Full transcript
0:07all right ninja nerds in this video
0:09we're going to talk about the
0:09development of the gastrointestinal
0:11tract as well some of the peritoneum
0:13coverings and cavity so we have a decent
0:16outline we got a lot to talk about in
0:18this video so the first thing I want to
0:20talk about before we even get into this
0:21actual GI tract stuff is I want to talk
0:23about the embryonic folding okay this is
0:25really important because this is gonna
0:27tell us a development of the
0:29gastrointestinal tract so we'll start
0:31off here with the embryonic folding and
0:33talk about the development of the gut
0:34tube the development of the peritoneum
0:36then after that we'll talk about the
0:38development of the foregut its
0:39components vascular supply and medicine
0:41Terry's the mid gut its components
0:44vascular supply medicine Terry's hind
0:46gut its components vascular supply and
0:48medicine Terry's then this is going to
0:49be really important we're going to take
0:51it a little bit of time talking about
0:52intraperitoneal organs versus
0:54retroperitoneal organs and then another
0:57thing is we're gonna determine the
0:58difference between primary or inter
1:00pares primary retroperitoneal versus
1:02secondary retroperitoneal and then we'll
1:04finish off with some cool pathologies
1:06like on fallow seals gastroschisis in
1:09the meckel's diverticulum
1:10so let's go ahead and get started first
1:11off on embryonic folding so the first
1:14thing we have to talk about is we have
1:16to start right around the third week of
1:18development so around the third week of
1:21development we have this structure
1:23called a try
1:24laminar disc okay we're not going to go
1:27into tons of detail in this video on the
1:30embryology aspect we're gonna keep it
1:33kind of simplistic here okay but the tri
1:35laminar disc is made up of three layers
1:37the first one is this blue layer is
1:39going to be called the ectoderm okay
1:41underneath the ectoderm we're gonna
1:44assume they've already developed what's
1:46called a neural tube which helped to
1:49develop the spinal cord and another
1:51structure here called the notochord okay
1:53which will become the nucleus pulsus
1:55within the intervertebral discs then on
1:58the side of it you're gonna have what's
2:00called your intra embryonic mesoderm and
2:05your entry an intra embryonic mesoderm
2:08actually has three parts
2:10okay one is you're gonna have what's
2:13called your par axial music term then
2:15your intermediate music and then your
2:17lateral plate Musa derms
2:19for right now just remember the par
2:20axial music room helps to form what's
2:22called your dermatome your sclera tomé
2:23your Maya tome and then the intermediate
2:26mesa term helps to form like the kidneys
2:28and the gonads but the lateral plate
2:31needs the durum which is made up of two
2:33parts that we're going to talk about the
2:35splanchnic Musa derm and the somatic
2:37Musa term these are very very important
2:40for the development of the peritoneum
2:42membranes alright so we're gonna have
2:45that on both sides over here so over
2:46here we'll have par axial Musa derm
2:48intermediate means a derm and then we'll
2:51have the splanchnic which is going down
2:54here around the actual yolk sac or the
2:56endoderm and then we'll have the one
2:58coming up here which is actually going
3:00to be the somatic underneath that we're
3:04gonna have the endoderm
3:06okay now the endoderm is important
3:08because the endoderm is going to be
3:10helpful for making the epithelial lining
3:12of our gastrointestinal organs some of
3:15the accessory organs and even some of
3:17the glands okay so this is what we have
3:21here now underneath the endoderm
3:24underneath it you're gonna have this
3:26thing called the yolk sac the yolk sac
3:29is important because it helps to
3:30beginning with the synthesis of red
3:33blood cells so it's very important for
3:34the production of red blood cells
3:36all right above that you're gonna have
3:39what's called the amniotic cavity now
3:42last thing the yolk sac secrets a type
3:47of connective tissue which is called the
3:49extra embryonic musa term
3:51now this extraembryonic mesoderm is
3:53going to surround the actual yolk sac so
3:58it's gonna surround the yolk sac and
4:01it's going to come over here and it's
4:03gonna surround the amniotic cavity okay
4:08now what's really cool is you see this
4:12part here that we said we they have the
4:13two parts of the lateral plate music we
4:15have the somatic and the splanchnic they
4:18develop a little cavity right here it's
4:20called the intra embryonic coelom and
4:22what happens is it allows for
4:24these guys to become continuous with
4:27this extraembryonic mesoderm okay so
4:30they become continuous with this extra
4:33embryonic music so again we can call
4:35this the splanchnic Mesa der we also
4:38call it the splanchnic Plurk and then we
4:40have this one up here which is called
4:42the somatic means a dirt or the somatic
4:44lurk okay and then just for the heck of
4:47it this last part here is you'll have
4:49what's called your chorionic cavity and
4:51there's going to be here around it is
4:55this outer layer of the extra embryonic
4:58museum so this is the outer layer of the
5:01extraembryonic mesoderm
5:02and the last part here is you have your
5:05connecting stalk all right with your
5:08land toys which will help to make the
5:09umbilical cord so that's the beginning
5:11part that's the third week now what
5:15happens is is we have this development
5:18of the gut tube this embryo is gonna
5:20undergo a folding process it's gonna
5:22fold in two planes one is going to be a
5:24transverse plane and the other one is
5:26going to be a sagittal plane and it's
5:29important to understand the difference
5:30between the two so let's go ahead and
5:31show that all right so here we go we're
5:33gonna have over here we're gonna take
5:35this bad boy here we're gonna have this
5:37one going into thee specifically into
5:40the horizontal plane
5:41I'm sorry transverse plane and we'll
5:43have this one over here specifically
5:45going into the sagittal plane alright so
5:48now what happens is if we draw it in the
5:50sagittal plane this is going to help to
5:52form what's called cranial and caudal
5:54ends okay so watch what happens it's
5:57gonna undergo this folding process when
5:59it undergoes this folding process
6:01something really cool happens here we're
6:04gonna get this little pocket right here
6:05and then we're gonna have this part
6:09right here okay so this is going to be
6:14important when we're developing the gut
6:16tube all right we're gonna have two ends
6:19here
6:19this is the endoderm all right so the
6:21endoderm aligning is going to undergo
6:22this expansion where it's going to
6:24expand outwards and it's gonna start
6:26folding when it does that we're gonna
6:29say that this end right here let's just
6:30say for the heck of it this is the
6:32cranial end
6:34and this is the caudal end right here
6:37the cranial end is going to help to
6:39develop what's called the foregut which
6:42is gonna be important we'll talk about
6:43all the organs in that the caudal end is
6:45gonna help the form what's called the
6:46hindgut and we'll talk about the organs
6:48of that in the middle right here you're
6:50gonna have the mid gut okay now let's
6:54talk about some of the stuff around this
6:55because it's going to be important here
6:56real quick all right so again what we
6:59have around it we might have a little
7:00bit of Mesa derm around it alright so
7:03here we'll have some knees a derm an
7:05important thing again remember is that
7:07you're gonna have a lot of stuff
7:10happening here that we're not showing
7:12we're just trying to focus primarily on
7:14the gut tube and the derivatives of this
7:18endoderm and some of the music durman's
7:20okay so you're gonna have some ease the
7:21dirham here that is gonna be surrounding
7:22it some of the means of dirham towards
7:24the cranial end will help to form what's
7:25called the pericardial cavity and the
7:27heart and you'll also have some other
7:30structures there developing too now
7:32around that what we should we have we
7:33should have the octo derm so now we're
7:36gonna have around that the ectoderm the
7:38active term is important because it
7:39helps to form the skin it also helps to
7:41form the central nervous system which is
7:43the brain and the spinal cord right and
7:46you also have these other structures
7:47which are going to be important too and
7:50that is going to be your neural crest
7:52cells and the neural crest cells are
7:53really important because they help in
7:55the development of what's called your
7:57ganglion cells which are important
7:59within the digestive tract for example
8:01to my enteric plexus in the submucosal
8:03okay and above this what should you have
8:06you should have the you know Miyata
8:09cavity right here and then down here
8:12what would you have connecting over here
8:14you're still gonna have the yolk sacs
8:16let me bring the yolk sac down here
8:18okay so we'll have the yolk sac down
8:20here okay alright so again what are we
8:26gonna have out of this then we're gonna
8:27have three guts that we need to remember
8:29one right here is going to be the
8:31foregut right here is going to be the
8:34mid gut and right here is going to be
8:36the hindgut okay another important thing
8:39real quick is at this end this end right
8:41here towards the fork up is going to be
8:43help in forming the mouth so you know
8:45what you know what membrane we call that
8:46we call this membrane right here because
8:49eventually it'll actually perforate in
8:50form hole this is going to be called the
8:52auro
8:53foreign geol membrane so what happens is
9:00this will perforate around this end
9:01right here and form the mouth alright
9:05towards this end that's gonna form the
9:07booty hole alright
9:08so towards this in the hindgut we're
9:10gonna call this the cloaca membrane and
9:14the cloaca membrane it'll actually
9:16perforate and help to form the anus it
9:18also helped to form the urogenital tract
9:20as well okay so now what happens last
9:25thing here before we continue is this is
9:28gonna happen pretty much around the
9:29fourth week now around the sixth week
9:31what should happen is the mid gut right
9:35the mid gut actually has your intestinal
9:37loops around there like so the small
9:38intestine so what's gonna happen is the
9:41jooshin of an ileum forms like a little
9:42loop and that little loop around the
9:45sixth week actually kind of herniates
9:47out into the umbilical cord okay so we
9:50can have the umbilical cord actually
9:51coming at it because you know originally
9:53they call this duct right here around
9:55the fourth week they called the vital
9:57and duct they called the light telling
10:00doctor the on fallow mesenteric duct I'm
10:03going somewhere what happens is around
10:06the fourth week you formed this it's
10:07what basically connects the mid gut to
10:09the the umbilical vesicle or we also
10:11called the yolk sac but what happens is
10:13around the sixth week the vital and duct
10:16should get obliterated and then now this
10:18will no longer be there so when this is
10:21gone then what should we have we should
10:23just have the umbilical cord okay so at
10:25that point when the vital induct is
10:27obliterated all we should have left is
10:29just going to be the umbilical cord okay
10:33so why am i mentioning this because you
10:37know the vital induct doesn't actually
10:39obliterate guess what you can have you
10:42can have that mid loop get pushed or
10:45herniated out here to where it forms
10:46like a pocket out into this area and
10:49what happens is the vital induct
10:50actually stays there and forms a
10:52ligament connection between the mid gut
10:54in the anterior abdominal wall guess
10:56what they call that
10:57meckel's diverticulum
10:59okay they call meckel's diverticulum so
11:02the meckel's diverticulum is going to be
11:04an issue whenever the vital and duck
11:06does not obliterate and forms an
11:08outpouching of the actual small
11:10intestine and it can be very very
11:12serious if not treated right the other
11:15thing I wanted to mention is another
11:16part of the mid gut right the intestinal
11:18loops and I told you it actually
11:19naturally herniates it naturally
11:21herniates around the sixth week and the
11:23reason why is as the embryo is
11:25developing the liver and some of the
11:27stomach and all those organs are really
11:29really increasing in size and taking up
11:30the space within the actual mid gut so
11:32what do you think is going to do it's
11:34gonna start pushing the intestines and
11:35naturally out here into the into the
11:37actual umbilical cord naturally that's
11:39okay that's all the natural herniation
11:41it usually happens around the sixth week
11:43but what happens is as the embryo starts
11:46developing and developing the abdominal
11:47cavity should increase as it increased
11:50then it makes room for the actual
11:51intestinal loop to get sucked back into
11:54the abdominal cavity around the 10th or
11:5611th week but what is really important
11:58is it by the 10th and 11th week it
12:00hasn't get pulled back into the
12:01abdominal cavity that would guess what
12:03you have you haven't on fallow seal
12:04okay so that's really important to
12:05understand and our phallus ill can
12:07develop whenever the intestinal loop
12:09does not come back in to the actual
12:12abdominal cavity all right so I have a
12:14peritoneum covering around it and again
12:16there is tests that you can do to
12:18determine if the actual fetus does have
12:19an FSO you can do like an ultrasound or
12:21they can do blood tests to test the
12:23maternal serum fetal alpha protein
12:25levels alright so whenever this embryo
12:26is folding what are we gonna get we're
12:28gonna get it and the four got the mid
12:29gut in the hindgut but specifically
12:31we're only gonna see this folding this
12:32cranial caudal folds when we're looking
12:35at this embryo folding specifically in
12:36the sagittal plane okay so this is gonna
12:42be in the sagittal plane okay alright so
12:44now we've already talked about the
12:45embryonic folding process in the
12:47sagittal plane now we have talked about
12:48the embryonic folding process
12:49specifically in another plane called the
12:50transverse plane
12:52alright so the embryonic folding and the
12:56transverse plane so now the only
12:59difference between this one is that
13:02what's going to happen is this area
13:04right here is going to start folding
13:05downwards and outwards okay so this area
13:09right here where the amniotic cavity
13:10nected erm is it's going to start
13:12folding out
13:13and downwards now the endoderm is gonna
13:16get sucked in
13:17so this area's gonna get sucked in and
13:19pushed out look what we get out of that
13:21so let's go ahead and redraw that then
13:24so look what we have here we're gonna
13:27have the ectoderm here right so there's
13:32our ectoderm and again what should we
13:34have right here
13:35we should have me we'll have the
13:39notochord and also the neural tube then
13:44we'll have the par axial music derm
13:47intermediate music derm in this area
13:51right here which is your lateral plate
13:52meezerman again par axial intermediate a
13:56lot of plate music right now again what
13:59did I tell you here what happened with
14:00the endoderm the end of derm is gonna
14:03start kind of like getting sucked in
14:05like this and this part here is gonna
14:07get pushed in and pulled outward when
14:10that happens we form that thing that we
14:12talked about before which is called the
14:15vital induct which is going to go to the
14:17yolk sac or the umbilical vesicle then
14:21what else do we have up here we have the
14:24amniotic cavity now what's really cool
14:26here is that the amniotic cavity starts
14:29kind of folding down like this okay
14:34starts kind of folding down like this
14:39now let's put our linings back on there
14:42again what do we have here before we're
14:44gonna have this as the splanchnic musa
14:47term so the splanchnic means the term is
14:49going to come right here right around
14:52the bite Allen dock the endoderm and the
14:55yolk sac right sweet deal let's show it
15:02going right here okay then what else are
15:06we gonna have here we're gonna have the
15:08somatic music the somatic music arm is
15:11going to come out here and it's gonna
15:14line this outer part here right the
15:16amniotic cavity
15:19all right and then outside of that we
15:20would have the chorionic cavity but
15:22we're not going to show that that's too
15:23much drawing all right so now after that
15:26it's gonna come in words and we got this
15:29now all right here's what's really cool
15:31as this continues as these lateral folds
15:34keep pushing down and coming closer and
15:36closer and closer this area is gonna
15:38fuse so it's gonna fuse remember I told
15:40you the vital and duck should obliterate
15:42and then eventually what will happen is
15:44you'll have the umbilical cord which
15:45will connect between the actual fetus
15:47and the mother right but again what
15:49should happen is the my talent duck
15:50should obliterate and these folds will
15:52mute merge together you know what
15:54happens if the latter folds don't merge
15:55together guess what the small bow could
15:57herniate
15:58out through that lateral fold you know
16:00what that's called gastroschisis so
16:02that's the difference between on fallacy
16:04and gastroschisis what happens is is the
16:08actual specifically parts of the gut
16:11herniate out through this point here
16:14where the lateral folds don't completely
16:16close that's called gastroschisis and
16:18what happens is the intestines don't
16:20have any peritoneal covering guess what
16:23they're completely exposed in the
16:24amniotic cavity which can agitate the
16:26intestines and that can be very bad all
16:28right so again let's show this part here
16:30where the lateral fold fuse because this
16:32is really cool this is where it gets
16:33good all right now we're gonna bring
16:36this bad boy down and we're gonna show
16:37the complete fusion process here because
16:40it's gonna lead us into our next topic
16:41here so again now what we have here if
16:43we draw everything the same way right
16:45here
16:45there's our gut tube what should be
16:47surrounding the gut tube what do we call
16:49this this is the splanchnic music erm
16:52the reason why I'm telling you this is
16:54because guess what this blank tech needs
16:55a term forms it helps to form the walls
16:59of the GI tract for example the
17:01submucosa the muscularis externa the
17:04lamina propria all those different parts
17:07and the visceral serosa
17:10or the visceral peritoneum which is
17:12extremely important now around the walls
17:16here what should we have around the
17:18walls we should have the somatic mesa
17:26derm
17:26so this should be the somatic Nizza derm
17:29right here
17:30now the somatic Museum is important why
17:33because it helps to form the parietal
17:35serosa or the parietal peritoneum which
17:38is extremely important what happens
17:41though is we have to develop a
17:43connection between the parietal serosa
17:47or the parietal peritoneum and the
17:49visceral serosa or the visceral
17:51peritoneum what do you think that
17:52connection is right there that keeps
17:54that organ suspended within this
17:55peritoneal cavity what are you guys
17:58called it's called a mesenteric okay so
18:01this right here is called a Mezen teri
18:04and these are extremely important what
18:07is this here called again this is called
18:09the parietal serosa or parietal
18:13peritoneum and this one right here is
18:16going to be called the visceral serosa
18:21or visceral peritoneum okay and this is
18:25going to be the para to neil cavity the
18:32reason why I'm mentioning this is is
18:35because any organ that has a mesentery
18:39and has this vessel or serosa and this
18:42parietal serosa
18:43and in to have the two connecting
18:45together through a mesentery are
18:47primarily going to be intraperitoneal
18:50organs so let's write that down here if
18:53this guy has a mesentery it's going to
18:56help us to determine that this should be
18:58a intra peritoneal organ okay this is
19:07extremely extremely important okay so if
19:11it has a mesentery and it has a visceral
19:13serosa and a parietal serosa it will be
19:15an intraperitoneal organ meaning it's
19:17inside of the peritoneal cavity
19:18suspended within it by a mesentery if it
19:22doesn't have a medicine Terry or if it
19:24did have a mesentery previously but it
19:27loses it as it's getting developed and
19:29pushing obliterate against the post tear
19:30down the wall they can be called
19:32retroperitoneal organs so let's say
19:35here's the peritoneum right if it has to
19:37be retro it has to be outside of it or
19:40behind it so what are we going to have
19:42back here
19:43draw a couple of examples here let's say
19:46back here I could have the kidneys so I
19:50can have the kidneys right here what
19:51else could be around this area what's on
19:53top of the kidneys I could have the
19:55adrenal glands right what else could I
19:59have back here I could even have the
20:01parts of the duodenum right so I can
20:04have parts of the duodenum right here
20:06that we'll talk about and we'll get into
20:09all this but I just want you guys to
20:10understand here that if there are organs
20:13located outside of the peritoneal cavity
20:15not suspended by a mesentery these are
20:18called retro peritoneal organs and we'll
20:29talk about these ok so what do we do we
20:33talked about intraperitoneal we talked
20:34about retroperitoneal but now we gotta
20:36have a little bit more of a discussion
20:37we have to talk about the differences
20:38between primary and secondary for
20:40example the big vessel in the abdominal
20:44cavity we call it the abdominal aorta
20:46that's one so the abdominal aorta that's
20:53a big one the vein that's right next to
20:56it which is called the inferior vena
21:00cava what else okay well what else is up
21:06in the top part of the actual abdominal
21:08cavity another one is going to be the
21:10adrenal glands so the adrenal glands
21:15what's below that the kidneys okay what
21:21else
21:22you know what's the tube that takes
21:24urine from the kidneys down to the
21:26bladder the ureter so we're also gonna
21:29have the ureters and then what's the
21:32structure that collects it the bladder
21:36alright and then one more part here is
21:39around the doodle hole right around the
21:42doodle hole you're gonna have the rectum
21:43but specifically the lower rectum
21:47okay lower rectum
21:51okay so primary intra I'm sorry primary
21:54retroperitoneal guns not a mesenteric
21:57right so that they don't have a
21:59mesentery they're not going to be found
22:00inside of the peritoneal cavity they're
22:02gonna find posterior to it now
22:05these are the abdominal aorta inferior
22:07vena cava adrenal glands kidneys ureters
22:09bladder lower rectum all right so the
22:12secondary for the secondary
22:14retroperitoneal organs the secondary
22:17retroperitoneal organs they did have a
22:19mesentery at some point time so when
22:21they have that mesentery right during
22:23the rotation of the gut as it rotates
22:26around the central axis some of these
22:29mesentery x' get obliterated against the
22:31post here abdominal wall and then when
22:33they get obliterated they lose their
22:34mesentery and then they develop outside
22:36of the peritoneum posterior to it those
22:40organs are secondary retroperitoneal
22:42organs for example one is going to be
22:45the second third and fourth parts of the
22:51duodenum okay if you keep going we'll
22:56get to the ascending call like I told
22:58you guys before the ascending colon and
23:02then also the descending colon now if we
23:10talk about some accessory structures
23:11around that right around the duodenum
23:14you have the head in the body of the
23:16pancreas so we also have the head and
23:20the body of the pancreas all right so
23:28these are going to be secondary
23:29retroperitoneal words but there's also
23:30going to be some other structures that
23:33we can include in there but I'm just
23:34trying to get the main ones here okay so
23:36the main ones that we're gonna be
23:37talking about with respect to these
23:38primary and secondary --is four primary
23:40primary you can have the abdominal aorta
23:42in free vena cava adrenal glands kidneys
23:45ureters bladder and the lower rectum and
23:47even one more technically we can have
23:50the esophagus
23:54okay okay now the last thing I want to
23:58say before we move on is if they don't
24:02have a visceral serosa right and they
24:05don't have a parietal serosa then what
24:07do they have to anchor them to the
24:08poster abdominal wall one in order for
24:11them to be anchored to the posterior
24:13abdominal wall retroperitoneal organs
24:15have to have a specific thing a specific
24:19connective tissue that anchors them to
24:21the post trap nominal wall this is
24:23called adventitia okay adventitia is
24:30actually going to be like a dense
24:32fibrous so what does it called its
24:34called a dense fibrous specifically
24:40irregular connective tissue okay and
24:44what it does is it anchors these organs
24:47to the post here abdominal wall because
24:49they do not have a visceral serosa or
24:51parietal serosa and they don't have a
24:54mesentery to keep them suspended there
24:55so they have to be anchored so there's
24:57not very much mobility there however
25:00things that do have a mesentery do have
25:03a visceral serosa and a parietal serosa
25:05and keeps them interfering they have a
25:07little bit more mobility okay hi guys so
25:10we talked about a lot of stuff within
25:11this video we talked about the embryonic
25:13folding process we talked about the
25:15intraperitoneal organs retroperitoneal
25:16and the pathologies associated with it
25:17right
25:18in the next video we're gonna do we're
25:20gonna talk about the four gut the mid
25:21gut and hind gut their components their
25:23vascular supply and their medicine
25:25Terry's okay iron engineers so I thank
25:27you guys for watching this video I
25:28really appreciate it if you guys did
25:30like this video please hit the like
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25:40please go check that out and also we
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25:51all right ninja nerds until next time
25:53[Music]
26:12[Music]
26:17you
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