Menstrual cycle

[00:00:00]Hi guys, this is Dr. Sithar Amar Raju and today we'll be talking about menstrual cycle.

[00:00:07]Coming to menstrual cycle, what is menstrual cycle? Menstrual cycle is the cyclical changes that occur in uterus, ovary, cervix and vagina in any reproductive woman during her reproductive life. So it starts from minarchy that's the onset of menstruation and ends at menopause and usually a menstrual cycle duration is around 28 days can be in between 18 to 40 days and we consider day one as the first day of bleeding.

[00:00:44]So coming to the ovarian cycle, ovarian cycle uh these 28 days are divided into the first 13 days is divided into follicular phase. So development of a graphian follicle then it is released that on 14th day it is called ovelation phase. Then it forms corpus lutium that is called as lutal phase which extends from 15 to 28 days.

[00:01:09]So here you can see from the primordial follicle to the ovelation it is called as follicular phase and the release of OM is called as ovelation. After the release of Om the remaining graphin follicle will become carpus lutium. Carbus lutium based on whether the pregnancy occurred or not it if pregnancy doesn't occur it regenerates. If pregnancy occurs, it remains for three more months for maintenance of the pregnancy.

[00:01:44]And coming to the follices, usually at birth there will be 7 million follicles and at birth it becomes 2 millions. So in fetus around 7 millions and at birth 2 millions and out of this only 1 million under goes the first miatic division and they are arrested in prophase one. So prophase one arrest will be there. After that during puberty there will be only three lakhs of follicles remained and out of this only 450 follicles will be released. remaining all will undergo atricia.

[00:02:26]So the phases of pime follicloenesis one the first one is primordial and the next one is primary secondary tertiary and graphin follicle. From this graphin follicle we'll get the oam which we call that as ovelation. So what are these phases? So primordial follicle is nothing but a wite surrounded by flat granular cells. So it is a deployed primary set around 10 microns in size and it is surrounded by flattened granulosa cells and they are incompletely covered and there is a baselina.

[00:03:08]Now it converts into primary follicle.

[00:03:12]So the primary follicle here the granulosa cells becomes cubuidal that means flattened will become cubuidal and they are completely lining the usite and the usite increases to 20 microns and there occurs a layer called as zona pelucida which occupies the space between granulosa cells and usite.

[00:03:42]After the primary follicle, it it develops into a secondary follicle which is also called as preantral follicle.

[00:03:50]Here the granulosa cells becomes multi-layered. There are multi-layered granular cells and you see the usite has become almost 100 microns and there is development of thika internal and tika external. Tikka externa becomes the capsular wall and this t thea internal will secrete hormones. Now it modifies into the next stage called as tertiary follicle or antal follicle. Antrum is the space. So the space that is developed in the follicle is called as antrum. So here the granular cell still starts proliferating and there appears follicular cavity and this cavity is filled with a substance called as liquor follicle which is rich in estrogen and the usite is pushed to the periphery and surrounding granulosa cells around this are called as cumulus and those cells which are attaching to the usite or called as corona radiator and now the usite has developed into a size of 150 microns.

[00:05:11]Now the final stage of development of follicle is graphian follicle. Here if you see it is around 2 to 5 mm. The side becomes 2 to 5 mm and the cavity becomes larger and we call that as antrum it becomes larger and the the interna becomes prominent.

[00:05:36]Thika interna becomes prominent and just before ovelation it completes its miotic one division that is it is arrested in proace. It just completes it and it forms secondary wite which is a hloid and first polar body.

[00:05:55]Still it has not completed its meiosis 2. Miosis one is completed and it produced first polar body and these granular cells are called as cumulus ofus and the cells around the usite are called as corona radiator.

[00:06:16]Now, now the graphen follicle at 14th day is ovulated and the reason for the ovelation is sudden increase of luteinizing hormone just 24 hours prior to ovelation. So what is happening here is there is two mechanisms. One increase in prostaglandon E2 and F_sub_2. Another one is activation of plasmogen activator. This plasmogen activator will activate plasmine which has a fibbrinolytic activity and it breaks the follicular wall. So it breaks the follicular wall and this prostaglandin E2 is the vasodilator and it increases the blood flow which increases the follicular fluid so that the pressure in the antrum increases and pushes the usite to the periphery and it appears on the wall of the ovary as a stigma and prostaglandin F2 alpha is primarily concerned with activation of lizoomes which again causes proteolyis and digestion of follicular belly. All these factors favors the rupture of the follicle and release of and the primary reason for this is LH search.

[00:07:37]So this is what stigma this is what the protruding oite and what are the indicators of ovelation. So one rise in basal body temperature around.3 to.5° centigrade rise in the basal body temperature and estimation of urine hormonal components like estone at ovelation and pregnant alone after ovelation their content increases or determination of plasma hormonal levels estrogen and luteinizing hormone just prior ovelation increases and FSH decreases just before ovvelation and progesterone's levels increases after ovelation and there might be a lower abdomen pain during midcycle that is called as metal smudge which is due to the release of a and celia ultrasonography can reveal the follicular development and empty follicle and firm pattern will be seen in the cervical mucosa when it was estrogen dominant. Once the estrogen level falls that means Om is released cervical mucus pattern loses its fern pattern.

[00:09:02]Next after the ovelation from 15th to 28th day we call that as lutal phase.

[00:09:07]Here the thicker cells and the granular cells undergo luteinization and now they are more sensitive to luteinizing hormone and accumulation of lipid droplets in those cells occurs.

[00:09:21]Now the these lutein cells will secrete progesterone and estrogen.

[00:09:30]After the ovelation the empty graphine follicle will be filled with blood and we call that as carpus hemorrhage and which so slowly converts into carpus lutium under the influence of luteinizing hormone and if at all fertilization occurs the sincio trophoblast will maintain the carpos lutium by secretreting hCG because LH is inhibited by circulating estrogen as well as progesterone. So no more LH once the lutal phase is about to over. If at all fertilization occurs the sincio trophoblast will secrete HCG and that will continue the carpus lutium for 3 months. After that placenta will come into the action and it will secrete progesterone. If no fertilization occurs so there is no HCG as well as no LH so carpass lutium degenerates into carpus albbeans.

[00:10:39]Now coming to the uterine cycle. Utiline cycle is divided into three phases. One menstrual phase that is bleeding.

[00:10:51]to proliferative phase that is division of the endometrium and secretive phase that is more development of the glands.

[00:10:59]So one to five days is called as menstrual phase 6 to 14th day is called as proliferative phase and 15 to 28th day is called as secretary phase.

[00:11:10]Why menstrual phase occurs? Why bleeding occurs? It's simple. Uh it's a invaluation of the endometrium because estrogen and progesterone are reduced because the FSH and LH are reduced.

[00:11:31]This causes as they are potent vasoddilators.

[00:11:36]Now vaso constriction occurs which causes hypoxia and necrosis to the stratum functional layer and this causes rupture of blood vessels and bleeding.

[00:11:48]Now around 35 ml of menstrual bleed along with the 35 ml of cirrus fluid is routine menstrual bleeding and the bleed contains one bleed blood as well as disclamed epithelium. As the blood clots it is liced immediately by fibbrronolyin so that it can easily flow out of the uterine cavity and now the thickness of the endometrium is around 1 mm after the menstrual phase.

[00:12:17]Now comes the proliferative phase. So whatever that is lost now we are getting back our estrogen.

[00:12:27]This estrogen will cause proliferation of endometrial cells, development of glands, development of new blood vessels that is called angioenesis and as the proliferation occurs now the thickness increases to 4 mm. So 3 to 4 mm. This primarily under the influence of estrogen. Coming to the secretary phase, it is from 15th to 28th day. Now secretary somewhat concerned with the glands. So the glands become torturous and the blood vessels become dilated and thickness increases to 6 mm and it is dependent on both estrogen as well as progesterone.

[00:13:11]And coming to the cervical changes primarily the mucus cervical mucus become thin and alkaline during proliferative phase that is primarily under the influence of estrogen and stretching of the cervical mucosa is called as spin bark test. If at all that mucus is stretched onto a slide and alert to dry it forms a fern pattern due to more uh sodium chloride in that that is called fern pattern. So estrogen will cause spin barky test and firm pattern and in secretary phase this mucus will become thick and this firm pattern will be lost.

[00:13:49]Coming to the vaginal changes the epithelium becomes quified during proliferative phase that is under the influence of estrogen and luccoytic infiltration as well as epithelial proliferation in secretary phase.

[00:14:07]Now coming to the hormonal regulation of menstrual cycle we have to primarily know that hypothalamo pitutary ovarian axis. So first of all hypothalamus is the one which secretes G&R and it won't secrete it continuously it secrete it in pulsatile manner and this acts over the antidiary antidiary will secrete gonadotropins like follicular stimulating hormone and luteinizing hormone which acts on the ovary to produce estrogen and progesterone. These estrogen and progesterone will act over uterus and there are two feedback mechanisms here. Most of the cycle estrogen will and progesterone will inhibit either pituitary or hypothalamus to stop G&R and FSH and LH. But exactly prior to the ovelation this increase in levels of estrogen will cause paradoxically a positive feedback mechanism that is only before the ovelation.

[00:15:15]So coming to the only ovarian changes so follicular phase so the name itself it's saying follicular phase so primarily dependent on FSH. Okay we'll see that.

[00:15:25]So J&R will be secreted pulsey for every 24 hours and the hgnrh will cause the release of FSH and LH. Now FSH will act over the granulosa cells to produce estrogen and LH acts over the cells to produce androgens.

[00:15:48]This estrogen which is produced from the granular cells will further help in the growth of the follicle.

[00:15:59]So the dominant follicle is the one which is having more number of FSH receptors. More the number of FSH receptors, more will be the estrogen, more will be the growth of the follicle.

[00:16:14]So the dominant follicle is recruited in that way. Okay. Uh early follicular phase what is happening is G&R FSH LH.

[00:16:26]This LH will act over the cells and this the cells will produce androgens. FSH will act over granulosa cells. Granulosa cells contain an enzyme aromatase which converts these androgens into estrogens.

[00:16:47]In midfollicular phase here these FSH is acting over the follicular cells granular cells which secrete a hormone inhib which inhibits the FSH secretion. So FSH is inhibiting itself by using an hormone inhibine.

[00:17:12]In the late follicular phase just before the ovelation this LH also causes activation of granular cells. Prior to that LH has only receptors over the cells but during just before the ovelation granulosa cells also will have LH receptors. Now the in that causes high levels of estrogen which favors the further more release of LH which causes the vvelulation. So there is a double feedback mechanism. Estrogen at moderate levels will cause negative feedback mechanism. Estrogen at higher levels positive feedback mechanism.

[00:18:01]And this causes the activation of more receptors on the granular cells FSH as well as LH receptors.

[00:18:11]So furthermore, so more the receptors more the growth of the graphian follicle and LH also stimulates the secretion of estrogen as because androgens are produced from the cells which are converted into estrogens by an enzyme aromatase which is located in the granulosa cells and LH also acts on the the cells to produce progesterone.

[00:18:41]While while in the lutal phase these theika cells produce progesterone and paradoxically it inhibits this aromatase ovelation. So LH surge which occurs just 24 hours and this positive feedback of rise of LH is due to rise in estrogen.

[00:19:03]So just prior to the ovelation there will be rise of estrogen which causes LH surge.

[00:19:09]Coming to the lut lutal phase mainly under the control of luteinizing hormone which converts the granulosa cells into lutin cells and secretion of estrogen and progesterone starts and this luteinizing hormone is the one which maintains carpus lutium and FSH also maintains the secretary activity of carpus lutium and also as we said it also stimulate the lutin cells to secrete inhib.

[00:19:42]So in the lutal phase the primary one is luteinizing hormone which acts over the corpus lutium to primarily secrete progesterone as well as FSH acts on the corpus lutium primarily for the secretion of estrogen. This act over the uterus.

[00:20:00]So progesterone which is estrogen creates a negative feedback and inhibin also inhibits the G&R FSH and LH and as there is no luteinizing hormone carpass lutium starts degenerating. So if carpus lutium is not there no estrogen and progesterone. So no estrogen and progesterone means endometrium sheds.

[00:20:28]Endometrium sheds and again G&R starts its production and which activates FSH and the next cycle repeats.

[00:20:43]So uh coming to the uterine changes one is proliferative phase another one is secrettory and minal. So menstrual phase we already know estrogen no progesterone vasa constriction death of the tissue that causes bleeding and proliferative phase is primarily under the control of estrogen and secretary phase is primarily under the control of progesterone as well as estrogen.

[00:21:09]So to summarize first G&R is secreted from hypothalamus which acts over the anterior pituitary to produce FSH and LH.

[00:21:24]This FSH will cause the growth of follicle and this LH surge will cause ovelation and this luteinizing hormone maintains this corpus lutium and just before the ovelation the levels of estrogen increases which causes the LH search. If estrogen is there that causes proliferative phase if progesterone is there that causes secretary phase. So in proliferative phase there is division of cells as well as angioenesis as well as glands. In secretary phase you can see glands become torturous, blood vessels become torturous. Once estrogen and progesterone are stopped here you can see there is bleeding that's a menstrual I think I'm clear. I think hope you understand it well. Thank you.

[00:22:20]Bye.