Gastrointestinal | Development & Embryology of the GI Tract: Part 2

iein engineers in this video we're gonna talk about the development of the GI tract this is part two if you haven't go and see part one alright because in part one we talked about the embryonic folding we talked about the intraperitoneal retroperitoneal and pathologies right in this video we're going to be specifically focusing on the foregut the mid gut the hindgut their components vascular supply in their medicine Terry's before we do that though there's something really interesting about the foregut ok the foregut is one of the only out of all of these guts the for

gotham a got in the hindgut the foregut if you remember during the embryonic folding process we said that it was actually near the cranial end where the oropharyngeal membrane is which helps to form the mouth the foregut is really special because it actually has two Mezen Terry's a ventral and a dorsal before we showed that though let's go ahead and put the gut tube here so we're going to show here's gonna be the foregut tube right and then around the foregut tube what do we have around that if you remember it was the visceral serosa

or the visceral peritoneum right then we had covering the walls if you remember we had the parietal peritoneum right that was the parietal peritoneum and then what was really special is that you have these Mezen Terry's and the medicine Terry's are what are connecting the visceral peritoneum to the parietal peritoneum so these are amazing Terry's so let's say this is the anterior end and this is going to be the posterior end or you can say dorsal and ventral right so here's our gut gut tube for the foregut this is a mesentery that which is in

the dorsal part of the posterior part what do you think were going to call that we're gonna call the dorsal mesentery but you always have to make things complicated don't we so we actually called the dorsal knees Oh gasp trium okay this is in the ventral side on the anterior side so we're gonna call the ventral mesentery but again we're actually gonna call the ventral music Astrium so they call this the ventral music Astrium real quick cuz I didn't really get a chance to explain it what is a mesentery you know mesentery is actually an

organ that's really cool too actually an organ a mesentery is a double layered membrane it's a double layer of membrane but what is that double layered membrane specifically if I just kind of look here for a second let's say here's what I'm gonna kind of show as a mesentery okay let's say here's the organ for a second here's the organ just the generic organ doesn't matter for this situation but the mesentery is a double layered membrane okay the double layer is mainly going to be made up of simple squamous epithelial tissue so it's actually going

to be having simple squamous epithelial tissue and then underneath this simple squamous epithelial tissue as a part of the basement membrane you have like an aerial or connective tissue which is kind of acting as the basement membrane you know what they call that they call that mesothelium so a Mezen teri is a double layered membrane made up of simple squamous epithelial cells double layered with a little basement membrane maven of areolar connective tissue guess what that mesentery is good for it's good for blood vessels to flow through to the organ it's good for veins to

come and drain the organ it's good for nerve fibers that are gonna come in here for example splanchnic nerves that are gonna go and innervate the organ and even lymphatic vessels too so it's a really really important structure okay so amazing teri is a double-layered serous membrane with epithelial cells simple squamous areolar connective tissue as the basement membrane and it allows for this potential space where blood vessels nerves and even lymphatic vessels can travel from the actual abdominal wall into the organ through these medicine Terry's that's so cool okay let's get back to this now

that I got off track now what happens is during this development the anterior portion where the venture music a stream is it's gonna start turning and it's gonna go clockwise so there's gonna be a clockwise rotation and then this is gonna start turning now what happens is the ventra means a gas stream is actually gonna help to develop one specifically important organ here which is going to be for our use and this organ is going to be the liver okay so the liver which we're gonna just represent here in this purplish color is going to

be developing within the bedroom is a gas stream okay and the dorsum music gas stream we're gonna have another organ here that we're gonna have representing back here let's have this one in pink and this organ is gonna be the spleen okay so the spleen is going to develop back here what happens is is while this is rotating right this this is gonna be rotating around the central axis in this gut tube it's mainly going to be for the stomach okay in the proximal portion of the duodenum as it rotates around the central axis this

stomach and proximal portion of the duodenum it moves the liver from this anterior portion over here to the right side so this is the right side and this is the left side so this is gonna end up on the right side and the actual spleen is gonna end up on the left side that's so cool now guess what that ventra means a gas stream is gonna become the ventral means a gas stream is going to become this main structure which is called the lesser omentum and we'll talk about these ligaments when we go over this

but there's ligaments that are associated with this like that part of the Wadden or ligament like the apado gastric ligament and even the falciform ligament right that are really really important for helping to keep some of these organs that are in the foregut intraperitoneal the dorsum means a gas Jim is going to be important because the dorsum needs a gas Jim this is left again just keeping these here this is right the dorsum music Ashton was going to be helpful in forming what's called the greater omentum and this is that big pizza cheese that you

see if you ever look in like cadaver labs or even look in the textbooks that big yellow stuff that's just hanging over in the intestines that's the greater omentum and there's many ligaments for this one also for example to name a few Yahshua Kolok gastro splenic also you're gonna have the splenorenal ligament and you can even have some other ones that we'll talk about in this process here okay now to get a good understanding of this we're gonna take one more view one more view so that we can get a better look at the greater

omentum because I think is gonna help us out so now what I'm gonna do is I'm going to take one more view let's say that we have let's do this let's put here anterior abdominal wall here's posterior abdominal wall let's put here let's make this the transverse colon let's make this right here the stomach and here's what we're gonna do right oh and then up here we'll put the liver here's gonna be our liver okay so now if you remember what was the connection between the stomach and the the proximal portion of the duodenum if

you remember it was going to be the lesser omentum okay was the lesser omentum then and again it was going to be the hepatic astrick and the apat of the Wadden ligaments there's a little ending point here where helps to form a structure called the epiploic foramen which can lead into a little area behind the stomach called the lesser sac we'll talk about that but what happens is from this guy the actual there's a part of the stomach called the greater curvature the greater curvature is where the greater omentum hangs the lesser curvature is where

the lesser omentum actually connects it to the liver and other associated structures right but look what happens here this mesentery kind of hangs down here like this and then it kind of doubles back up now there's a ligament or mesentery specifically which is anchoring let's actually do this one in a different color it's anchoring this actual transverse colon to the parietal peritoneum they called the transverse music hole what happens is is this actual all mental like apron this greater omentum it actually kind of doubles back and as it doubles back it actually kind of fuses

with parts of that actual transverse colon right the actual ligaments there and when I say ligament so I want you guys understand it's not the ligaments that you think of whether they're connecting bone to bone they're actually peritoneum covering so some of you might be like ligaments what the Frick is he talking about they're not really true ligaments connecting bone to bone there are these pair tonio covering like structures okay so now that we understand that this is what I wanted to do guys to look at so there's like imagine here where the pad Oda

wadda ligament ends there's like a space here like a little space okay little hole here and that hole can lead you into this structure here this area right here is called the lesser sac okay so they call this area right here the lesser sac and this hole that we can use to go through that and into the lesser sac this is called the EPI Loic foramen okay anyway so I just want you guys to get an idea of here of really what the greater omentum is and what the lesser omentum is okay that's just a

little tidbit again we can cover that more detail in other videos but for right now that's good enough and again just remember that this is the anterior body wall and this is the posterior body wall so again we covered that so we covered the the different the mesentery is a little bit more in detail because I wanted to talk about those a little before we go into the guts so now we know the dorsal music gaseum the ventra means a gas stream the derivative of that within the foregut greater omentum which again hangs down here

is like this omental apron that doubles back kind of fuses some of the ligaments around the transverse music : and helps to form this little area in the back behind the stomach called the lesser sac but you can get to the lesser sac through this hole here without how did the walnut ligament ends there's a little hole there called the epiploic foramen or if you want to even called the epic flow experiment of Winslow right now we talked about that we got the anterior posterior body wall now what I want to talk about is I

want to go into the divisions right of the gut tube so we're gonna have three divisions of the gut tube okay so we got the four gut and again a floor gut developed right around the cranial end where the oral pharyngeal membrane was remember that helps to form the mouth then after that we're gonna have the mid gut if you remember this was our relationship that we talked about with the UM fallow seal and we also talked about this with the meckel's diverticulum right and then the last one is going to be the hind gut

and this is a really cool one - okay we'll talk about this guy and this was towards the caudal end where the cloaca membrane was which helped to be able to form the anal canal as well as the urogenital tract okay so now for Gunn we want to talk about organs medicine caries and vascular supply so let's get the vascular supply down for these bad boys so the first one is going to be the celiac trunk the silly act trunk is going to be the main vessel that's going to supply all the components of the

foregut what about the mid gut what about the components or what about the vascular supply to that guy that's going to be the superior mesenteric artery and again these guys are coming off of the abdominal aorta right what about the last one the last ones will supply the hindgut is going to be the inferior mesenteric artery right so these guys are pretty cool now this I'm not going to go over every single branch of these arteries okay we did make a video on that so on the thoracic abdominal circulation it's a flowchart when we talk

about all the branches I'll mention them in passing but I'm not going to write them all down okay so silly act trunk what are the three main branches the splenic artery the left gastric and the common hepatic so if you remember that you pretty much be able to remember what organs it supplies so splenic spleen so one of the organs of the foregut is going to be the spleen what else I said left gastric so left gachigasm gonna go to D stomach so we're gonna have the stomach then we said the common hepatic the common

hepatic is going to branch one of the branches it's actually going to be specifically going so the common hepatic artery actually out of the liver it'll give off branches that give out like Cystic artery branches which would go to the gallbladder so it's gonna give organs to like the liver and the gallbladder now another branch of the common hepatic arteries the gash with the Walden artery which helps the supply the proximal half of the duodenum okay because they'll give out the gash of the Wadden artery which will actually form what's called the oil action branch

into the superior pancreatic duodenal artery so it's gonna get it's going to be two more organs what are those gonna be one is actually gonna be the pancreas there's actually arteries that come off of the splenic artery like the pancreatic arteries and they can supply the pancreas as well but the other one is the gash or the Walden 'el and the gastro dewater can go to the superior pancreatic duodenal and supply the proximal half of duodenum okay cool deal now we know these are the organs that the four got basically divides into there is some

other ones like the part like the lower respiratory tract the esophagus and some other structures but we're gonna mainly focus on these ones but again this offic is another one we're gonna try to focus below the diaphragm I some medicine Terry's medicine tears are gonna be those double layered serous membranes that help to keep these organs intraperitoneal some of them might have it some of them might not okay so for example spleen does it have a mesentery yes what is the name of that mesentery the specific medicine Terry is called the splenorenal ligament do you

remember here whenever there was the rotation of the foregut there was the dorsal Mesnick music gaseum here's the spleen when it rotates the dorsum music gas room is gonna mainly become the greater omentum one of the ligaments of the greater omentum is called the specifically the gastro splenic ligament okay so this is going to be the specific ligament or Mezen tear here is the gastro splenic ligament now understand again these ligaments are not the same ligaments that you think of when they're connecting bone to bone their peritoneum membrane coverings which are basically connecting to these

actual digestive organs anchoring them within the peritoneal cavity and helping them to be suspended in their line for them to be slightly mobile what about the stomach the stomach has so many mesentery if you remember whenever it rotates you have the greater omentum and the lesser omentum and there are so many individual ligaments of that to mention a few the gastro fin phrenic gastric Olek gastro splenic there's so many hepato gastric we're not gonna name them all I'm just gonna say it's going to be the greater and lesser omentum okay so we're gonna put here

the greater and lesser omentum all right throughout the liver remember where delivered of I derive from the venture means the gastrea so the venture means of gasher is going to form the lesser omentum whenever it rotates right so the lesser omentum if you remember the main ligaments of this one is the apado gastric up out of the wall now in the falciform ligament but this is going to be connecting not just to the liver but also it's gonna be helping to hold the gallbladder intraperitoneal as well so the liver and the gallbladder are gonna be

maintained intraperitoneal by the lesser omentum okay so this is specifically going to be the lesser omentum but there's another one too which is going to be specifically the falciform ligament - okay so you're gonna have a couple of these guys here lesser omentum and then you're gonna have another one here called the falciform ligament okay unless row mentum is specifically the pad of the Wadden of had a gastric there's another one too for the liver which is the coronary ligaments we're not going to mention that okay so for the liver and the gallbladder it's going

to be the lesser omentum and the falciform ligament okay what about the pancreas no the payer is you got to be careful the pancreas actually has three parts head body tail head in the body are actually secondary retroperitoneal meaning they had a medicine tarry but they lost it the tail maintains a mesentery and remember when as it's rotating okay the pancreas has a specific component specifically a part of the greater omentum they call it the spleen Oh renal ligament but this is only for the tail of the pancreas not the head in the body all

right whatever the proximal half of the duodenum so the first part and the second part of the duodenum the first part of the duodenum but the first two centimetres of the hwadam actually does have a mesentery it's called the hepato duodenal ligament which is a part of the lesser omentum so again this one will have it but only the first part it is called the hepato duodenal ligament but again this is only the first part the second third and fourth part are actually going to be secondary retroperitoneal all right so that's these guys let's go

to the next one mid gun mid yacht it's gonna be this applied by the superior mesenteric artery there's so many branch with is this sucker right but let's go from the top so what happens is remember we ended up with approximately half of the duodenum well we have the third and fourth part so let's go on to that part so the superior mesenteric artery gives off intestinal arteries those intestinal arteries are gonna go and specifically supply thee we'll just put the distal half distal half of the duodenum so this will happen to the Wadden them

right now let's let's just keep going right the next one intestinal artery supply the jus genome do you know actually how we separate where the duodenum ends in the jujin begins there's a special ligament it's called a ligament of treitz right the suspensory muscle the duodenum it's actually the point which is suspending the fourth part of the duodenum right and it's keeping it retroperitoneal but it's the nice point of where the fourth part of the duodenum ends and the jujin it begins right so jus genome ileum right these are these main ones here right a

part of the small intestine now another branch of the superior mesenteric artery is the iliac Olek artery which helps to supply the distal part of the ileum right around the ileocecal Junction or on the valve area and as well as the cecum so now we're gonna have two ileum and we're also gonna have the cecum what else do we have hanging from the cecum once a nice little sucker hanging from there the appendix there vermiform appendix okay then after that it gives off arterial branches that go to the right side right nor towards the ascending

colon so we're gonna have the right kolak arteries which supplies the ascending colon and then we're gonna have these other branches which are going to go upwards and supply the transverse colon called the middle Kolak arteries okay they're going to supply the transverse colon but we have to again be very very particular because the transverse colon we only supply it to around the proximal two-thirds so proximal 2/3 okay close to around the area of what's called the splenic flexure or the left kolak flexure all right so now we got that what's the mesentery the mesentery

distal half of the duodenum does it have one no no Mezen terry's so let's put here no Mezen terry's it's actually going to be retroperitoneal what about the jew genome in the ileum they're both actually anchored through what's called the small bowel mesentery okay are some people even call it the mesentery proper right but the small bowel mesentery is fine now what about the cecum the c comes odd sometimes in some people it's intraperitoneal and sometimes it's retroperitoneal so sometimes it's actually kind of tough because sometimes the small bowel mesentery might actually keep the cecum

intraperitoneal and sometimes it might not so for here we're gonna put that it varies okay what about the appendix well the appendix is also gonna have one two it does have mesentery they call this any time you hear the word me so it's probably gonna mean a mesentery or something this is called the mezzo appendix so it is going to be a mesentery that keeps the an appendix intra peritoneal what about the ascending colon nope this sucker has retroperitoneal it also has this little kind of like white fibrous tissue on the side of it called

the white line I've told we're not gonna talk about that though but again they're sending colon the main thing is it is retroperitoneal okay so it's not going to have a messenger it did previously called the ascending musical one but during the rotation it gets obliterated against the posterior abdominal wall okay so here no mesentery okay transverse colon proximal 2/3 yes it's actually called the transverse mieze Oh : okay so pretty simple there for that one right okay sweet deal so now we cover foregut mid gut now we go on to this last sucker right

here which is called the hind gut now the hind gut is primarily going to be supplied by the inferior mesenteric arteries so remember the branches of the inferior mesenteric artery one of the branches is gonna be called be left Kolak so now we're gonna have ones that are going to the left side which is called the left colocar thérèse so now if we remember the inferior mesenteric artery alright well actually let's make it even easier on ourselves transverse colon proximal 2/3 that's where the mid gut ends so what do think it's gonna begin the distal

1/3 of the transverse colon so let's put here the distal 1/3 of I'm gonna put TC your transverse colon actually I'll just finish this part out : right now we got that part that's gonna be kind of the branches of the left colon garters can give some supply over to that area right what else okay well now we got to go to the next guy we gotta go down so now we have the descending colon then the descending colon wraps in like a nest like shape so they call that the sigmoid colon and then it

goes into the next part which is the rectum rectum dang near killed him right so we got the upper rectum now I thought you said rectum yeah it is the upper rectum but it stops at a specific point you know where the upper rectum actually kind of hits where the hindgut ends it's actually going to be called the pecten eight line so the pecten a line is really good at being able to separate the upper rectum from the lower rectum okay so now we got hindgut here distal one-third descending colon sigmoid colon upper rectum pectin

a line and again if you remember the arteries you can remember left kolak for the distal 1/3 and the descending colon you can remember the uh what is the other guy here we're also going to have the sigmoid arteries and we're gonna have the superior rectory okay so again the sigmoid artery the superior rectal artery and again you'll have the left kolak now what about the mesentery okay well we already said the distal 1/3 of the transverse colon the transverse colon has to have a messenger we already know that so what does it gonna be

let me get back down here and destroy my knees here right so this is going to be the transverse knees a colon all right what about the descending colon the descending colon actually did have at some point time and mesentery what's called the descending musical but again during that rotation it'll got obliterate against the posterior bound on the wall and it lost its mesenteric so this sucker has no mesentery okay sigmoid colon it actually does develop one it's called the sigmoid mezzo : okay and then the upper rectum now the upper rectum doesn't have any

mesentery here okay so it's actually not going to be considered to interpret in an organ it's considered a retroperitoneal organ okay so we have covered the foregut its components the mesentery and the vascular supply as well as the same thing for the mid gut and the hindgut all right engineers so that covers pretty much everything that you guys would need to know about the development of the GI tract and all this large outline that we covered all right engineers I can't say thank you enough for watching these videos I hope that they helped I hope

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