Gastrointestinal | Development & Embryology of the GI Tract: Part 1

all right ninja nerds in this video we're going to talk about the development of the gastrointestinal tract as well some of the peritoneum coverings and cavity so we have a decent outline we got a lot to talk about in this video so the first thing I want to talk about before we even get into this actual GI tract stuff is I want to talk about the embryonic folding okay this is really important because this is gonna tell us a development of the gastrointestinal tract so we'll start off here with the embryonic folding and talk about

the development of the gut tube the development of the peritoneum then after that we'll talk about the development of the foregut its components vascular supply and medicine Terry's the mid gut its components vascular supply medicine Terry's hind gut its components vascular supply and medicine Terry's then this is going to be really important we're going to take it a little bit of time talking about intraperitoneal organs versus retroperitoneal organs and then another thing is we're gonna determine the difference between primary or inter pares primary retroperitoneal versus secondary retroperitoneal and then we'll finish off with some cool

pathologies like on fallow seals gastroschisis in the meckel's diverticulum so let's go ahead and get started first off on embryonic folding so the first thing we have to talk about is we have to start right around the third week of development so around the third week of development we have this structure called a try laminar disc okay we're not going to go into tons of detail in this video on the embryology aspect we're gonna keep it kind of simplistic here okay but the tri laminar disc is made up of three layers the first one is

this blue layer is going to be called the ectoderm okay underneath the ectoderm we're gonna assume they've already developed what's called a neural tube which helped to develop the spinal cord and another structure here called the notochord okay which will become the nucleus pulsus within the intervertebral discs then on the side of it you're gonna have what's called your intra embryonic mesoderm and your entry an intra embryonic mesoderm actually has three parts okay one is you're gonna have what's called your par axial music term then your intermediate music and then your lateral plate Musa derms

for right now just remember the par axial music room helps to form what's called your dermatome your sclera tomé your Maya tome and then the intermediate mesa term helps to form like the kidneys and the gonads but the lateral plate needs the durum which is made up of two parts that we're going to talk about the splanchnic Musa derm and the somatic Musa term these are very very important for the development of the peritoneum membranes alright so we're gonna have that on both sides over here so over here we'll have par axial Musa derm intermediate

means a derm and then we'll have the splanchnic which is going down here around the actual yolk sac or the endoderm and then we'll have the one coming up here which is actually going to be the somatic underneath that we're gonna have the endoderm okay now the endoderm is important because the endoderm is going to be helpful for making the epithelial lining of our gastrointestinal organs some of the accessory organs and even some of the glands okay so this is what we have here now underneath the endoderm underneath it you're gonna have this thing called

the yolk sac the yolk sac is important because it helps to beginning with the synthesis of red blood cells so it's very important for the production of red blood cells all right above that you're gonna have what's called the amniotic cavity now last thing the yolk sac secrets a type of connective tissue which is called the extra embryonic musa term now this extraembryonic mesoderm is going to surround the actual yolk sac so it's gonna surround the yolk sac and it's going to come over here and it's gonna surround the amniotic cavity okay now what's really

cool is you see this part here that we said we they have the two parts of the lateral plate music we have the somatic and the splanchnic they develop a little cavity right here it's called the intra embryonic coelom and what happens is it allows for these guys to become continuous with this extraembryonic mesoderm okay so they become continuous with this extra embryonic music so again we can call this the splanchnic Mesa der we also call it the splanchnic Plurk and then we have this one up here which is called the somatic means a dirt

or the somatic lurk okay and then just for the heck of it this last part here is you'll have what's called your chorionic cavity and there's going to be here around it is this outer layer of the extra embryonic museum so this is the outer layer of the extraembryonic mesoderm and the last part here is you have your connecting stalk all right with your land toys which will help to make the umbilical cord so that's the beginning part that's the third week now what happens is is we have this development of the gut tube this

embryo is gonna undergo a folding process it's gonna fold in two planes one is going to be a transverse plane and the other one is going to be a sagittal plane and it's important to understand the difference between the two so let's go ahead and show that all right so here we go we're gonna have over here we're gonna take this bad boy here we're gonna have this one going into thee specifically into the horizontal plane I'm sorry transverse plane and we'll have this one over here specifically going into the sagittal plane alright so now

what happens is if we draw it in the sagittal plane this is going to help to form what's called cranial and caudal ends okay so watch what happens it's gonna undergo this folding process when it undergoes this folding process something really cool happens here we're gonna get this little pocket right here and then we're gonna have this part right here okay so this is going to be important when we're developing the gut tube all right we're gonna have two ends here this is the endoderm all right so the endoderm aligning is going to undergo this

expansion where it's going to expand outwards and it's gonna start folding when it does that we're gonna say that this end right here let's just say for the heck of it this is the cranial end and this is the caudal end right here the cranial end is going to help to develop what's called the foregut which is gonna be important we'll talk about all the organs in that the caudal end is gonna help the form what's called the hindgut and we'll talk about the organs of that in the middle right here you're gonna have the

mid gut okay now let's talk about some of the stuff around this because it's going to be important here real quick all right so again what we have around it we might have a little bit of Mesa derm around it alright so here we'll have some knees a derm an important thing again remember is that you're gonna have a lot of stuff happening here that we're not showing we're just trying to focus primarily on the gut tube and the derivatives of this endoderm and some of the music durman's okay so you're gonna have some ease

the dirham here that is gonna be surrounding it some of the means of dirham towards the cranial end will help to form what's called the pericardial cavity and the heart and you'll also have some other structures there developing too now around that what we should we have we should have the octo derm so now we're gonna have around that the ectoderm the active term is important because it helps to form the skin it also helps to form the central nervous system which is the brain and the spinal cord right and you also have these other

structures which are going to be important too and that is going to be your neural crest cells and the neural crest cells are really important because they help in the development of what's called your ganglion cells which are important within the digestive tract for example to my enteric plexus in the submucosal okay and above this what should you have you should have the you know Miyata cavity right here and then down here what would you have connecting over here you're still gonna have the yolk sacs let me bring the yolk sac down here okay so

we'll have the yolk sac down here okay alright so again what are we gonna have out of this then we're gonna have three guts that we need to remember one right here is going to be the foregut right here is going to be the mid gut and right here is going to be the hindgut okay another important thing real quick is at this end this end right here towards the fork up is going to be help in forming the mouth so you know what you know what membrane we call that we call this membrane right

here because eventually it'll actually perforate in form hole this is going to be called the auro foreign geol membrane so what happens is this will perforate around this end right here and form the mouth alright towards this end that's gonna form the booty hole alright so towards this in the hindgut we're gonna call this the cloaca membrane and the cloaca membrane it'll actually perforate and help to form the anus it also helped to form the urogenital tract as well okay so now what happens last thing here before we continue is this is gonna happen pretty

much around the fourth week now around the sixth week what should happen is the mid gut right the mid gut actually has your intestinal loops around there like so the small intestine so what's gonna happen is the jooshin of an ileum forms like a little loop and that little loop around the sixth week actually kind of herniates out into the umbilical cord okay so we can have the umbilical cord actually coming at it because you know originally they call this duct right here around the fourth week they called the vital and duct they called the

light telling doctor the on fallow mesenteric duct I'm going somewhere what happens is around the fourth week you formed this it's what basically connects the mid gut to the the umbilical vesicle or we also called the yolk sac but what happens is around the sixth week the vital and duct should get obliterated and then now this will no longer be there so when this is gone then what should we have we should just have the umbilical cord okay so at that point when the vital induct is obliterated all we should have left is just going

to be the umbilical cord okay so why am i mentioning this because you know the vital induct doesn't actually obliterate guess what you can have you can have that mid loop get pushed or herniated out here to where it forms like a pocket out into this area and what happens is the vital induct actually stays there and forms a ligament connection between the mid gut in the anterior abdominal wall guess what they call that meckel's diverticulum okay they call meckel's diverticulum so the meckel's diverticulum is going to be an issue whenever the vital and duck

does not obliterate and forms an outpouching of the actual small intestine and it can be very very serious if not treated right the other thing I wanted to mention is another part of the mid gut right the intestinal loops and I told you it actually naturally herniates it naturally herniates around the sixth week and the reason why is as the embryo is developing the liver and some of the stomach and all those organs are really really increasing in size and taking up the space within the actual mid gut so what do you think is going

to do it's gonna start pushing the intestines and naturally out here into the into the actual umbilical cord naturally that's okay that's all the natural herniation it usually happens around the sixth week but what happens is as the embryo starts developing and developing the abdominal cavity should increase as it increased then it makes room for the actual intestinal loop to get sucked back into the abdominal cavity around the 10th or 11th week but what is really important is it by the 10th and 11th week it hasn't get pulled back into the abdominal cavity that would

guess what you have you haven't on fallow seal okay so that's really important to understand and our phallus ill can develop whenever the intestinal loop does not come back in to the actual abdominal cavity all right so I have a peritoneum covering around it and again there is tests that you can do to determine if the actual fetus does have an FSO you can do like an ultrasound or they can do blood tests to test the maternal serum fetal alpha protein levels alright so whenever this embryo is folding what are we gonna get we're gonna

get it and the four got the mid gut in the hindgut but specifically we're only gonna see this folding this cranial caudal folds when we're looking at this embryo folding specifically in the sagittal plane okay so this is gonna be in the sagittal plane okay alright so now we've already talked about the embryonic folding process in the sagittal plane now we have talked about the embryonic folding process specifically in another plane called the transverse plane alright so the embryonic folding and the transverse plane so now the only difference between this one is that what's going

to happen is this area right here is going to start folding downwards and outwards okay so this area right here where the amniotic cavity nected erm is it's going to start folding out and downwards now the endoderm is gonna get sucked in so this area's gonna get sucked in and pushed out look what we get out of that so let's go ahead and redraw that then so look what we have here we're gonna have the ectoderm here right so there's our ectoderm and again what should we have right here we should have me we'll have

the notochord and also the neural tube then we'll have the par axial music derm intermediate music derm in this area right here which is your lateral plate meezerman again par axial intermediate a lot of plate music right now again what did I tell you here what happened with the endoderm the end of derm is gonna start kind of like getting sucked in like this and this part here is gonna get pushed in and pulled outward when that happens we form that thing that we talked about before which is called the vital induct which is going

to go to the yolk sac or the umbilical vesicle then what else do we have up here we have the amniotic cavity now what's really cool here is that the amniotic cavity starts kind of folding down like this okay starts kind of folding down like this now let's put our linings back on there again what do we have here before we're gonna have this as the splanchnic musa term so the splanchnic means the term is going to come right here right around the bite Allen dock the endoderm and the yolk sac right sweet deal let's

show it going right here okay then what else are we gonna have here we're gonna have the somatic music the somatic music arm is going to come out here and it's gonna line this outer part here right the amniotic cavity all right and then outside of that we would have the chorionic cavity but we're not going to show that that's too much drawing all right so now after that it's gonna come in words and we got this now all right here's what's really cool as this continues as these lateral folds keep pushing down and coming

closer and closer and closer this area is gonna fuse so it's gonna fuse remember I told you the vital and duck should obliterate and then eventually what will happen is you'll have the umbilical cord which will connect between the actual fetus and the mother right but again what should happen is the my talent duck should obliterate and these folds will mute merge together you know what happens if the latter folds don't merge together guess what the small bow could herniate out through that lateral fold you know what that's called gastroschisis so that's the difference between

on fallacy and gastroschisis what happens is is the actual specifically parts of the gut herniate out through this point here where the lateral folds don't completely close that's called gastroschisis and what happens is the intestines don't have any peritoneal covering guess what they're completely exposed in the amniotic cavity which can agitate the intestines and that can be very bad all right so again let's show this part here where the lateral fold fuse because this is really cool this is where it gets good all right now we're gonna bring this bad boy down and we're gonna

show the complete fusion process here because it's gonna lead us into our next topic here so again now what we have here if we draw everything the same way right here there's our gut tube what should be surrounding the gut tube what do we call this this is the splanchnic music erm the reason why I'm telling you this is because guess what this blank tech needs a term forms it helps to form the walls of the GI tract for example the submucosa the muscularis externa the lamina propria all those different parts and the visceral serosa

or the visceral peritoneum which is extremely important now around the walls here what should we have around the walls we should have the somatic mesa derm so this should be the somatic Nizza derm right here now the somatic Museum is important why because it helps to form the parietal serosa or the parietal peritoneum which is extremely important what happens though is we have to develop a connection between the parietal serosa or the parietal peritoneum and the visceral serosa or the visceral peritoneum what do you think that connection is right there that keeps that organ suspended

within this peritoneal cavity what are you guys called it's called a mesenteric okay so this right here is called a Mezen teri and these are extremely important what is this here called again this is called the parietal serosa or parietal peritoneum and this one right here is going to be called the visceral serosa or visceral peritoneum okay and this is going to be the para to neil cavity the reason why I'm mentioning this is is because any organ that has a mesentery and has this vessel or serosa and this parietal serosa and in to have

the two connecting together through a mesentery are primarily going to be intraperitoneal organs so let's write that down here if this guy has a mesentery it's going to help us to determine that this should be a intra peritoneal organ okay this is extremely extremely important okay so if it has a mesentery and it has a visceral serosa and a parietal serosa it will be an intraperitoneal organ meaning it's inside of the peritoneal cavity suspended within it by a mesentery if it doesn't have a medicine Terry or if it did have a mesentery previously but it

loses it as it's getting developed and pushing obliterate against the post tear down the wall they can be called retroperitoneal organs so let's say here's the peritoneum right if it has to be retro it has to be outside of it or behind it so what are we going to have back here draw a couple of examples here let's say back here I could have the kidneys so I can have the kidneys right here what else could be around this area what's on top of the kidneys I could have the adrenal glands right what else could

I have back here I could even have the parts of the duodenum right so I can have parts of the duodenum right here that we'll talk about and we'll get into all this but I just want you guys to understand here that if there are organs located outside of the peritoneal cavity not suspended by a mesentery these are called retro peritoneal organs and we'll talk about these ok so what do we do we talked about intraperitoneal we talked about retroperitoneal but now we gotta have a little bit more of a discussion we have to talk

about the differences between primary and secondary for example the big vessel in the abdominal cavity we call it the abdominal aorta that's one so the abdominal aorta that's a big one the vein that's right next to it which is called the inferior vena cava what else okay well what else is up in the top part of the actual abdominal cavity another one is going to be the adrenal glands so the adrenal glands what's below that the kidneys okay what else you know what's the tube that takes urine from the kidneys down to the bladder the

ureter so we're also gonna have the ureters and then what's the structure that collects it the bladder alright and then one more part here is around the doodle hole right around the doodle hole you're gonna have the rectum but specifically the lower rectum okay lower rectum okay so primary intra I'm sorry primary retroperitoneal guns not a mesenteric right so that they don't have a mesentery they're not going to be found inside of the peritoneal cavity they're gonna find posterior to it now these are the abdominal aorta inferior vena cava adrenal glands kidneys ureters bladder lower

rectum all right so the secondary for the secondary retroperitoneal organs the secondary retroperitoneal organs they did have a mesentery at some point time so when they have that mesentery right during the rotation of the gut as it rotates around the central axis some of these mesentery x' get obliterated against the post here abdominal wall and then when they get obliterated they lose their mesentery and then they develop outside of the peritoneum posterior to it those organs are secondary retroperitoneal organs for example one is going to be the second third and fourth parts of the duodenum

okay if you keep going we'll get to the ascending call like I told you guys before the ascending colon and then also the descending colon now if we talk about some accessory structures around that right around the duodenum you have the head in the body of the pancreas so we also have the head and the body of the pancreas all right so these are going to be secondary retroperitoneal words but there's also going to be some other structures that we can include in there but I'm just trying to get the main ones here okay so

the main ones that we're gonna be talking about with respect to these primary and secondary --is four primary primary you can have the abdominal aorta in free vena cava adrenal glands kidneys ureters bladder and the lower rectum and even one more technically we can have the esophagus okay okay now the last thing I want to say before we move on is if they don't have a visceral serosa right and they don't have a parietal serosa then what do they have to anchor them to the poster abdominal wall one in order for them to be anchored

to the posterior abdominal wall retroperitoneal organs have to have a specific thing a specific connective tissue that anchors them to the post trap nominal wall this is called adventitia okay adventitia is actually going to be like a dense fibrous so what does it called its called a dense fibrous specifically irregular connective tissue okay and what it does is it anchors these organs to the post here abdominal wall because they do not have a visceral serosa or parietal serosa and they don't have a mesentery to keep them suspended there so they have to be anchored so

there's not very much mobility there however things that do have a mesentery do have a visceral serosa and a parietal serosa and keeps them interfering they have a little bit more mobility okay hi guys so we talked about a lot of stuff within this video we talked about the embryonic folding process we talked about the intraperitoneal organs retroperitoneal and the pathologies associated with it right in the next video we're gonna do we're gonna talk about the four gut the mid gut and hind gut their components their vascular supply and their medicine Terry's okay iron engineers

so I thank you guys for watching this video I really appreciate it if you guys did like this video please hit the like button comment down the comments section please subscribe also guys we have an Instagram we also have a Facebook account down in the description box please go check that out and also we have a patreon account developed every dollar helps us guys please it helps us to be able to get good equipment make these videos as high-quality and as beautiful as possible for you guys all right ninja nerds until next time [Music] [Music]

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