Embryology | Development of the Urinary System

all right ninjas in this video we're going to be talking about the development of the urinary system before we get started please hit that like button comment down in the comment section and please subscribe also down in the description box we have links to our facebook instagram patreon account go check that out all right ninjas let's get into it all right so when we talk about developing the urinary system the basic foundation for developing the urinary system if you guys remember from the mesoderm video is the intermediate mesoderm right so what we have to do

is kind of really quickly go through how do we make the intermediate mesoderm and then how does that intermediate mesoderm make the urinary system that's kind of the basics those steps right so first things first let's start up here with our bilaminar disc around week two if you guys remember up here we have the amniotic cavity right and then you have these cells here these blue cells which is called your epiblast then below that you have these green cells which is called your hypoblast and then below that you have the yolk sac now what happens

is if you guys remember you develop a little cavity or a little like space called the primitive streak the epiblast cells move through the primitive streak and take the hypoblast and turn it into a new layer what is that new layer here it's called the endoderm so it replaces the hypoblast cells and converts that into endoderm then it makes a new layer right it comes down replaces the hypoblast that makes a new layer above the endoderm which is called the mesoderm right then what happens is the epiblast cells differentiate themselves and turn into ectoderm so

what do we know we went from a bilaminar disk to a triliminar disk and again amniotic cavity and yolk sac all right this process for which we went from a bilaminate to a triliminar disc is called gastrulation right ba-boom now the next thing that we have to talk about is when you look at the mesoderm there's actually three components of it right what are those three components this first one will label it as one then two then three one is what this is the par axial mesoderm right then two is what that's the intermediate mesoderm

that's the one we really really care about in this lecture and then the last one just for kind of consistency steak the third one is your lateral plate mesoderm and the lateral plate mesoderm has two layers right which is going to be this top layer going with the ectoderm which is called the somatic layer and this layer here going with the endoderm which is called your splank nuclear we know that we're pretty good at that part right what happens though in the next step here is that we have to undergo folding and we're going to

fold this kind of three layer disk which kind of looks like a pancake in this situation we're going to fold it in a lateral folding process and then another way which is cranial caudal which you can't really see in this type of two-dimensional space with the board but it would be coming out at you it would be this type of process when we go through the lateral folding process it gives us this nice little kind of like structure that looks somewhat similar to our actual internal organs right and what you see here is very important

to kind of build your foundation here we're going to kind of consistency go off of this number system par axial mesoderm was one two here was your intermediate mesoderm and then this portion here which is going outwards right this one here it would be your somatic layer of ladder plate mesoderm and then this one going here to wrap around your gut tube would be the splanchnic layer of the ladder plate museum right we have an idea here of where that intermediate mesoderm is right here right number two what i want you guys to remember here

is that once this intermediate mesoderm is formed it starts to really condense and really really condense near this splenic layer of the lateral plate mesoderm it makes a little dividend to it and what does that start to look like so what starts happening is you start getting condensation condensation of the intermediate mesoderm and once it starts kind of really condensing and kind of bulging in look here so now you have what is this your par axial mesoderm right here your intermediate mesoderm here and then again you have your lateral plate mesoderm which will go out

this way as the somatic layer and then this one here which will be your splank neclare if you look here you see how the intermediate mesoderm kind of condensed near this blank nuclear and created like a little divot that little divot there which is created by that this big chunk of mesoderm is called your euro genital ridge and this core of mesoderm which is a part of that eurogenital ridge is given a really special name that is called your nephrogenic cord it's called your nephrogenic cord now what i want you to remember is that the

urogenital ridge will become the urinary system but it'll also become your reproductive system so what we're going to do is we're going to focus on a portion of that urogenital ridge which is going to be the nephrogenic cord now the nephrogenic cord in a cross-sectional view isn't the best way to view it the best way to really see the nephrogenic cord is from a sagittal section so this was kind of our cross section and this is a sagittal section here so we're going to look at this in a sagittal view and it's already undergone that

cranial caudal folding process so here you're going to see this long nephrogenic cord you see this nice long nephrogenic cord and it's actually going to be found behind what your gut tube so this right here would be your gut tube and we already know that you would have your foregut your mid gut your hindgut all that good stuff what we really need to focus on throughout the rest of this lecture is that we started off with our intermediate mesoderm it condensed it made this really important structure called the nephrogenic cord it spans really far down

the length of the embryo what i want us to do now is to take this nephrogenic cord and make our urinary system and we're going to look at that now so let's go ahead and start with the nephrogenic cord and start building a bunch of stuff so we're taking a look here at our nice little embryo our cute little embryo right now again what is this structure here called this is called your nephrogenic cord now here's what i want you to remember remember i told you that the gut tube was kind of located anteriorly to

this nephrogenic cord there's a real important portion of the gut tube that we actually do care about it's right here at the bottom you know what this bottom portion here is called it's called the cloaca and the cloaca is basically what will become your drainer and your stainer right so it's going to become the pooper and the pier it's going to become your anal canal and the bladder and urethra so that's important because what do we say the nephrogenic cord is really becoming your urinary system and guess what that nephrogenic cord has to kind of

can interact and we'll talk about a little bit later interact with the cloaca so let's start off taking the nephrogenic chord and looking at it how it develops from the beginning of week four so we're going to start around week four within the nephrogenic cord around the cervical region so around the cervical region of the actual baby right around the cervical region of the nephrogenic cord you start to have some development of a very specialized structure called the pro nephros when i say special it's not really special because it actually digresses a little bit later

but the pronefrost is going to be developing around week four and this is one of the parts that are you know developed derived from the nephrogenic chord the pronefrost is made up of two parts it's made up of a duct and little tubules that form in front of it called a nephrotome okay so little tubules that form in front of it called the nephrotome what i want you to remember here is big thing pronefrost develops at week four starts where cervical region made up of a ductal system so let's draw here a nice like long

tube here cervical region the duct and then in front of it what do we have your nephrotomes here's the big thing though the the pronefros it actually starts kind of digressing and degenerating by the end of week four it's pretty much gone so it's pretty weird right so generally the pro-nephros starts kind of degenerating by the end of week four so what's its purpose we don't really know to be honest with you one of the things that we may say that it actually could be important with is that it helps with the kind of providing

a structure that the next part from the nephrogenic chord derives so we start off with the first thing which is your pronefrost which is your duct and your nephrotome in front of it by the end of week four it starts to degenerate but something starts to build off of that and that's what's important and i'm gonna start kind of showing it we're not gonna develop it yet because we're gonna go into the next stage but another structure starts to start slowly forming by the end of week four that develops off of the pronefros what is

that called it's called the mesonephros so that's what we have so far week four developed the pro nephros which is made up of the duct and the nephrotomes in front of it starts degenerating by the end of week four and the cervical region so now let's show this pro-nephros starting to kind of break down and what starts actually forming coming off of it the next structure here which extends all the way from the thoracic region because remember the pro-nephrons develops in the cervical region the mesonephros develops within the thoracic region and extends down to like

the lumbar region and connects with the cloaca so around week five let's say by the beginning of around week five that pronefrost degenerates and what starts to developing off of it so the mesonephros starts developing developing right and what is the mesonephros made up of the same thing like the pronefrost it's made up of a mesonephric duct and little tubules in front of it called mesonephric tubules so let's show that now so the mesonephric duct and the mesonephric tubules kind of come off of the degenerating pronefros and that's going to be forming within what region

from the thoracic region so it develops where and the thoraco lumbar region here's what i want you to remember the mesonephros is going to become pretty much our primitive urinary system up until week 10. i'll explain how because we've only just seen the formation of the duct and the tubules but what i want you to remember is that this will become the primitive urinary system so what have we had talked about so far mesonephros develops off the pro nephros with abduct tubules develops in the thoracolumbar region and once starts degenerating the prone afros next thing

i wanted you to remember is that this mesonephros will become the primitive urinary system and you'll see how in just a second all right beautiful so just one thing to remember before we move on to the next step is that that mesonephric duct is connected to the cloaca and again what does the cloaca become with respect to the urinary system the bladder and the urine the urethra so this will become part of your kidneys and ureter connecting to the bladder and the urethra which will drain that right that's why it's important all right so now

let's move on here let's what do we have degenerated what's gone up here we'll draw this in orange just so you know that this was kind of degenerate what was degenerated at this point here your prone afros what was built off of the pronefrost from the thoracolumbar region here your mesonephric duct i removed the cloaca here for a second because we're going to focus on this next structure here but again this was your mesonephric duct what was coming off of that mesonephric duct mesonephric tubules now here's what's kind of really cool these mesonephric tubules when

you start to form them they continue to keep growing from the mesonephric duct and there's a structure kind of located uh in between around the area of where the gut tube is and the nephrogenic cord so we just remove that gut tube particularly the cloaca and we're seeing this vascular structure developing along the length of the embryo you know what the vascular structure here is called it's called your aorta it's called the aorta and guess what the aorta and the mesonephric tubules start meeting one another they start kind of forming some structures you know what

this is called when you have a vessel that you've already formed and it starts making new vessels off of it what is this called angiogenesis so off of the aorta it starts forming these kind of little vessels called glomeruli if you will little capillary structures that come off of it via the process of angiogenesis and these mesonephrotubules will grow from the duct and form like little capsules around that little primitive glomerulus you know what this is actually called our primitive urinary system so if we were to actually look at this and kind of zoom in

on it you would have here a duct here's your mesonephric duct here's your mesonephric tubule this mesonephric tubule will continue to grow and kind of form a capsule here like a bowman's capsule so again what is this here called this is your tubule the tubule extends and forms a bowman's capsule then coming off over here deriving from our actual mesoderm you had the aorta and the aorta is doing what having a arterial kind of butt off here via the angiogenesis process and then making a capillary that will filter into this bowman's capsule so then guess

what happens blood will run through the aorta as it runs through the aorta it has to run through this little arterial and then through the glomerular capillaries and then via the filtration process some of the plasma and solutes and stuff like that will get filtered into this bowman's capsule then move down the mesonephric tubule into the mesonephric duct what does the mesonephric duct connect to the cloaca what does the cloaca drain urine that's our primitive urinary system so we've already started to see that process here so now let's actually see it drain into the cloaca

and then where that actual cloacal stuff goes to okay so we go to this next part here we have our mesonephros here well particularly the mesonephric duct going to where connecting to the cloaca then we have coming off of this the mesonephric tubules forming a bowman's capsule then we have coming off of the aorta the angiogenic process making the little glomeruli from this you're filtering the plasma from the blood moving through the bowman's capsule through the mesonephric tubules down the mesonephric ducts emptying into the cloaca you know what the cloaca actually does if we were

to kind of look at it like this the cloaca has two kind of points where two things come into it let's say here's one part and here is where it kind of drains there's a structure here called the alantois but coming from the back end you're going to have this mesonephric duct so this mesonephric duct is emptying in this kind of primitive urine if you will right so it's kind of dumping in urine here but coming here is your hindgut what's the hindgut making poopoo and that pupu is coming down and emptying into the cloaca

so now you have feces and urine coming into this cloaca and then exiting the cloaca is going to be a very special structure here called the elantois the alien toys okay so that's the big thing that i want you to remember is that the cloaca is actually draining two structures both the hindgut and the mesonephric duct so it's emptying out both urine and feces into the atlantos so now as you can see here we finally formed our primitive kidney kind of structure here which is what what is the primitive kidney this primitive urinary system urinary

system is actually going to continue to make urine so it makes urine from about week five till about week ten and we'll see what the next step kind of happens here but again to remember what it's actually pretty much made up of is your mesonephros okay pretty stinkin cool but guess what a bad man about to come in the meta nephro so we started with the pro nefros it was like i'm done i can't do this then the mesonephros came in it's like i got this but then the bad man came in the metanephros and

it says don't worry i got this so here's what i want you to think about in the pelvic region all right so we had cervical thoracolumbar so cervical is the pronefrost thoracolumbar was the mesonephros and the pelvic region some intermediate mesoderms kind of kind of starts condensing kind of in front of the mesonephric duct or the mesonephros in general so what is this intermediate mesoderm core here you start to develop what's called the metanephric mesoderm but they also like to give it another name you know scientists love to do this they actually also call it

the metanephric blastoma and what you need to remember is that this develops where in the pelvic region okay and again this is intermediate mesoderm just like the the mesonephros is intermediate mesoderm so it starts to develop here what we need to do now is talk about how the mesonephros starts kind of losing its job of being the primitive urinary system and how the meta nephrops will then become our adult urinary system so now let's do that let's zoom in on this area and talk about that next step we have this little metanephric blastoma that's starting

to kind of form out here from that intermediate mesoderm right so again what is this here called metanephric blastoma again metanephric blastoma you know it's really cool the metanephric blast man knows that it's about to be the big dog so it starts releasing growth factors and these growth factors that it starts releasing starts coming over here and stimulating this mesonephric duct coming off of the mesonephric duct then will be this next little kind of bud so the metanephric blast will release growth factors that'll stimulate the mesonephric duct to make a little kind of bud here

you know what this butt is called this bud that's made here is called the ureteric bud you have an idea now what this is going to become the irritating blood is going to become the girder and then eventually become the collecting system the meta nephroblastoma will become your nephron so i'm kind of prefacing all of this so metaphoric blastoma release growth factor stimulates the mesonephric duct to make the meta eurotech bud now let's go on to the next step here we have our ureteric bud so what is this portion here called that's called the uroteric

bud and this portion here is called the metanephric blastoma now the metanephric blastomal was rece secreting those growth factors right that was causing the eurotech blood to grow at the same time the uroteric bud starts releasing more growth factors and these growth factors start stimulating the metanephric blastoma to begin growing and getting bigger and bigger and bigger that's an important thing to understand here signaling wise what is it called when you have a two-way interaction between two structures in that case meta-network blastomer is releasing growth factors stimulating the ureteric blood to form then the ureteric

board blood was released in growth factors stimulating the metabolic blastometer form there's a particular name for that type of process and it's called reciprocal induction pretty straightforward right so again what is that process called it's called reciprocal induction very important for the growth of the kidney all right beautiful so now as this reciprocal induction is occurring growth factors being released between the two structures the ureteric bud starts to kind of form a nice little as it continues to grow and grow and grow it now creates a nice stalk so now we have to kind of

really define this eurotaric bud a little bit more technically this knobby portion here that's kind of invading into the meta network blastoma because of that reciprocal induction process this portion is technically called the uroteric bud and then this this little stalk-like structure that connects the ureteric blood to the mesonephric duct this is actually called the ureteric stock okay very important to understand so to quickly recap it metaphoric glass and releasing growth factors stimulating the mesonephric duct to make eurotaric bud the eurotearic bud starts releasing more growth factors stimulating the metabolism to grow as it continues

to occur the ureteric blood continues to grow inwards to the metabolasma and makes elongated tube that connects the eurotech bud to the mesonephric duct which is called the eurotech stock beautiful now as the eurotech blood continues to grow and grow and grow it then kind of takes on a larger structure that we really have to start defining now and we're going to go in kind of a sequential order so the eurotech bud continues to grow under the influence of the reciprocal induction process and as it grows it makes this big kind of like tubular structure

in this metanephroblastoma this right here is called your renal pelvis so we started off with the eroteric bud invading the metanephric blastoma continuing to grow the next thing that it becomes is the renal pelvis all right so now what happens is the renal pelvis right from that urotaric bud we had uriteric bud invade the metanephric blastoma it started growing the next thing it grew into is the renal pelvis now the renal pelvis is going to again bifurcate and form more structures so here we had at the center here this is our renal pelvis growing off

of that you see how it comes off of that it kind of grows these little knobbies coming off over here these little knobbies are going to become what's called the major calyx and over here this would be another major calyx beautiful now what happens next we're going to continue to keep kind of replicating proliferating and going through that growth process so now we had here the renal pelvis you guys are going to get the just here then here we're going to have the major calyx and then guess what happens to the growth off of that

major calyx it's going to butt off even more and this is going to make your minor calyx pretty crazy right now the minor calyx is going to continue to keep replicating and growing and growing and growing more structures off of it so this is going to become consistently pretty repetitive here but in the center is the renal pelvis here coming off of this portion here is your major calyx coming off of that portion here is going to be your minor calyx and then coming off here you see like all these little blue like finger projections

coming off this right here is going to be your collecting tubules and you're going to make millions of these collecting tubules that come off of that minor calyx so here's what i want you guys to remember we had over here coming off again what was that eurotech bud started became became renal pelvis major helix minor calyx collecting tubules what was the eurotech bud connected to the mesonephric duct what was that structure called what is this one here called this was called the eurotech stock right but what does the eurotech stock start to look like the

ureter right so the euro taric stock technically is going to start really becoming the ureter what have we formed from the ureteric stock and eurotaric blood we have pretty much formed all of the collecting system for the urinary system we formed the ureter we formed the renal pelvis the major minor killings and the collecting tubules we're ready to collect urine now what we've got to do is we've got to start making structures that are going to help to filter and really make urine that's the next step let's do that now it's also really important to

remember what is pretty much still functioning as our urinary system our primitive urinary system at the same time all of this is happening that mesonephros so remember that mesonephros is still continuing to be our urinary system while this is developing all right now let's go in and zoom in on this next part which is we got to really start making our nephron the structure that's going to help to filter and make urine so we're going to zoom in on this portion now and look at it all right so now we're going to zoom in on

these collecting tubules and look at two portions the collecting tubule right and then all of this actual metanephric mesoderm that's around it okay so when we zoom in on this portion this is your metanephric mesoderm right but we kind of give it a little special like weird name because technically it's capping this collecting tubule we call this a metanephric mesoderm cap that's stupid but that's what they call it then what is can like what is actually in communication if you will with this metanephric mesodermal cap this is your collecting tubule one of them right now

what the collecting tubule does is the cells of the collecting tube you'll start secreting lots of growth factors and it starts influencing this metanephric mesodermal cap and really starts causing it to proliferate proliferate and condense into kind of one singular kind of structure if you will okay so it really starts proliferating and condensing so after you release a lot of these what are these chemicals that you're releasing here a lot of growth factors it triggers the proliferation and con condensing of this meta-network mesoderm and this now turns what i'm going to abbreviate this is your

collecting tubule and now this metadata mesoderm cap becomes what's called the metanephric vesicle then the metanephric vesicle there's going to be a continuous release of growth factors the metanephric vesicle then starts kind of becoming s shaped kind of like a little bit coiled and when it does that it makes this kind of metanephric tubule if you will right and then what happens is you start having a connection between the collecting tubule and the metanephric tubule and once they fuse they start to begin this production of the nephron so here we're going to have the collecting

tubule that metanephric tubule when it connects to the collect to the collecting tubule we now give this kind of structure here a very special name we call this the distal convoluted tubule so the metanephric tubule then becomes the distal convoluted tubule we have that distal convoluted tubule right that we form from that metanephric tubule collecting it's connecting to the collecting tubule it's going to continue to keep growing and replicating and growing and coiling and becoming s-shaped as it does that look at what happens next here we still have our distal convoluted tubule here we have

our collecting tubule but look what it started to make now this next structure here at the end it makes so we had the distal convoluted tubule this becomes your proximal convoluted tubule so we started with the metanephric vesicle metanephric tubule dct and then dct makes the pct or the proximal confluent tubule the next thing that happens here is that from the proximal convoluted tubule it starts to kind of change its conformation it's configuration if you will so we still have the collecting tubule we have our distal convoluted tubule from the distal convoluted tubule we made

our proximal convoluted tubule and then off of that it starts to make this cup shape and this cup shape is called your bowman's capsule very similar to what the mesonephric tubules did oh we're getting there we're really getting there then here's the next step okay i know there is another structure if you guys know you're a kind of micro anatomy there's you're like well where's the loop of henle something else has to happen before we make the loop of henle if you guys remember we had that aorta that was coming down the length of the

embryo if we just zoom in on a portion here here's a portion of the aorta at the level of very interesting the common iliacs because where do we say that the metanephros developed do you guys remember in the pelvis so at the pelvic region is your common iliac arteries so you've got to remember here because you commonly think oh it's the renal arteries the kidneys the actual mature kidneys develop in the pelvis and then ascend upwards so technically we're down in the pelvis so this is your abdominal aorta this is your right common iliac this

is your left common iliac off the common iliacs i'm only looking at one there would be the same thing on this other side coming off that left common iliac you're going to have arterials and then you're going to have the capillaries and all that stuff like that but guess what it does it makes your glomerular capillaries guess what the glomerular capillaries interact with your bowman's capsule guess what the bowman's capsule is developed from the pct guess what the pct is derived from the dct and guess what the dct is actually kind of stimulated from the

collecting tubule and then guess what we're starting to make the urine why because if you remember blood will move through the iliac system through the glomerular capillaries and get filtered across this bowman's capsule into the proximal convoluted tubule go to the distal convoluted tube into the collecting tubule and then down all those structures to drain into the cloaca right but something else has to happen so then we got to do another thing so here we have the proximal convoluted tubule the distal convoluted tubule the collecting tubule your bowman's capsule and then you have your glomerular

capillaries coming off of your common iliacs then what happens is that the actual tissue the metanephric mesoderm between the pct and dct starts to grow downwards and form a loop now you finally get your loop of henle so we're kind of going in an order of how the nephron is developing but what have we made when we start here with the the glomerulus the bowman's capsule proximal convoluted tubule loop of henle distal convoluted tubule we've made our nephron so we made our nephron from the metanephric mesoderm and we made the collecting system from this point

all the way down from the ureteric bud beautiful all right so we've kind of now formed our nephron and again the nephron was the bowman's capsule the pct the loop of henle the dct right we made that from again what metanephric mesoderm collecting system all the way down to the ureter was developed from the uroteric bud now we started with the blood feeding via the glomerular capillaries coming from the abdominal aorta but what portion of the abdominal aorta the common iliacs so blood was filling into this actual kidney because we've now made a kidney the

actual mature type of kidney at this point blood was feeding into it via what structures again your common iliacs but guess what happens the common iliac arteries start kind of breaking down they start degenerating and as that happens the kidneys start ascending so the kidneys will start kind of moving upwards as the kidneys move upwards and they lose their vascular supply they move kind of into the upper quadrants of our abdomen and then what happens is blood vessels from the top part of the aorta and we'll go over the development of the vascular system in

another video but the aorta will develop these lateral branches that'll move and invade the actual kidney and what are these arteries that they will become the lateral branches of the aorta this will become the renal arteries pretty straight forward right this will become your renal arteries so we have now completely gone through the entire process of making the collecting system of the kidney and making the actual nephrons the structural and functional unit of the kidney but guess what we did not finish yet we've made our kidney by representing all that brown tissue that's our nephron

we made the collecting system with the collecting duct the minor major renal pelvis and the ureter but guess what we haven't done yet we haven't actually talked about how the cloaca becomes the bladder and the urethra that's the next step in order for us to do this again by week 10 by week 10 we have actually kind of taken over the metanephros takes over the job of the mesonephros if you guys remember we had that mesonephros here right and that mesonephros was getting blood from the aorta but again that starts breaking down and the mesonephros

no longer will be making any urine who will be making it the metanephros so now what we have to do is understand the next step here what i want us to understand is how we now take the mesonephric duct and this ureter and how that empties into the to the cloaca at this point so again what is this structure here this was that urotech stalk but it becomes the ureter right but again technically it's the eroteric stalk but it will become the ureter and then this right here is your mesonephric duct this was the structure

that was draining urine from the mesonephric tubules before week 10 making urine both of these empty into what is this structure here the cloaca and again the cloaca is getting urine from this structure and getting poop from the hindgut emptying it out via the lantoys what happens is the next step is that imagine this kind of connecting portion here right this connecting portion where they both kind of empty into the cloaca this is going to get absorbed into the cloaca so as this gets absorbed into the cloaca imagine this portion here where they join is

disappears gets absorbed into it we're in this step here so now if you look here what is this structure emptying into the cloaca the meso nephric duct and then what is this structure over here this is going to be the ureter eventually they're going to fuse in with the cloaca and then what happens is the mesonephric duct will actually kind of move a little bit more backwards and then the ureters will move a little bit more towards the sides now technically this portion here where they're kind of joining is going to be what's called the

vesicular trigone or the trigone of the bladder it's represented by the uh the urethra as well as the two ureters where they enter into the bladder what i want you to remember here for right now is that the mesonephric duct we don't care about that with respect to the urinary system the reason why is we'll talk about this within the reproductive system the mesonephric duct will become a part of your ejaculatory ducks right the the vas deferens the epididymis the seminal vesicles the common ejaculatory ducts stuff like that and the females have become the uterine

tubes part of the uterus stuff like that so we don't really care about that what we do care about is the ureter emptying into the bladder but this does not look like a bladder so guess what happens the next thing that has to happen is we got to make this cloaca look like a bladder and urethra so what happens is here's your cloaca okay you develop kind of a little like a septum in between the cloaca right it's called the urorectal septum and what that urorectal septum does is it starts to separate the cloaca into

two distinct parts so again what is this little septum here called it's called the euro rectal septum and what it does is is it separates the cloak into two parts an anterior portion which is going to move this way and a posterior portion which is going to move this way the anterior portion is what's going to become the bladder okay and then the posterior portion is going to be what's uh the anal canal so if you imagine here imagine the zero rectal septum comes in here and it starts actually kind of working its way backwards

and eventually will kind of separate the hindgut away from the cloaca so that if you come down here as the urectal septum kind of comes backwards here would be your hindgut it would kind of move into its own little space here which would become the anal canal and then anterior to this what is this going to be this is what's going to become the bladder and the urethra so now we've separated this and what we actually call this anterior portion besides the bladder and the urethra we actually call the urogenital sinus now the urogenital sinus

actually has three distinct parts okay this pink part is the most proximal in other words it's closest to the ureter so here's the ureter this portion here the proximal portion of the urogenital sinus is going to be what becomes the bladder it's pretty straightforward right this middle portion here is actually going to be come the urethra okay and there's actually an important thing to distinguish here when we talk about the urethra in females it's just called the female urethra but in males there's actually three parts of the urethra there's the prostatic urethra the membranous urethra

and the penile urethra the prostatic and membranous urethra is made by this middle portion but the penile urethra is made by this bottom most distal portion so we're actually going to put here p now urethra and then here for this blue portion i want you to remember that this is we'll put pr for prostatic and membranous urethra so now we have our ureter emptying into the urogenital sinus which as it starts to continue to grow and grow and mature this portion closest to the ear will become bladder the middle portion will become the prostatic and

membranous urethra of males are just urethra and females and the distal portion of male will become the prostatic urethra so now come down here to the bottom so now to put all of this into perspective the brown portion this is going to be making the nephron this is where the nephron was coming from that was from the metanephric blastoma or mesoderm this entire collecting system from the collecting tubules all the way down to the ureter this was coming from the uroteric bud but this was your collecting system we went through all of that right then

the mesonephric duct again we said don't worry about that but that will kind of come here in the back and that'll make a lot of the uh the ejaculatory duct and some of the actual ducts of the male and female reproductive system but again the ureter will connect to what we said was the cloaca right and we said that the cloaca will actually get separated by the urethral septum and separate into a posterior anal canal in an anterior urogenital sinus the anterior urinal genital sinus forming from proximal to distal will become the bladder and the

urethra the other thing that i want you guys to remember was we said that there was a structure that drained the cloaca what was that called the elantois the land toys what i do want you to take away at the end of this is it becomes another structure called the uragus and then the uracis will actually start becoming a ligament right and it becomes what's called the median umbilical ligament so that's an important thing to take away as well is that the structure that was draining the cloaca was called the a lantoys and to remember

here that the elantois becomes the uracus and then the uracus actually becomes an umbilical ligament called the medium i remember on for in elantois median umbilical ligament okay so now we have completely covered the development of the urinary system all right ninja nerds in this video we talk about the development of the urinary system i hope it made sense and i hope that you guys did like it alright engineers we love you thank you and as always until next time [Music] you