The Pituitary, Hormones, & Ovulation | The Female Reproductive System | Part 2

welcome back to part two of our female reproductive series in this video we're going to be talking about ovulation in our previous video we broke down the timeline of the menstrual cycle or the female reproductive cycle in an average of about 28 days but we only got into the first few days with period cramps till about day five or six we needed to finish up that first half which was referred to as the follicular phase and that's going to be going into this topic of ovulation now again if you missed that video check it out it'll help the rest of this stuff make more sense but let's jump right into this video with this question [Music] let's first talk about this idea of why do they call it the follicular phase now we are trained to think of hair when we think of the word follicle because yes we do have hair follicles that hair grows and erupts out of however women have these structures called ovarian follicles so if we were to zoom in to this structure here that we refer to as the ovary just zoom in and zoom in and zoom in we would see these tiny little bag-like structures essentially a circular or spherical cluster of cells and inside of that follicle is a cute little egg that we call an ovum or an oocyte so think of this when you associate an egg you kind of need to associate with what carries it which is a follicle and there are tons of follicles inside the ovary so hopefully that kind of makes sense egg is inside follicle multiple follicles are inside each ovary now a woman is born with about one to two million eggs and so therefore follicles when puberty happens they're left with about three hundred thousand so take a look at this picture what you're seeing is an ovary with one follicle and therefore an egg inside the follicle remember the follicle is just a little cluster of cells on the outside creating that circle and the egg inside of there and what's happening is this primary follicle that you can see at point number one is starting to get larger and larger and larger as it goes from two to three to four there and it's maturing now this is illustrates a really important point because what has to happen during the first 14 days of the female reproductive cycle is that some of the follicles are going to have to mature but i need to differentiate between these two terms there are these follicles called primordial follicles versus a primary follicle in that picture you're seeing a primary follicle so primordial just means first or beginning and the majority of the follicles and therefore the eggs inside the follicles are considered primordial follicles remember that figure we mentioned about three hundred thousand but what changes the primordial follicle into a primary follicle what happens at the beginning of each cycle this follicular phase is a handful of those primary primordial follicles become primary follicles about six to twelve of them so say you've got two to three hundred thousand primordial follicles just hanging out in the ovary the beginning of the female reproductive cycle during this follicular phase a handful six to twelve become primary follicles now what causes this to happen funny you should ask it has to do with hormones so the first two hormones we're going to talk about are follicle stimulating hormone and luteinizing hormone follicle stimulating hormones a pretty good name for a hormone that's going to stimulate the ovarian follicle however these hormones aren't released from down below they're actually released from a brain structure or structure within the brain called the pituitary gland let's take a look at that here i'm probing this cool structure called the pituitary gland this thing is nicknamed the master gland because it secretes all sorts of different hormones but we're only going to focus on those first two like we mentioned follicle stimulating hormone and luteinizing hormone now what's crazy to think about is that these have to get into the bloodstream so they can actually get down to the ovarian tissue and have their effect so the pituitary gland release them into the bloodstream since blood vessels go everywhere eventually those hormones will make it down to the female reproductive structures what's also helpful to see is this graph now if you look at this chart here in this graph you can see the levels of follicle stimulating hormone in blue and the levels of luteinizing hormone in red going throughout the 28 day cycle now there's a huge spike right before ovulation on day 14. we'll get to that in a minute but i first want to focus on is that little blip at the beginning during the first few days and that kind of correlates with the period so those hormones go up just a little bit and what that does is creates this pulling from the primordial follicles so of all those primordial follicles because of that little blip in follicle stimulating and luteinizing hormone some of those primordial follicles get pulled into becoming primary follicles about 6 to 12 what we mentioned a little bit earlier so now we've got six to 12 follicles that are going to start maturing throughout this first 14 days now i know that picture just showed one and i'll explain why it just showed one but we start with about six to 12 combined between the two ovaries that are potentially going to mature over the next 14 days so i want to have a little bit of a checkpoint here we have six to 12 maturing follicles at this point through this first 14 days do we want all of those to mature and to have an egg be released the answer is no not unless you want to have 6 to 12 babies at the same time now there are exceptions people have had triplets or quintuplets but typically a female will only have one follicle fully mature what happens is one of those six to twelve follicles tends to grow a little faster than the others and the others tend to disintegrate over that 14-day period and that's why that picture was kind of more simplistic it was showing you that one follicle that grew faster than the other 6 to 12 potentially and becomes what they call the dominant follicle that dominant follicle will move all the way to the edge of the ovary and kind of wait a wait for something to happen around day 12. so let's go back to that chart one more time look at what happens close to day 12 with luteinizing hormones specifically you get this huge surge of luteinizing hormone and yes a lesser degree of a surge from follicle stimulating hormone but that big surge essentially signals ovulation and what happens is this egg is released from the ovary and now we're into this next phase of what's going to happen to this egg and we'll answer that in a minute but there's one other thing i need to jump back to remember we had originally 6 to 12 follicles starting to mature again we know only one of them fully matured but out of those 6 to 12 as they're starting to mature they start releasing estrogen so estrogens coming out of these follicles and therefore the ovaries and these levels tend to spike up take a look at another chart this other chart is showing you estrogen in blue and progesterone in red you can see progesterone stays relatively low in that first 14 days but look about look at about day six or seven what happens to estrogen that correlates with the same time that those ovarian follicles are starting to release their estrogen that's where it's coming from and that's really important to starting the process of building up the uterus again we'll jump up to the other graph and you can see right around the same time day seven the uterus or the inside lining of the uterus is starting to build up again and that's a really important function of those ovarian follicles releasing estrogen before most of them actually disintegrate or don't become the dominant follicle there is one other purpose to having the estrogen spike prior to ovulation i'm going to have you kind of think about that for a second and see if you're right by the end of the video because i'll address that at the end of the video but just kind of think about is there any reason to maybe spike estrogen levels right before ovulation besides just building up the uterus kind of think about that and we'll talk about it at the end and what i meant by the end was during the fourth video sorry a little bit of a cliffhanger there but it'll be worth it again thank you guys for watching hopefully that gave you some more information on another step in this female reproductive cycle namely ovulation again if you're not new to us if you're not new to us no if you are new to us please subscribe ring the bell let us know your feedback your comments below we love your guys's questions we can address them in the comments or even our weekly live sessions and until next time happy ovulation [Music] you

Channel: Institute of Human Anatomy

Views: 133,920

Rating: 4.9743795 out of 5

Keywords: female reproductive cycle, corpus luteum, anatomy and physiology, follicle stimulating hormone, menstrual cycle, luteinizing hormone (hormone), reproductive system, menstural cycle, follicular and luteal phase, female reproductive cycle video, female reproductive cycle ovulation, ovulation, corpus luteum after ovulation, follicular phase, institute of human anatomy, institute of human anatomy tiktok, ovulation cycle, ovulation process, follicular ovulation and luteal phase

Id: 07rxFGPJV2Y

Length: 9min 25sec (565 seconds)

Published: Wed Sep 09 2020