Embryology | Development of Reproductive System

hi ninja nerds in this video today we're going to be talking about the development of the reproductive system before we get started though please continue to support us by hitting that like button commenting down the comment section and please subscribe subscribe also down in the description box we have links to our facebook instagram patreon account go check those out all right engineers let's get into it all right ninjas when we talk about the development of the reproductive system we have to remember from what germ layer this actual reproductive system develops you guys remember it's the

mesoderm but let's even be more specific if you guys remember from the mesoderm there was three different parts of it right the one closest to the neural tube was called the par axial mesoderm then you had the one next to what's called the intermediate mesoderm and then you had these two layers that splayed out that was the lateral pleumesider right and the part of the ladder plate mesoderm that was closest to the gut tube was called the splanchnic layer of the ladder plate miser and the layer of the lateral plate that was going with the

ectoderm was called the somatic layer of the lateral plate museum which one of these layers gives rise to the reproductive system do you guys remember it's the intermediate mesoderm that's the one that we need to focus on so again the primary one here that i want us to talk about is the intermediate mesoderm now what happens with this intermediate mesoderm so the next thing you guys need to remember is that the intermediate mesoderm starts condensing and as it condenses it forms a specialized structure here called the urogenital ridge the urogenital ridge what you guys need

to remember is that the eurogenital ridge is what gives rise to the reproductive system particular parts of the reproductive system though it's going to give rise to the gonads and you know gonad's looking to get you can actually have either give rise to the male gonads which will be the testes or the female which would be the ovaries the second thing that you guys need to remember is that it also can give rise to the ductal system and there's two ductile systems for uh the developing embryo we'll talk about that so the ductal system okay

that's very important to remember now the next thing that you have to realize is that when we talk about the urogenital ridge it is a core of mesoderm there's a little bit of epithelial tissue around it but what happens is that you guys remember your embryology this is actually your gut tube right this is your gut tube a better view of the gut tube is in a sagittal section let's take a look at the sagittal section this is there's a reason why i'm trying to mention this if you take a look at the sagittal section

this right here this entire green tube is your gut tube and you have different portions of the gut tube correct you have the four gut the mid gut and the hindgut and at the bottom portion of that hindgut what is this portion here that's close with the ectoderm that's called the cloaca we'll talk about that portion in a second because that also give rise to a part of the reproductive system but what i want you to remember is here's your yolk sac okay this is your yolk sac your yolk sac has very particular types of

special cells called primordial germ cells and these primordial germ cells will migrate from the yolk sac towards this duct what is this duct this is called your vitalin duct so from the yolk sac these primordial germ cells will move towards the gut tube and then start infiltrating around this red structure what is this red structure here called we already talked about it this red structure here just in a sagittal view is the urogenital ridge and that's going to give rise to the gonads in the ductal system the next thing i want you to know is

that these primordial germ cells they love to infiltrate into the gonads that's very important so what i want to add on here is that from this actual urogenital ridge the primordial germ cells from the yolk sac will infiltrate into it and these primordial germ cells will give rise to the gametes so this will give rise to sperm for the male gonads and it will give rise to the oocytes for the female gonads that's very important the last part that i want to talk about that's going to be important for the development of the reproductive system

is the cloaca you know the cloaca gives rise to two structures it gives rise to the anal canal which is going to be posterior there's a posterior portion of the cloaca you get like a little septum called the urectal septum it separates that cloak into two parts a posterior anal canal and the more important one prevalent to this actual discussion is the urogenital sinus and this is going to be the anterior division of the cloaca this is what gives rise to a part of the external genitalia so this will give rise to parts of the

external genitalia so now that we understand how we actually kind of start developing our primitive reproductive system we've got to start going over more detail and talking about okay we understand the primitive gonadal system the primitive ductal primordial germ cells all that stuff let's talk about how they differentiate and become specialized towards male and female let's do that now okay so now we understand how the intermediate mesoderm gives rise to parts of the reproductive system and how the cloaca which is at the end part of the hindgut how that's going to give rise to other

parts of the reproductive system primarily the external genitalia let's kind of annotate though a diagram very important diagram very important for us emily step one that you have to understand the primitive reproductive system what is these structures here so let's talk about these the first primitive structure here is these red structures these are going to be the gonads this is this is the first one okay now they're gonads because we don't know yet if they're going to become male or female the next one that are on the sides of the gonads is one of those

ductile system remember we said that we'll actually develop ductile systems from that urogenital ridge these here in blue are called the mesonephric ducks there's another name for these okay and they're also called the wolfian ducks also called the wolfian ducks the next ducks which are also on the sides of the gonads are these like royal blue or baby blue ones and these are called the pera meso so para means on the side of the mesonephric duck so pero peramiso nephric ducks also referred to as the muellerian ducks the last one here this is i honestly

know it sounds like a made up name but it's real it's this brown structure which is actually going to be on the sides of the actual ductal system as well and the gonads and this brown structure here is called the guber naculum so you have the gubernaculum which is these kind of like brown structure on the side the last thing here is as you kind of follow these mesonetric ducts and the paramesonephric ducts down they empty into this structure here this green structure which we talked about came from the cloaca it's the anterior division guess

what this structure is this is the urogenital sinus urogenital sinus so now what we have here is we have kind of the beginning parts of our reproductive system now that we understand this what i need us to do then is talk about what steps do we have to go through chemically and cellularly to convert the gonads into ovaries or testes the mesonephric ducts into the male ejaculatory system the pyramids and nephrotics into the female ductal system and then talk about the urogenital sinus and talk about the gubernaculum and what function it has all right so

the first thing we have to talk about is how do the gonads know to lead to the male or female type of sexual gonads let's talk about that first okay so the first thing that i want us to do is understand the differentiation of the gonads that's the first part so let's say we take the gonads we're going to start with how the gonads become the testes or how it becomes the ovaries that's the first goal well the first thing you need to realize is that the changes in the gonad the structure within the mesoderm

the changes occur when it comes to the male so let's put x y and the changes in the female xx occurs in different parts of the actual gonadal structure the changes in the male what will become the male testes is going to occur first in the medulla of the gonad okay that's the first thing that i need to remember the changes will start occurring first and the medulla of the gonads for the female the future female gonads this is going to occur in the cortex the edge of the gonad structure so again the changes that

are going to occur in the gonads that occur in the medulla are for the male will become male and the ones that occur in the cortex of the gonad will occur for the female what do i mean by this just that we're completely understanding this because i want you guys to be confused here imagine we take that gonad here right the changes that are occurring here in the center that's the medulla of the gonad the changes that are occurring around the edge are the cortical region that's going to be for the female gonads okay so

now we understand that let's talk about how we actually start leading to this differentiation there's a special gene and this gene is called the s-r-y gene let's write that down this gene here that actually starts being expressed on the x-y chromosome particularly the y chromosome is called the s r y gene okay very important gene why because the sry gene is going to lead to the expression of a particular type of molecule called testes determining factor and testy's determining factor is what gives rise to testes so let's kind of follow that down then if we

take here understanding that the x y which was particularly for the male they have the y chromosome the y chromosome expresses the sry gene if they are sry positive what will they produce they'll produce testes determining factor what will testes determining factor do it'll convert the primitive gonad into testes but that leads to the next question what are the testes actually made up of that's the next important question we have to answer so let's talk about that when you actually take a look at the testes and look at the microscopic structure of it the testes

are made up of a couple different things one is they're actually made up of a lot of tubules little tubules inside of them kind of a little tubules that are all kind of like thrown throughout the entire structure these tubules kind of come in different names one is it's called the seminiferous tubules another one is called the retta testis and there's another one too called like the straight tubule but again these are the two main ones the next structure that comes from the testes that is very important here is going to be called your lydig

cells very important cells light egg cells the reason why your lighting cells are important is they produce a very important hormone called testosterone very important the next thing that actually is going to be within the testes is some other special cells called sertoli cells and sertoli cells produce a very important hormone called malarian inhibiting factor and we'll talk about what that is and we'll abbreviate this the malaria inhibiting factor it can also be called the malaria inhibiting hormone but malaria inhibiting factor now we understand that this is what the testes are made up of for

the most part there's one other component though this was primarily coming from that epithelium and mesoderm core but remember we had those primordial germ cells that were coming from the yolk sac remember what i told you those primordial germ cells do the primordial germ cells infiltrate into the testes in this case and those primordial germ cells will give rise to sperm so the sperm will also be a component of the testes but that's going to be coming from the primordial germ cells so now we understand this okay let's move on to the next part now

that we know that the testes are actually formed due to the presence of the testes determining factor what's the next thing that happens well we formed all these different components but the really the only two components that we're really worried about here is the leidig cells okay that produce what hormone testosterone so now the testes will start producing testosterone that's one thing the other hormone that's going to be produced here is going to be malaria inhibiting hormone or malaria malaria inhibiting factor so malaria inhibiting factor what will these two things do i'm glad you asked

testosterone will then stimulate some very important pathways you know there's that ductal system we talked about the mesonephric ducts it'll help to stimulate the mesonephric ducts to continue to grow to maintain their structure that's the first thing so it'll stimulate the growth of the mesonephric ducts that's important why the mesonephric ducts are what's another name for them the wolfian ducks will give rise to what structures do you guys know it's going to give rise to that male ductile system what connects to the testes you have your epididymis what else do you have your vas deferens

what else do you have well the vast difference comes down and gives off a little like gland called the seminal vesicles seminal [Music] vesicles and the last part is where it kind of moves through the prostate gland it empties into the prostatic urethra what's that duct called the common ejaculatory duct common ejaculatory duct so when the sry gene is activated it releases testy's determining factor generates testes testes produce testosterone testosterone maintains the growth of the mesonephric ducts what will the mesonephric ducts continue to grow into throughout the embryonic development the ductal system primarily made up

of epididymis vas deferens seminal vesicles common ejaculatory duct all right here's the next thing you know the female ductal system we don't want that to grow if a male if you're going to become a male you don't want to have the female ductile system growing at the same time you don't want to have epididymis and vas deferens and have a fallopian tube in the uterus so because of that guess what the malaria inhibiting factor does the malaria inhibiting factor inhibits the perimesonephroducts or what's another name for them the malarian ducks so it's going to inhibit

the growth of the malarian ducks what does the malaria ducks give rise to well i already kind of told you right one is the fallopian tubes that's going to give riders the fallopian tubes if you're becoming a male you don't want to have fallopian tubes it's going to give rise to the uterus you know you have the fundus the body the cervix of the uterus and it's going to give rise to the upper two-thirds of the vagina you don't want to have a vag if you're going to be a male as well so the malaria

inhibiting factor will inhibit the formation of the malaria ducts which will inhibit the formation of the actual female ductal system what's the next thing all right testosterone there's one more thing that we have to talk about we've talked about how the testes are developed for the from the gonads we talked about the male ductal system how it develops and how we inhibit the female ductal system but we didn't talk about the external genitalia we'll get into more detail of it later but what i want you to know is that testosterone also gets acted on by

a particular enzyme called 5-alpha reductase and what this enzyme does is it converts testosterone into dihydrotestosterone and you know what dihydrotestosterone does it stimulates the development of the male external genitalia so it's going to stimulate the male genitalia and again we'll go over that in more detail a little bit later so we understand how we develop the male stuff now actually that we've done that the female development of the reproductive system is actually very easy now watch this so we need the sry gene on the y chromosome well guess what the female does not have

the y chromosome so she's going to be s r y negative if that's the case then she does not express there's no testes determining factor that means that this will not give rise to testes as a result by default it'll give way to ovaries now this begs the question what are the ovaries made up of you know what ovaries are made up of it's actually much easier thank goodness there's two particular kinds of cellular components let's actually mark them over here so the first one is you have those epithelial cells and the mesoderm that are

part of that urogenital ridge of the gonad what happens is they become particular structures called follicular cells these follicular cells are very special you want to know why the follicular cells are what produces estrogen and another one called progesterone but particularly uh pertinent to this lecture is estrogen that's the first thing the second thing which we're going to switch the colors that were consistent here remember those primordial germ cells that came from the yolk sac infiltrated the gonad what did that become it became sperm for males but it also becomes oocytes for females so that's

another important thing because this whenever it combines with the sperm will give way to the ovum the fertilized ovum so that's the next thing so now we understand the actual activity of the ovaries now the ovaries whenever these are formed they're going to produce estrogen guess what estrogen is going to do well the first thing is that the estrogen in particularly in the form of what's called estradiol we really want to be specific it stimulates the formation of the female genitalia and again we'll go over that in a little bit more detail later so it's

going to stimulate the formation of the female genitalia so so far we have the development of the female genitalia due to estrogen we have development of ovaries due to the lack of sry gene but what about that female ductal system well follow along with me for a second come back over here and we're going to change the color here for a second let's just do it in red if the actual female is forming there's no sry gene no testes that are forming so because of that no testes determining factor that means that you're going to

develop no testes correct if there's no testes you don't form what type of molecules i mean what types of cells the lytic cells which form testosterone so testosterone isn't going to stimulate the formation of the mesonephric ducts and it's not going to be able to form male external genitalia by getting converted into dht so that process is gone but more important than that the other component of the testes was the malaria and inhibiting hormone or malaria inhibiting factor it was released by the sertoli cells well if you have no testes you have no sertoli cells

no sertoli cells means that there's what means that there's no malarian inhibiting factor if there's no malaria inhibiting factor because there's no sertoli cells what happens then you're no longer able to inhibit the formation of the malaria ducts now the malaria inductive formation will be disinhibited and you'll be able to stimulate the formation of the malaria ducts or what's another name for them the perimesonephric ducts if you stimulate the formation of that that'll give rise to the fallopian tubes that'll give rise to the uterus and that'll give rise to the upper two-thirds of the vagina

boom we've formed the female reproductive system up to this point with the exception that we haven't talked too much about the genitalia yet but upper two-thirds of the vagina okay boom we covered a big chunk there so now that we've done that let's talk about one last thing and that is the gubernaculum that's the one thing that we didn't talk about yet the function of this is actually pretty darn cool not to mention it also has like a pretty cool name as well the gubernaculum has different functions within the male and within the female obviously

right but the concept of how it performs these things is the same the whole function of the gubernaculum is to guide the descent of the male or the female reproductive system down into the pelvic region because when your gonads are developing they're actually developing at the abdominal cavity so what the gubernaculum does is is it guides descent of the testes right into the pelvic cavity but particularly there's a little structure called the processes vaginalis and then you develop a little a little tube later on life called the inguinal canal that pushes these actual structures the

testes down into the scrotum so it guides the descent to the testes from the abdominal cavity into the scrotum that's important because once it's guided down into the scrotum what happens is you're going to pull down the gubernaculum will pull down the testes it'll pull down the male ductile system and it'll pull the blood vessels that are going to the testes what is that whole structure if it's kind of circled around it's called the spermatic horde so the gubernacular helps to guide the testes and the entire reproductive system of the male down into the scrotum

to help with the formation of the spermatic cord so the gubernaculum within the female it guides the ovaries it guides the fallopian tubes the uterus all that stuff down into the pelvic cavity so again it guides the ovaries and the entire kind of reproductive system the ovaries in the ductal system into the pelvis but as it does this what happens is the gubernaculum kind of splits into two portions two little portions and when it does it forms two ligaments with that are actually very important around the uterus one ligament that it forms is called the

ovarian ligament and the ovarian ligament is going to be between the ovary and the uterus so that's one of the ligaments that the gubernaculum gives rise to the other one again what happens is the gubernaculum connects up near the gonad near the ovary but as it does that it clicks into the side of the uterus and then the the bottom part of the gubernaculum here will connect to the labia so what happens is the bottom part of the gubernaculum connects from the uterus to the labia and that's called the now that we understand how we've

formed for the most part the formation of the male and female gonads and we've also discussed their ductal system and we talked about how we guided their descent from the abdominal cavity to the pelvic cavity we now can identify the differences in an anatomical diagram so now that we kind of have a very good understanding of how we develop and differentiate the gonads into male and female gonads the ductal system into the male and female ductal system and how the gubernaculum kind of guides the descent down let's kind of identify these structures that's very important

here so let's say on this side this is going to be what happens to the male differentiation and over here this will be the result of the differentiation to the female sex so what will the gonad become here it'll become the testes then the next part is what does the uh particularly the ductal system for males become this would become the mesonephric or the wolfian ducks and what does that give rise to a nice little quick quick recap epididymis vas deferens seminal vesicles and then the common ejaculatory duct the next thing here now that we've

understood that is that the gubernaculum again it'll pull this entire structure downwards and into the scrotum for the for the female what does the gonad become this will give rise to the ovaries okay this will give rise to the ovaries and then this blue structure here that's connecting with the ovaries because again what happened the mesonephric duct got degraded for them the mesonephric gut duct got degraded for the females and all that's remaining is the perimesonephroduct so this is the para mesonephric duct and again this is also referred to as what other name is this

this is also called the malarian duct and again what does the malaria duct give rise to it gives rise to the fallopian tubes the uterus and the upper two thirds of the vagina and then again the gubernaculum will pull this kind of whole structure downwards into the pelvic cavity as well as giving rise rise to those particular ligaments the next thing that you guys need to remember is we kind of you see how there's a change in the structure remember the urogenital sinus we talked about that one a little bit here the urogenital sinus gives

rise to a particular structure that we'll talk about more in detail over here but with respect to this structure here the urogenital sinus connects and gives rise to particularly the bladder in this diagram it also gives rise to a part of the urethra it also gives a rise to a part of the urethra and again to kind of correlate with this remember we said that for the male they have a common ejaculatory duct that right there is the common ejaculatory doctor look where it's emptying right into the prostatic urethra region so that's why that's important

okay so we have an understanding of how we form the male and female reproductive system for the most part let's finish up talking about the development of the external genitalia all right so we've we've got to finish up talking about the development of the external genitalia because again this is a very important component of the reproductive system so a generalized diagram of a primitive kind of uh external genitalia not specific to male not specific to female this is just kind of how it starts off so if you look at kind of the base of like

the bottom of the embryo where the genitalia are going to start developing you kind of notice there's uh if you were to imagine here you can't see the urogenital sinus but if you kind of imagine here i'll draw it in green it would be inside of this kind of structure here and again we'll talk about what that is but again you can't really see that portion of the urogenital sinus it's better seen in the sagittal section so here we're kind of looking at the genitalia when we look at it there's complete identifiable structures the first

one here is this brown structure and this brown structure is called the genital tubercle it's called the genital tubercle that's the first thing that you guys need to know that's the first structure that you need to know it's kind of on the top part on the sides in pink these are called your labia scrotal swellings so labia labial scrotal swellings that's the next important part then in blue right here this portion here this is called the urethral folds so again what are these called these are called urethral folds and again it's important to realize you

can't really see the urogenital sinus in this diagram but if we took a sagittal section of the embryo it's better seen here so here's our sagittal section we're kind of looking at a sagittal view here and what you see here is you can even see a small little piece here of the genital tubercle so you can still see a piece of that genital tubercle here but what is important is you have this green structure here again this goes back to that diagram that you have to remember there was a very particular structure kind of dilated

structure where the hindgut emptied into and where the mesonephric duct empties into or the you know the mesonephric duct empties into and that was called the cloaca remember the cloaca splits and when it splits it splits by this structure called the what is this structure called this is called the euro rectal septum and that separates the cloaca which is this whole structure into two parts this portion here which i'm going to kind of like break apart now this portion here which is going to be the anal canal which is going to be the posterior portion

and then this portion here anteriorly this is going to be the urogenital sinus and what happens is remember that mesonephric duct that mesonephric duct is coming down here and it's going to empty into that urogenital sinus remember it empties in near the urethra that was the important thing to take away from that that was the important thing to take away well what you need to remember is that this urogenital sinus it's going to be this whole portion here we're going to kind of outline it in blue we're going to say it's from here to here

that's the urogenital sinus and this last structure here from the top from this blue line to this point here this structure here is called the elantois okay so we have i've been able to identify from these anatomical diagrams the main components that are going to give rise to the external genitalia what are those main components that we need to focus on it is the genital tubercle the labial scrotal swellings the urogenital sinus and the urethral folds these are the primary primitive external genitalia that we need to know then what we need to understand is how

these structures become either male genitalia or female genitalia we kind of know a little bit about this the first thing that i need you guys to remember if it's going to become male what hormone was guiding this process do you guys remember remember we had testosterone and the testosterone was get converting remember we had testosterone and there was an enzyme called 5-alpha reductase and that was converting testosterone into dihydrotestosterone that dihydrotestosterone is what's stimulating each of these steps and trying to push these primitive structures into forming male genitalia for the female do you guys remember

what hormone was guiding the development of the external genitalia for the female this was estrogen released by those follicular cells or the granulosa cells that's going to be trying to stimulate the guidance of these primitive genitalia structures into making female genitalia okay now enough of that let's know what the heck the genital tubercle becomes in the male and in the female in the male this gives rise to what's called the gland's penis it also gives rise to very important ejaculatory type of tissue or erectile tissue and that is called the corpus spongiosum and the corpus

cavernosum these are very important structures that you need to remember for the female the genital tubercle will give rise to the clitoris and the vestibular bulbs vestibular bulbs okay beautiful the labial scrotal swellings if stimulated this is actually pretty easy thank goodness labia scrotal what do you think is going to become if it's for the male the scrotum so this will become the scrotum and for the female this would become the labia majora labia majora all right sweet pretty straightforward there the next one a little bit more difficult not too crazy with respect to the

reproductive system the external genitalia and the presence of testosterone the urogenital sinus will give rise to what particular structures it'll give rise to the the prostatic urethra so you know you have the different parts of the urethra right the prostatic urethra it's also going to give rise to the what's called the membranous urethra and here's the important part here it's there's also glands okay that are going to be around the prostatic urethra and glands that are going to be around the membranous urethra there's a gland that is going to be around the prostatic urethra what

do you think that's called it's called the prostate gland so it's also going to give rise to the prostate gland in the presence of dht and then the membranes urethra is going to give rise to what's called the calpers glands they're also called the bobo urethral glands so that's going to be for the urogenital sinus and males and females it's pretty straightforward it's going to give way to they don't have multiple urethras so it's just going to give rise to the female urethra and another thing which is called the uh the para urethral glands so

the para urethral glands and there's also a little other glands called bartholin's glands so other small little glands around the area called barthlins glands so that's going to be what the eurogenital sinus gives rise to now again it's important to remember that it's for the urinary system it also gives rise to the black but again we're talking about reproductive for the urethral folds for the male it's primarily going to give rise to the shaft of the penis so it's going to give rise to the shaft of the penis or pretty much the body of it

as well as there's a particular urethra that runs through the shaft of the penis the primary body of it and that is the penile urethra all right beautiful last but not least the urethral folds for the female this is going to give rise to the labia minora so this would give rise to the labia minora and that will cover the development of the female and male external genitalia as well as complete our understanding of the development of the reproductive system all right engineers in this video today we talk about the development of the reproductive system

i really hope that it helped and i really hope it made sense all right engineers thank you love you and as always until next time [Music] you