulating and then it is going to enter the fallopian tube. Now it's going to undergo mitosis to to finish the production and create an egg. But only if it is fertilized. Which is crazy. So technically the cell that is fertilized by the egg is the secondary oocyte and the secondary oocyte only finishes mitosis to after the sperm has already engaged and penetrated into the egg. So may Asus two occurs in the secondary oocyte to create another unequal division of cytoplasm to create the ove. Um and the secondary polar bodies. So the album is going to be what we think of as the egg and the secondary polar body. It's going to be another cell that is going to be discarded basically. We don't use the polar bodies whatsoever. They're going to be discarded. Now the ovum is going to be the mature female gamete that is hap Lloyd. So both of those cells are gonna be hap Lloyd. Now the ovum is going to be made and it's gonna be a gigantic cell and this cell is the largest cell in the human body. Male or female. It is the largest cell in the human body I believe If I am correct, It's 10,000 times the size of a sperm and sometimes we can even see that particular cell without a microscope. It is so big which is insane. But it has to be so big to have all of the nutrients, the cytoplasm, the organelles, the cytoplasmic determinants for the zygote. So that one cell basically holds everything except the father's genetic material to create a new being. So it's going to be quite large, it's going to need all of those things. So then the ovum which is fertilized will then develop into the zygote and into the baby eventually. Okay, so I'm going to go through this again like I did with fermanagh genesis but in a figure because sometimes it's just easier to see it um in the figure. But I wanted to write for you guys just so you guys know me aosis to only finishes after fertilization. So mitosis to only finishes after fertilization. Do you guys know why this might happen? Why doesn't the secondary oocyte just go through my S. S to to create the egg and then the egg can wait around to be fertilized? Well they think that it's because why go through the trouble if the cell isn't going to be fertilized anyways then there's no point in going through the second round of mitosis. There's just no point. But if the sperm makes ca contact with the secondary oocyte and begins to fertilize it. Then it will finish the process of mitosis to and it will create the egg which then the eggs genetic material will fuse with the sperm's genetic material. And a zygote will be made. Okay guys, alright, so let's have a look at this figure which is going to be another representation of what I already told you guys. So we're going to have the primary oocyte. The primary oocyte is going to go through some maturation process is similar to the maturation that the sperm had to go through. And remember that the primary oocyte is going to undergo mitosis. One to create the secondary oocytes. We have let me write this, we have mitosis one. Now remember the primary oocyte is going to be deployed and whenever it goes through mitosis one, it is going to create the secondary oocyte and the first polar body, both of which are going to be hap Lloyd. You guys can see that the secondary oocyte is a lot bigger than the first polar body and the secondary oocyte is kept and generally the first polar body is discarded. You may see that it goes through mitosis too as well. Sometimes this happens. Sometimes it doesn't happen. All I want you guys to know is that all of the polar bodies will be discarded. They're not going to be utilized to create an egg or a zygote. They're just not utilized. So the secondary oocyte is going to go through mitosis two and once it goes through mitosis to it is going to create a hap Lloyd mature egg or ovum and it's going to create another polar body. So all of these polar bodies are going to be discarded. So all of these guys are going to be discarded and they will not be utilized. So what's another difference here that we can see between sperm A genesis and O genesis? What do you get from sperm A genesis? You should get four sperm, right, because you had four cells that were made at the end of stamina genesis or my Asus too. But what do you get out of O genesis? You get one cell and this is it? One cell is all you create via the whole process of media genesis. You get one egg cell. So obviously you can see that whenever they talk about reproductive energy, the female puts so much more energy into each of her gametes in comparison to the mail because she only makes one with each round of o genesis. While males make four with each round of spermatozoa genesis. And I mean she makes the largest, she makes the largest cell in the entire human body. That's pretty impressive as well. But this is going to be the basic understanding that I want you guys to know about the process of oo genesis. If you guys want to know when those steps happen. I mean like at ovulation or fertilization, you guys can learn that as well. But I don't think that it is going to be needed. What I think they want you to know is how these cells are going to divide. What types of cells are they going to create? Which ones are going to be discarded? Which ones are going to be kept? I think that's going to be the important thing to take away from this lesson. Okay guys, so I hope that was helpful. Just remember that gamma to genesis is the production of gametes. And specifically when you're talking about male gametes, it's called sperm A. To genesis and you create four sperm. And specifically when you're talking about females, it's O genesis and you create one egg. Okay, everyone, let's go on to our next lesson.