Female Menstrual Cycle - Part2: Pre-Ovulatory Phase (Follicular Phase and Proliferative Phase)

0:01 after that overview of female reproductive cycle now we will discuss that what happens in pre-ovulatory phase that what what are the events that occur before the process of ovulation so now in this lecture we will be discussing what what is the pre ovulatory phase of female reproductive cycle so again this is a pre-pubescent girl and in her ovary there would be a about 40 000 primordial follicles that would be present in her ovary and what are these primordial follicles they consist of primary oocyte right they consist of primary oversight rested in prophase one

0:51 of meiosis and these primary oocytes they are surrounded by a layer of a flattened layer of follicular cells so this whole structure this primary oversight surrounded by layer of prime these follicular cells this whole structure is it is named as primordial follicle and we have already discussed this but let's just repeat here that from where this came we have discussed that before a female is born she start creating these primordial follicles and these primordial follicles they remain in her ovary till she is born and then she become a prepubescent girl but meanwhile many of these primordial follicles they die out

1:43 and those that remain each month uh they one of them is released right so let's start the lecture so what is the what is there is a term called monarchy when the menstrual cycle first time start in the lifetime of a female it is called menarche so what is menarche monarchy simply means start of menstrual cycle or the first menstrual cycle of a female the event when first menstrual cycle of female start we call it menarche and menarche is of course the start of female menstrual cycle and then this female menstrual cycle it continues each month right each month a new cycle start and

2:37 this process continues month by month till the menopause and menopause is about the age of 50 years that is average of course there is some danger we will not discuss that right now and monarchy the average age of menarche is about 13 years 13 or 14 years i'm not good at remembering numbers right so let's discuss that what happens with a single primordial follicle each month what happens that about 15 to 20 primordial follicles start growing and out of these 15 to 20 primordial follicles single best follicle and that will not be

3:23 primordial follicle by that time single best follicle single best grown up follicle is released out of the ovary into fallopian tube we will discuss just that and just now so this is a single primordial follicle what is the first step the first step is that these flattened or squamous cells follicular cells they grow up a bit right and as they grow in size they are now no more flattened they become cuboidal right so as these follicles they become from flattened to cuboidal they are now not primordial follicle but they are now called but they are called primary follicle

4:13 and because it is it is consisting of a single layer of follicle so it is of course unilar this is also unilar but because it is always primordial follicle is always having a single layer so we do not call it uni lamellar as it is obvious we just call it primordial follicle but primary follicle later on we will learn that primary follicle can be having can be consisting of single layer or more than one layer so primary follicle can be unilamellar or multilaminar right now at this point uh this this follicle it is not having any receptor to mate with its mate

5:03 what is the mate of this follicle of course the sperm so it forms a special glycoprotein code a special glycoproteinicius layer is formed in between this follicular cell and oocyte and this this glycoprotein coat it harbors species specific sperm receptors right and and this layer is called this glycoprotein layer is called zona pellucida pellucida mean transparent or translucent and zona is layer so it is kind of translucent so that is why it is called zona pelosita and what does it contain zona species specific form receptors right

5:58 clear after law then what happens that of course as the female is maturing she is advancing in her age her brain also start maturing and her hypothalamus it starts releasing a special substance called gonadotrophin releasing hormone and grandiotrophin releasing hormone passes to the interior pituitary and here it stimulates particular cells in the interior pituitary to release gonadotrophes what are

6:44 gonadotrops gonadotrophs are special hormones that have effects on gonads what are female gonads ovary right so these are namely these are called fsh and lh fsh and lh are called gonadotrophs are gonadotrophic hormones traffic means to provide nutrition to provide nourishment to provide to help in growing right and gonadmin ovary so they help these follicles to grow inside the ovary so that is why they are called gonadotrophs and gonadotrophs are from where they are released they are released from anterior pituitary but they are released on the order of hypothalamus

7:33 and hypothalamus is very small part of the brain it is the size of about a fingernail and it is very very important part of the brain rather i should say it is very important part of your whole body it it has many different functions and it has some role in your mood as well as in the control of autonomic nervous system right so here something important to mention is that because this follicular phase we are talking this pre ovulatory or follicular phase because this follicular phase it is orchestrated by fsh and lh and this fsh and lh because they are released on the orders of hypothalamus and orders come in the form of gnrh

8:27 that is why this part this phase of uh ovarian ovarian cycle or female reproductive cycle this phase i mean follicular phase of this cycle it is much more variable and it it is affected by the mood of a woman it is affected by environmental factors surrounding the woman right why so you got the point because hypothalamus is involved in in in all these things right hypothalamus has an important role in mood right so that is why because this part is controlled by hypothalamus it is much more likely to be variable as compared to post ovulatory phase

9:18 right previously we have i have just told you that this part is variable but i have not mentioned this important detail so here is the one of the reason of course it is a multi-factorial thing we are not sure the exact reason and one of the reason is this so fsh it was at this baseline so fsh started increasing so here is that fsh level of fsh in blood increased right its rise rise up right along with that level of lh also increased in blood and as it increased as the level of these two hormones it increased in blood it they affected the

10:07 these follicles in the in the ovaries right so here another important thing is that from primordial follicle the up to formation of primary follicle i mean uni laminar primary follicle it is said that it is independent of fsh and lh from this point and beyond fsh and lh are important and out of this if i ask you what is the most important factor for growth of follicle especially at this point that would be fsh as the name indicates it is follicular follicle stimulating

10:52 hormone nh also has important role in development of these follicles but we will discuss a bit later so mainly under the effect of fsh and to some extent lh this prime mode this primary follicle which is unilamellar it proliferates it increases in size as well as it increases the number of cells so new layer will be formed more than one two three four and so on new layers of follicular cells are formed and not just that it is not depicted in this in this diagram but size of primary oocyte also increases right these two things are going on side by side primary oversight

11:43 is also growing as well as the these follicular cells they are also growing and proliferating right so now this primary follicle it is no more uni lamellar it has now become multilaminar multi lamellar primary follicle lamella lamellar or lamella means layer so it is having multi layers of follicular cells so it is primary follicle that is multi-laminar then what happens that some interstitial cells right the cells that are present in the interstitium surrounding this place some interstitium or interstitial connective tissue

12:28 it surrounds the this follicle interstitial connective tissue surrounds the follicle and it surrounds it surrounds the follicle like a casing or covering outer casing or covering and this casing are covering it is called what it is called it is called thicker right so thicker is formed and this thicker consists of two layers thicker internal which is more cellular and outside the thicker antenna is thicker externa which is less cellular but more uh vascular it has more vasculature it has more blood vessels right so thicker antenna and thicker external

13:17 now here a very important role of lh that must be discussed that of course as i have told you that level of fsh and lh both are rising in blood so here along with fsh and especially acts and it especially acts on these thicker cells especially thicker internal cells and it causes these thicker cells to release testosterone you know in males we have lead cells and you remember these leading cells they also came from interstitium they are also called interstitial cells and another name

14:02 of lyric cells is interstitial cells i am talking about males in females these interstitial cells they are not leading cell but they are similar to lead excel they are called thicker cells but as they say nature cannot be changed so leading cells were secreting which hormone in males testosterone testosterone so in this case these are not lydic cells but these are you can say female counter part of leading cells these thicker cells they are also secreting testosterone and on the order of lh so those cells in maize lead excel they were also secreting

14:52 uh testosterone on the order of lh and here they are doing thicker cells are doing the same but fortunately these thicker cells and maybe this is the reason that these thicker cells they are closely associated with these follicular cells and these follicular cells being the real girlish cells they convert this testosterone into estrogen they have special aromatic compound not compound not aromatic compound there is an enzyme called aromatase so they have special enzyme called aromatase which converts the testosterone into estrogen so thicker cells they produce testosterone but this testosterone it is picked up by follicular cells and converted

15:44 into estrogen and they use rheumatoid enzyme to do so right so estrogen has many important functions in female development of primary and secondary sexual characteristics development of breast development of that particular hip shape in females right so along with that estrogen here inside it uh is also having a special function now as this estrogen as these follicular cells they start secreting estrogen they also become filled with granules of estrogen right they become filled with

16:30 granules of estrogen so these cells are called now called granulosa cells so follicular cells now they are called granulosa cells estrogen as i have told you here estrogen has is having another important function and that function is to form to produce special lh receptor on these follicular cells previously lh receptors were mainly present on thicker cells but now lh receptors are also present on granulosa granulosa cells right and that is due to history then of course it is not that simple

17:20 many different factors are involved but i am just trying to simplify it as much as possible so as it continue to grow as these follicles of course this is not single follicle that is growing i'm just showing single follicle but about 15 to 20 follicles are growing they start growing each month so as these follicles are growing the level of estrogen rises in blood level of estrogen rises in blood and what this histogram will do estrogen will go to uterus and it will order the

18:06 uterus that start preparing the home for baby as i have told you that females are quite optimistic creatures of god that if as soon as these follicles start growing they hope that pregnant i'm i'm not i should not say hope but rather i should say they are so sure that pregnancy will occur that they start creating the home for baby and this is a very special beautiful home multi-story home with a special tree and windows here and where the home will be formed home will be formed in the endometrium endometrium is the innermost it is the innermost layer of uterus and

19:00 before uh this home start forming it is having only single layer and that single layer of endometrium that is always present this single layer is called basal layer it is called basal layer of endometrium and on the order of estrogen from ovary this home start growing on this land a beautiful multi-story home began to form what i mean by this is that this endometrium proliferates right it it has become now multi-layered now it is having three layers along with that

19:46 these windows i mean these glands are formed right and these trees are these blood vessels are these are trees so this basal layer are stratum basil it is always present then the new these two new layers are formed the middle layer is stratum spongiosum or spongy layer stratum spongiosum it contains this mainly this major part of these glands these uterine glands and finally the innermost is the compact layer and it is called what it is called stratum compectum it consists of dense connective tissue compactly arranged and necks of these glands right so what

20:35 happened due to the order of estrogen this uh this endometrium of uterus it proliferated right and it formed a multi-layered it form multiple layers and that is the home for baby that if pregnancy occurs then baby will come into this into these areas and it will grow in these layers right then what happens again on the orders of fsh and lh it continue follicle continue to grow and again it is it forms many more layers eight to ten layers may be formed right then uh

21:25 some follicular some special pockets of fluid are formed in between these cells and this fluid it is mainly secreted by these follicular cells and mainly it consists of substances that are secreted by these follicular cells but it also has a contribution from transodate of blood vessels that some blood vessels that are present here some fluid it seeps out of these blood vessels right and this fluid it it forms this pockets of follicular fluid so these pockets of follicular fluid they they coalesce to form this complete structure that is entering and as soon as

22:16 these pockets of follicular fluid they form this structure it is no more primary follicle it is now a scandaly follicle right what it is it is secondary follicle clear up till now and this this structure it is now called antrum and again it is still scandaly follicle but inside this skenery follicle this oocyte that is present it is still primary oocyte it is still arrested in meiosis one prophase one of meiosis one specifically in deploying stage now here something important i should discuss and rather i should mention that there is some

23:02 discrepancy in naming scheme some authors they like to call this as primary follicle and as soon as this follicular layer follicular layers become multiple that is multi multi-layered that that this follicle become multi-layered they call this as secondary follicle and when this anterim forms they call it tertiary follicle right so there is some discrepancy so i thought that i should have mentioned it here so that is why i'm mentioning but this classification which i have and i have mentioned in this slide it is most accepted one most of the book the most of the

23:53 books they follow this classification for example even the keith moore and langman larson and major books of embryology they are following this type of classification then these then these follicle these follicular cells rather i should say granulosa cell now they are granulosa cell so these granulosa cells that are surrounding this primary oocyte right they look like a cloud a cloud of cell a cloudy substance that is surrounding the oversight so these and this structure that they form by surrounding this oocyte it is called cumulus or forest cumulus mean

24:44 clouds over porous mean that they are surrounding the oversight so this is cumulus or forest and it's worth mentioning here that it is still arrested in prophase one meanwhile many more lh receptors are formed up till now almost all of the granulosa cells they are primed to listen to lh so here what happens that of course as i have told you 15 to 20 primordial follicles started growing but they were growing at their own pace some grow slowly some grow

25:31 quickly and swiftly right as you you might have observed that in your class not every student is super brilliant and super excellent academic wise similar to that these follicles they also can not each and every follicle they it cannot grow at much faster pace and only one of the follicle will dominate all others as as you have some topper in your class who domin who dominates academically who dominates all other students so here also this single follicle is which is dominating which has

26:17 overgrown which has outgrown all other follicles it is called dominant follicle and all other follicles they are non-dominant follicles now here something interesting happens of course estrogen level will continue to rise because follicles they continue to grow and follicles will continue to secrete more and more estrogen right but here what happens that as estrogen grow as estrogen rises too much it probably through feedback inhibition it decrease it causes a decrease or decline in fsh level so as estrogen so here you can see as estrogen level

27:07 rises for fsh levels slightly it it slightly continue to it gradually continue to decline right but lh level it remains mostly unaffected and now what happens as we had many follicles growing at their own pace the dominant follicle can tolerate the decrease in fsh because it is dominant it is not just dominant but it is also now have become independent of fsh and because it has become independent of sport from fsh it will still survive even

27:53 if fsh level drops but these poor kids they were still dependent upon fsh so they die out and this process is called follicle follicular atresia right dr najib has used a beautiful analogy to illustrate this concept and with his permission i am gonna re-mention that analogy here you know what he says dr najib says that this anterior pituitary it is like a father and these growing follicles these growing follicles are like children of that father and because

28:46 they are still kids and they are growing right so interior pituitary provide them financial support to help them grow and it provides financial help to them in the form of fsh and when these children they continue to grow and they start secreting their own estrogen on hormone they're on estrogen and estrogen is their cash right so as they as they start earning their own cash that is their own estrogen the father i mean interior pituitary it pulls up the cash it pulls up that financial sport in the form of fsh and as it pulls that

29:35 financial sport and fsh level starts declining only one single child which which is which has now become financially independent of fsh only that is able to survive and all other poor children they die out right so that's what happening in this pre-ovulatory phase so what's happening in the pre-ovulatory phase uh these follicles are growing right so follicles are growing and this is called follicular phase right so pre ovulatory phase is follicular phase of ovarian cycle and in regards to ovary what is sorry in regards to uterus what is happening in uterus

30:27 that in first four or five days the the uterine wall which was formed the functional uterine wall the other two layers what were these two layers stratum spongiosum and stratum compectum bizarre remains there but these two layers compactum and spongiosum they are shed out they are shed off in initial four or five day days and that is called menstruation and in later days estrogen from these follicles it causes the proliferation it causes the proliferation of uterine wall proliferation of endometrium so it is proliferative phase of uterine cycle

31:16 so pre ovulatory phase is also follicular phase of ovarian cycle and it is also menstruation in first five days followed by proliferative phase of uterine cycle right so i think the cycle is very easy to understand even this much information is enough for you and it is happening like a falling domino everything is very logically happening that first first of all what happens that hypothalamus starts releasing gnrh which causes release of fsh and fsh causes follicular growth and follicular growth leads to formation of estrogen and estrogen causes uterine proliferation

32:01 and this much is the pre-ovulatory phase of the cycle i don't think it is any difficult i don't know why the textbook makes so much fuss about this cycle it is very easy and simple so this much information is enough for most of you people but i i want to mention some important points that brilliant doctors and brilliant students must know that so you know this part of uterus this is called cervix okay so here is the cervix

32:47 what is cervix cervix is the part of uterus it is the part it is the lower part of uterus which connects the body of uterus with vagina right it connects the body of uterus with vagina and as the as i have told you previously as with the this this reproduct female reproductive cycle changes occur in almost every part of the female body and of course as cervix is a part of uterus in some important changes also occur in cervix first of all what is the what is the situation of

33:32 cervix before the cycle start that these these holes of cervix these are called cervical os these cervical os in tender and external cervical loss they are almost completely closed at the beginning of cycle but as estrogen level rises as estrogen level as estrogen level rises these cervical loss they slightly open up at the beginning of cycle cervix was quite firm but now before the ovulation start and we will discuss ovulation in next lecture before the ovulation start as the historian level is too high this estrogen this too much high historian

34:23 it causes the cervix to become elastic and soft and this cervical us open up because this is the fertile period of female and in this during this duration sperm has to come and bomb can easily enter but that is not just that cervical glands present here they secrete special hair like strands of mucus so these mucosal strands these hair like structure they are arranged parallel to each other to allow a special to welcome the sperm into this uterine cavity

35:10 right along with that what happens to mucus the the mucus that is secreted by these mucosal glands what happens to cervical mucus is that initially the mucus is thick and dry but as estrogen level continued to rise gradually the mucous levels start to become thin and watery so here mucus was dry but at this point mucus is very thin and watery what is the significance of this is that this thin and watery mucus it allows the sperm to easily go inside of course there are many other changes that occur but i don't think we should discuss all the

36:00 changes here but because that should be discussed in a separate lecture finally another important point is that as the estrogen level peaks up as estrogen reaches estrogen level reaches a peak there is slight dip in basal body temperature curve there is slight decrease in basal body temperature and this is a screwed sign of ovulation that now ovulation will start within a day or two right along with that because this is a fertile period of female and estrogen level is very high estrogen causes increase in libido of a female

36:50 as i have told you there is a even behavioral changes in female with the with the cycle initially as the menstruation occurs and bleeding occurs female is a bit aggressive but during this fertile period female sexual desire increases right and i i think she becomes more polite right so this was about pre-ovulatory phase of female reproductive cycle in next lecture we will discuss ovulation and peri-ovulatory phase that what happens before immediately before and after ovulation thank you so much for watching this video