Menstrual Cycle and hormones

so we're talking about the uterine or menstrual cycle which is of course fundamental to human reproduction and an idealized cycle starts in day one the middle part is day 14 and the end part is day 28 so that would be an idealized cycle now day one is the onset of menstruation now menstruation is the sloughing off of the stratum function Alice the inner layer of the endometrium so the endometrium the inside layer of the uterus is in two layers now this layer here between these lines wherever in my numbers this is the permanent layer here and this permanent layer is called the stratum bacillus so that's the start and bizarreness that doesn't change but this functional layer the stratum function artists on the top does and menstruation as I said is taken as the first day of the menstrual cycle now this bit I'm drawing here this second bit is that is the functional layer so that's going to degrade in the first few days of the menstrual cycle and that is actually when menstruation takes place those first few days days that is menstruation I mean the number is completely arbitrary we just take day one as the first day of the menstrual cycle as the first day of menstruation because it's the day we can be certain about it we can see it is obvious and then after that in the uterine or menstrual cycle there's going to be a buildup of the thickness of the endometrium like this getting thicker towards the end of the month and then there's going to be a drop off again at the end of day 28 as we have the the onset of the next menstruation for the next cycle like that so we have these this 28-day cycle here so we're thinking about specifically the you try nor the menstrual cycle at the moment that first part there is a menstruation we're going to get menstruation then we're going to get an increase in the thickness of the functional layer of the endometrium so that's called the proliferative phase because it occurs as a result of mitosis there's a proliferation of cells then this last part here is called the secretory phase the security phase and that's the crease nutrients which are going to be useful if any fertilized embryo comes along to implant itself in this nicely prepared functional layer of the endometrium so we see a menstrual phase and we've said the ovulation in an ideal cycle occurs on day 14 if it's an ideal cycle so that means that this bit here is before ovulation so after the menstrual phase we have this preovulatory we have this preovulatory phase here just there before before ovulation and after ovulation this next part is called the post ovulatory phase so they're the changes in the endometrium that's why we're calling this part the uterine or the menstrual cycle now it's this preovulatory phase from day 1 to day 14 that tends to be the variable component form ovulation to the end of the cycle is much more consistently 14 days so the length of the cycles can vary significantly could be 24 days anywhere up to say 35 days but it was the second 14 days that are consistent then it was a 24 day cycle then that would mean the ovulation occurred on day 10 14 days before the end of the cycle or 14 days before the onset of the next cycle well it was a 34 day cycle that means that ovulation would have occurred on on day 20 now all of this of course is controlled by the endocrine system so up here as you probably know from previous videos we have the hypothalamus and we have the pituitary gland on its stalk and the pituitary gland is in two lobes and the lobe of interested in is the anterior lobe the adeno hypothesis so a cycle will begin with activity in the hypothalamus and the hypothalamus will produce gonadotrophins releasing hormone and that will pass down the portal system from the hypothalamus to the anterior lobe of the pituitary gland so that starts we start off in the hypothalamus and this gonadotrophins releasing hormone will go through a group of cells in the Edina hypothesis in the anterior pituitary called the gonadotropin the gonadotropin by releasing the gonadotrophins that is the follicular stimulating hormone and the luteinizing hormone and this is all going to be mediated via the ovarian follicles so let's have a look at what's going on so a baby girl is born with tens of thousands of primordial follicles these are immature follicles a simple layer of cells and inside there's a low site a potential ovum stuck in an ER what's not stuck suspended in an early phase of them meiosis so they're there like that now the reason puberty happens or the reason any menstrual cycle happens is follicular stimulating hormone will stimulate these follicles it does exactly what it says it's a follicular stimulating hormone so the gonadotropin-releasing hormone stimulates the release of the gonadotrophins from the gonadotropin ago not a trope and we're interested in at the moment is the follicular stimulating hormone that's stimulating our follicles and initially it's going to start stimulating the air primordial follicles these immature follicles and it's going to cause cell division in these and we're going to develop primary and then secondary follicles and eventually we're going to develop a Chua follicle and the mature follicles called the gravy and follicle we've actually seen this before in a diagram here where we have an immature follicle just there and this is acted on by the follicular stimulating hormone that causes mitosis and growth of development the some secondary follicles developed and one of these becomes the dominant follicle and we can see that there's lots of granulosa cells in this in this follicle he run indeed in the earlier stages of follicular development lots of these granulosa cells so let's think about what these are secondary follicles and mature gradient follicles are like in more detail so several secondary follicles will develop and the cells in these are cells in these are the granulosa cells and that eventually will not become the dominant follicle and we have a large follicle with many of these granulosa cells as we saw in this diagram so the ovum is in here the developing ovum's in there this fluid and there's many of these follicular cells now what actually happens here is this is going to produce the Eastridge ER the granular cells are going to produce the east region and as it produces east region the dominant follicle produces east region and that estrogen is going to go back in the circulation to the anterior lobe of the pituitary gland and the high levels of estrogen from the developing follicle are going to inhibit the release of further follicular stimulating hormone and what this means is that the follicle that's producing the the most east region is going to become the dominant follicle so we end up with one dominant follicle now sometimes it doesn't quite work and we can have two dominant follicles and in that case that means two ovum can be released and if – over me released and fertilized in the same menstrual cycle that means that um none identical or dizygotic twins can be the result so we've said that this is producing the follicular cells and producing lots of estrogen and it's the East region from these follicular cells that are going to stimulate the development of the endometrium during the first half of the menstrual cycle so the gonadotrophins hormone stimulates the release of the gonadotrophins the FSH that stimulates the development of the follicles but it's the follicles that release the east region that cause the development of the endometrium so we're going to get growth proliferation and increase vascularization of the endometrium preparing it for possible implantation now at day 14 the activity of the other gonadotrophins becomes increased there's a spike in increase of the other gonadotrophins and that one is luteinizing hormones so we've got that in green remember the blue one was the the follicular stimulating hormone so but now at around about day 42 what 14 we're going to spike in the production of luteinizing hormone and what the luteinizing hormone does is it causes ovulation so the granular cells are still going to be there but the the ovum is going to be released so the ovum goes out and is released where it could potentially be fertilized so it's the spike in luteinizing hormone actually triggers the process of ovulation which of course is good because it gives us the potential to reproduce but also the luteinizing hormone changes the nature of the granulosa cells we've seen that on this diagram the granulosa cells now become what we call luteal cells they're luteal cells luteinizing hormone means that the yellowing hormone that these take up fat and become a yellowy color and it changes from being called the gravy and follicle at this stage to being called the the corpus luteum as well it will be a few hours after the luteinizing hormone has been acting on these on these cells to change them into luteal cells and we get a collection of these luteal cells now in this corpus luteum corpus body luteum yellow yellow body so we now have a collection of luteal cells and that's why I recall this first half of the cycle here that first half we refer to as the follicular phase and this second half we refer to as the luteal phase of the cycle because of the presence of the corpus luteum there now the corpus luteum does carry on producing some east region but it also produces large amounts of progesterone so the corpus luteum is going to produce progesterone and we'll draw the progesterone in there in black earthing so the progesterone from the corpus luteum is going to influence the endometrium of course and it maintains the endometrium so east region is a developing hormone progesterone is a maintaining hormone and this corpus luteum will stay around for the second half of the cycle the second 14 days of the cycle in or carry on producing progesterone it produces a mutagen as well but it produces progesterone to maintain the developed fate of the developed stage of the functional layer of the endometrium so we're now in this post of you later if a is here so the ovarian follicle has released the ovum and is now called the corpus luteum we are in the luteal phase and the luteal cells are going to produce some east region quite a lot of progesterone and they also produce another hormone called relaxin and relaxing prevents contraction of the muscular layer of the uterus the– the myometrium because we don't want any fertilized products to be injected as a result of over vigorous uterine activity now if fertilization doesn't occur the corpus luteum just going to degrade as we said after 14 days and it forms a residual non-functional structure called the ER the the corpus albicans but that's basically it dentist and his job and that's finished now but because of the development of the the corpus albicans that progesterone is no longer produced the progesterone no longer maintains the vascularity of the endometrium and that's why we get the onset of the next the next menstrual cycle now if there is fertilization then the corpus luteum will be it will persist and it's actually supported by human chorionic gonadotropin produced by the chorion of the embryo eight days after fertilization and this of course is very useful because it means we can test for pregnancy at a relatively early stage by testing for human chorionic gonadotropin in the blood or urine now we did mention that this is also called the the secrete early phases in terms of the activity of the endometrium because if populations don't well ovulation occurs on day 14 but if fertilization occurs the released ovum is only going to last for 12 to 24 hours in the internal environment so if fertilization is going to occur it's going to be round about this stage of the menstrual now that's not the only fertile period of course because sperm can last for about probably five five some people even say more realistically five days in the internal female tract or even potentially more so sex occurring any time in this period can result in fertilization but if fertilization is going to occur the actual act of fertilization not necessarily the act of sex that brought about that fertilization the actual fertilization is going to occur around about day fourteen fifteen in this idea life cycle and fertilization if it does occur her occurs high in the fallopian troop so it's going to take about a week for the emperor to get down so if the embryo does come down it's going to arrive about here and that means that the endometrium is secreting nutrients such as glycogen to support it before the placenta develops the interesting levels of control here from the hypothalamus to the anterior pituitary to the follicular cells to the new teal cells that follicular cells stimulated by the follicular stimulating hormone the luteinizing hormone stimulating ovulation and the activity of the corpus luteum and the luteal cells

5 Replies to “Menstrual Cycle and hormones”

  1. Thanks doctor for explanation in a simpler way….
    Kindly upload on parturition please as per your convenience

  2. Brilliant video.

    If I may, I'd like to make a few suggestions for some complementary videos (perhaps one would be sufficient for the first two suggestions), unless you have considered and/or began producing them. These are:

    – A brief review of this video with a more in depth look at pregnancy (with perhaps the best times to try to conceive) and natural family planning

    – The use of contraceptives (from IUD's, implants, and of course, pills) and their effects on menstruation

    – Pathologies of reproductive health such as Polycystic Ovary Syndrome, and any other conditions that interfere with menstruation

    It would make good viewing and great learning – especially through your medium as you are such a great educator.

    Thank you for this upload, Dr. Campbell 😀

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