if you like when we studied hormones you did me too which is good because the uterine cycle and the ovarian cycle require hormone signaling mechanisms to sync up their behaviors in other words when the ovary is ready to a view late the uterus has better be ready to possibly receive a fertilized egg for implantation and so we need to think back on our different hormones to understand both the uterine cycle and the ovarian cycle which collectively we refer to as the menstrual cycle so what kind of hormone should we think about here's a slide from the endocrine chapter follicle stimulating hormone good that will stimulate these follicles which are little protective shells around the developing eggs and stimulate those to develop luteinizing hormone remember luteinizing hormones help with pregnancy preparation but the big thing is it causes ovulation so you can buy over-the-counter ovulation test kits ot case and pee on the stick to monitor your LH levels if you're trying to get pregnant of course estrogen and progesterone will come up and remember we said that those are made by the ovaries so now we'll get a little bit more specific and find out where in the ovaries these hormones are made and why and when that's five so far five hormones and there will be a six HCG one more hormone to learn about in the whole signaling process between the uterus and ovaries so let's look at the uterine cycle it has three phases menstrual cycle proliferative cycle it's like a rebuilding phase in the secretory phase is when the uterus is really getting ready for the possible implantation of a fertilized egg sigh goo and let's make sure we understand our basic uterine anatomy really what I want to look at right now is the uterine wall and recognizing that the uterine wall is made of three layers parameter iam is this outermost layer it is a serosa layer at least in part part of the uterus has some of the peritoneum which is found in the abdominal pelvic cavity draping down and covering part of the uterus the myometrium is a pretty important layer it's the thickest layer it has the term Myo in it which means muscle meter by the way means uterus so the muscular layer of the uterus is in the middle and that has smooth muscle to help with childbirth of course and to expel menstrual fluids and tissues during menstruation but we'll talk mostly about the endometrium the innermost mucosal layer of the uterus and this layers both highly vascularized with lots of blood vessels and will grow lots of different glands as it prepares for these I go to implants and there are two sub layers and this is going to be relatively basic just think of it like this about once a month part of the endometrium is slough tauf is shed during menstruation in females that are have reached puberty and before menopause so when that portion of the endometrium is left off another portion has to stay behind to regrow and then the top is left off in the bottom portion regrows so the two sub layers are just one layer is always there and one layer gets left off during menstruation so the bottom or basal layers stratum ViSalus it always stays there stratum function Alice is the one that actually has the important function to receive the zygote or if not to beasts left off here we can see these a little more closely the stratum ViSalus at the bottom remains relatively unchanged all the time it's the layer next to the myometrium and it will give rise to stratum function Alice because the stratum function Alice will get very tall and very highly vascularized with lots of these glands growing but if implantation does not occur the blood supply will get cut off those tissues will start to die and we'll gets left off and then need to regrow we can name those three phases trollface the proliferative phase and the secretory phase so the phase of the uterine cycle in which blood supply is cut off and you slough off some dead tissues you regrowth phase or the proliferative phase where the cells are proliferating or dividing and dividing the endometrial wall is thickening to prepare for implantation in the secretory phase when these glands uterine glands grow and you get a lot more blood vessels growing and those at this point you're really ready for implantation in fact the whole stratum function Alice has to be a hundred percent ready to receive and nourish a very rapidly growing zygote so that's a lot of tissue to get built up all around the lining of the uterus okay that was pretty fast and fairly basic we didn't talk about any of the hormone signaling yet so now as we go through the ovarian cycle we will need to add on those hormones so we can understand why uterus does what it does when it does what it does so now in cycle we also have three phases follicular phase ovulatory phase are just ovulation and the luteal phase in short follicles grow during the follicular phase ovulation happens during the ovulatory phase and a structure called the corpus luteum is going to hang around for a couple weeks in the luteal phase during this like a transition period so let's look at ovaries first they make OVA these eggs and female hormones ovaries are in the pelvic cavity on each side of the uterus and they have a cortex and a medulla medulla is mainly just where the large blood vessels come in and kind of branch out to nourish the ovary the cortex is where you get all of the follicles growing and developing and ovulating from here we can start to see some of the detail we'll study meaning the specific names of the follicles as they grow and develop we can see the act of ovulation occurring here and then there's some structures that are left behind after ovulation including the corpus luteum of which the luteal phase is named after so the first thing we need to do is make sure we have some eggs made sess in which these eggs are made is called oogenesis so we've got spermatogenesis to make sperm oh oh genesis to make eggs or OVA this process begins as embryos when these stem cells called ol Gonia make about 5 million primary oocytes when you're born you have about 2 million of these primary oocytes left so in sperm development we have spermatogonia are the stem cells and they make spermatocytes here we've got BOGO Nia are the stem cells and they make auto sites the big difference is we've only made it to birth so far in females and females have millions of primary Auto sites ready to go whereas in males you won't start making all this sperm until the male's reach puberty so here's the thing about these primary oocytes they are not ready for primetime meaning we need to get these Auto sites to transition through several more phases so that they can become haploid they need to have half the amount of chromosomes needed for a full human life they try to get there so these primary auto sites they start meiosis 1 this process that will cause them to become haploid but everything gets stopped put on pause until the female reaches puberty and by then a couple million most of these primary oocytes have gone away you still have hundreds of thousands of primary oocytes left behind but the number is starting to shrink and once the female reaches puberty then every month some of these primary oocytes will re-enter meiosis one they will become unpause and they'll form secondary oocytes but they're still not ready to go they're still not use haploid cells and they're going to get paused again before they truly can finish this process so if we were to think about this 200-thousand primary oocytes is more than enough buy so many more than enough then you then you would need to ovulate a single egg each month for the reproductive lifetime of a female right you'd only need like 12 ish per year and you're talking about maybe from this early as the age of 10 ish to 50 ish and a big long reproductive lifetime like you just need hundreds of eggs not hundreds of thousands of eggs but each month a whole bunch of eggs are gonna start the developmental process and only one normally one will get chosen to be ovulating so you do use up a lot more of these eggs than you might think okay so our goal here though still is to get a haploid egg right so it can fuse with the sperm we're still not there in fact even when your egg is ovulated it's still not done well Genesis still isn't done this is totally bizarre but this is the way it is it's the sperm fertilizing the egg that causes the secondary oocyte to be like oh like oh crap I gotta I gotta get ready and it will finish meiosis 2 and then officially become haploid if you watch that fertilization video that was mentioned during the male reproductive system you actually see this happen you see the sperm fertilize the egg and then the nucleus of the egg is like real busy all of a sudden wrapping up the division of the chromosomes but seems to work just fine meiosis 2 will finish and now officially you have this haploid egg that the sperm will combine its DNA with to form a full complement of chromosomes with animation so here's one way of looking at Genesis starting with a logo Neum one of many go go Nia the stem cells so that will divide one will stay behind one will continue on and it will have a primary Auto site that will eventually become a secondary Auto site that will eventually become a mature haploid gamete once fertilization occurs along the way during these division processes you'll create these things called polar bodies that's just one way for the egg to kind of get rid of this these extra copies of DNA that it doesn't need or want so unlike in sperm you kind of start with this stem cell and eventually you get four unique sperm with eggs you start with a stem cell and you get one gigantic egg cell and I kind of already have mentioned this but make sure you're noticing some of the terminology here is kind of helpful oh Gonia spermatogonia Oh a site spermatocyte but there are differences in this process like I just mentioned for unique sperm verses one egg and a bunch of these things called polar bodies this junk we don't need okay so that was the creation of the eggs now we have to look at what's going on in the ovaries of a reproductively mature female body so one of the phases of the ovarian cycle is the follicular phase this is when the follicles that surround the egg cells surround the oocytes start to develop at birth remember you've got about two million primary oocytes and they are protected by primordial follicles they're tiny they're dormant remember because now nothing's gonna happen till puberty so they're dormant they're just simple squamous epithelial cells making a very thin protective layer of cells but when the female reaches puberty follicular stimulating hormone FSH will cause every month some of these primordial follicles to start to develop I'm not sure the exact number if it's under a dozen or dozens but you know it's not thousands of them and it's not - it's like a several of these follicles will start to develop to become primary follicles so they will grow in size the cells will thicken to become simple cuboidal cells a little bit more protective and then over time it will become stratified cuboidal epithelium for even more protection these follicles are growing and getting larger and then over the course of a few days some of these primary follicles will then be selected to become secondary follicles any of them that aren't selected are now going to just be degraded and go away but some few will become secondary follicles they'll be even larger they'll start to accumulate some fluid in a little space called an Antrim we'll see this in another slide and then within a few days of that typically just one follicle one secondary follicle will be selected by the body in some mysterious fashion to be the one that becomes a tertiary follicle those are sometimes called mature follicles or graafian follicle x' but that's the one that will be ovulated it's gonna get really big like half an inch in size very big follicle and it will have this secondary oocyte inside ready to be ovulated when these follicles start to get a little bit bigger like secondary follicles or that mature tertiary follicle there's a bunch of cells in the follicles that start to secrete estrogen because remember we said that hormones are needed to sync up the ovarian cycle and the uterine cycle and there's gonna be five hormones to discuss so estrogen made by the follicles when they get bigger and the uterus and track the progress of the ovary by these hormones right meaning a secondary follicle is pretty small it will just send out a little bit of estrogen but as it becomes a bigger and bigger secondary follicle or it becomes a massive tertiary follicle I mean half an inch is humongous it's gonna be making a lot of estrogen so the uterus can see that increasing amount of estrogen and ensure that its progress is synced up with the ovarian progress here's a look at the morphology of these follicles and so here's one primordial follicle these are very tiny so the magnification here is at 1440 so like way beyond anything that you've probably used in a lab course so they're very tiny primary follicles we can just start to see some simple cuboidal cells showing up this follicle and use your magnification is going down going down here's a secondary follicle so we've got a stratified layer of epithelial tissue we have a little bit see these bubble shapes here forming these bubble shapes will eventually become a big Antrim but only one of these secondary follicles that are starting to develop to develop will be chosen by the body to make a big Antrim filled with fluid and at this point what you can see is you have your your egg or what will become your mature egg here the secondary auto site and then there's also a ring of cells or let's call it a crown of cells radiating off of the OA site so this structure that's just this ring of cells here is called the corona radiata and that's important because that's going to be obviated with the egg with the secondary bowl of site and there are lots of other structures here different types of cells that are secreting the estrogen and things like that but you'll talk about those in physiology so let's all ate this thing this is triggered partially by FSH levels but this big push of luteinizing hormone will be the real cause of ovulation we call it the LH surge and maybe I mentioned during the endocrine system this is a big thing not just in trying to get humans pregnant but when I was in the zoo industry if you're trying to breed endangered species and you know you're spending a lot of time and money and effort to do all this you really want to know when your females are ovulating so that you can put them with the males or provide some extra mating opportunities so looking for this LH surge is a pretty crucial component of any at least mammalian reproduction so there are a few things that aren't understood about this process though like the hypothalamus is going to trigger the pituitary to release all this LH so how does it know when to make the LH surge so in addition to the ovaries and the uterus communicating we've also got to be communicating up to the brain and back and that signaling mechanism is not that well understood I mean we know a lot more than I'm telling you but it's not very well understood the other thing is so the hypothalamus decides to release all this LH how does it actually cause ovulation and that's not totally clear either although you know we have been able to study usually not in humans but in other mammals what happens to the ovaries during ovulation so some things that happens are things like the pressure inside the follicle increases remember this thing has been growing but there's also on that fluid inside the antrum it's kind of pushing the follicle walls to burst there's this inflammation response that occurs right remember inflammation brings a lot of fluid to an area causes swelling there right there smooth muscle in the ovary that seems to contract and maybe add to the pressure buildup and there are proteolytic enzymes meaning the enzymes that can cut apart protein and they attack the wall of the ovary to thin it out so some combination of all of these is leading to the eventual bursting of the ovarian wall and the release of the what we could believe just called the egg but it's really the corona radiata a ring or halo I say ring but it's a sphere of cells all the way around the secondary oval site and yeah that's what's released and remember we have those fimbriae making a current to hopefully pull that egg into the oviduct so now we're in our final phase of the ovarian cycle the luteal phase and at this point the luteal phase is all about this what happens to the follicle it bursts the eggs on its way do we need that follicle anymore yes we do need that follicle and we even have a name for this leftover first follicle called the corpus luteum that means the yellow body right a corpse is a body Lutie is yellow so the yellow body forms so this is gonna have a blood clot and it'll be surrounded by cells left behind but it will very quickly start to secrete progesterone and semestre gene but the big thing is progesterone progesterone is a signal to the uterus that ovulation has occurred remember we are sending out a lot of estrogen saying that we're giving close to ovulation but when ovulation occurs we are switching and and secreting mostly progesterone so the uterus is listening right and listening and when that progesterone starts to be circulated through the body then it says AHA there's an egg on the way and you know like okay is everybody ready is everybody ready here we go could this could be the time this could be the one uh-huh uh-huh and the corpus luteum keeps sending out the progesterone okay yeah so it happened so any time now but that that egg is only gonna live like 24 hours so the corpus luteum will keep secreting progesterone for about two weeks but eventually it will stop if fertilization does not occur the corpus luteum just becomes scar tissue we call it corpus albicans and alb is white so this is the white body piece of scar tissue and that's it now the corpus luteum is done no more hormones it's just a chunk of scar tissue but zatia does occur if the sperm fertilizes the egg and the egg implants in the uterine wall then within that two-week period the zygote is developing life form will start to make a new hormone called HCG human chorionic and add atropine that hormone tells the whole body that implantation has occurred but it also tells the corpus luteum that implantation has occurred now the corpus luteum is going to keep sending out its message now for months think of the corpus luteum as doing this the job of the corpus luteum is to send out progesterone to tell the uterus don't menstruate because I sent out an egg ovary sent an egg so even after the zygote implants right it's not gonna be deep or well developed yet you still want to make sure the uterus does not menstruate so the corpus luteum is going to hang around for months and months and months now saying you know don't menstruate don't menstruate protect the lining of the uterus save the endometrium that's where the zygote lives now and then within like five ish weeks that zygote will be an embryo and within 11 ish weeks that embryo will be a fetus and then within a few more months that corpus luteum can finally stop telling the uterus not to mention because once you've got a fetus and it's got some organ systems rocking and rolling then it has its own endocrine system and now the fetus can communicate on its own to the uterus and to the rest of the body to make sure that uterus is maintained okay so this is just our last slide or two to show us that indeed these phases have to be synced up so that when ovulating occurs that uterine wall needs to be just about ready for possible implantation and if the implantation doesn't occur then the uterine wall can enter the menstrual phase and so on you can also layer over images like this lines showing the changes in the hormone levels but that's something I think you do in Physiology so all this can get complicated fast but that's gonna happen when you're trying to you know create life and then you go from something like this to something like you thought I was gonna give my baby didn't you this is my baby hi hey hey hey mister madami [Music] [Applause]