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Female Reproductive System – Menstrual Cycle, Hormones and Regulation

Female Reproductive System – Menstrual Cycle, Hormones and Regulation


Armando Hasudungan biology and medicine videos Please make sure to [subscribe] join the forum in group for the latest videos please visit Facebook Armando Hasudungan In this video we will look at the hormonal regulation of the female reproductive cycle so we will be looking at the menstrual cycle basically and Yes, so the menstrual cycle the Hormones of the female is So much more complicated the Male’s but hopefully we’ll be able to understand it by the end of this video, so [we] begin with the hypothalamus and the pituitary glands which are made up of the anterior and posterior pituitary glands We’ll be focusing on the anterior pituitary gland the hypothalamus regulates hormones released by the anterior pituitary through the portal blood here in The female reproductive system the hypothalamus produces a hormone called gonadotropin-releasing hormone which will travel here to the anterior pituitary via the portal blood and It will cause the cells in the anterior pituitary gland to produce two important hormones known as FSH, follicle stimulating Hormone and LH luteinizing hormone Please note that in males this same process also occurs Males also produce Gonadotropin releasing hormone which will Cause the anterior pituitary to release Luteinizing hormone and follicle stimulating hormone, so what will these hormones do in the female body? Well these hormones will travel to the female ovaries where the female eggs are produced So let’s just recap quickly. What the ovary is and where it is. So here. We have the uterus and the Ovaries Which connects to the Uterus via the Fallopian Tube essentially But it’s now known as a uterine tube so we [will] focus on this over here, so let’s zoom in so here is the ovary and it has blood vessels and This and it’s through these capillaries these blood vessels that the hormones can enter Now in each ovary there are follicles Women have many many follicles in the ovaries and each month only some will begin to mature But only one will ovulate and become essentially will ovulate and produce an egg Now let’s just say it’s the beginning of the menstrual cycle. So just after female has shed her uterine wall just had the period now within the ovaries females have many many many primordial follicles and Each month only some of these primordial follicles will mature Into primary Follicles, and they will keep maturing but only one will ovulate So here. I’m drawing one primary follicle, and it’s the beginning of the menstrual cycle Before we continue on let’s look at the let’s look at the changes [of] the hormone concentrations That come from the brain by looking at a graph so here we have a y-Axis which shows the concentration of the hormones in blood and On the [x-axis] is a duration of the female menstrual cycle which normally goes for about 28 days So the dotted line in the middle is 14 days. Which is halfway Now just to simplify things even more the menstrual cycle can be divided into two phases the first 14 days is known as the follicular Phase and the Last 14 days Is known as the luteal phase and this is important to keep in mind, so the first is the follicular Phase II is the luteal Phase Now initially in the beginning of the menstrual cycle there is an increase in Gonadotropin releasing hormone secreted by the hypothalamus because it’s the start of the menstrual cycle and this should cause a steady increase in Follicles stimulating hormone and luteinizing hormone but instead we see a Increase and then a slow Dropping level of follicle stimulating hormone, and we have a steady level of luteinizing hormone Why is this? Well the reason is actually quite complicated, but just hold on to that thought and hopefully it’ll make sense So let’s go back to the ovary So follicle stimulating hormone Will initially rises remember? Because the follicular phase is the first phase of the menstrual cycle Follicle stimulating hormone will enter the ovaries and what they will essentially do is stimulate it will stimulate follicle Maturation of these primary Follicles and so some of these primary follicles will mature into A secondary follicle, I’m only drawing one secondary follicle for simplicity While these follicles are maturing they produce another hormone called Estrogen Now Estrogen has many effects in the first ten days of the menstrual cycle So in the beginning estrogen has a negative feedback on the pituitary gland inhibiting the release of luteinizing hormone To put it simply at low concentrations estrogen inhibits luteinizing hormone secretion from the anterior pituitary And that is why we only see a steady level of luteinizing hormone in the blood Because even though gonadotropin-releasing hormone from the hypothalamus is stimulating the release of luteinizing hormone at low concentrations estrogen will inhibit luteinizing hormone release Another fact is that follicle stimulating hormone is secreted primarily in response to Low Estrogen concentrations, so when Estrogen levels rise Follicle stimulating hormone levels will fall and that is why we see in the graph a steady drop in Follicle stimulating hormone because there’s a increase in Estrogen levels from the follicles So let’s draw another graph and see the concentrations of the hormones produced by the ovaries during the menstrual cycle Which goes on for 28 days So as the follicle matures they will produce more estrogen which as I mentioned at low concentrations estrogen will inhibit the secretion of luteinizing, hormone and Also the increase in estrogen concentrations will cause a decrease in Follicle stimulating hormone secretion Estrogen is an important hormone Especially for females because Estrogen is basically males equivalent of testosterone, Estrogen Peripheral effects include stimulating bone and muscle Growth it stimulates endometrial growth Maintains female Secondary characteristics and maintains a female the glands the breasts amongst many other things So just to draw this graph up to Ten days of the Menstrual cycle. We see a steady a steady low concentration of luteinizing Hormone due to the inhibitory effects of estrogen remember in the first ten days and We also see a steady drop of follicle stimulating hormone due to the increase in estrogen levels as well. Which has a negative feedback So what happens after 10 days? well after 10 days estrogen levels will continue to rise as the follicles mature in the ovaries and After 10 days as estrogen levels rise. It will have a positive Feedback and It will stimulate the release of luteinizing hormone so at low concentrations estrogen will inhibit luteinizing hormone secretion however at High concentrations, Estrogen will stimulate luteinizing hormone secretion Now things are changing the increase in gonadotropin releasing hormone and estrogen will stimulate then luteinizing Hormone secretion And you see this massive spike in luteinizing hormone concentration It’s this massive luteinizing Hormone concentration that will trigger ovulation of the Most Mature Follicle in the ovary The ovulation of the follicle will release what we know as the female egg the oocyte or Oocyte After ovulation the luteinizing hormone levels will drop back down gonadotropin releasing Hormone will slowly drop as well follicle stimulating hormone also had a small spike as a side effect of the surge of luteinizing hormone release so luteinizing Hormone triggers ovulation and oocyte is released after The Follicle ovulates the follicle will turn into a corpus luteum which is a dead follicle, basically Now that is why the first 14 days of the menstrual [cycle] is called the follicular Phase Because it all has [to] do with the follicles and its maturation and the last 14 days is known as the luteal phase Because we have the formation of the corpus luteum The corpus luteum will essentially slowly degrade However it also has a purpose it in that it secretes hormones. It secretes three hormones estrogen again inhibin and Progesterone So what we see in the concentration levels of these Ovarian hormones Estrogen will increase until ovulation and then drop slightly Inhibin was not present until after ovulation then it begins to increase thanks to the corpus luteum Progesterone levels will were low until after ovulation during the luteal phase so at 21 days of the female reproductive cycle progesterone is increasing inhibin is increasing and Estrogen is still detectable and all these hormones are all produced. Thanks to the corpus luteum So what do these hormones do? Well inhibin has a negative feedback And it will essentially inhibit the secretion of follicle stimulating hormone because we are at the luteal Phase We don’t need any more follicles to mature just yet So that is why inhibin is preventing follicle stimulating hormone release to prevent follicle maturation So here. I wrote as the secondary corpus luteum develops inhibiting secretion will suppress follicle stimulating hormone release Progesterone is the most important Hormone in The Luteal phase and has many functions [one] of which is having a negative effect on the hypothalamus inhibiting the secretion of gonadotropin releasing hormone Now after ovulation during the luteal phase The progesterone levels will increase slowly and the estrogen levels will decrease Slowly kind of and this will suppress gonadotropin releasing hormone release and So progesterone will inhibit gonadotropin releasing hormone release Which will also [effect] the release of luteinizing hormone and follicle follicular stimulating hormone? So during the luteal phase as progesterone and inhibin increase This will essentially cause a decrease in gonadotropin releasing Hormone, luteinizing Hormone and follicular stimulating hormone But the main effect of progesterone is that it will stimulate endometrial growth the endometrial lining is the lining of the uterus which will shed each month or Or the endometrium is where the egg? Will implant if it’s fertilized by sperm okay, let’s just say there was no fertilization because this is just a normal menstrual cycle and Of course all good things have to come to an end the corpus luteum in the ovary will degenerate allowing a new set of Follicles to mature So as the corpus luteum degenerates all these hormones that are that were produced by the corpus luteum the estrogen, inhibin and progesterone, they will decrease like so so when the corpus luteum degenerates Progesterone will Decrease and this will mean that progesterone cannot inhibit gonadotropin releasing hormone release and So gonadotropin releasing hormone levels will increase and this will allow a new menstrual cycle to occur also because of the decrease in Progesterone and estrogen in part means that these hormones cannot maintain the endometrium the endometrial lining in the uterus and so the endometrium will shed and this is known as the period and After the endometrial lining sheds this allows a new cycle to occur and though And then you see a increase in gonadotropin releasing hormone again and the cycle continues Hope you enjoy this video. Thank you

100 comments on “Female Reproductive System – Menstrual Cycle, Hormones and Regulation

  1. Thank you so much for your clear explanation! this is so helpful for me as a medical student. I'll keep watching your videos sir

  2. "estrogen is an important hormone, especially for females, because estrogen is basically male's equivalent of testosterone" hmmm, is that really why it's important? We all understand the GREAT IMPORTANCE of testosterone, so it only makes sense to use this analogy in explaining the importance of estrogen 🙄

  3. Tnk u sir for u'r kindnes. I learn more and more from u'r video.
    Greeting from indonesia
    I'm a nurse😇

  4. If you're studying for your GCSEs, watch my illustrated video to learn about reproductive hormones at the right level 🙂
    https://www.youtube.com/watch?v=l-RV8dcoYoI

  5. Out of a lot the the medical education videos online, I find yours better because of the way you enunciate your words. It feels like your actually talking to us. As compared to most other videos they sound like robots talking at us. Thanks for the high quality free content you provide us.

  6. This was so straightforward. You know they never explain to girls in school what Is happening to our body our whole lives on a horomonal level. That's why I went searching and I found this. Really easy to understand. Thank you!!!!

  7. If estrogen inhibits LH release. What happens when to much free estrogen is within the body such as from pesticides, organic in organic Xenoestrogens Phytoestrogens etc bisphenol A, 4-nonylphenol, 4-tertoctylphenol.
    What happens when we introduce these endocrine disrupters into our systems? The medical literature on this stuff blows my mind.

    “Do EDC exposures impair fertility in men or women? Can they cause sexual organ malformations, stunted reproductive development, or testicular or breast cancer? Do fetal exposures to EDCs alter sex phenotypes? Do they change later gender-related neurobiological characteristics and behaviors such as play activity and spatial ability? Could such exposures even be involved in the etiology of children born with ambiguous gender?
    EDCs include a spectrum of substances that can be loosely classified according to their known or suspected activity in relation to sex hormone receptors and pathways.

    The most-studied and best known are the environmental estrogens, which mimic estradiol and bind to estrogen receptors (ERs). ER agonists include the pesticide methoxychlor, certain polychlorinated biphenyls (PCBs), bisphenol A (BPA; a high production volume chemical used to make polycarbonate plastic), pharmaceutical estrogens such as diethylstilbestrol (DES) and ethinyl estradiol, and phytoestrogens, which occur naturally in many plants, most notably in soybeans in the form of genistein and related substances. There are a few known ER antagonists, or antiestrogens. Antiandrogens, or androgen receptor (AR) antagonists, include the fungicide vinclozolin, the DDT metabolite p,p′-DDE, certain phthalates (a group of chemicals used to soften polyvinyl chloride plastics), and certain other PCBs. And there are other types of EDCs that affect particular endocrine targets. The various EDCs differ greatly in their potencies relative to natural hormones, and in their affinity for target receptors. Some have been shown to act via non–receptor-mediated mechanisms, for example by interfering with hormone synthesis.
    In many well-documented cases of high-level fetal exposures to known EDCs such as DES, certain PCBs, and DDT, the answer to the question of whether exposure is associated with gender-related effects is clearly yes. But high-level exposures such as these are relatively rare and isolated. The debate today centers on low-dose exposures—generally defined as doses that approximate environmentally relevant levels—and the idea that low-dose intrauterine exposure to some EDCs during certain critical windows of development can have profound, permanent impacts on subsequent fetal development and adult outcomes.”

    “The endocrine system, comprising the hypothalamus, pituitary, testes, ovaries, thyroid, adrenals, and pancreas, is one of the body’s key communications networks. It regulates the function of specific tissues and organs by secreting hormones that act as precise chemical messengers. Development and regulation of the reproductive system is one of the major functions of the endocrine system.
    Sex determination and development begin early in gestation, with the differentiation of the embryonic gonad into either testes or ovaries. If the Sry gene is present on the Y chromosome, it will, when activated, trigger a complex cascade of hormonal events that ultimately results in the birth of a baby boy with all of the requisite male equipment in place and functioning properly. In the absence of the Sry gene, the end product of the process will be a baby girl. The female phenotype is considered to be the “default” pathway for mammalian reproductive development.

    These studies showed that in multiple-birth species it was possible for adjacently positioned male and female fetuses to transmit tiny amounts of hormones to each other, with pronounced phenotypic consequences. “We found that a difference of about a part per billion of testosterone and about twenty parts per trillion of estradiol [endogenous estrogen] actually predict entirely different brain structures, behavioral traits, enzyme levels, and receptor levels in tissues, hormonal levels in the blood—there is nothing you look for that . . . doesn’t differ in these animals,” says vom Saal.
    Such a delicately timed and precisely controlled process presents a myriad of opportunities for perturbation from exposure to EDCs. These chemicals mimic hormones, and can disrupt differentiation and development in a wide variety of ways, by duplicating, exaggerating, blocking, or altering hormonal responses.”

    Also, tissues are rapidly dividing and differentiating in the fetus, and such a high level of cell activity is vulnerable to disruption of normal development. With such small body mass in the fetus and child compared to an adult, exposure levels may be amplified in terms of relative dosages reaching target tissues. And sometimes, exogenous EDCs may show very low binding to plasma hormone-binding proteins and thus roam the body in an unbound state, with unknown effects.
    Much of what remains to be discovered about the impacts of EDC exposures on the fetus relates to a new concept called the developmental origins of health and disease (until recently known more commonly as the fetal basis of adult disease). “People are just now recognizing that this is indeed a possibility,” says NIEHS scientist Retha Newbold, a pioneer in the study of endocrine disruption who has spent decades researching the effects of exogenous estrogens, particularly DES. “Developmental exposure to low doses of EDCs may not lead to malformation or to anything you can look at and immediately recognize as a problem,” she says. “But it still could have long-term effects, such as alterations in metabolism, alterations causing cancer later on, or alterations causing infertility.”

    Seriously 😒 that’s scary to say the least… and there is much more to this.

    What’s your view?

  8. You saved my life with this video. I was having a difficult time with finding out which hormone is secred when and why but this made it very clear. Thank you!!!

  9. Took A&P 3 years ago. Watching back now in DMS school; still as amazingly helpful as it was then. Thanks for this gift!

  10. It’s not completely wrong
    But to start with gnrh is secreted in a pulsatile manner and not linear and the FSH doesn’t drop initially
    It increases and not a dropping level or a steady level instead it starts increasing to have a primary peak around the 6th day and then it drops and again a secondary peak at around the 12th or 13th day
    First peak is due to the fading corpus luteum to reach a peak after which due to the rising levels of the estrogen it drops after the peak………..second peak is due to the rising pulsatility of Gnrh which also stimulates LH and Second peak onFSH

  11. Try out the “Gοfαt Fanvuko” (Goοgle it) when you`re an infertile partners. The results of Western medicine didn`t make me happy. Nevertheless, my pregnancy was successful right after getting a proper diet and going through planned acupuncture treatments for a couple of months. Witnessing my year old daughter roaming around the house is genuinely wonderful. Check Goοgle to understand more about this great plan..

  12. I read somewhere that estrogen starts causing positive feedback when there is only one dominant follicle, is this correct ? Thanks.

  13. Finally starting to understand … thanks to ViolinMD who mentioned your channel in a video. Thank you so much for all the ressources and explanations you give, it is the most helpful videos I’ve found. Between you and NinjaNerd I might have a chance at passing my physio exam 😀 thank you so much

  14. LH stays constant due to negative feedback and FSH stays constant due to inhibin, is that correct ? Great video.

  15. oestrogen at moderate levels such as in the luteal phase should cause a positive feedback on the hypothalamus, increasing LH and FSH right? so why is it used in combine oral contraceptives?

  16. Hi! I'm taking my units in Anatomy and Physiology this semester and your videos are really great! I could easily visualize the contents in my book by just watching your collection! Thank you so much 😀 . Greetings from Philippines!

  17. Well done! Great detail! Thank you! I do wish you had panned back (is that even possible?) or somehow captured the completed drawing all in one frame. It would be helpful to be able to review the entire drawing.

  18. i would like to make a correction here, the menstrual cycle has 3 phases which are menstrual, proliferative and secretory phase, the ovarian cycle has two phases which are mentioned by the video follicular phase and luteal phase

  19. I've been struggling the learn the menstrual cycle for the MCAT for months. Every review book I came past just put up a picture of that stupid graph and I didn't understand anything until I found this video. Saying this video is a lifesaver is an understatement. Armando, you not only explained this concept amazingly but your approach of explaining WHY each step happened made this topic seem so easy. Thank you, seriously.

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