 Okay everybody, Dr. Rill. So we're going to look at gametogenesis, which is the production of a gamete, but in a female it's called oogenesis, where it was spermatogenesis in males. So oogenesis are the production of this functional egg that can be fertilized to become a zygote. So we're going to start at the top with the oogonia, which is what I call it, the oogonia, which is the stem cell. So notice we have mitosis, that 2N means these cells are diploid or diploid, they have two sets of chromosomes. So when they undergo mitosis, now we have two primary oocytes that are still diploid. So they have too much genetic material to be a sex cell yet. Notice that the one on the left becomes the oogonium again, so that's how stem cells work. They produce a new cell plus another stem cell, so they can constantly be churning out new cells. So now we have the primary oocyte, and now this is going to undergo meiosis 1, and it's going to be stopped here at prophase 1, but this is really cool. All this has happened before birth. So the cells that are going to become the functional oocytes later in life, that happened while a girl is in her mother's womb, these oocytes are starting to develop. So this happens before puberty. So it's very, very fascinating. I guess think about it kind of like an apple obviously has the seeds inside of it already, but it's just pretty cool that the next generation is already getting started while a female is in her mother's womb. But the downside here is this means that a female is never genetically isolated from their offspring, and that means that if something happens, if a kid is exposed to chemicals at a very young age, it can affect their sex cells. If it's a girl, it can affect their sex cells in ways that it really can affect male sex cells. So you could say that a male is genetically or isolated from their offspring until puberty, because that's when all this process begins. So I don't know how big of a deal it is, but it's just kind of worth noting. So all this has happened before birth. Now then the female is born and goes through life until puberty. So the process is going to kick back in when we get to puberty. But prior to this point, so when this female was born, she probably had one or two million of these primary oocytes. They're going to undergo a process called atresia where many of them are just going to degrade and wear away. Maybe 400,000 left by the time this girl reaches puberty, only going to need a few hundred of them anyways, but there's a lot of them there. So this is all that's happened prior to puberty. Then we have the initiation of ovulation. So the first time that the ovarian cycle works, and we have that spike in luteinizing hormone leading to an oocyte rupturing out or a follicle rupturing out of the ovary, is going to be what triggers this for the rest of a woman's reproductive years until menopause. This process will occur every 28 days. We'll talk about that in more detail in a separate video. But this is what's going to move. So once that happened, once the girls reach puberty, now meiosis one resumes, as you can see there, and we're going to have our primary oocyte finally becoming a secondary oocyte. So that process took from when before that girl was born until that girl reached puberty, and now we have these secondary oocytes developing. So then you see here on the left side, you have that one functional cell. On the right side, we have what are called polar body. So with sperm production, one primary sex cell becomes four functional sperm. In females, you only need one egg at a time, one oocyte at a time. So one primary sex cell becomes one functional oocyte or egg, and the rest can become either a single or three up to three more polar bodies, which are degraded and recycled. So that's another kind of interesting tidbit. It's different in males and females. So the last thing here or the last step here, as you can also see, which is just so fascinating. So this process began before birth and then it picked back up at puberty, but it doesn't actually finish until sperm penetrates this oocyte. So this the cell is stuck there at metaphase two until it says before sperm penetration. So once sperm penetrates the egg, this oocyte, the egg will finish oocyte production and then it will complete myosis. And for an instant, it will be this functional oocyte. But then the second that occurs, it's going to fuse with that sperm that's made it through into the oocyte and then it's going to become a zygote. So whereas the sperm that produces an offspring has been a sperm for as long as it's been born, right? If you want to look at it that way, the oocyte has not been a fully functional oocyte until it with the moment of penetration from the sperm. So that's pretty cool. One last thing to note here that as you can see in the bottom picture there, the sperm is really only, only going to be contributing DNA. The cytoplasm is all from the egg, which means that the oocyte or the egg is going to be nourishing this cluster of cells until it reaches the uterus. But the other reason that's important is that the mom, mom's responsible for all the cytoplasm, all the cytoplasmic contents. So whereas the sperm, so dad will offer a little bit of DNA, one set of the two pairs of DNA, but mom, mom offers all the cytoplasmic contents and that includes mitochondria. And that's why all of your mitochondria come from your mother and you can actually, you can actually look at mitochondrial DNA to make ancestral trees based on that, but it's, it all comes from the mother, at least in most cases. That is kind of interesting. All right. So that is, that is the process of oogenesis to the production of functional egg cells. So now we have functional egg, functional sperm, put them together and you have fertilization. Now we won't cover that in this unit. Pregnancy fertilization, pregnancy and development, that's going to be covered in a unit that I'll probably make in quite a while. It's not actually in this course, but I've got some ideas for some videos I want to do there. But this is how we make functional eggs. I hope this helps. Have a wonderful day. Be blessed.