Female reproductive cycle (menstruation)

so today we're going to focus on the female reproductive system and have a look at the female reproductive cycle so before we begin we need to have a look at some of the important anatomical features of the reproductive system so what I've drawn up here very quickly is first of all the vagina which then moves up into the cervix and then up into the uterus now the uterus has a number of different important anatomical structures such as the body of the uterus the fundus of the uterus and also the uterine walls which is made up of a number of different layers one layer which we're going to focus on today is the internal layer called the endometrium now you can see that the uterus feeds through into two tubes these are called uterine tubes also known as fallopian tubes and I've exaggerated just one of those uterine tubes so you can see as we follow it through it starts to branch out like little finger tips now these little finger tips are called fimbriae and what's the importance of this fimbriae this fimbriae hold the ovary okay so you know that you've got one ovary on either side now the ovary holds Bua science so what's in the asite at our site oh oh C Y T and boom site is basically an egg now which is also known as an ovum now for females you'll find that there are thousands of other sites what we call primordial or sites in one ovary where they come from and how long have they happened well basically females when they are in utero themselves so for example when a female is within their mommy's tummy so to speak they already have all the other sites they need for their entire life their ovaries even when they are in utero that ovaries already contain all the other sites they need okay thousands of them so if I were to take this over and just drop a couple of ill science to begin with there's going to be thousands and thousands of and we know that every single month the reproductive cycle begins and these four sites start to prepare themselves for fertilization and the uterus starts to prepare itself for fertilization so what we're going to talk about today is how does the body do this so we know that many hormones are involved this interplay of systems is involved and we need to look at exactly what happens with stimulating those hormones and what happens as a response to releasing those hormones so I've drawn up a little graph here or at least the start of a graph but we're going to have a look at hormone levels over the reproductive cycle so how long does a reproductive cycle go for well on average is 28 days but it can be as short as 21 days or as long as 35 days but the average is 28 days so I've gone one to 28 days here and this is going to represent hormonal levels of the reproductive cycle okay so what are we beginning with well day 1 of the reproductive cycle ovary has a number of other sites and we call them primordial follicles so these sites are called primordial follicles and day one of these primordial follicles between 10 to 20 of them okay but I'm just going to drop one for reference between 10 to 20 of them start to develop now what does a primordial follicle develop into it develops into something called a primary follicle now our primary follicle again has the lower side or the open and this filler site is surrounded by some cells some flat looking cells which are called follicle cells or follicular cells and again the whole structure is called a primary follicle now these follicular cells was the point of them being around the other side while they basically provide nourishment for the other side they keep it alive now this primary follicle or at least between 10 to 20 of these primary follicles that have just been made starting at day one they will not turn into the next form which is called a secondary follicle unless there is a stimulus to tell it to do so now the stimulus is going to be a hormone so we need to talk about the first hormone that's released within this process now what we need to talk about quickly is where this hormone released from and what its stimulus so if we were to draw up very quickly central nervous system we've got the cerebrum and the cerebellum and we've got the midbrain pons and medulla and then the brainstem there's a very important part which you've spoken about before and this important part is called the hypothalamus now the hypothalamus is located around about here and you know that just below the hypothalamus is a projection called the anterior pituitary gland and the posterior pituitary gland so this is what we need to focus on to begin with so I'll just get rid of this and I'll draw them up in more detail so I've got the hypothalamus I've got the anterior pituitary gland and posterior I'll just work them up for reference hypo damas anterior pituitary gland and this one's the posterior pituitary gland okay so what's happening well the primordial follicles are now turned into primary follicle follicles with these follicular cells providing nourishment to the oversight now they want to go to the next form which are called secondary follicles but they can't unless this particular hormone is released now the hypothalamus has a number of different hormones that it releases one is called gonadotropin-releasing hormone get out open releasing hormone so let's write that down can edit open releasing hormone what this means is this hormone releases gonadotropins cuz it's again a Detroiter releasing hormone what I get out of trope ins well doneita refers to sex cells so this is going to be either be ovaries for women or the sperm cells for males or testes I should say the ovaries for women or the testes for males so let's go that Oh tropen means it's a hormone that stimulates the release of another hormone okay so you know that Ropin means it's a hormone that goes to the gonads to tell it to release another hormone and this gonadotropin-releasing hormone without trying to confuse it releases get out of tropen so the hypothalamus produces gonadotropin-releasing hormone and this travels down to the anterior pituitary gland to tell it to release get out of Turpin's because that's a gonadotropin-releasing hormone so here in the anterior pituitary gland we have get out of tokens which are released now please get out of tokens there's two one is called follicle stimulating hormone and one is called luteinizing hormone so let's write that up very quickly FSH is follicle stimulating hormone and LH is luteinizing hormone so which one of these two do you think is going to stimulate this follicle from out from primary to secondary well it's going to be the follicle stimulating hormone so the primary follicle will not turn into a secondary follicle until FSH is released from the anterior pituitary gland and FSH like I said is going to travel to the ovum well to the ovaries and stimulate primary movement to secondary follicle now secondary follicle cell again has these follicular cells but these follicular cells have now turned into something else this something else it's called granular cells so the over your site the granular cells which are now surrounded by another group of cells called thicker cells and very importantly surrounding the biller site is a layer called the zona pellucida so I'm just going to write that down here your zona pellucida what's the importance of this zona pellucida layer surrounding the other site well when this uber site has been released from the ovary into the uterine tube this zona pellucida allows for because remember is going to be hopefully a number of sperm coming in to try and fertilize that other site and what the zona pellucida does is as soon as one sperm gets in to the zona pellucida it shuts all the doors and doesn't allow any more sperm in so if I want to draw that up very quickly if after all this has happened so I'm jumping forward a little bit we've got the other site surrounded by the zona pellucida sperm cells coming in once one sperm cell has penetrated through the zona pellucida no other sperm cell can get into the egg to fertilize it okay very important that's the function of the zona pellucida now once the follicle stimulating hormone released from the anterior pituitary gland has told the primary follicle to turn into the secondary follicle I said that there's the oocyte in the secondary follicle there's the zona pellucida important for letting sperm in there's granular cells and figure cells they're together they're granular cells and thicker cells produce something very important and this important something is estrogen the hormone estrogen and what does estrogen do well estrogen will travel to the uterus and we tell the uterus to start to prepare its uterine lining why is it doing this because it's saying hey there's a baby coming fingers crossed we need to prepare the uterine lining for implantation so that's what this estrogen does so estrogen will travel and prepare that uterine lining for implantation now let's go to this graph what you haven't drawn up yet what two hormones have I've spoken about predominately I spoke about FSH being released and I spoke about estrogen being released so if we want to first focus on FSH so look for FSH in blood what you'll find is from day one FSH starts to increase okay why well because once this primary follicle cell wants to turn to secondary we need FSA to be released and it's happening a couple of days after day one starting from day one and moving forward once this has happened and will produce secondary cells estrogens being released which means that a cell that's right estrogen even great estrogen starts to release and starts to go up now this secondary cell turns into something called a mature follicle so from audial follicle primary follicle secondary follicle mature follicle also known as a graafian follicle and what happens with this follicle is that again has the oversight the zona pellucida we're never important for letting sperm in has granular cells and these granular cells start to really grow really get thick and then has the thicker cells as well on the outside and what you see happens is that it starts to protrude against the wall of the ovary okay and this is a mature follicle now this mature follicle because it's producing so many remember thicker and granular cells it again starts to release more estrogen so estrogen levels start to go up and up and up so that means estrogen goes up and up and up and up and up now the important point is as estrogen goes up it feeds it back to the hypothalamus and stops what follicle stimulating hormone for baby waste so negative feedback so this follicle stimulating hormone starts the job down again however once these in the chill follicles start to produce more and more and more and more estrogen what happens is the estrogen levels get so high that it hits a point in which for some reason we don't know why instead of negatively feeding back it positively feeds back and so what do you think happens well we get a surge in the production of both follicle stimulating hormone and especially luteinizing hormone so high levels of estrogen have now sold follicle stimulating hormone to peak and have now told luteinizing hormone to search and before that luteinizing hormone was quite low but now what's happened is luteinizing hormone has bumped up like that really important so just before day 14 luteinizing hormone has bucked up now what does a luteinizing hormone do luteinizing hormone travels to this missional follicle and it starts to weaken the wall of the ovary that's the first thing luteinizing walnuts that's the weak in the wall of the over here without mature follicle has started to protrude out and what does this do well this results in the boomer site or the egg from being released oops now once that egg is being pushed out in released its surrounded like I said by that de zona pellucida and what's remaining well the granular and thicker cells so what you end up having is a remnant group of cells that look like that now this remnant group of cells cuz remember we've got the Woodside has just been injected so now about the other side with the zona pellucida cells would think ourselves here okay now a continual release of luteinizing hormone at this point here continues to stimulate this little remnant group of cells what's it tell these groups our cells to do it tells them to release another hormone this hormone that it's telling it to release is called progesterone just progesterone do progesterone travels again to the uterus and it tells the uterus to really start to prepare its lining for implantation because think about it that eggs then be released is gone okay babies coming really starts to prepare for implantation so thickens up that endometrium and this is also what progesterone does is it makes it highly vascularized we've now got a huge amount of blood vessels in this individual wall really important now think about what's going to happen this thing here which is now called the corpus luteum think about it luteinizing hormone luteinizing means it turns it into something called the corpus luteum so the luteum body means yellow body because this yellow stuff is fat and cholesterol and producer progesterone and as is progesterone was released further thickens up being a meet room makes it highly vascular vascular as I said okay baby's coming baby's coming it will continue to do this for about ten days so think about at day 14 what happened luteinizing hormone was released to tell the ovum to come out that ovulation so day 14 was ovulation and we've got follicle stimulating hormone has dropped off luteinizing hormone is continually telling this system to release progesterone progesterone progesterone the estrogen levels have gone up and then start to drop back down again but for ten days progesterone is continually being released by the corpus luteum to continually prepare this endometrial lining which means that if I want an hour gesture and up starts off flow and then jumps up high again now for ten days because think about it if no sperm comes to fertilize the egg what happens at the end of the 28 days menstruation occurs so let's talk about that very quick no sperm has come in do you think this corpus luteum has any idea that no sperm has come in has no idea so what it's thought what's going on is that because I can't for at least the ovum and that ovum is going to get in fertilized by sperm and then implants itself into the individual wall that's what it thinks and so guys I can I'll keep preparing in a Mitchell wall for ten days and then what should happen is if that all of them does get fertilized and implants once that fertilized egg is implanted in the wall a signal should get sent if it doesn't happen no signal gets sent now after ten days this corpus luteum if no fertilization has happened Gaza you're hearing anything what's going on so it starts to degenerate it starts to die and what happens to progesterone levels starts to drop off as progesterone that will start to drop off this endometrial lining which is now thick thickened and highly vascular vascularized also starts to die off and it begins to slough off that means it starts to fall away from the wall and this highly vascularized tissue starts to bleed out at day 28 and this is called administration so if no fertilization occurs what happens well what happens is no signal is sent progesterone drops off administration occurs so just as a very quick recap what's happened well every female starts off with thousands of primordial our science primordial follicles and day one of their cycle reproductive cycle these primordial follicles between 10 to 20 of them turn into primary follicles these primary follicles under the influence of follicle stimulating hormone tow from primary follicles into secretary follicles these secondary follicles have granular cells and thicker cells which release estrogen this estrogen prepares the endometrial lining for implantation a fertilized egg in addition to that it also sends a negative feedback signal to the hypothalamus saying stop releasing FSH and LH but has this secondary follicle turns into mature follicles it produces so much estrogen and for some reason that negative feedback reverses and becomes positive feedback and you get this huge influx of both FSH and LH specifically this LH results in this surge of luteinizing hormone that's been released this luteinizing hormone is important because it tells the egg to ovulate so that's what luteinizing hormone does tells you to of you later also tells the corpus luteum to release progesterone this progesterone will continue to be released for about 10 days and will further prepare the endometrial lining for implantation if that egg does not get fertilized and does not implant itself progesterone levels start to drop off this happens at around about day 28 once this progesterone levels start to drop off in the mutual lining starts to die and slough off and this is called menstruation in the next video I'll talk about what happens if that egg does get fertilized

Channel: Dr Matt & Dr Mike

Views: 213,934

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Id: L4adODFmmtI

Length: 24min 58sec (1498 seconds)

Published: Mon Oct 17 2016