Transcript for:
Reproductive System Overview

hi this lecture video is on reproductive physiology where I'll be covering covering an overview of what the male and female reproductive organs so I'll begin with an introduction of some some terms and some basic concepts first stuff that reproduction is by parental and that you know the male and female produce gametes although eyes known as sex cells and the the gametes have to join to produce what we refer to as a zygote or a fertilized egg so the so the gametes in the male or the sperm and the game to the female are the eggs so there's two things necessary for reproduction there's first off the sperm has to be more so you know there's three sperm motility because it has to travel and that the egg usually has to be larger and contains a lot of nutrients for the events of the eventual possibility of you know fertilization and then last I just wanted to kind of touch on some definitions of sex in terms of male/female identity so for example you have the more common phenotypic sex which is you know physical characteristics of a male or physical characteristics of a female but then you have the gonadal sex and so the gonads are the ovaries in the female and the testes of the male so that'd be another way which we would identify male from female but then there's also the genetic sex which is males have an X Y chromosome chromosomes and the female have X X chromosomes and you know in in certain cases you might have actually somebody who's let's say X Y so genetically there are male and they for some reason they may not produce a lot of testosterone or the receptors are not responding to the testosterone that's there during development and so they're born with female genitalia so in that case you would have sort of a change of what would be like our gonna add a sex versus the genetic sex and so on okay so chromosomal sex determination our cells contain 23 pairs of chromosomes and 22 of those pairs are what we refer to as autosomes and then there's one pair of sex chromosomes so as I mentioned on the previous slide there would be XY chromosomes in the mail and the XX chromosomes and the female the male's produce half Y carrying sperm and half x carrying sperm the X and y are separated from each other through a process known as meiosis and all the eggs carry an X chromosome then again the X the two x chromosomes are separated from each other via a process known as meiosis as well and so when a Y sperm fuses with the egg it's going to produce an XY set of sex chromosomes which would become a male if an expert fertilizes and I and I think that it would be an X X which would be a female okay so these sex hormones in the males versus the females they're actually the same same hormones found both in males and females however the quantities differ so for example in males have higher higher amounts of testosterone versus females having higher levels of estrogen for example so the antigens in males are comprised of like testosterone which comes primarily from the testes and testosterone is important for internal the development of the internal genitalia in males which requires the staffs throat actually signal during the during development to maintain something called a wolffian duct and also to inhibits the mullerian the malaria ducts and so this well promote the internal genitalia such as the epididymis and the vas deferens seminal vesicles and so on testosterone is responsible for libido and spermatogenesis the production of sperm skeletal muscle growth changing the voice during puberty there's also another type of testosterone or androgen scuse me known as dihydrotestosterone or DHT and so this actually promotes the formation of the external genitalia such as the scrotum and the penis for example it also is responsible for male pattern baldness body hair like chest there are facial hair as well as prostate growth they interesting down in DHEA are weaker engines that are released from the adrenal glands the estrogens in males are primarily estradiol and estriol are their produced mostly in peripheral tissues because the these peripheral tissues contain an enzyme known as aromatase and the tissues that that contain our adipose skin brain and liver progesterone as there's a small amount that's actually released from the adrenals as well as from the testes of males in the females which you know they primarily have more estrogen extra dial and estrin particularly come from the ovary and it helps to maintain the female reproductive organs during development so it maintains the malaria ducts for example and it's also responsible for growth of breast tissue helps to maintain pregnancies which we'll discuss and some some of the interesting down is converted to in the peripheral tissue as well in females and so it's the same tissue adipose tissue skin brain liver containing aromatisse enzymes to help produce more estrogen from those areas and it's not an insignificant amount so for example an adipose tissue if we take you know very well-trained athletes or cases of very very low body body fat conditions are maybe in cases of starvation they can actually have what we call a materia or you know lack of a menstrual cycle or a sexual cycle due to the the lack of estrogen production during pregnancy the placenta produces another type of estrogen known as estriol which is the least potent of the estrogens but is relevant again important for the the production in the growth of the the fetus progesterone is produced by the corpus luteum of the ovary primarily we'll discuss that in this lecture and the end regions and females there's usually lower levels and the adrenal production of interesting down of DHEA makeup for most of that testosterone and interesting down are produced by the growing follicle in the ovary and we'll discuss its role there as an intermediate to producing estrogen so just briefly in terms of male development just to kind of give you guys an idea of what's happening here the testes okay here so in the testes we have two very important cell types one known as the living cell and one is a sertoli or an ER style and the sertoli cells produce a mullerian inhibiting factor now mullerian the malaria ducts in the female are what eventually become the the female reproductive organs and so it causes regression of the malaria ducts meanwhile the lydic cells they produce testosterone but the testosterone helps to promote the growth of the wolffian ducts as well as in the presence of an enzyme known as 5 alpha reductase 5 alpha reductase converts testosterone into that other energy known as DHT DHT actually promotes growth of the urogenital sinus which promotes the growth of the male external genitalia as I mentioned in the previous slide the wolf inductor comes the internal general organs for the male and so kind of interesting here to point out is that in females in females if there's no testosterone or low levels of testosterone the malaria ducts are not inhibited and it becomes female reproductive organs in the male even if they are XY chromosomes if they lack testosterone are insensitive to testosterone during development the mullerian ducts are not inhibited and it becomes female reproductive organs so the default in either case is female organs now this slide has a lot going on here it's showing you the the structure of cholesterol here that ring structure that's it's very recognizable and how cholesterol is the the precursor to a lot of steroids and so the sex one was that we've been discussing our steroid hormones produced from cholesterol and this was discussed in my lecture video on the adrenal glands but here okay just kind of remind you on the on some of the pathways this is pregnenolone which is our next common precursor and ultimately we have one pathway here that can lead to cortical stearin and also aldosterone and from in the presence of our stuff 17.5 rocks at least we can convert that into cortisol so the cortisol cortical stearin pathway there from the adrenal cortex and then over here what we do is we have DHEA and interesting down which can also be produced in the cortex of the adrenal gland as was discussed in that video now in the the presence of enzymes like 17 beta HSD it can convert that DHEA an interesting down into testosterone as well as into dihydrotestosterone or DHT which is the ones i just previously previously discussed in the last slide so those are two forms of testosterone that are primarily produced these two right here two starts when DHT in the in the testes now in the female as well as in the male the adipose tissue brain tissue liver and so on they continue aromatisse an enzyme which is right the aroma taste enzyme can actually convert testosterone into estrogen like ester own and estradiol which are the primary ones in the female you can also see in the placenta alright during pregnancy it also produced they also produce estriol so we have three different forms there the most the most abundant of which are most supportive which is estradiol okay and again males will also produce you know extraordinary dial peripherally females also produce it peripherally as well in the same type of usually adipose tissue for example okay so we're gonna start with the male reproductive system and here on the first slide we're gonna talk a little about the anatomy of the the testes so again in the males the male gonads are the testes and so you can see here the testes actually reside outside of the pelvic cavity in the scrotal sack but look at this cartoon it's connected via what we call a spermatic cord and spermatic cord has these structures like blood vessels arteries and veins contained within that nerves as well as something referred to as the ductus deferens which you see here this ductus deferens also referred to as the vas deferens and the ductus deferens is connected to this structure right here which is known as the epididymis and the epididymis is actually where the sperm are stored to also mature so when they're first produced they're not mature they get stored in the epididymis and then mature there and are stored there now looking at the the testee itself it's actually surrounded by this tunica albuginea which is this fibrous capsule and you can see that it's actually inside that capsule it's separated you can see the septa here I'm drawing it in and those septa actually separate portions of the inside of the testes into what we refer to as a lobby wall and each lobule contains that you can see these this coiled up structure here is coiled up to known as a seminarist to mule so the seventy-first to mule is actually where spermatogenesis takes place this is where the sperm are being produced and it's a fluid-filled structure so when they're produced they're sent towards the we refer to the Reedy testes over here and then that gets deposited into the epididymis for storage and maturation and then during ejaculation it would leave the epididymis and go into the vas deferens of the ductus deferens and travel up the spermatic cord and into the into the pelvis so the seventy-first tools so this is the coiled structures in those lobules in the testes and it's sort of the sperm are produced so each to Buell is in line with this thick what we call a germinal epithelium okay and this is where the these cells these stem cells will become sperm and so they contain something referred to as a cistern tacular cells now the Susteren tacular cells go by a couple names their assistant Acula cells sertoli cells or nurse cells so I apologize in advance if I switch between some of those names I'll try to be consistent so these nurse cells in between these these nurse cells or I should say actually would be the function of these nurse cells are to protect the germ cells to protect the cells that are going to become sperm eventually and it helps to promote and provide the nutrition for the development of the the sperm there and it also helps to get rid of the wastes helps with providing growth factors and other needs of that of those germ cells and another important role that they play is that they actually form tight barriers between each other and the testes actually the germ cells actually develop in between these tight junctions between the the nurse cells and these tight junctions have a very important role in providing what we call the blood testes barrier then the blood test disease barrier is similar to a blood-brain barrier in that it prevents you know certain substances from being able to move in there so for example the immune system can make contact with these germ cells because if they could they would actually activate and destroy or kill off those germ cells because as you know foreign bodies the the nurse cells are stimulated by FSH or follicle stimulating hormone and they secrete inhibin as a negative feedback so inhibit inhibits the release of FSH specifically and the nurse cells they also produce something called androgen binding protein which actually binds to testosterone so the energy of binding protein when it's released stays fairly local right there in the testes and the testosterone that's produced since it is a steroid it can travel through membranes it helps to keep testosterone levels concentrated within the testes there by binding to this protein and remaining in what we call a dynamic equilibrium so any free testosterone will get used up by the cells that are required for the development of the sperm and it will be the equilibrium with what's bound to the protein so the proteins will then release more to make up for that so you kind of have a constant replenishing source coming from the proteins that are holding onto the testosterone the testosterone itself actually comes from the interstitial lighting cells which I mentioned I should infuse slides earlier so the lighting cells they're actually located between the tubules and they produce testosterone and they're stimulated by a luteinizing hormone so the LH stimulates the lytic cells produce testosterone as testosterone levels go up the FSH will actually stimulate the nurse cells that ourselves will release the energy binding protein which will bind to those testosterone to keep it at a good concentration for the developing sperm then it's just a histological slide looking at particularly a cross-section through warned of the tubules this is just a cross-section through the seminar stool but you can see it's hollow in the center which it where it's white okay and that red line that I just drew around is actually the connective tissue that's let's surround the outside of the tube you'll and then there's mix of you know nurse cells big nurse cells that are connected to that connective tissue and can extend so we can have nurse cells that extend all the way into that lumen so they're quite big in addition you also have our germ cells okay so here are the germ cells alright and the germ cells when their stem cells okay aren't differentiate into sperm yet they're located next to the connective tissue on the outside there and what they do is as they're signaled to develop they signal and progress towards the lumen in that direction to eventually become sperm okay to eventually become sperm in the lumen and then be shuttled over to the epididymis ultimately and over here you can see the interstitial cells or the lytic cells which would be releasing testosterone to help support these growing sperm okay so a little bit more about the anatomy as it pertains to really the the physiology of the production of sperm sperm actually require a lower temperature that body temperature usually anywhere from about one and a half to three degrees Celsius lower body temperature so they actually that's why they're not in the pelvic cavity but actually hanging below the pelvic cavity in the scrotal sac and so it's important to actually maintain that temperature for their optimal development and so there's a couple of things in place to help maintain that temperature so for example here we can see the external inguinal ring and you see the Kree master muscle here this was the crew master muscle and so the pre master muscle actually extends all the way down around the testicle which you can actually see on this side over here a little bit better goes and wraps around the test line and it's actually the extension of the internal oblique muscle and one of its jobs to help maintain temperature of the testes is that it will actually constrict and bring the testes up close to the body when it's too cold so it helps to warm them and if it's if it's too warm they'll actually relax and distend away from the body in order to cool off the testes in addition if you were to cut open as it has you can see in this cartoon if you cut open the Kree master muscle there you can see the the veins there the arteries and the veins former plexus in fact the name for that is called the pimp in a form plexus and it wraps closely around the arteries and its function is very important so it happens is the arteries are bringing warm blood to the testes and that blood is body temperature I that would actually negatively impacts the development of the sperm so this plexus of veins that are returning from the testes they wrap around this artery and any of the heat that's given off by the by the artery is actually taken up by the pimp in form plexus on its way away from the testes it actually takes the heat and transfers it back to the body and so it's a town recurrent mechanism where the warm blood moving towards the testee that warmth is taken away in parts or some of the warmth that's taking away in parts or some of that heat is taken part by the pimp uniform plexus that's moving in the opposite direction so it takes it back to the body so that the blood that's actually reaching the testes by the arteries this has been cooled someone and then also you have what we refer to as the the dark toast muscle alright and so this is this is muscle located within the around the testes that can also contract or relax to help draw the testes either close to the body or further away from the body so that's what this slide here is is going over you can see this is the crew master muscle which I referred to before and so again that's going to help modulate the the temperature by contracting and relaxing the darkest muscle which is the subcutaneous layer of smooth muscle contracts with colds relaxes when it's it's warm and then you have the uniform plexus so again that's our counter current heat exchanger which I've underlined down here for you this helps to remove heat from the descending arterial blood so these are several mechanisms to be able to regulate the temperature for optimal sperm production now with this slide really what I wanted to just touch on was that during development the testes have to descend out of the pelvis in order to make sure that we can regulate the temperature appropriately and the descent since they're actually formed they're actually formed within the pelvic cavity initially during the element and you can see it's connected to the structure referred to the gubernatorial inferior surface so here's the testes in a circle there's a structure called the GU binocular then you see the epididymis there you can see over here this is the ductus deferens which is the vas deferens and so during development that goober noctilum actually retracts as you can see over here you ever attract and it's a important structure I want to show you over here is this one too it's called the pubic symphysis so that's actually the the anterior part of the pelvis there so you see the testes is actually brought anteriorly over the the pubic symphysis and then as the Guru Nicola retract the testes is pulled inferior ly and down to you know what the future scrotal sac is going to be right here and the ductus deferens of the vas deferens is it elongated following that into the scrotal sac which eventually by the time they're about one month old this wall really I've sealed off and under normal circumstances you know the testee should have decided either just prior to birth or within the or the first month or so after birth the danger of you know having an undescended testes after birth is the risk of infertility due to to a higher temperature but also more severe than that is they also increase their risk for cancer in this slide is showing the hormonal relationships between the hypothalamus the pituitary and the testes so let's pick a color here it's you have somewhat easy to follow let's just see if I'll stick with red so here in the hypothalamus alright gnrh organic rope and releasing hormone is released and stimulates the anterior pituitary to release FSH and LH so that's our FSH and LH right here FSH as I mentioned earlier FSH is going to stimulate the nurse cells otherwise known as system tacular cells and then are going to produce energy by the protein which is what the ABP stands for now the LH the LH is going to stimulate the interstitial cells or the lighting cells and they're going to produce testosterone in response to the LH now the nurse cells in response to FSH are going to release inhibit inhibin inhibits the release of FSH specifically it doesn't affect STV doesn't affect LH levels so this is is this has its own mechanism so LH on the other hand LH or luteinizing hormone stimulates the light H cells to produce testosterone as testosterone levels increase that's going to negatively they easily feedback on the pituitary gland as well as the hypothalamus and so that's going to reduce the production of luteinizing hormone now the testosterone will also bind to the ABP which is going to help in keeping concentrations high for stimulation of spermatogenesis testosterone levels as it rises is also responsible for secondary sex organs ok secondary sex characteristics we kind of mention some of that already with you know increasing muscle mass deepening of the voice changes in hair facial hair chest hair pubic hair and also stimulation over here you can see white in libido and the in the hypothalamus okay so in regards to spermatogenesis ok so this is now happening in the seminiferous tubules and in response to FSH LH stimulation of the nurse cells and the lytic cells and I'll produce testosterone it helped the production of these sperm they so really this this production involves three principal events where we just go from one stem cell we produce four sperm cells that have flagella so that there have more tivity we're going to need to reduce the number of chromosomes by half so if we have 23 hairs each of those four sperm cells should contain 23 chromosomes not 23 pairs or 23 chromosomes and so this is the difference between fertilize diploid and haploid so by definition most of cells in my body are diploid meaning they contain 23 pairs the pair's meeting the homologous pairs one from the mother one from the father okay so that's or one from the male one from the female excuse me so this is what we refer to as diploid haploid means we've separated homologous pairs from each other okay so by definition haploid cell has only one of those of those pairs okay so we need to make sure we separate them all with this pairs and then we need to shuffle genetic information so that the chromosomes contain you know new gene combinations and so this process is referred to as crossing over which is an important step for genetic diversity and then finally just in terms of the semen so the term seaman actually is the entire fluid that's activated which is on average about three to five milliliters and only about 10% or less is actually sperm so it's not entirely sperm it's it's about less it's about 10% or less in terms of production by the Scimitar for stimulus it's about close to a hundred million sperm per milliliter and it produced there produced daily and the sterility is usually defined as you know less than 40 million per milliliter per day so if you're looking at an average of say 3 3 mils of semen it ejaculate that looks that's about about 300 million or so sperm okay to illustrate those three principle events what we have is our single cell okay which is our stem cell which is initially what we call 2n or diploid again that just means that it has two pairs of chromosomes from the from the male and the female now ultimately with spermatogenesis this stem cell which starts out diploid after undergoing meiosis 1 and meiosis 2 which is a two-step process it's going to result in four sperm cells that are each we call haploid I want to draw a little in in there and so each one is in number meaning we've separated homologous pairs from each other during the process of meiosis 1 and meiosis 2 and so this is a one of the primary steps and again that's stimulated via the hormones we've discussed earlier now in addition the this the importance of glue from diploid to haploid this is so that we can create this this set so we can have one set of chromosomes that will pair up with ultimately a set of chromosomes from the from the egg now during this process of meiosis we also have a step in meiosis now it occurs during meiosis one and I mentioned it before as crossing over and what that actually entails is this let's take for example I have one a chromosome and it's homologous homologous pair over here okay so one came for the mother won't give her the father one give the male we came from female alright so this is one of those pairs okay of course it replicates and when drawing that centromere so another one replicates over here and this is its centromere here so these are homologous pairs okay now in meiosis what happens is there is a step in which and over here a step in which this chromosome links up with one of the sister chromatids of the other chromosome so there's a crossing over point right about here and let's say right about there so we have this crossing over and what happens at this point is that basically you have an exchange of genetic information and the result is when you finally separate homologous pairs from each other during the natural process of division during meiosis what you're going to end up with is now is one pair here I'm just going to draw it like this and the other one is separated over here those will be in separate cells but this one has let's say a piece of that genetic information over here this one over here and I'll draw this one in blue over here so as they're in separate cells I have been separated from each other these are no longer identical copies connected by that centromere which we saw previously which we get over here those are identical copies from replication connected by this centromere right here and the same thing goes for this one right here because of this crossing over of it that it took place right here there's an exchange of genetic material that occurred on one of those chromatids and so now these are no longer this one is no longer identical to this one here because of that exchange of information this increases the diversity that can occur during during fertilization so this would be the first step so this occurs during meiosis one and then in meiosis two - is - we're going to separate these sisters from each other I'm going to separate these two from each other and we're end up we're going to end up with four cells in this case would be for sperm since we're talking about the male all right and I'll each have that chromosome however one of them is going to continue that little bit there and the other one is gonna have that one over there okay so they're all separated and then the the end result is you have four cells at the end of meiosis two that each have different genetic material from each other adding to the diversity then they are all considered haploid so these are all haploid haploid cells [Music] okay so so the actual process of spermatogenesis so let's talk about that so in this this cartoon here you can see this is again a cross-section through the seminiferous tubules so if we blow up just a section of that which is designated by that little black box that you see if we blow that up you can see here this would be the connective tissue the outer edge of that's some inner force to Buell and so this would be the luminal side over here that's the lumen and you can also see that there's these what looks like these barriers here I'm going to trace one of them out for you actually I'll trace them both out those are actually the junctions between the nurse cells so in fact this is one nurse cell this is another one and it's another one this is a big yellow blocks that you see there those are the nurse cells in this cartoon at the base here on the outer rim here of the seminiferous tubules you see what we refer to as a spermatogonium so that's our stem cell it's going to undergo mitotic division one of those cells that divide is going to stay behind and remain as a stem cell so it keeps our we're constantly replenishing those stem cells and then the other cell will actually migrate more towards the lumen now and undergo changes to ultimately become you can see here migrants we ultimately become a sperm sperm cell and you'll notice the little designation is 2n as I was using on the previous slide the two and does it just designates that it's still a diploid cell it still has both pairs of chromosomes and so we have what we refer to as a spermatogonium here all right and then the other goes alright it's division here alright we still have our look like a primary spermatocyte and then from primary spermatocyte you see here that it goes meiosis one after meiosis one we do it we only actually produce two cells so you can see two cells but else is one though gives us two haploid cells okay because during meiosis one we separate homologous pairs from each other so he gets two cells that are both haploid which is why they're designated as and and then they undergo meiosis 2 so in meiosis 2 we actually separate these sister chromatids from each other and so what we end up with is four cells and those four cells are still haploid because we've already separated the homologous pairs from each other and then those four cells will undergo another step of maturation referred to as sperm biogenesis which will give them sort of the the more common appearance of the sperm with the with the head the neck and then the tail region and they'll eventually be released into the lumen which is filled with fluid and actually transferred to the epididymis for further maturation okay so here I want to draw out the spermatogenesis so sperm at Oh Genesis all right so we're little bit's prejudices and so we start out with again this is on the outer and the outer edge of the seminar first tubulin we have our cell which is 2n or diploid and that is our sperm at O Gonia and it undergoes mitosis so therefore it's still going to be diploid and it's referred to as a primary spermatocyte until the primary spermatocyte okay again one of them's gonna stay is a stem cell but the primary spermatocyte is going to actually progress and undergo meiosis 1 so we produce two cells now but now they're each n which means they are haploid okay and in those two cells each one of those cells in which you divide once more this is meiosis 2 and these by the way these haploid cells that I just drew in here are referred to as secondary spermatocytes those are secondary spermatocytes we're gonna produce four new cells that are all in meeting they're all haploid okay and at this point that we referred to them as spermatids so those are spermatids and then each one of them is going to undergo that's my film so I apologize but this is undergo a process called sperm EO Genesis to become sperm and again once they become sperm they will still need time to mature in the epididymis that they can become so they can increase their motility and so on to be ready to actually fertilize okay so the male cells contain what they call accessory glands so there's actually three sets of these glands in the male reproductive system the seminal vesicle the prostate gland and we refer to the bubble urethral glands with the caliper glands the seminal vesicles are actually all the glades are responsible for producing the the fluid that supports the sperm during the ejaculation so this the this makes up for the rest of the fluid of the semen so in the seminal vesicles they're going to form about 65% of the seminal fluid and it contains an abundance of fructose which actually provides energy for the sperm that's way too empty until we refer to as the ejaculatory ducts which I'll show you in a different different slide and its location is actually there's a pair of them behind or just posterior to the bladder then there's the prostate gland the prostate surrounds the urethra and some structures refer to as the ejaculatory duct just inferior to the bladder and it primarily secretes an alkaline secretion which helps the aid in the motility of the sperm as well as neutralizing the acidity of the solution or of the of the ducts and that forms about 25% of the seminal fluid and then the calpro glands which provides like the last small percent that's near what we call the ball of the penis I had during sexual arousal it produces a clear mucus or record fluid that helps to lubricate the glans of the penis or the head of the penis in in preparation for intercourse it does aid someone in protecting the sperm by neutralizing the acidity of any residual kind of urine in the urethra as well the spermatic ducts which you see here in this anatomy of the male you're looking at from the posterior aspect so this structure up here let me draw it over here so this structure right here is the bladder and behind the bladders we're looking at the posterior aspect of a bladder you see this structure right here okay this structure right here that's the ampulla so the ampulla is connected to the vas deferens so here's the vas deferens the epididymis of the testes so the sperm is initially stored in the epididymis and with during ejaculation I can move through the vas deferens and actually some sperm can still be stored here in the the ampulla and then in the ampulla you'll notice that they connect down here this structure right here is the prostate gland through the middle of the prostate you'll notice the prosecutor is just beneath the bladder so the middle of it is the prostatic urethra which connects it to the to the bladder actually above it so this would also be the the pathway for urine from the bladder through the prostatic urethra out to the penile urethra so they share that's that's similar anatomical site but you'll see here there's these seminal vesicles that I just spoke of the seminal vesicles which is secreting a high fructose type solution that will combine with the sperm coming from the ampulla into what we refer to as the ejaculatory duct and then it enters into the prostatic urethra the prostate can actually secrete indirectly to the the prostatic urethra there and then you have what we call the the membranous urethra which is a small section there as it's moving through some of the the muscles of the pelvic floor there and that becomes the the penile urethra after that and so that's the the pathway that the sperm would take all the way from the epididymis vas deferens ampulla through the ejaculatory duct into the prostatic urethra the members urethra into the penile that reads from and this is the underside of the penis which are seeing here spongy tissue which is continues with the glans of the head of the head of the penis there and also the corpus cavernosa on more of the upper surface of the penis which I'll show you a better image of that in another slide okay on this slide we're looking at it from from a sagittal section and you can see in this mid sagittal section here the same structure so we'll start here this is the testes you can see the epididymis located really the superior and lateral poles there and here's the vest the vas deferens you'll notice that the vas deferens actually hooks over the pubic symphysis it enters into the the pelvic cavity this structure here is the bladder and this vas deferens does not go into the bladder through it despite what this cartoon kind of looks like he goes around the side of the bladder and behind it okay so the bladder so it goes actually behind the bladder where it connects with the seminal vesicle so there's the ampulla and the seminal vesicle and you have the ejaculatory duct okay which is located right here alright and then you have the prostatic urethra and here's the prostate and then you have a very small membranous urethra and then you have the penile urethra from there what I didn't mention on the previous slide and show you but it is located there you can look for it is this structure right here just underneath the prostate at the the base of the penis here is the caliper gland or the ball boy you'll reach for gland so those are our three glands we have our seminal vesicle prostate and then the bulb when you're reasonable gland now some structures to take note of here as well in the penis itself on the on the top top portion of the piece you'll see two structures one on either side here I left the right side you have the corpus cavernosa okay which actually connects to the to the pelvis and then you see here just underneath on the inferior surface there you have the the glans or the head of the penis which is continuous with the the tissue that surrounds the urethra then it goes all the way back towards the sort of what we call the the the base of the penis here in this region here so the penis is in an erectile tissue and so the mechanism for the erection is actually based on vasodilation and engorgement of blood and so what happens is you have three bodies if we take a look at the cross-section of the penis here you have three bodies on the outside here or in the top part here do you see this is the corpus cavernosum so one on either side you'll notice that there's a in artery that runs deeper in the middle of that and then there's one of the inferior side here and that's called the corpus spongiosum and that's one that contains the urethra and so during arousal you you increase blood flow to these areas to these corpora cavernosa because these cabinets are actually contained what we refer to as mucuna or like little lakes and it's surrounded by smooth muscle as well as a more rigid connective tissue structure that surrounds each one of those and separates them and so what happens is during arousal the get vasodilation of the arteries which increases flow into these lacunae and it causes them to fill up with blood rapidly and in doing so when it fills up with blood it expands because it's like a spongy type material so it expands and it expands rapidly against and you can then compress against the more rigid connective tissue that surrounds each one of them and in doing so it actually can compress some of the veins that run peripherally along that more dense connective tissue so it has two-fold effect that increase in arterial flow which fills those areas up of blood and it gorges them and at the same time that compresses the more rigid connective tissue and actually pinches the venous blood so thereby reducing the venous venous return or you know venous blood flow and increasing arterial blood flow so it's a change in the dynamic of flow the spongy awesome similar in principle and that it will in gorgeous blood it is sort of a spongy tissue does not contain the same kind of rigid wall structure that's around the cavernosa but its main function really engorges is also to help keep the urethra open or paint so that ejaculation can occur so ejaculation occurs through the urethra and that has to stay open if you look at it from just the the lateral view over here on the left you can see the spongy um over here and then the the cavernosa would be on this region right here and the the glans or the head of the penis here which is actually continuous with the sponge be honest it was all part of the spongy ocean now over here this box over here the mechanism by which this actually occurs is you have parasympathetic innervation to the endothelium that lines the the blood vessels there so this is our endothelium alright here's our parasympathetic nerve and when the parasympathetic stimulate the endothelium it stimulates nitric oxide synthase in the in the billion which means the endothelium then produced nitric oxide nitric oxide they can diffuse to the nearby smooth muscle so this is the smooth muscle so it diffuses into the nearby smooth muscle and actually initiates or converts gtp into cyclic GMP through various mechanisms and by inducing cyclic GMP activity it causes smooth muscle relaxation so the net result of nitric oxide is to reduce to reduce smooth muscle relaxation which causes vasodilation therefore an increase in arterial blood flow phosphodiesterase v or pde5 over here is really kind of constitutive leon and in activates the cyclic GMP so if there's an abundance of nitric oxide it overpowers the ability of phosphodiesterase v to inhibit it and so it will visa dilate however is nitric oxide or parasympathetic inputs start to decrease the phosphodiesterase v to take over and cause a constriction and so therefore a loss of erection so you know this phosphodiester is five is an important target for treating erectile dysfunction so if you have for example sexual stimulation which is causing the state of arousal parasympathetic initiate or stimulate the endothelial cells to release the nitric oxide nitric oxide converts inactive guanylate cyclase into active guanylate cyclase which can then convert GTP into cyclic GMP cyclic GMP results in vasodilation and erection however phosphodiesterase inhibitors remember pde5 degrades the cyclic GMP so we have loss of erection okay phosphodiesterase inhibitors will block the actions of pde5 so viagra for example is a phosphodiesterase inhibitor blocks the actions of pde5 therefore cyclic GMP these stays around longer at higher concentrations and maintains an erection okay so in the male sexual response the the nervous system plays a large role here so prior to arousal if there's a large sympathetic response that actually inhibits the arousal state however in the parasympathetic state the the signals will produce an erection via the mechanism I talked about through induction of nitric oxide it's likely GMP and so on the sympathetic to do however play a role after arousal in signaling ejaculation and so what it does is it'll actually coordinate the the muscle move within the the contractions of the you say the vas deferens is the seminal vesicles and so on to secrete their fluids and to also propel the sperm through the urethra at the same time during orgasm heart rate goes up respiratory rates blood pressure you know as well as an increase in skeletal muscle tone and sweating and so on so here just to kind of touch on this the the sexual response this is also be found in your notes on typology for the small writing here but this isn't the the entourage state here and then you have the excitement phase and the plateau phase which are just Continuum's of the same thing essentially where you have parasympathetic inputs increasing nitric oxide and cyclic GMP engorged with a blood of the cavernosa and the spongy awesome as well as contraction of the the skin and the muscles the Dara's muscle for example which pulls the testes up closer towards the body and then also release of the fluid from the CalPERS glands and the Bulbul urethral glands to coat the the glans of the penis in preparation for intercourse and then you have what we call the the orgasm phase I which is the sensation and then the ejaculation phase and again it's a continuum but it during the orgasm phase again there's gonna be sympathetic input which is going to reduce a lot of the the contraction of say the the vas deferens and the seminal vesicle in the prostate glands to start to secrete the fluid into the into the lumen of the urethra is there and then during the ejaculation phase you're going to have you know strong pulsations of the bulb of the penis which is right at the base of the penis to help project or to reject cv the seminal fluid from the penile urethra out through the glans and then you have finally resolution and refractory period okay so now only to be talked about the female reproductive system it's a begin we got to talk about some of the anatomy of the female genitalia so in this sagittal section here what you can see moving from enter the posterior to start this is the structure right here is analogous to the cavernosa in the males which is an erectile tissue it's called the clitoris okay it can be covered by what was referred to as the the prepuce when the prepuce is homologous to the foreskin in males and also see some of the external structures here the labia minora which is the internal and the labia majora which is the outer and then as you work more towards posteriorly the opening here is to the urethra which connects to the since the structure here is the bladder just posterior to the bladder the opening here is to the vagina and then here is the cervix and this structure just superior to the vagina is the uterus which you can see it's a flexed over the bladder and it's typical position and then connected to the uterus you see the fallopian tubes over here and then the ovaries we only see one of them here but you'd have a fallopian tube on either side and - two ovaries then posterior to the the vagina then you have the the anal canal and the rectum over there okay and then what you're seeing here is the muscle on the floor of the of the pelvis now the internal genitalia of the females are the ovaries the uterine tubes the uterus and the vagina the external genitalia is comprised at the clitoris the labia minora and the labia majora the primary sex organ for females are the ovaries and the secondary sex organs you know our you know other than the internal external genitalia so we include these at the breast tissue which stolen so the uterus the structure here so this in this cartoon this would be the the vaginal canal right here this structure right here right here sorry this is the cervix this is the what the comfort of the external us which is the the opening into the vaginal canal then you see laterally along the cervix there's what we call the the lateral fornix then you have the cervical canal which is the canal through the cervix that opens up into the the opening of the the end of the uterus excuse me so the structure of the uterus you see the fundus over here and then the body is over there and then the the neck so the cervix cervical actually means neck so for example something where's the cervical collar it's the collar that goes around the neck in the in the uterus cervix this is considered the the neck of the body and then there's the fundus at the top there you notice that uh laterally on either side will be an opening from the uterus it's what we call the fallopian tube and the fallopian tube for these fimbriae at the at the end which are these like finger like projections that come close to approximately to the ovary the ovary is not directly connected to the fallopian tube you can kind of see that over here is the other ovary you see the fimbriae over here of the of the fallopian tube all right so the general process here is that you'll see inside the ovary there are follicles a follicle will contain an OS I'd the outside is the edge and so what it releases that our site it goes into the fallopian tube and it travels into the uterus and will implant in the uterine wall in the inner layer known as the endometrium so the endometrium is this inner layer then you have the thick part portion which is the myometrium which contains a lot of the muscle okay and then you have the parameter which is the outer part of it so again they would try to embed into the endometrium if there were any fertilization that took place so we'll start with the ovaries so these are the female gonads and they produce the you know the outsides of the egg cells so these are almond shaped structures that are nestled in what we call the ovarian fossa of the posterior pelvic wall they're surrounded by a tunica albuginea capsule just like we saw with the testes they have an outer cortex which is where the germ cells develop so that's where the other sites are actually developing within those follicles and then you have an inner medulla which is pretty much occupied just by the major arteries and veins and each egg okay actually develops its own fluid-filled follicle so every egg has its own follicle to give you an idea though how many eggs there are at Birth there's about a million of these oh these eggs that are produced and that's the end of the production of any more eggs at that point it was a million by the time puberty lets on puberty there's about four hundred thousand and then by the time menopause most of them have already been are Muslim or essentially gone by them usually throughout the lifespan of the female though ovulates and release about four hundred eggs with a with a wide range there depending on how regular people cycles are and whether or not there were pregnancies and so on ovulation refers to actually the bursting of one of these follicles and the releasing of the egg that it contains so here's the structure or this is the cartoon of the ovary and you can see you know within the within that you've seen the cortical region these primordial follicles these primordial follicles were actually developed during early developmental stages and that's when I was referred to in the last slide as having produced about a million of those and you have cells called Oh a Gonia that undergo a lot of mitotic divisions and produce all these all these egg cells that then have a very thin layer of supporting cells around them referred to as granulosa cells and so this thin layer of granulosa cells that helps to support that egg referred to as like our primordial follicle and I'll stay essentially locked into in meiosis one it's all given the signal to actually grow and divide and so what happens is let's say it gets that signal to grow and divide it basically goes from a primordial follicle to a primary follicle to a secondary follicle tertiary and so on so what we get what we call any mature follicle and you'll notice the Oh site in the center that's this little orange out here alright that's that's the other site that's the egg and so this pink layer here these are supporting cells that grow along with it and make up the follicle that surrounds and supports and nourishes that's that dividing on the site now usually the signal for this device is hormonal in nature and comes about during puberty which on average is you know somewhere between anyone from nine years old up to about 14 years or 15 years old probably the average being about 12 years old but so you can see as this follicle develops it gets larger and larger so does the OA site itself and it starts to develop these fluid-filled pockets called natural fluid so the bill referred to that large pocket fluid as the antrum so sometimes it's mature follicle I would go by several names a little by the name of neutral follicle vesicular follicle there's no referred to that fluid filled area as a vesicle or sometimes a graafian follicle so all those were referring to the mature large follicle that is essentially ready to rupture and release so you see over here mature follicle given this the hormonal signal will actually rupture and release the oocytes surrounded by this you know some of those supporting cells that'll then enter into the fallopian tubes of the uterus but leftover cells that were supporting cells for that growing Oh a site they don't go instantly die off instead they actually have a very important function here and they'll undergo some changes and become something we refer to as the corpus luteum which will secrete hormones to help support the oocytes and the uterus and then the then lastly over a certain amount of time the corpus luteum will actually in volutes and become a tree deck and just because the corpus albicans which is essentially just a remnant but is non-functional so for follicular development i given the follicles are all the supporting cells that surround the the the OSI so you see the oocyte in the middle which is our egg that's our primordial follicle which which females are born with and then you'll see that if given the signal it becomes the primary primary fodhla see the OA site enlarges you see there's a thin layer of cells that support it there's also a layer between the OA site and those supporting cells known as the zona pellucida which is like a glycoprotein type matrix which is supportive to the OA site and is actually an important structure particularly fertilization so over here what you're noticing is the the oocytes is still enlarged and you notice that the layers of cells surrounding it have grown so it becomes thicker there's more of these cells and the granulosa layer which is the original layer becomes quite thick and it starts to develop another type of cell on its outer rim out here on the outside called a fika cell so the granulosa cells and theca cells are important in supporting the the OA site and then the follicle further develops and it's just an increase in the number of cells increase in the thickness of the theca cells and the cell number we also start to develop a fluid-filled sac they're called the antrum so this is what we call an early antral follicle and then our mature follicle which is a big one you see down here you can see the multiple layers you see the granulosa cells in the inner layer then you see the theca cells which is the outer darker colored layer and then you'll notice that the antrum surrounds most of the OA site the other side still keeps a small layer of cells surrounding it I know is the the cumulus oprah's because the cumulus oprah's and it's still connected by a little stalk right there to the other granulosa cells now this is the histological side showing you the follicle and so in the follicle here you see the multiple layers you have out here so if we can Circle it here and we circled in blue for a second here so we can see the whole follicle and you have the Figo which I mean I've actually missed some of them actually my drawing here but you have the fecal letter right here you have the granulosa layer right there and then this the structure right here is the interim so that's a fluid-filled antrum here's the OA site and then you can see these on Appaloosa which is that glycoprotein that surrounds it all right and then the cumulus oh forest which is which are the supporting granulosa cells that are still surrounding the OSA so our Genesis call the sexual cycle the sexual cycle is the more common term for it now used to be referred to as the the menstrual cycle so in all Genesis we're talking about egg production so it's the same idea as we talked with with the talk about spermatogenesis where we have to go from any diploid to haploid cells and but the process you know differs quite a bit especially in its timing so in this case we're gonna produce haploid gametes by a means of meiosis again so the eggs will also do meiosis 1 and meiosis 2 and the difference that here is that instead of producing four haploid cells the the egg undergoing division is only going to produce one one haploid cell the other three it still produces them but it produces what we referred to as a polar body which is just like a very very tiny cell with very little cytoplasm and it often just they just die off so so this is where we differ quite a bit from the sperm production where all of them we have for equal sized haploid cells in females you end up with just unit before haploid cells but three of which die off and we refer to them as polar bodies because they're very small and then one cell that's supposed to survive and so there's gonna be some cyclical hormonal changes that we're going to discuss and in promoting this growth and differentiation in these divisions and so there's also gonna be changes occurred in the uterus as well as in the ovary every month and then the cycle repeats itself so the sexual cycle will refer to this monthly cycle and you know this occurs obviously when pregnancy doesn't doesn't intervene with it so it consists of two interrelated cycles what happens is there's two parts of the sexual cycle that are occurring simultaneously so you have what's happening in the ovaries and we fertilize the ovarian cycle and then you have what's happening simultaneously to the uterus and this refer to as the uterine cycle so these are parallel changes so there's two different things happening in the ovary versus what's happening the uterus but the changes that are occurring have to occur simultaneously because when the ovary ultimately releases its egg the uterus has to already been prepared for it so this slide is showing you the the oil Genesis and the development of the follicle sort of side by side so what happens is just looking at the egg and not the follicle as a whole but just the egg in the before birth achieves the toyotas though so before birth the return development we we actually have undergone mitosis okay so we have Oleg onea so similar to spermatogonia we have all Agana which are diploid so that's 2n and I want to go mitosis so they go a lot of mitosis and produce identical cells and we refer to them as primary oocytes similar to the primary spermatocytes so we have the primary oocytes now that these primary oocytes however will actually start to undergo meiosis one but they'll get locked in meiosis one okay without any without progressing all the way through meiosis 1 so they end up getting kind of frozen in meiosis 1 and they stayed that way some of them for their entire lifetime or some of them until they get signaled to actually move or to progress during puberty so this happens all during developments where they get locked into meiosis one and stay as a primary oocytes up until puberty so that's what we have now adolescents alright during puberty all the way from the side the average age of about 12 up to about the age of 50 or so which would be menopause you're gonna there's you there's gonna be this cycle it's gonna be repeated every month and so what happens is some of these cells some of these oocytes will then progress through meiosis one and finish meiosis one and produce a secondary oocytes now you'll notice that there's a difference here we have two cells to see that I've been produced this little one over here and this one so there were two cells have produced but one of them had very little cytoplasm remember we really only want to produce one cell that has an abundance of cytoplasm and to support and be able to provide the nutrients for possible fertilization with the sperm so what we're gonna do is you know what's gonna happen is the there's gonna be a one of the cells going to have very little cytoplasm we refer to as a polar body and that just dies off so meanwhile this now secondary oocyte has completed meiosis one and it's going to get locked in meiosis two now it's not going to finish my house is - okay and in fact it will never finish meiosis - unless it's fertilized so that's the key it doesn't finish my house is - ever unless there's fertilization so here we have our secondary outside it gets ovulated meaning it gets released from the follicle it's moving through the fallopian tubes okay and that's why this here if it's not fertilized okay then it just dies if it becomes fertilized so here's the sperm okay so they haploid sperm eating the haploid egg it will finish meiosis two and that's where the next polar body gets released okay so that's where it divides again but one's a polar body and that's gonna die off and now you have a diploid cell which is we refer to as a zygote now in terms of how this OA site compares with the follicle development it's happening again it's a simultaneous type thing but what's happening here is the this Gonia are located in a follicle so there's just a small layer of supporting cells or granulosa cells that surround this primary other site and so when it ceases to develop any further you know after the after the female is born it'll still be what we call a primordial follicle trapped in you know meiosis one or the other side chat the meiosis one and then during puberty if if the primordial follicle is signaled to to grow it'll go from a primary follicle to a secondary follicle tertiary follow where the follicle gets larger and larger as I've discussed in the previous slides where the antrum develops and ultimately leads to ovulation in the formation of the corpus luteum the lowest site that's located within those follicles will remain after its signal will actually remain locked in meiosis 2 as I suggested before so what happens is during this time in the growing follicle you know it'll finish meiosis 1 and you get locked in meiosis 2 and I'll stay in meiosis 2 unless fertilization occurs in Genesis this slide is actually reiterating some of the points that I made previously in that the old Gonia which are those stem cells that multiply you know many times over via mitosis and produce millions like 6 to 7 million primary oocytes that's will pause in meiosis one specifically prophase and you know most of those will actually degenerate via a process known as a tree Jie by the time the female is born so this is usually about a million or so so that by the time the female reaches puberty there's usually about 400,000 all sites that remain and over a lifetime as I mentioned before they're usually optilead approximate about 400 times give or take again depending on on the person the sexual cycle also known as the emotional cycle on average lasts about 28 days now there's a wide range from about 25 to maybe 35 days long and there's a a complex arrangement of hormones and signalling that occurs but it starts about the hypothalamus which regulates the pituitary pituitary gland and then there's the pituitary hormones which regulates the ovaries and then the ovaries secrete hormones that going to regulate the uterus and there's feedback from all of them from the ovaries and the uterus so the basic hierarchy basically from the hypothalamus pituitary ovary the ovary talks to the uterus and the ovaries a dessert that a feedback control over the hypothalamus and the pituitary with normal conditions but the uterus can as well and so there's a sort of a complex arrangement here based on this hierarchy okay so the sexual cycle the cycle lecture begins with the follicular phase which is part of the old Varian cycle so reminding you that the sexual cycle has the ovarian cycle in the uterine cycle and they simultaneously so in the ovaries we have follicular phase so this is what's happening with the follicles the growing of the follicles and so it starts with registration which occurs usually the first or usually lasts for about three to five days of the cycle so that's the beginning of the cycle and then you know at the same time the uterus is replacing lost tissue from the menses via mitosis and at the same time in the ovaries the cohort of follicles are growing so we'll talk about them separately and what's happening ovulation in the ovaries occurs around day 14 so at the end of the follicular phase ovulation occurs so that would be the rupture the follicle in the ovary to release the egg and then the follicle that is left behind will become the corpus luteum in the next two weeks of our 28-day cycle we had turned - it's called the luteal phase so after ovulation the ovaries undergo change now interested - what they call the luteal phase and the corpus luteum stimulates the uterus the uterus is a endometrium to secrete and start to thicken and so on and if pregnancy does not occur the other metrium in the uterus starts to breakdown the last two days of the luteal phase and then menstruation begins and the cycle starts over so in the luteal phase this is primarily just the corpus luteum secreting hormones to support the uterus in case of pregnancy occurring now this is looking at the ovarian cycle as a whole here you can see here we have okay the primary follicle so we had a primordial follicle I was stimulated to become primary which became secondary so you see the growing follicle the O site in the follicle is finished meiosis one is locked in meiosis two you see this enlarging follicle here you can see the other site there you see the antrum and all that so we have our tertiary which is mature follicle or graafian follicle and then there's ovulation so here's day 14 which is depicted by this arrow right here so the follicular phase is the growing and developing of the follicles to maturity to reach the point of ovulation ovulation is then the release of the egg with its sum of its surrounding supporting cells okay the cumulus offers and so on the follicle that gets left behind in the ovary becomes the corpus luteum the other site that's been ejected is now at this point traveling through the fallopian tubes towards the uterus so what's left behind in the ovary here is the corpus luteum which is the remnant of that follicle which actually starts to secrete different hormones and high abundance like progesterone for example and then that's gonna be the next 14 days and this is the luteal phase if someone's blocked on my video but if there is no pregnancy ultimately the corpus luteum is going to involute and become the corpus albicans which is just a remnant non-functional and then new primordial follicles will be you know ready to be kind of initiated for the next cycle so if they get it initiate and so on now one thing I want to clarify with this is to understand that these primordial follicles we do not go and from in the follicular phase in 14 days we don't go from a primordial follicle all the way to a tertiary and mature follicle that then have you lates no the reality is that actually every 14 days in the follicular phase starts it's actually initiating follicles that are already pretty mature okay they might be in the secondary stage or the tertiary stage already and so over that 14 days it's gonna stimulate a secondary or tertiary follicle to the point of ovulation so it'll get one of those follicles to survive and ovulate meanwhile there'll be you know subsets of primordial follicles and primary follicles in various stages in the ovary so every single time this follicular phase develops it will stimulate these primary follicles it will stimulate the primary follicles to confer the develop so what you have is a series of these going on at the same time so cohorts of them that are in various developmental stages every single month until they reach the secondary or tertiary point I wish weren't they they're sort of sort of the next up if you will to to be the ones to ovulate now at the top of this the hormones that are regulating this are the ones that we've discussed before which are the FSH and LH thought stimulating hormone and luteinizing hormone and so you'll see that FSH goes up early on in the follicular phase because the follicle stimulating hormone so it's level starts to increase to stimulate the growth of the follicles and the luteinizing hormone levels will also be fairly elevated as well and then you'll notice Tory an ovulation that there's a surge in LH whereas there's kind of just a little bump in the FSH there that LH surge is very important for a violation without the LH surge there is no ovulation so let's talk about the hormone that are involved in this so goodnight atropine releasing hormone or GnRH increases FSH and LH release at the beginning of the follicular phase so when on the first day of menses which lasts again 3 about 3 to 5 days what's happening is the GnRH levels start to rise and that stimulates theatre pituitary to release high levels of FSH and LH that stimulates the ovary the father's in the ovaries to start to develop so usually it'll start to stimulate a cohort of follicles to continue maturing and what happens is the growing follicle it responds to the FSH and LH is going to actually produce estradiol which is one of the estrogens we spoke about and so the increase so it'll start to increase its production of estrogen as it matures so the more mature it is the more estrogen it's producing at the same time the estrogen is increasing the number of FSH and LH receptors on the follicle so it's actually it's a positive feedback in the sense that the estrogen is acting on the follicle itself to increase its own sensitivity by having more and more receptors for s FSH and LH estrogen weren't in the blood though however when it feeds back to the anterior pituitary or to the hypothalamus is actually a concentration dependent effect so early on when the estrogen levels are relatively low that actually inhibits FSH and LH release and so it decreases FSH and LH but even though it's decreasing FSH and LH is decreasing their secretion so it's not being released from the cells however it seems to increase the synthesis and storage of FSH and LH so it's inhibiting its being able to be released but it's really kind of stockpiling FSH and LH in those cells because what happens later on is the estrogen if the follicle gets more and more mature its releasing more and more estrogen over time that estrogen level actually Peaks so to get a large concentration of estrogen and so what happens with that time-dependent release of high levels of estrogen it actually stimulates the release of Kannada trope and releasing hormone or GnRH from the hypothalamus which actually causes the release of LH and FSH and which causes the surge so in other words estrogen early on during the follicular phase is relatively low it's being produced more and more but it's relatively low and it has an inhibitory effect on the hypothalamus and the pituitary in terms of secretion of FSH and LH however though there starts to stockpile FSH and LH inside their cells and then towards the end of the follicular phase the estrogen levels increase and during that you know increase in estrogen concentration that actually stimulates GnRH released from hypothalamus which stimulates the release of that ellis of that LH and FSH which have been stockpiling this whole time so it creates a large concentration or a surge in the blood stream which actually is what triggers the induction of ovulation ok so here I want to draw out the hormonal pathway so we start here at the top is going to be gnrh and this is good and chopped and releasing hormone from the hypothalamus and so that level would be increased at the beginning of the sexual cycle and then that will stimulate the release of FSH + LH from the anterior pituitary and in turn that will cause the stimulation of the follicles and the follicle is again located in the ovary so that stimulates the follicles and then the follicles in response to that are going to release or produce estradiol or estrogens now the the estrogen is being produced can actually cause a little positive feedback loop with the follicles so as the follicle produces the estrogen the estrogen actually causes the follicle to increase the number of FSH receptors it has as well as increased the number of LH receptors that it has so what happens is ultimately the follicle becomes more and more sensitive to FSH and LH and causes the follicle to grow and develop even faster in addition the estrogen is being produced is going to act on the uterus specifically the endometrial wall and [Music] that's going to cause proliferation of the endometrial lining during this time so the estrogen is there now as the estrogen being produced from the follicles as it initially starts to increase is that it's still at a very relatively if she's a relatively low concentration so this relatively low concentration has a feedback to the hypothalamus as well as the answer pituitary the feedback here is actually complex though because relatively low estrogen levels cause in the anterior pituitary cause it to inhibit a little bit a little negative sign and inhibit secretion secretion of FSH and LH however it stimulates the production of it in the cells as well as the storage some production and storage of FSH and LH so what happens is it starts to accumulate those hormones within the cells but it's not secreting it so the FSH LH blood levels would be going down at this time but the cells would be producing more and more of it and sort of stockpiling in those cells now the the natural producing level would be inhibited with these low levels of estrogen so now this is occuring again early in the follicular phase within the ovary ok and then ok during that time addition levels are increasing it is still stimulating the uterus as well so now let's say we're further along in the follicular phase now and so as we go on further in the follicular phase we're approaching ovulation we have one one mature follicle that has survived and it's producing a lot more estrogen and it's you know it's quite large at this point so relatively the estrogen concentration has gone up has increased significantly and so the result of that is this let's get rid of our inhibitory responses here for a second and instead what's gonna happen here now in as we approach a violation is the estrogen is primarily going to give a positively backwash stimulate the release of gnrh which can also stimulate FSH and LH release now remember earlier the follicular phase FSH aknowledge was being inhibited B from being released however it was stockpiling that those hormones within the cell so when it's when estrogen levels increase it stimulates gnrh to release FSH and LH but it's gonna release it at very high high concentrations very suddenly so we get that surge particularly a surge in LH so FSH does go up by LH is very vital so luteinizing hormone surge is important for ovulation so that's surge that's going to stimulate the follicle to to then undergo ovulation so I'm going to draw that over here so this is ovulation and the follicle itself becomes the corpus luteum all right so that's surge this LH surge stimulated ovulation became the corpus luteum and now it's going to enter into what we call the luteal phase and so the corpus luteum will secrete estrogen just like the follicle did plus progesterone so progesterone is now the new one that's being added from the corpus luteum so the corpus luteum is actually very very sensitive to luteinizing hormone and in fact the follicle which I've been developing more and more FSH and LH receptors is now very sensitive to the LH hormone in the luteinizing hormone stimulates the corpus luteum to secrete estrogen and progesterone particularly progesterone here the high levels of progesterone will also act on the uterus so the estrogen progesterone will continue to act on the uterus to develop the uterus and thicken the endometrial line at the same time though this estrogen and progesterone is being produced by the corpus luteum will now act to inhibit when you get rid of this will now act to inhibit the release of gnrh FSH and LH so that in this way after ovulation the the ovary is no longer going into any follicular phase or follicle development because it's going to suppress those hormones now with this high level of estrogen plus this high level of progesterone now keep in mind that the corpus luteum is responding to LH in order to secrete estrogen and progesterone so it starts to inhibit its own its own signal to release and what happens is it gradually drops off the luteinizing hormone levels due to its negative feedback this takes usually again about 12 to 14 days so what happens is as it inhibits its own LH stimulation progesterone and estrogen levels start to decline at the end of the luteal phase the result is that the corpus luteum completely stops secreting and in volutes and becomes the corpus albicans which is just an inert structure and then estrogen progesterone can no longer can no longer stimulate the uterus and help to support the growing in the metrium and so the endometrium of the uterus swaps off and thus the cells there will die off and become part of the the menses okay so this cartoon is really just depicting when estrogen levels start to rise towards the the end of the follicular phases were approaching ovulation the the rise in estrogen causes the stimulation of stimulation of the release of GnRH which can also stimulate the release of LH and FSH and then that's that's going to cause a surge which results in down here for my videos cutting off some results in a surge that resulted in ovulation so again the LH surge is absolutely necessary for for ovulation now in the uterine cycle what happens here now is this is again this is parallel to what's going on in the ovary so again you have the dimensional phase okay which is day one to about day five or so but also it's three other phases the proliferative phase a secretory phase and then a premenstrual phase which is blocked when my video is a premarital phase which you can see up here all right that's our promotional phase so initially we have that menstrual phase so this is actually the discharge or sloughing off of the tissue so let me kind of explain what we're looking at here this is the thickness of the the endometrial tissue and you can see here this kind of blue blue line right here alright this blue tissue that is the the basal layer so that basal layer stays consistent throughout the entire cycle there and in fact that's where what's gonna be stimulated by the hormones the beginning of each cycle so you'll notice that the functional layer on top that which is like the pinkish layer it starts to increase the thickness not the basal layer when ends up happening is the the basal layer gets stimulated by the increasing estrogen levels which at this point are still fairly low but the estrogen being coming from the ovary stimulates the production of or the the the initiation of mitosis so cells start to divide start to vascularized and so you see each of the blood vessels and the cells that start to grow and the the the endometrium of the uterus becomes thicker and thicker and then all the way up until we have our our surge in estrogen which you can see here which causes ovulation the ovary in the uterus what's happening is we switch over from the proliferative phase after ovulation into what we call this secretory phase so what happened is in the proliferative phase estrogen was actually not only thickening up the the endometrial layers there but it was also increasing the number of progesterone receptors and so it's increasing its sensitivity to progesterone so after ovulation when the corpus luteum which starts to secrete high amounts of progesterone the progesterone in addition with the so here's a progesterone in addition with the STI oestrogen levels causes the secretory phase so we get again further the thickness but most of the thickness coming here is not necessarily from mitosis but from secretion of the cells and accumulation of fluid in an interstitial space as well as you can see some of the glandular tissue starts to coil which you can kinda see here you see the coils of the glandular tissues and further development of the blood vessels and secretion of glycogen zand and proteins in there and kind of picking it up thickening it up overall and then finally if if there is no fertilization the corpus luteum in about 14 days will involute and that's a fairly fixed time so even if even if females have different variations in the length of their their sexual cycle the the corpus luteum is fairly fixed in about a 14-day lifespan essentially so usually most the variability in cycle comes in the foot during the follicular phase not during the luteal phase of the ovary so in the uterus in response to this again we have this corpus luteum secreting progesterone estrogen which stimulates further thickening and more secretions and if the if the corpus luteum then involute sand dies off that's when the premarital phase will start and you'll see that the they'll drop the drop in progesterone and estrogen that was being secreted by the corpus luteum results in spasms of the the blood vessels and ischemia and what happens is the [ __ ] or closure of these blood vessels causing this acute ischemia and the cells start to die off and slop off and there it can be bleeding and so on and so the menstrual fluid is actually a mixture of some of this dead cellular debris as well as the the blood and some of and then enters you know that starts the dimensional cycle and then the whole thing starts over again so what happens is if there is fertilization then the fertilized egg gives feedback to the corpus luteum to keep it to keep it alive and to keep it producing estrogen and progesterone to maintain the endometrium of the of the uterus so that so that that stays alive and can nourish the growing embryo so this is a kind of a summary of you know the ovarian cycle the uterine cycle during the third in the overall sexual cycle so you see the gnrh and FSH and LH levels all right to the stimulates theater pituitary to release the FSH and LH which in the ovarian cycle stimulates the follicular phase up until we have ovulation and then that's releasing the oocyte into the fallopian tube and then here you have the core the formation of the corpus luteum which you can see here in yellow which secretes progesterone and estrogen and can ultimately become the corpus luteum or excuse me the corpus albicans if if it involute so there's no feedback from the uterus now during the follicular phase the follicle is producing more and more estrogens they said the estrogens have a feedback mechanism on the pituitary and hypothalamus which causes the surges and so on that I spoke about but the estrogens also stimulate the uterine cycle so that it continues to thicken during the proliferative phase and then during the corpus luteum phase is releasing progesterone and estrogen and so that's when we enter into the secretory phase of the uterine cycle and then again if they if there's no feedback they enter into the premenstrual phase and so on so in terms of the corpus luteum the corpus luteum is very sensitive to luteinizing hormone so that's why you see this over here the luteinizing hormone so remember the mature follicle had developed more and more FSH and LH receptors and so even after it ruptures during ovulation and it becomes the corpus luteum the corpus luteum has a lot of LH receptors and so it's stimulating the corpus luteum to release progesterone and estrogen however though the high levels of estrogen progesterone will actually feed back so this will actually feed back and inhibit gnrh FSH and LH so during this time the follicle stimulating hormone drop off and so does luteinizing hormone and this prevents further maturation of any of the follicles during this time and so this is that's important to kind of halt all that activity now at the same time as those levels are dropping that means the LH levels are dropping which is stimulating the corpus luteum but since the corpus luteum has a lot of LH receptors it can kind of survive for you know for a little while longer so it happens is the h levels drop further and further during that 14-day period it eventually starts to reproduce less and less progesterone and estrogen and eventually will become the corpus albicans and so once that dies off and the estrogen progesterone levels drop off GnRH levels rise again because it's not being inhibited and so therefore the FSH levels will rise the LH levels will rise and a cycle will start all over