Hello everybody. We're beginning our lectures on the female reproductive system for this module, or for this week, I guess we could say. Now, many of you told me that male reproductive system was pretty complicated.
Well, guess what? The female reproductive system is actually more complicated. Hormones, some of the names will be very, very familiar, but there's different mechanisms being used.
And so... We have to make sure that we have you understanding some of the general principles associated with this. We're going to start our mini lectures by looking at a little bit of the anatomy, making sure you understand the areas that we're talking about, kind of refreshing your memory about this from anatomy class.
And then, just like we did with the male reproductive system, we're going to talk a little bit about the genetics, the actual cell biology that's kind of taking place. at least with the development of the follicle. Everybody ready? Let's see what we've got here. Okay, folks.
All right. Let me get my pointer together here. There we go. In this image, we are looking at a mid-sagittal section through the female pelvis so that we can look at female reproductive organs.
And again, we're going to spend a little time just kind of looking at anatomy here, folks, to make sure we understand where... everything is. In this image, I'm going to point out the bladder sitting here, the urethra associated with the bladder, and the structure here in kind of a whitish color. This is the pelvic bone, the pelvic bone. So you can see the bladder sitting right behind that pelvic bone, the pelvic, the pelvis, the pubic symphysis, sorry, the pubic symphysis.
So get your bearings associated where the bladder is sitting. For the female, you can see down below, you can see the clitoris, which is the analogous structure to the glans penis and some of the other cardiovascular networks associated with the penis itself. The corpus spongiosum, corpus cavernosum, all of these derive actually from this kind of structure, the clitoris. So it has all those same sorts of principles. And hopefully a little bit later we'll get a chance to talk about this.
Externally, we have the labia majora and the labia minora. All right, larger lips, minor lips. As we move into the labia minora, we go inside, we can see the opening of the vagina. The vagina itself, and in this image, for many of you, boy, this looks mighty small. Well...
It is. It's a very fairly small area to tell you the truth. That area or that tissue, stratified squamous epithelium sitting along the inside with a thin coating of muscle.
Thin coating of muscle. Large number of mucus secreting glands and a lot of tissue associated with immune response. Again, this tissue is trying to...
protect itself as much as possible. And you may remember from when we were talking about the male reproductive system and the production of sperm and the semen going along with the sperm that there were a lot of products associated with trying to reduce the immune response over in the female reproductive organs. As you move to the back end of the vagina, you'll see the opening or the beginning part of the uterus and this beginning component.
opening is called the cervix. You can see the main part here of the uterus itself. And remember, the uterus is mainly a muscular structure that does have a fairly interesting inner layer.
The endometrium is very, very important and made up of very specialized types of epithelial cells and huge numbers of connective tissue and blood vessels that are designed for growing. meaning that over the menstrual cycle of the female, these tissues will expand, trying to prepare themselves for the actual fertilized egg to be able to implant and have all the nutrition it will need. So, the uterus, the uterus here. Now, the uterus, and in this image, since it's a mid-sagittal section, it's difficult to see, but you can see off to one end here, you can see, the fallopian tube extending from one end or one lateral end of the uterus.
There would be a second one that would be probably in the other half of this image if we were to show it. The fallopian tube up here and, of course, the ovary. Now again, these are the main structures that we're kind of looking at here. We're going to get into a little more detail associated with this right now. In this image, We're looking at an anterior view, an anterior view of female reproductive organs.
Down below, the labia minora and labia majora at the opening of the vagina itself. You can see the vaginal canal sitting here with its circular muscles sitting around the outer components of the vagina. And you can see the opening of the uterus, the cervix, sitting here in this area. Now, before I go any further trying to point out other components of the reproductive organs, I do want to make sure that I don't forget to tell you to look at the large vascular network that is associated with this tissue.
All these blood vessels are, and it's one of the reasons why I chose this image, was to make sure you realize the vascular network that is responsible for helping to maintain these tissues. And these tissues are... incredibly important.
They need the blood supply to help them make sure that the tissue is working properly. Remember, in this uterine tissue, we will have the developing fetus trying to live. And so providing the nutrition that that developing fetus will need is going to be very, very important.
As we move from the cervix and back into the main body of the uterus, There are different components to it, and again, this is not an anatomy class. I don't want to spend a lot of time on anatomy, but it's trying to talk to you or show you different components of the uterus, from the fundic area to the isthmus of the uterus and the body itself along the wall. What I do want you to notice, though, is if we take a section out of the uterine wall, and that's what this image is over to the right, this histological image, it's trying to show you over to the right, to the far right, more of the muscle.
So the in so the myometrium associated with the uterus. And here's that specialized inner lining called the endometrium, the endometrium, connective tissue and epithelial cells, large number. This tissue, along with the muscle, will change in size and development during the whole menstrual cycle.
A few other things to kind of pay attention to. We have our uterine tubes or fallopian tubes extending away from the uterus itself. Remember these fallopian tubes have different parts to them as well. In this case the fallopian tube over to the left for you in this image comes over to an ampulla, kind of an enlarged area, and that enlarged area will empty into or kind of move over to an area that's called the infundibulum, which is kind of a large area that has these finger-like projections that are called fimbria extending away. Now remember, this tube is open.
It's open to the actual pelvic cavity. Now that's something that is very very odd for whether we're talking about males or females to have a tube open to literally the outside world. We'll talk a little more about that a little later here or in one of our other mini lectures. You can see the ovary here in kind of a light bluish color, and what's hanging onto the ovary, this structure called the ovarian ligament. Remember, the ovary is literally kind of floating in the tissues of the pelvic cavity.
If it wasn't for that ovarian ligament kind of holding it in place, it would probably float around all over the place, making it even more difficult for the primary follicle, or excuse me, the ovum. that's going to be expelled from the ovary to make it over to the fallopian tube. Again, I want to mention the fallopian tube and the ovary are not connected to each other specifically. There are some connective tissue strands that kind of keep the fimbria close by the ovary, but technically they are not connected, which means when the ovum is pushed out of the ovary, it literally has to swim over. or move over to the fallopian tube before it gets into the actual tube itself.
There are lots of mechanisms for trying to maintain that ovum over to the fallopian tube. But as you know, things can go wrong with that as well. Over to the left, you can see a histological view of the actual ovary with its connective tissue coating around the outside called the tunica albigini. And the matrix or the cortex of the ovary, this is materials within the ovary that are there to help supply nutrition and other needs for the developing follicle, the developing follicle, which is showing you just a piece of it up here at the top.
Now, we're going to take this and go a step further and kind of focus on the ovary itself. In this image. Many things that are similar from the last image we looked at, trying to show you the ovaries to each of the lateral sides of the uterus, next to the fallopian tubes and the fimbria of the fallopian tubes there. We're going to look just inside of the ovary and blow that up so that you can look at it, so that you can see the developing follicles inside. And these follicles moving from a primary stage to these...
secondary, tertiary, and quaternary stages. Now, for the remainder of this mini-lecture, I'm going to ignore these other developmental stages of the follicle, and we're going to focus just on the oocyte and the primordial follicle. All right, so we're going to take this image, and we're going to do a little genetics here, folks.
In this image, at the very top, we have the oogonium. This is the developing ovum. This development of ovum and the beginnings of the dividing and creating of the different primary oocytes, this is mitosis. If you remember our definition of mitosis from the male reproductive system. This mitosis helps cells to divide and create more of these primary oocytes.
And in fact, this all takes place before birth. This is in the developing fetus, the female developing fetus, already producing these primary oocytes. What's really fascinating, or before I get to the really fascinating part, this beginning mitotic stage of these primary oocytes before birth, The female reproductive system in this developing fetus is going to produce somewhere in the area of 2 million primary oocytes. 2 million of them. Now, these primary oocytes, they will start the meiotic or meiosis process going into its first phase.
But what's really fascinating is that as they move into this first phase, they all become literally frozen in time. So, meiosis does not complete. It stays in the first prophase and this will stay this way all the way until puberty, all the way until puberty.
So, we have all of these developing primary oocytes sitting and waiting. Now, unfortunately, unfortunately, not all of these will make it and we'll get to that component of it here in a few moments. What gets us to puberty?
Well, puberty is set off by really the development of the hypothalamus in your forebrain. Those hypothalamic nuclei will start to secrete gonadotropin-releasing hormone. You probably remember that from male reproductive system.
Same hormone, GnRH, will be released from the hypothalamus and stimulate the pituitary gland, anterior pituitary gland to secrete luteinizing hormone. and follicle stimulating hormone, LH and FSH. LH, once it's being released, will go down and start to stimulate. It'll link to receptors on what are called fecal cells that are sitting around the developing oocytes, and those cells will start the process of creating hormones like estrogen and progesterone. FSH will bind to another set of cells inside of the primary follicles or in the developing follicles, which will help finish off the production of estradiol, which is estrogen, which is estrogen.
Now, as puberty occurs, already, already, we're down to 400 oocytes, 400,000 oocytes. So literally, in the process of going from birth and trying to make it just a puberty, the female has already degraded, broken down three quarters of the oocytes that they had right before birth, right before birth. So we're losing these oocytes over and over. And so the ones that are remaining are the strongest ones left. Now at puberty, as these hormones are being set off, starting meiosis so that it can resume the development of these primary oocytes, we will start to get the branching off of these sites, these oocytes, so that we can prepare for sperm interaction.
Now many of these primary oocytes, well as they develop off, only a few of them will make it. Many of them will develop into what are called first polar bodies and second polar bodies. And once they develop into these, they will be degraded.
They will be broken down. They will not be functional any longer. The remaining secondary oocytes, they will wait.
They will wait kind of in a frozen kind of state in the ovary, waiting to be expelled and waiting for... sperm interaction. Now, these secondary oocytes are still diploid, meaning they have a full complement of genetic material.
Now, this full complement of genetic material, that's not going to work. Remember, the sperm cells are carrying half of another set. Once sperm penetrates the wall of the ovum, the cell will complete its meiosis process. meaning it will separate its genetic material, part of it will move away in a polar body and this is what this is showing here.
The other half of the genetic material, if the sperm cell is successful at moving in, it will link up or those sets of genetic material will come together. We have fertilization. We have fertilization.
I have a plane going over. I'm out in the backyard giving this lecture and I have a plane coming over, zooming across, and it sounds kind of like a sperm cell zooming over to kind of fertilize the egg here, so it's very apropos. Everyone got this process down?
Please go over this. Listen to this one more time and take notes on this developmental phase of the oocytes. In our next mini-lecture, we will talk about how to do this. how this particular primary oocyte actually gets to this point ready for fertilization. All right, folks, we'll talk to you later.