Full transcript
0:14all right ninja nerds in this video we
0:16are going to talk about the development
0:18of the heart before we go ahead and get
0:19started though please continue to
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0:33appreciate it all right ninja nerds
0:34let's get into it
0:35all right ninja nurse what we're going
0:36to do is we're going to talk about the
0:37development of the heart but in order
0:38for us to do that we're going to do this
0:39in kind of like sections
0:41the first thing that we're going to try
0:42to do is develop a heart
0:44tube okay one singular heart tube
0:47and then surrounding that heart tube
0:49we're going to try to develop what's
0:50called a pericardial cavity
0:52okay so that's the goal so in order for
0:55us to do this we have to start with this
0:57top of the diagram and we're going to
0:58work our way down doing two different
1:00types of folding process don't worry
1:01i'll explain it to you
1:03the first thing i want you to look at
1:04here is the top of the embryo right
1:07when you're looking at the top or the
1:08superior view of the embryo first thing
1:10i want you to remember here is you have
1:11two
1:12portions of this embryo this portion
1:14here very simply is the cranial
1:17aspect of this developing embryo and
1:20then this portion down here
1:21is the caudal aspect of the embryo
1:24another way of saying this is this is
1:25the head and this is the tail
1:27of the embryo it's pretty simple right
1:30well if you guys remember
1:31during the gastrulation process remember
1:35cells from the epiblast are moving down
1:36through that primitive shriek right
1:38we have the primitive streak right here
1:39and the primitive node right there
1:41if you guys remember some of these
1:42epiblast these blue cells are moving
1:45through the primitive streak
1:46and when they move through that
1:48primitive streak do you remember what
1:49they do
1:50they convert the hypoblast if it's a
1:52bileminer disc
1:53it turns the hypoblast into the endoderm
1:56and then it makes a new layer between
1:59this blue layer called the
2:00epiblast and the new endoderm layer
2:03which is going to be called the
2:04mesoderm that mesoderm is going to be
2:07sandwiched between
2:08the ectoderm and the endoderm what i
2:11want you to understand out of all of
2:12this though
2:14is that a collection of mesoderm really
2:16starts to kind of take
2:18its place in the cranial aspect
2:21of this developing embryo right so
2:24you're going to have kind of this
2:25really interesting mesoderm clumped here
2:29in the cranial aspect of the developing
2:32embryo
2:33in front of your procoral plate so
2:35technically what i want you to gain from
2:37this is the heart actually develops in
2:38the head
2:39and then it starts to move down into the
2:41thorax we'll talk about that and you'll
2:43see that best with this type of
2:45view here with the sagittal view what i
2:47want us to do is look at this actual
2:49development of the heart
2:50tube in two views one is we're going to
2:52look here in the cross-sectional view so
2:54we're going to kind of take
2:56like this okay and we're going to look
2:58at it here in this
2:59cross sectional view
3:03okay and this is going to be very very
3:06important i
3:07really think this view is really really
3:09important
3:11the next thing that we're going to do is
3:13we're going to take and look at the
3:14actual development of the hardtube
3:16from a sagittal section so we're going
3:18to take a sagittal section here
3:20so now we're going to be doing is taking
3:22a look at this in a sagittal
3:24section sagittal sections are good for
3:26being able to see the movement or the
3:28migration from the head
3:30into the thorax all right so we have two
3:33sections here that we're going to be
3:34kind of looking at to understand the
3:35development of the heart tube
3:37cross section and a sagittal section
3:39let's start here with the cross section
3:41when you take this cross section this
3:43one here so we'll number it just we
3:44understand
3:45this is the first section which we're
3:47going to be talking about here
3:48and this is the second section which
3:49we'll be talking about over here
3:52when you take a cross section and you're
3:53looking at it after gastrulation has
3:56occurred
3:57you have three layers here this layer
3:59here is your
4:00ectoderm this layer here in the middle
4:03is your
4:03mesoderm and this layer here on the
4:05bottom is the endoderm or
4:08the blue is the ectoderm the red is the
4:09mesoderm and the green
4:11is the endoderm when you look at it you
4:14have
4:14particular particularly this mesoderm is
4:17the area that we
4:18really want to focus on when you're
4:21looking at it you have
4:22three components of it this one here
4:24which is next to this called the
4:25notochord
4:27this is actually called your par axial
4:31mesoderm okay
4:34this one here which is just lateral to
4:36it is called your intermediate
4:41mesoderm
4:44and this one over here both of these
4:46sections this one kind of coming up here
4:48and this one going down there
4:50this is what's called your lateral
4:54mesoderm your lateral plate mesoderm if
4:56you will to kind of give you guys an
4:58understanding here this part of the
4:59ladder plate mesoderm is called your
5:01somatic
5:05and then this one here is called your
5:08splank nick layer of the lateral plate
5:11music
5:12what i want you to understand is the
5:15heart tube develops
5:16from the splanchnic layer of the lateral
5:20platenessiderm
5:21so when we're talking about this
5:22mesoderm up there really the mesoderm
5:24that i really want you to focus on that
5:26is the cardiogenic area
5:28is this splenic layer of the lateral
5:29plate mesoderm here's something very
5:31interesting that happens
5:34this endoderm starts secreting lots of
5:37growth factors
5:38so it starts secreting lots of growth
5:40factors that are going to try to
5:42influence this
5:43splenic layer of the ladder play music
5:45and what are these growth factors that
5:46it's releasing
5:47it's releasing a lot of what's called
5:49vascular
5:50endothelial growth factors
5:53vegf is another way that we kind of
5:55refer to it
5:56and what vegf does is it stimulates the
5:59lateral plate mesoderm to kind of start
6:01differentiating and specializing if you
6:03will what does that mean
6:05let me explain let's say imagine here
6:08that we're just taking the mesoderm
6:09okay so here's our mesoderm okay a clump
6:12of mesoderm
6:14the vascular endothelial growth factor
6:16are going to do something very
6:17interesting where it's going to
6:18stimulate this mesoderm to kind of
6:20differentiate
6:21and when it differentiates
6:25it actually kind of does two things one
6:27is it forms this outer core
6:29and then one is it forms this kind of
6:31inner core
6:32the outer portion is going to become
6:34what really will become our blood
6:36vessels and our heart tube
6:38okay and we call this outer portion here
6:41we actually are going to call this the
6:43angioblast cells
6:45okay your angioblasts
6:48and then the inner part which will
6:50become our blood cells our reds
6:52red cells white cells all that stuff
6:54this is technically what we call
6:56the hemo cytoblast
7:00so what vegf is doing is is it's causing
7:03the
7:04mesoderm to differentiate into what
7:09blood vessels right and actually the
7:12heart tube itself
7:13and blood cells now
7:17let's actually take a look and see how
7:19vegf actually influences the latter
7:21plate mesoderm in the next step so what
7:23we had here was ladder plate mesoderm
7:24vegf was stimulating it causing it to
7:26differentiate make heart tubes
7:29now take a look here you see how from
7:31the lateral plate mesoderm
7:33this actual chunk of mesoderm grows off
7:36of it
7:37and it starts specializing and you form
7:39little cavities
7:41what are these cavities here this
7:43cavities right here
7:45these are called your heart tubes
7:48these are called your heart tubes
7:52and then these cavities here that are in
7:54the back
7:55these are called your pericardial
7:59cavities these are called your
8:01pericardial cavities
8:03so from the lateral plate mesoderm what
8:05did we do we released vegf
8:07stimulate the ladder plate mesoderm to
8:08form heart tubes
8:11and a little cavity starts to develop
8:13within that lateral
8:14plate mesoderm and these are called your
8:16pericardial cavities
8:18now what happens is this embryo imagine
8:21these edges
8:22i'm going to start trying to bring them
8:24closer to one another so i'm going to
8:26bring this ectoderm layer
8:27cause it diffuse together bring the
8:29mesoderm layer cause it to fuse together
8:31and bring these two edges here together
8:34when i do that
8:36guess what happens these heart tubes are
8:39going to
8:40fuse together and make one singular
8:42heart soup so two hard tubes come
8:44together and make
8:45one heart tube
8:50these pericardial cavities whenever
8:51these two edges come together they fuse
8:53and takes two pericardial cavities and
8:55makes it into
8:56one pericardial cavity
9:04and we'll just keep going here
9:08where did that actual green part you
9:09know what this green part is actually
9:11where he said that the endoderm right
9:12the endoderm
9:13will make the epithelial lining of the
9:15gi tract
9:16that's going to get invaginated more
9:18posteriorly and look
9:20there's the actual endoderm lining which
9:22will become the the epithelial lining of
9:23our gi tract
9:25so that's that step okay so we took the
9:28lateral plate mesoderm stimulated it
9:29with vegf
9:30formed heart tubes pericardial cavities
9:33during the lateral folding the heart
9:34tubes pericardial cavities
9:36fuse become one heart tube one
9:39pericardial cavity
9:40one more thing that we have to
9:41understand you see we have the heart
9:43tube kind of sitting in the pericardial
9:45cavity
9:45well it doesn't just sit there without
9:47you know it's going to just flop around
9:48we can't let that happen we
9:50have to kind of like hold it against
9:51this actual posterior wall a little bit
9:54and so what happens is some mesoderm
9:57connects the pericardial cavity to the
9:59heart tube what is this structure here
10:01called
10:02this is called your dorsal
10:05mesocardium so this is called your
10:07dorsal
10:08mesocardium okay so we have our dorsal
10:12mesiocardium which is
10:13connecting the pericardial cavity to the
10:15heart tube
10:16let's now zoom in on the heart tube a
10:18little bit so let's just kind of focus
10:19on the pericardial cavity and the heart
10:21tube
10:22so again here's the pericardial cavity
10:24here's your dorsal mesocardium
10:26when you look at the heart tube the
10:27heart tube is actually made up of a
10:29couple layers
10:31the most inner aspect of the heart tube
10:33this red part
10:35this is actually called the endocardium
10:39it's made up of those endothelial cells
10:41which we developed from what
10:43from the mesoderm right we said that the
10:44mesoderm gets stimulated by vegf and
10:46makes angioblasts
10:48and we also said hemocytoblast the
10:49angioblasts are what's going to become
10:51the endothelial lining
10:52and make the endocardium on the outer
10:55part here this blue layer here
10:57this blue layer is called
11:01the myocardium this is called your
11:03myocardium
11:04and your myocardium is actually
11:06developed from
11:08cardiac myocytes so this is cardiac
11:10myocytes
11:11now what's very interesting is that
11:13these cardiac myoblasts
11:15they start secreting kind of a little
11:17connective tissue or
11:18jelly-like substance which forms between
11:21the endocardium and the myocardium
11:23what is that pink like jelly substance
11:25which is made by the myocardium
11:27that is called the cardiac
11:30jelly not even joking it's called the
11:33cardiac jelly
11:34okay so what we've done up to this point
11:38is we started with
11:39lateral plate mesoderm stimulated with
11:41vegf made two heart tubes two
11:43pericardial cavities
11:44from lateral folding we fused the two
11:46heart tubes made one heart tube
11:48fused the pericardial cavities made one
11:50pericardial cavity
11:51suspended the heart tube in the
11:53pericardial cavity by the dorsal
11:54mesocardium
11:56and if we zoomed in on the heart tube
11:58and looked at the layers
11:59the inner layer is the endocardium which
12:01is made from the angioblast
12:03and then you have the myocardium on the
12:05outside which secrete a substance called
12:07cardiac jelly which sits in the center
12:10boom we hit this from the
12:11cross-sectional view
12:13now let's take a look at this from the
12:14sagittal view alright so we took and
12:17looked at the development of the heart
12:18tube from what in a cross-sectional view
12:22undergoing lateral folding now let's
12:24talk about the development of the heart
12:25tube
12:26in the pericardial cavity in a sagittal
12:28view as it undergoes cranial caudal
12:30folding
12:32so if we take a look here again we're
12:33looking at this section here we're
12:35looking at a sagittal section
12:37and again we kind of numbered that too
12:40so first thing we have here is our
12:41sagittal section obviously up here in
12:43blue
12:43is your ectoderm here is your
12:47endoderm right now
12:51what i want you to remember is we're
12:52looking at this in front of in the top
12:55in the cranial most portion
12:57so here is that actual cardiogenic area
13:00or that clump of mesoderm
13:02which would become the heart tube so
13:04right here is your clump of mesoderm
13:07that is going to become the actual heart
13:09tube so this is basically your
13:11mesoderm which will become the heart
13:14tube
13:16now what we're going to do is we're now
13:18that we understand that they're actually
13:20oh one more thing here you know how in
13:22between here
13:22between this actual portion here there's
13:24a little membrane which is kind of
13:26connecting this
13:27cardiogenic mesoderm to the ecto and
13:29endoderm you know what this little can
13:30like little stalk is here
13:32that's called your buccopharyngeal
13:34membrane that'll actually become the
13:35opening right the stimodium will become
13:37the mouth now what happens here is that
13:40this mesoderm
13:41starts to undergo the differentiation
13:43process right how
13:44remember what the endoderm does it
13:46releases
13:48vegf vagef will then stimulate the
13:51mesoderm to do what
13:53start to form angioblasts which would
13:55become kind of the endocardial lining
13:57help to form like pretty much your heart
13:58tube
13:59and then inside of that heart tube the
14:01other parts of the mesoderm will become
14:03your blood cells your hemocytoblasts
14:05so now go on to the next step veg f
14:07stimulated the actual
14:08mesoderm here to start differentiating
14:11now look what we have here
14:12still same thing here we have our
14:16ectoderm we have our
14:19endoderm and again remember this is the
14:22cranial portion where the actual
14:24cardiogenic center is
14:25this is the caudal portion now the next
14:28thing you need to notice is look what
14:29happened it's no longer just one clump
14:31of mesoderm here on the top you see how
14:33this is all dark
14:34this dark portion here is what's going
14:36to become that is the heart tube
14:39and then this here that's actually kind
14:40of like a little cavity that is going to
14:42be the
14:43pericardial cavity so it's kind of it's
14:46the same
14:47process in the actual cross-sectional
14:49view
14:50but you're just looking at this as it
14:52folds something different happens and
14:54i'll explain it
14:55so ectoderm endoderm endoderm releases
14:58vegf stimulates the actual mesoderm to
15:01differentiate
15:02forms a heart tube and a pericardial
15:04cavity here's where it gets really cool
15:07the ectoderm and endoderm start folding
15:10so they start
15:11folding it at the ends right so the
15:12cranial end starts kind of turning in
15:14and the caudal end starts turning in as
15:16it does that it pulls this mesoderm
15:19structure
15:20towards the actual bottom part it pulls
15:23it caudally
15:24so then what happens is it moves from
15:26the head kind of a little bit more to
15:28like maybe the neck area
15:30so now it's kind of towards the neck
15:32area
15:33as it continues to keep folding so now
15:36we have our embryo kind of folding here
15:38look where it actually goes it
15:40completely turns in here
15:42and goes into your actual chest cavity
15:45so during this process of what's called
15:48cranio
15:51caudal folding what is actually
15:55happening
15:57you're actually moving imagine like this
16:00is the best way i think to imagine
16:01imagine your heart is developing above
16:03your head as you start kind of
16:05folding as the baby is actually folding
16:08the actual heart is
16:09moving inwards in front of the face in
16:13front of the neck
16:14and into the thorax that is what you're
16:16seeing in this sagittal section
16:19now one more thing
16:22remember how we had the heart tubes fuse
16:25pericardial cavities
16:26fuse and basically the heart tube formed
16:29in the pericardial cavity
16:30the same thing has to happen here so
16:33what happens is here
16:34you're going to have your pericardial
16:36cavity
16:38during this cranial caudal folding guess
16:40what it does
16:41it kind of pulls the actual heart tube
16:44into the pericardial cavity
16:49so now here's my heart tube sitting
16:52in the pericardial cavity before during
16:55this actual process they were separated
16:58but during the craniocaudal folding as
16:59it moves from the head
17:01over the face over the neck and into the
17:03thorax the heart tube gets stuffed
17:06into the pericardial cavity so that is
17:09what i want you to understand
17:11the last thing that we have to do here
17:13is what i want you to do is take the
17:15heart tube
17:16from this cross-sectional view take the
17:18heart tube
17:19from the sagittal view and let's yank it
17:21out and look at it and it's
17:23lengthwise what it actually looks like
17:25in all the different kind of vesicular
17:26portions
17:27so let's say that we take this heart
17:28tube here we're just gonna for right now
17:30abbreviate them we'll kind of denote
17:32them a little bit later in what they
17:33become
17:34but i want you to kind of know this is
17:35the top of the hard tube
17:38and then as we kind of go work our way
17:40down this is the bottom of the heart
17:41tube
17:43at the top of the heart tube you have
17:46these little things that are coming off
17:47here these are basically going to be
17:48your outflow tracks so
17:50blood will actually come in from the
17:52bottom and then
17:53leave out via the top okay these outflow
17:56tracks
17:57are basically your dorsal aorta
18:01okay these are called your dorsal aorta
18:05okay so same thing over here i'm going
18:06to abbreviate a dorsal aorta
18:08right the dorsal aorta come from this
18:10area here at the top
18:12called the aortic sac but really
18:15this portion here at the top most top
18:18portion here
18:18we're going to abbreviate this ta this
18:21is called your truncus arteriosus
18:23what i really want you to know is the
18:25truncus arteriosis really makes up the
18:27top of the heart tube
18:30below the truncus arterios this is
18:31what's called your bulbous
18:33cortis okay below the bulbous cordis is
18:36what's called your primitive
18:37ventricle below the primitive ventricle
18:40is the primitive atria and below the
18:42primitive atria is what's called the
18:43sinus
18:44venosus and then again blood will come
18:47in via the sinus venosus
18:51through the primitive atria through the
18:52primitive ventricle through the bulbous
18:53cortes
18:54through the truncus arteriosis and out
18:56through the dorsal aortae
18:58so you kind of already start to get an
19:00idea
19:01of what some of these structures will
19:04become with respect to the adult heart
19:06all right so we've formed our heart tube
19:08we've denoted the portions of it
19:10let's really dig into it a little bit
19:11more and talk about what these actual
19:13components become
19:15all right ninjas we've formed our heart
19:17tube we've accomplished this we know
19:19that the heart tube is coming from the
19:20lateral plate music and particularly the
19:22splanchnic portion of the lateral plate
19:24mesoderm we know that it's under the
19:25influence of vegf
19:27we finally made it now let's go back
19:30let's denote these different portions
19:32right what did we kind of abbreviate
19:33them as just real quick here
19:35remember this was the aortic sac
19:39right so the top part here is going to
19:40be what's called the aortic
19:42sac and we said that the aortic sac goes
19:45into what what structure does that
19:46actually fill into
19:48we said that it actually leaves out
19:51via what structures it'll leave via the
19:55dorsal aorta
19:59right then below
20:02the aortic sac what was the next
20:03structure this was the
20:05truncus arteriosus so then we have the
20:08truncus arteriosus
20:10here's what i really want you guys to
20:12know the truncus arteriosus
20:16is what becomes the pulmonary artery
20:20and the aorta so the truncus arteriosus
20:23is what becomes the pulmonary trunk
20:25which is pretty much going to make up
20:26your pulmonary arteries and
20:29your aortic arch okay
20:33so first thing i want you to know
20:34truncus arteriosus becomes those two
20:36structures
20:37what is below this what do we say the
20:39bulbous cordis all right so this is
20:41called our bulbous
20:44cordis now what does the bulbous cordis
20:46become
20:47this becomes the right ventricle right
20:49so this becomes the right ventricle
20:51and the right and left
20:54outflow tracks so it's the actual
20:56outflow tracks from the right ventricle
20:58and the left ventricle
21:00very very important okay
21:03beautiful the next structure here
21:07below the bulbous cord is here in pink
21:09is what
21:10the primitive ventricle so this is
21:13called your primitive
21:15ventricle it's obvious what this is
21:18going to become this was the right
21:19ventricle in the outflow tracks what do
21:21you really have
21:22left ventricle wise this is going to
21:24become your
21:25left ventricle the next thing
21:29below the primitive ventricle is going
21:31to be the primitive
21:33atria it's obvious what these will
21:35become the primitive atria is going to
21:37become
21:37both the left and right
21:42atrium it's going to become the left
21:44atrium and the
21:45right atrium the last portion here
21:49below the primitive atria is called the
21:52sinus venosus
21:54before we kind of write that down though
21:56the sinus venous as we said has inflow
21:58right so there's these are the inflow
22:00tracts we'll name these in a little bit
22:02but there's three inflow tracts entering
22:05into the cytospinosis via this horn and
22:07this horn
22:08this is going to be the right horn
22:12of the sinuspinosis and this is going to
22:14be the
22:15left horn of the sinus venosus but the
22:18the names of the veins that are actually
22:20entering into it
22:21are the same so again what is this
22:23structure here called it is called the
22:26sinus venosus now coming in
22:29via these horns what are the names of
22:31the veins that enter into it
22:34you have the common cardinal veins so
22:37you have what's called the common
22:38cardinal veins
22:43and then generally that's going to be
22:44the ones that are on the most outer part
22:46okay then if you come inwards you have
22:49the umbilical veins
22:50so then you'll have the umbilical veins
22:55and then as you become the most inward
22:57these will be your vitelline veins
23:01these will be your vitelline veins
23:04beautiful so now do you remember how i
23:06told you that
23:07once you kind of have an understanding
23:09at this point it's pretty easy
23:11that blood is coming in via these veins
23:14into the sinus venous which will empty
23:16into the primitive atria go to the
23:17primitive ventricle
23:18go to the bulbous cortes which is pretty
23:20much going to make your outflow tracks
23:23that'll then spit that out into the
23:24pulmonary trunk into the aortic arch
23:26and then eventually you'll you'll have
23:27what's called the aortic sac and the
23:28dorsal aortic
23:30right now does this
23:33look like what a heart looks like no
23:36so now what we have to do is there's a
23:39process called
23:40cardiac looping so now what we have to
23:42do is go through a process called
23:44cardiac looping which is annoying as all
23:47crap
23:48but what i really need you guys to take
23:50away from this
23:52is the reason why cardiac looping is
23:54important is it depends upon particular
23:56types of proteins called dyneins
23:59okay and if these dyneins are absent
24:02it can lead to what's called cardiganer
24:04syndrome
24:05and this is basically where someone can
24:08have they either have absent cilia but
24:10the big part here
24:11is that the heart doesn't actually loop
24:13properly
24:14and form properly you know what happens
24:17it actually doesn't normally for a
24:18normal person the heart will kind of
24:20actually bend kind of two thirds to the
24:22left of the midstern line
24:24if you have some type of dish issue with
24:26these dyneins
24:27guess what happens the art doesn't
24:28actually bend to the left it bends to
24:30the right
24:31and this can lead to dextrocardia or
24:33sometimes what's called situs inversus
24:36okay so it's important to understand why
24:38cardiac folding
24:39is important because you need these
24:41dyneins to allow for that to occur
24:44all right nonetheless what i want you to
24:47take into consideration here is we're
24:48going to start this cardiac looping
24:50process
24:50let's kind of denote these just the
24:52truncus arteriosus here
24:54right trunk is arteriosus this is our
24:56bulbous cortis
24:58this is our primitive ventricle this is
24:59our primitive atria
25:01and then here at the bottom you'll have
25:02your sinus phonosis okay
25:05what i want you to know here is that
25:06what happens is that the the truncus
25:08arteriosus and the bulbous cortis start
25:11kind of like
25:11moving to the right and downward so the
25:14first part of cardiac looping
25:16is the truncus arteriosus and the
25:18bulbous cortes
25:20kind of start moving downward and to the
25:23right
25:24all right so truncus arteriosus and
25:26bulbous cordis
25:28move down
25:31and to the right
25:35and by doing that you start to get this
25:37configuration okay
25:40then what happens is the bulbous cordis
25:42and
25:43continues to kind of move downward the
25:45truncus arteriosus
25:46continues to kind of move downwards and
25:48to the right but then the primitive
25:50ventricle
25:51starts to move towards the left of the
25:53midline
25:54so now the primitive ventricle is going
25:55to start moving to the left of the
25:56midline so now look what happens
25:58as that happens the truncus arteriosus
26:00bulbous core to start moving a little
26:01bit towards downwards and to the right
26:04so you get this kind of configuration
26:05here the primitive ventricle is going to
26:08move
26:08left of the midline so then this is
26:10going to be your primitive ventricle
26:11and the primitive atria actually kind of
26:13gets sucked into the back they start
26:15kind of moving
26:16backwards so then back here you're going
26:18to have your primitive atria
26:20and your sinus phonosis with your inflow
26:22tracts right
26:24now here's what i want you to understand
26:28because it's
26:28very difficult to imagine this you're
26:31looking at this
26:32from kind of a frontal view okay so
26:35you're looking at this kind of head-on
26:38if i were to take this and turn it where
26:41you were looking at this from a side
26:42view
26:43you would get kind of something like
26:45this so remember
26:47what connects the primitive what
26:48connects to the primitive atria above
26:50the primitive ventricle so here let's
26:51have kind of the primitive ventricle
26:53here
26:54and what happens is here we'll have
26:55bulbous cordis primitive ventricle
26:58and then coming here backwards
27:03is going to be your primitive atria and
27:05then coming off of that is going to be
27:07your sinus phonosis
27:08right so what you actually see here is
27:11when you're looking you're looking at
27:12this view
27:13the primitive atria is actually going to
27:15start moving
27:16backwards and then upwards
27:20so the primitive h will move backwards
27:22and upwards
27:24and then look what happens here all
27:25right so we understand right with the
27:27primitive atria it has to move where
27:30it moves backwards and then it starts
27:32moving upwards
27:33right so as it starts to move backwards
27:36and
27:37upwards they start to pop up over
27:40the bulbous cordus and the primitive
27:42ventricle so now you have the primitive
27:44atria here
27:46right you still have your truncus
27:48arteriosus
27:50you have your bulbous cortis you have
27:52your primitive ventricle here
27:54right and then again you can't see it
27:56but again what will be coming
27:58off of the primitive atria coming behind
28:00this
28:01this is going to be the sinus venosus
28:05right so it's starting to somewhat look
28:08like a heart right
28:09because the primitive ventricle will
28:10become the left the perimeter of h will
28:12form your right and left atrium
28:14your bulbous cortis will form the right
28:16ventricle and then the outflow tracts
28:17and the truncus arteriosis will make the
28:19pulmonary
28:20trunk and the aortic arch right so we're
28:22starting to get some of this view
28:25now what happens is you got to remember
28:27as this cardiac looping is occurring is
28:30actually kind of occurring
28:31inside of this pericardial cavity here
28:34so what i want you to think about here
28:36is we have this
28:38type of pericardium here right this is
28:40our pericardium
28:42okay and you have the pericardium
28:45you have the different portions of it
28:46right like you have the outer fibrous
28:48pericardium and then you have the inner
28:50what's called parietal pericardium don't
28:52worry about that right now
28:54what i do want you to understand is
28:57is that if you guys remember you had
28:59that structure here called the sinus
29:01venosus
29:02right the sinus venosus does two very
29:05interesting things
29:07it starts to actually allow some of the
29:09cells within this area
29:12to move into the pericardial cavity
29:15and as it moves into the pericardial
29:17cavity
29:18it starts to form around the heart
29:22okay and as it starts to form around the
29:24heart you start to get this layer
29:26underneath of the pericardium what do
29:28you think this is called
29:30that's called your visceral pericardium
29:32so the sinus venosus
29:34is giving way to what structure the
29:38visceral
29:40pericardium all right
29:43one more thing that i also think is
29:45important
29:46in the beginning weeks like week four
29:49week six
29:51some of the cells of the sinus venosus
29:53even infiltrate into the heart
29:56and start to form some small like
29:59primitive conduction system
30:01that allows for the heart to start
30:02beating and you can detect that on
30:04transvaginal ultrasound around week six
30:06so not only does the sinus venous give
30:08way to the actual visceral pericardium
30:11but it also gives way to what's called a
30:12primitive kind of conduction
30:14system that can be detected during the
30:18gestational development
30:20all right cool now we've taken and
30:24developed our heart tube we looped the
30:26crap out of it
30:27we formed it inside of the pericardial
30:29cavity we layered it with a visceral
30:31pericardium
30:31and now it's starting to even have a
30:33little bit of a primitive beating type
30:35of activity
30:36now what i really want us to do is to
30:39take these primitive atria
30:42right and then your primitive ventricle
30:44and your bulbous cordis
30:46and really start developing septations
30:49or
30:50forming chambers that separate the atria
30:52from one another
30:53and separate the atria from the
30:55ventricles that's the next step
30:57let's do it all right so now let's go
30:59ahead and take and start kind of
31:01first forming the next goal we formed
31:04the heart tube
31:04we looped it we put in the pericardial
31:07cavity we made some layerings we have
31:08some conduction
31:10the next goal that i want us to
31:11accomplish here
31:13is to actually form um what's called an
31:17two av canals in other words a canal
31:21between the atria and the ventricles
31:23both a right av
31:24canal and a left av canal that's the
31:26first goal
31:27let's do it so if you guys remember what
31:30was the structure here you guys will
31:31know this by the end right so truncus
31:32arteriosus
31:34bulbous cortis primitive ventricle
31:36primitive atria
31:38sinus venosus there's actually a little
31:41sulcus
31:43between the primitive atria
31:46and the perimeter ventricle so right
31:47here i'm coming through that little
31:48sulcus there
31:49that's called your av sulcus i'm making
31:53a
31:53section right here between the primitive
31:55atria and the primitive ventricle
31:57what i want you to imagine is when i
32:00make this
32:00cut this is what we're looking at we're
32:02literally looking at the inner aspect of
32:04the heart tube
32:05okay this is going to be the posterior
32:08portion of the heart tube
32:10and this is going to be the anterior
32:12portion of the heart tube
32:13now the next thing i need you to imagine
32:16out here coming at you like it's coming
32:20out into actually hit you in the face
32:22is going to be the primitive atria okay
32:25then going
32:26into the board is the primitive
32:28ventricle okay
32:29so you're looking at the posterior
32:31anterior portion
32:32and this view coming out primitive atria
32:35going in
32:35primitive ventricle what i need you to
32:38first understand is
32:40is that you guys remember those pesky
32:42little neural crest cells
32:43i know you guys do those pesky little
32:46neural crest cells
32:48start actually kind of migrating here so
32:50here we're going to draw a couple neural
32:51crest cells
32:52so here's some neural crest cells
32:56those neural crest cells will start
32:58migrating into this area
33:00and start forming little kind of like
33:03cushions that come off the posterior
33:06portion
33:08and that come off of the anterior
33:10portion
33:11so these neural crest cells are going to
33:13move in here and they're going to start
33:15forming like little cushions
33:16okay what are these things here called
33:18they're called endocardial cushions
33:20these would be your anterior endocardial
33:22cushions and this would be your
33:24posterior endocardium collisions right
33:26so here we'll put here endocardial
33:28cushions endocardial cushion this would
33:31be the post here that would be the
33:32anterior
33:34as these endocardial cushions coming
33:36from the neural crest cells continue to
33:38grow grow grow grow grow
33:39guess what they do they fuse
33:43together and when they
33:46fuse together something very interesting
33:49happens
33:51where you start to develop two little
33:54canals right so now i have a little kind
33:58of like canal here
34:00a little canal here and a little canal
34:02here and what was above here
34:04primitive atria what was going into the
34:06board primitive ventricle
34:08that's very interesting we'll talk about
34:10what that is in just a second but what i
34:12do need you to know
34:13is that when those endocardial cushions
34:15come together and fuse
34:16they make a special name we got to give
34:18it a special name
34:20this is called the septum
34:24intermedium so the septum intermedium
34:28is the structure that is formed when the
34:30posterior and anterior endocardial
34:32cushions from the neural crest cells
34:33come together and fuse
34:35when they fuse they now beautifully
34:38separate
34:39the primitive atria and the primitive
34:40ventricle and form two little canals
34:43what are those little canals okay let's
34:45do it again
34:46here's our septum intermedium formed by
34:49those other cardio cushions coming
34:51together
34:53and then here on one side
34:56of the septum intermedium is going to be
35:00an av canal this one here
35:04is called your right
35:08a v canal
35:11and this one here is called your left av
35:16canal so now i have
35:19a separation of some form between
35:23the left side of the heart in some ways
35:26and the right side of the heart
35:27is that cool let's take it and look at
35:29this in a different view
35:31so now what i want you to do is i want
35:32you to take the heart like we had over
35:34here
35:35and kind of cut it okay cut it like in a
35:38coronal section
35:39and you're going to get this view here
35:42so if we kind of take a look here
35:44imagine this wasn't here for a second
35:46imagine that wasn't there
35:48up here would be your primitive atria
35:50and let's just say here's primitive
35:51ventricle
35:52here's part of that bulbous cordis again
35:53right so if you wanted to say this here
35:55let's just say that this was part of the
35:56bulbous cordis
35:58let's say this was the primitive
35:59ventricle and this was a primitive atria
36:01this was a primitive atria
36:07remember what was forming between these
36:09two but it was coming
36:11like this what was it those endocardial
36:13cushions come together
36:14and they made what septum intermedium
36:18now here's what's really cool coming off
36:21of
36:22the septum intermedium some of these
36:26actual endocardial cells start kind of
36:28forming these little like
36:30valves that come off of them
36:34so they form like these little valves
36:36and then they connect the valves
36:38together
36:39you know how they connect the valves
36:40together they make this thing called an
36:42annulus ring
36:44and then from that annulus ring comes
36:45these little valve flaps
36:47and then guess what comes from the valve
36:49flaps guess what comes off of those
36:51little pesky valve flaps
36:53your chordae tendini so
36:56now from that septum intermedium
37:00what did i do i formed valves on both
37:03sides of it
37:04and a valvular annulus and little i tend
37:07tonight i just formed the valvular
37:08apparatus
37:10but i formed a valvular apparatus on one
37:13side
37:13particularly this is the left side guess
37:15what this is going to become get this
37:17guess what this valvular apparatus will
37:18become this will become the
37:21mitral valve this will become the
37:24mitral valve apparatus or sometimes
37:28referred to as the
37:28bicuspid valve guess what this one will
37:31become
37:32the tricuspid valve oh man isn't that
37:35cool
37:37that is so cool okay so now i form the
37:40tricuspid valve
37:41apparatus so from the septum intermedium
37:45i formed a right av canal what is this
37:48canal here
37:50right av canal and over here i form a
37:54left av canal and off of the septum
37:57intermedium what comes off
37:59the mitral valve on the left side
38:00tricuspid valve on the right side
38:02and then also what forms along with
38:04those valves the valvular apparatus
38:06which is the annular ring
38:08and the chordae tendonite let's keep
38:11going
38:11we've now formed a right kind of
38:14inflow from the atria to the ventricles
38:17right
38:18and we formed a valvular apparatus to
38:20provide what is the purpose of the
38:21valves to provide a one-way flow in
38:24other words to prevent backflow
38:25from these ventricles in this case
38:27primitive ventricular bulbous cord is
38:29back into the primitive atria
38:30that's the whole purpose now
38:33the next thing that we have to do we
38:35formed these kind of av canals on the
38:37right and left side
38:39now let's separate the primitive atria
38:40let's form a right atrium and left
38:42atrium
38:43now this is very i can't stress this is
38:45so high yield
38:46if there's anything that you guys take
38:48away from this this is one of the big
38:49ones because
38:50a lot of like diseases can develop
38:53because of
38:54a malfunction in this process okay
38:57so from this point here here we have our
39:00primitive atria let's actually kind of
39:01annotate this here's a primitive atria
39:04on this side primitive atria on this
39:06side and then you still know you have
39:07bulbous cordus and primitive ventricle
39:10coming down the middle of this primitive
39:13atria
39:14you get a little septum and this septum
39:17comes almost comes all the way down to
39:19meat
39:20with this what is this little brown
39:22structure here in the mental middle
39:25that is our septum intermedium so you
39:27have this kind of like tissue here
39:30that tries to grow downwards from the
39:32top of the primitive atria down towards
39:33the septum into medium
39:35but doesn't actually reach it what is
39:37this tissue here called
39:39this tissue is called the septum
39:45primum it's called the septum primum
39:49and because it doesn't reach all the way
39:51down to the septumenter medium
39:53it creates a little space if you will
39:56what is that little hole there called
39:58well guess what the name of this was
39:59septum primum you know what a name for
40:01holy ostium
40:02so it's ostium primum so this little
40:05hole here is called the
40:08osteum
40:12beautiful okay so in this first step of
40:16developing chambers between the atria
40:17you have a septum prima come down to
40:19approach the septum intermedium doesn't
40:21reach it
40:22creates a space called the osteum primum
40:24what's the next thing that happens
40:26let's come up we have again
40:30septum primum but guess what septum
40:33primum continues to grow
40:34grow grow grow and eventually it does
40:37reach
40:39the septum intermedium the septum
40:42intermedium was here in the center and
40:43again what color was it in this
40:44situation
40:45it was brown
40:49so what happens here the septum prime
40:51finally went down
40:52closed off the osteon primer but guess
40:54what
40:55another hole develops but it develops
40:58towards the top
40:59of the septum primum what is this little
41:03hole here called so this is still
41:04what is this structure here called this
41:06is we're going to abbreviate it septum
41:07primum but a little hole in the septum
41:11primum develops towards the top after it
41:13completely moves all the way down
41:15what is this little hole here called
41:17this is called
41:19the ostium
41:22secundum
41:25crazy names so this is called the ostium
41:28secundum
41:29all right so now we formed the ostium
41:31secondum within the septum primal what's
41:33the next thing that happens all right
41:34let's let's get into it right
41:36sounds like i'm naming transformers
41:37right now osteum secondum and
41:40septum prima all right let's get back
41:42into it
41:43so first thing that we have here is what
41:44do we do we formed the
41:52all right so now let's tell you what's
41:54the m second man
41:55from the septum primer here so we're
41:57gonna put that down right there
41:59so now we have our septum primum
42:04with this little space there called the
42:06osteum secundum
42:07right so again right here septum primum
42:10and then what is this little space here
42:12called
42:13this is called the ostium secundum
42:17now another thing happens here
42:21another piece of tissue starts growing
42:24and this son of a gun starts coming down
42:26to try to block
42:28the osteon secundum what is this one
42:31it's another transformer it's called the
42:33septum sequundum
42:35alright so we got the septum secundum
42:38what is this one here called
42:39this is called your septum secundum
42:45so now here's what's really important
42:48we've now
42:48formed a septum
42:51secundum to block the ostium secundum
42:55but there's still a little space here
42:58you see this tiny little space like
42:59right here between the septum secundum
43:02and the ostium secundum there's a name
43:05for that little structure there
43:08this is called the foramen
43:12oh val you know why that's really
43:14important
43:15is the baby's sitting in utero and
43:17amniotic fluid it can't really breathe
43:19so what happens is the blood will come
43:22into this
43:24eventually the right atrium bypass the
43:27right atrium because you know the right
43:28atrium goes to the right ventricle
43:29pulmonary circulation goes to the lungs
43:32we don't need blood to go to the lungs
43:33when the baby's in utero that much
43:35so what we do is we bypass the blood
43:37from the right atrium
43:38into what's called eventually going to
43:40be the left atrium
43:41left atrium left ventricle goes to the
43:43systemic circulation which doesn't go to
43:45the heart
43:45i mean go to the lungs okay why is this
43:49important
43:50because eventually the foraminal vowel
43:52will close but if it doesn't
43:54it can lead to what's called a patent
43:55foraminal valley you know why that's
43:57important
43:58is because sometimes if people develop
44:00like little clots in their legs called
44:01dvts
44:02they can come up via the right atrium go
44:05to the left atrium
44:06left ventricle and guess where they can
44:08go up into your brain and cause a stroke
44:10it's called a paradoxical embolus
44:12they're not very common
44:13but again it's if this does not close
44:17alrighty so now we've developed a
44:20septation
44:22between the primitive atria so now i can
44:25technically call this side what
44:27the right atrium and i can now
44:30technically call this side the
44:32left atrium oh that's so cool
44:36now let's separate our bulbous cortes
44:42and our primitive ventricle because we
44:44know primitive integral is going to
44:45become what
44:46left ventricle bulbous quarter should
44:48become the right ventricle and then the
44:49other part the other the superior part
44:51of the bulbous cortes
44:52becomes the outflow tracks watch this
44:56all right so now let's erase this and
44:59again what was this little tissue here
45:01this was called your septum intermedium
45:04at the apex of the heart at the apex
45:08you start to develop some tissue here
45:12that starts moving its way upwards
45:15from the apex and this tissue here as it
45:18moves
45:18upwards towards the apex is given a
45:21particular name we're trying to form
45:23another
45:23septum but this septum that we're
45:26actually making here
45:28is called the muscular portion
45:31of the interventricular septum what is
45:33this one here called
45:34it's called the muscular portion
45:38we're going to abbreviate this of
45:41interventricular
45:42septum then guess what
45:46we still have a little space here
45:49between the bulbous coordinates which
45:50become the right ventricle
45:51and the perimeter ventricle which will
45:53become the left ventricle this space has
45:55to get filled
45:56so what happens is from the septum
45:59intermedium
46:00some tissue moves downwards
46:03and starts to fuse with this
46:07muscular portion of the interventricular
46:08septum what is this tissue here called
46:11this is called the membranous
46:15portion of
46:18the interventricular septum why is that
46:21important guess what
46:23if the membranous portion of the
46:24interventricular septum doesn't come
46:26down and meet the muscular portion of
46:28the interventricular septum guess what
46:29you develop
46:30a little hole a ventricular septal
46:33defect
46:33so that's another reason why this is
46:35very important
46:37so what have we done now technically
46:41i now have this portion of the bulbous
46:44cortes
46:44is technically now the right ventricle
46:48and now this primitive ventricle is
46:49technically now the
46:51left ventricle now remember i don't want
46:53you guys to get confused the bulbous
46:55cordis makes two things
46:56right ventricle and the outflow track so
46:58we still have to talk about the other
47:00portion of the bulbous cortes
47:02but one portion of it just made our
47:03right ventricle what have we done
47:05we took a heart tube septated it to form
47:08an
47:09interatrial septum an interventricular
47:11septum a right av canal a left av canal
47:15what do we got to do now let's get some
47:17inflow tracks coming into that right
47:19atrium
47:20all right so the next thing i want to do
47:21is i want to kind of develop an inflow
47:23tract
47:24into particularly the right atrium
47:28so the next thing we have to do is take
47:29another section here remember this was
47:30our primitive atria here
47:32this was our sinus phenosis i'm going to
47:34come
47:35right around this level here
47:38and we're going to look at this
47:40structure here so i'm cutting it off
47:42here
47:43you're just getting the top portion here
47:45of the primitive atria
47:47or the bottom portion of the primitive
47:48atria and then here you're still getting
47:49a little bit of that sinus venosus
47:52i remember what were the veins
47:55where i just want i'm not going to
47:56actually write them down i want to see
47:57if you guys remember them
47:59coming into the sinus gnosis we have the
48:00inflow tracts
48:02from the outsides what were these your
48:04common cardinal veins
48:06here what were these umbilical veins
48:08here what were these
48:09vital and veins the the common cardinals
48:12the umbilical and the vitelline veins
48:14empty into their
48:15horns this was the left horn
48:19and this is the right horn
48:22all right so what i need you guys to
48:23understand is again we have the left
48:24horn right horn
48:25feeding into the sinus venosus which
48:27will feed into the primitive atria
48:29okay now remember
48:32left horn right horn are fed by three
48:34vessels right we had again
48:35what were these common cardinal veins on
48:37the outside and the middle
48:39is your umbilical and on the most inner
48:41part are your vitalin veins
48:43what happens is all of the veins on the
48:45left horn break down
48:47all that's left over is just the left
48:48horn so now i just have the left horn
48:53okay then on the right horn we're just
48:56going to abbreviate this
48:57r h what happens is
49:00the um umbilical vein actually starts to
49:04degenerate and all that's left over
49:06feeding into the right horn
49:08will abbreviate this is the common
49:10cardinal vein and the
49:12vitalin vein so all that's feeding into
49:15the right horn is the
49:16common cardinal vein and the vitelline
49:17vein and all the tributaries off of the
49:19left horn
49:20break down the next thing is not only do
49:23those actual tributaries break down
49:25but the left horn starts kind of
49:27shifting towards the right
49:29and actually kind of fuses with the
49:31right horn
49:32a little bit before it enters into the
49:34sinus phenosis
49:35so again here we had above this
49:39where these horns enter in your sinus
49:41vinosus and then above this would be the
49:44primitive atria now here's what i want
49:45you guys to remember
49:48when this is actually fusing right
49:51whenever
49:51these structures are all kind of like
49:53changing and going through their kind of
49:54digression and
49:56specializing this sinus phonosis gets
49:59absorbed
50:01into the primitive atria so the sinus
50:03venosus will get absorbed into the
50:05primitive atria
50:06so whenever the sinus venous gets
50:08absorbed into the primitive atria the
50:09left horn
50:11is going to develop a very special
50:12structure guess what this little
50:14little structure is this is called your
50:17coronary
50:19sinus so the coronary sinus is formed
50:22from what
50:22from the left horn
50:26then again whenever the sinus vinosus
50:28gets absorbed into the primitive atria
50:30the common cardinal vein
50:31is going to be up here towards the top
50:34this
50:35common cardinal vein will be what's
50:37called the superior
50:39vena cava the superior vena cava is
50:42formed from the
50:43right common
50:47cardinal vein
50:52and then this bottom part here remember
50:54how the actual from the right horn you
50:55had the
50:56vitelline vein whenever the sinus venous
50:58is absorbed into the primitive atria
51:00this right here is the inferior vena
51:03cava
51:04and the inferior vena cava is formed
51:07from the
51:09vitalin vein which one particularly the
51:12right
51:13vitality okay so that's what i wanted
51:16you to understand so the inflow tracks
51:18coming into the atria
51:20because of the left horn shifting
51:22towards the right
51:24and all of its tributaries breaking down
51:26and kind of
51:27feeding into the right horn a little bit
51:30before it enters into the sinus phonosis
51:32whenever that gets absorbed into the
51:33primitive atria it gets absorbed into
51:35the right side of the primitive atria
51:38and again coronary sinus is formed by
51:40the left horn
51:42the supreme vindicator is formed from
51:43the right common cardinal vein
51:46and then the inferior vena cava is
51:47formed from the right vitalin vein
51:50beautiful and then these are taking
51:51blood
51:53and emptying them into
51:56the right atrium isn't that cool so now
51:59not only formed
52:02left atrium right atrium right ventricle
52:04left ventricle
52:05right av canal left av canal we also
52:07have the inflow tracks coming into the
52:09right atrium
52:10isn't that cool now we got to come to
52:13the annoying part
52:14now we finally have to go over the
52:17bulbous cordus and the truncus
52:18arteriosus
52:19and how they make those outflow tracks
52:21let's do that now
52:22all right so we're looking at another
52:24kind of again kind of a coronal section
52:26of the heart
52:27and again so you can kind of have an
52:29idea here we've already formed our right
52:31atrium
52:32we've already formed our left atrium
52:35we have let's say that we we haven't
52:37covered let's just kind of
52:38rewind a little bit and say at this
52:39point we haven't formed
52:41the membranous part of the
52:42interventricular septum but for the most
52:44part
52:45we have our right ventricle we have our
52:48left ventricle here and here you can see
52:50like these little canals you see those
52:51little canals those little holes there
52:53that's your right av canal and that's
52:55your left av canal okay
52:57now remember we said that the this
52:59portion of the right ventricle is made
53:01by the
53:01bulbous cortis right but we also said up
53:04here we have another portion of the
53:05bulbous cortes
53:07and up here we have a portion of the
53:08truncus arteriosus
53:10okay what i want us to do is i want us
53:14to take a
53:15cut from here and here
53:18and really kind of look and see what is
53:21actually
53:22happening that we form a defined aorta
53:26and a defined pulmonary trunk and then
53:29on top of that the valves that are going
53:32to be allowing for a one-way flow
53:34from the right ventricular outflow tract
53:36and left ventricular outflow tract
53:38into their respective pulmonary trunk
53:40and aorta okay
53:43so if we take a section here and here we
53:44get this kind of structure here
53:46so again at the top top portion here is
53:49going to be your truncus arteriosus
53:52and towards this bottom portion here is
53:54going to be
53:55the bulbous cordis okay
53:59all right beautiful now what
54:02happens is you start to form
54:06little again neural crest cells what are
54:08they for what are they called again
54:10neural crest cells start to infiltrate
54:14into these areas here so some of these
54:16neural crest cells
54:19are important for forming what's called
54:20the aortic pulmonary septum
54:22but some of these neural crest cells
54:26they kind of migrate into this area here
54:28okay
54:30when they migrate into this area they
54:32start forming
54:33little like endocardial ridges or kind
54:36of
54:36cushions kind of coming outwards at the
54:39truncus arteriosus is the top part
54:42you get a truncal ridge that forms like
54:45this
54:47okay and then another truncal ridge
54:50that forms like this okay
54:54at the bottom part of the bulbus cordis
54:58you get a bull bar ridge that kind of
55:00comes in like this
55:02and again you get another bull bar ridge
55:05that comes in like this
55:06okay now there's another
55:10ridge in here that has actually formed
55:12but it's not in a view that we can see
55:13this is forming like on a left side and
55:15a right side
55:16kind of coming towards each other
55:18there's another one
55:19in the middle you can't see the way it's
55:21forming
55:22but it's forming from like an anterior
55:24posterior view
55:25so what i'm going to do here is i'm just
55:26going to kind of draw it like this
55:28so you have a ridge coming from the
55:29anterior portion and you have a ridge
55:31coming from the posterior portion and
55:33they're trying to approach
55:34one another whenever these ridges kind
55:36of approach one another and come
55:38together
55:39they do this kind of like spiraling
55:43around the central axis all right so now
55:46what i want you to remember is that
55:47those truncal ridges
55:49right they come together and whenever
55:51those truncal ridges come together at
55:53the top part
55:54right where the truncus arteriosus is
55:56they kind of form this like little
55:57septum that separates this
55:59kind of whole what is going to become
56:02the aorta and the pulmonary trunk into
56:03two sections which will again
56:05give us one portion of that little
56:07septum will flow into the pulmonary
56:09trunk
56:09one of that section will fall into the
56:11aortic arch but again what happens here
56:14at this level of the truncus arteriosus
56:15here
56:17okay this is going to be forming what's
56:19called truncal ridges
56:20and again what happens is the truncal
56:22ridges
56:24come together fuse and then kind of form
56:28a nice little septum here
56:30same thing at the bottom right here at
56:33that
56:33bottom portion here where the bulbous
56:35cordis is
56:37again you get those bull bar ridges
56:38coming from both of these edges
56:40and they meet in the middle and form a
56:43nice little septum
56:44okay so again you have those nice bull
56:46bar ridges
56:49they come together and they make a
56:51little septum
56:52and then we said here in the center
56:54still part of the bulbous cord is
56:56technically another area we call the
56:57conus cordis we're not going to get too
56:59much into that
57:00but they form anterior to posterior so
57:02we're just going to kind of draw a
57:03central line there
57:05what i want you to now do is that
57:08because
57:09the way the coconus cordis
57:12ridges form and lead to a septum it
57:15causes this entire
57:17septum that runs down the link of the
57:19top from the trunk of arteriosus to the
57:21bulbous cordus
57:22to kind of corkscrew and so now
57:25follow this edge and have it kind of
57:27move through
57:28the middle here and kind of come to the
57:31other
57:32edge here come from this edge here
57:36have that go through the center and meet
57:39at that point
57:40now all this does is this creates
57:43a nice little septum here
57:47what is this septum here called this
57:50septum here
57:51is called the aort let's actually erase
57:53this part here
57:54this is called the aortico pulmonary
57:56septum so what is this called here
57:58this is called the aortico
58:02pulmonary
58:06septum and it's basically just kind of
58:09separating the aorta
58:11from the pulmonary trunk pretty
58:13straightforward right
58:14now from the
58:18bulbous cortes and the primitive
58:19ventricle we already said that the blood
58:20was kind of moving up through this right
58:23as it moves up through this here's
58:25what's really interesting
58:28the blood flow okay
58:31from the left ventricle will move
58:35through this posterior portion okay from
58:38this bulbar septum
58:39it'll move via this posterior portion
58:43when it moves via the posterior portion
58:45it'll move through the
58:46back part of this aortic pulmonary
58:48septum so it'll kind of move under
58:50it when it moves under it it comes out
58:52from here
58:53like this so it kind of moved under it
58:55from the back
58:56when it does that it then moves over the
59:00top part of this aortic pulmonary septum
59:04and then out through this anterior
59:07portion
59:08okay out through this anterior portion
59:10formed by that truncal septum
59:11so this blood flow coming from the left
59:14ventricle
59:15moving outwards and coming up through
59:17this front portion here
59:19this is going to be giving way to the
59:22aortic arch okay
59:26in the same way let's follow this front
59:29portion here
59:29so in the anterior portion of the bulvar
59:32septum at this point
59:33the blood will be coming through this
59:36anterior portion here when it moves
59:39through the anterior portion it moves
59:41in front of the bottom part of the
59:44aortic pulmonary septum
59:48and then when it gets to this kind of
59:50like corkscrew point at the conus
59:52it moves behind this top part of the
59:56aortic pulmonary septum
59:57and when it moves behind it comes up
59:59through the
1:00:01back part of that actual truncal septum
1:00:05and this is going to give way to the
1:00:07pulmonary
1:00:10trunk and this blood
1:00:13is going to be coming from the right
1:00:15ventricle
1:00:17so the aortic pulmonary septum is formed
1:00:20from
1:00:20neural crest cells that lead to little
1:00:22ridges truncal ridges at the top
1:00:24bulbar ridges in the bottom forming from
1:00:26kind of like the left and right
1:00:28towards the center and the center what's
1:00:30called the conus cordis
1:00:32there's ridges that are forming from
1:00:34posterior to anterior
1:00:36because the way these ridges actually
1:00:38form
1:00:39and the center anterior posterior and at
1:00:42the top
1:00:42and bottom from left to right it creates
1:00:45a
1:00:46corkscrew type of fashion here which is
1:00:48called the oracle pulmonary septum
1:00:50blood flowing in through the back part
1:00:53at the bulbar region
1:00:54where that septum is comes underneath
1:00:57the bottom part of the
1:00:58oracle pulmonary septum and over the top
1:01:01of the top portion of the oracle
1:01:03pulmonary septum out via the aortic arch
1:01:05and then blood flowing through the
1:01:07anterior portion or ventral portion at
1:01:09the bottom
1:01:10part of the bulbous cortex will move
1:01:11over this bottom portion of the aortic
1:01:13pulmonary septum and move
1:01:15under this top portion of the article
1:01:17pulmonary septum and come out via the
1:01:18pulmonary trunk
1:01:20the next thing that happens is this
1:01:23actual whole kind of aortico pulmonary
1:01:25trunk like structure
1:01:27will rotate and so once it undergoes
1:01:30this rotation
1:01:32it kind of splits
1:01:36these structures up it splits them up
1:01:39and then you get this beautiful little
1:01:41set up here
1:01:42and this is how i remember this kind of
1:01:44blood flow where it's moving with
1:01:46respect to this
1:01:47blood flow coming from the left
1:01:49ventricle moves up via the aorta
1:01:52and where does it go with respect to the
1:01:53pulmonary trunk it moves underneath
1:01:56the pulmonary trunk and then moves over
1:02:00the pulmonary arteries so you can kind
1:02:02of follow that same flow
1:02:04with respect to the aortic pulmonary
1:02:06septum it goes underneath
1:02:08and then over the same concept here with
1:02:11the pulmonary trunk
1:02:13blood is coming from the right ventricle
1:02:17moving up via this pulmonary trunk where
1:02:19is it going with respect to the aorta
1:02:21it's going above the aorta
1:02:24and then underneath
1:02:28the aorta look over here it's going
1:02:30above
1:02:31and then going behind so it's a nice
1:02:33little way to remember kind of that
1:02:34blood flow pattern
1:02:37now let's take this structure now we've
1:02:40formed
1:02:41our aorta we've formed our pulmonary
1:02:43trunk
1:02:44we start having our outflow tracks let's
1:02:46now just connect
1:02:48that to the ventricles and you now see
1:02:51this beautiful little setup here look
1:02:53what we've made
1:02:54we've made a right atrium we've made a
1:02:58left atrium we've made a left ventricle
1:03:00a right ventricle
1:03:02the right ventricle form from the
1:03:03bulbous cordis and again these
1:03:05top portions here this portion here and
1:03:07this portion here
1:03:08the outflow tracks from the right
1:03:10ventricle and the outflow traction from
1:03:11the left ventricle are made via the
1:03:13bulbous cordis so this is your outflow
1:03:16tract
1:03:17outflow tract then coming out into the
1:03:21pulmonary artery coming out here into
1:03:23the
1:03:24aorta beautiful look at that
1:03:28we've made something here it's pretty
1:03:30cool
1:03:31but we're not done yet now what we have
1:03:35to do is
1:03:36is we have to form little valves between
1:03:39the ventricles
1:03:41and their corresponding arteries let's
1:03:43do that now
1:03:44all right ninja nerds we are so close to
1:03:46being done
1:03:47okay the next thing we got to do is we
1:03:50got to start talking about making the
1:03:51semilunar valves
1:03:53so where we got to go is again go back
1:03:54to this structure here
1:03:56where we the where the trunk is
1:03:57arteriosus and the bulbous cortes is
1:04:00we're going to go right here kind of
1:04:02along that that
1:04:03junction okay technically remember i
1:04:05told you there's the bulbous cortes and
1:04:07then technically in the center between
1:04:09the bulbous cortes and the truncus
1:04:10arteriosus is called the conus cortis
1:04:13we're going to make a section right
1:04:16there so what we're looking at here
1:04:18is a cross section
1:04:22at the bulbous
1:04:29cordis and conus
1:04:33cordis junction
1:04:36it's one heck of a thing there okay all
1:04:39right so what we're looking at this
1:04:40in view wise is this anterior here
1:04:43posterior here
1:04:45right side here left side here okay
1:04:49what starts to happen is you start
1:04:52making these little endocardial cushions
1:04:54so again
1:04:55those neural crest cells kind of come
1:04:57here and they start making these like
1:05:00endocardial cushions that form from the
1:05:01right side here
1:05:04form from the posterior portion
1:05:09form from the left and then
1:05:12form from the anterior portion here so
1:05:15again i have four total cushions
1:05:17one from anterior one posterior one from
1:05:19the right one from the left side
1:05:21then what happens is during that process
1:05:25where you were kind of doing this little
1:05:27bit of rotation
1:05:28it's starting to kind of form like this
1:05:30little like uh
1:05:31invagination if you will and what that
1:05:34does is it kind of like
1:05:36splits these little cushions here the
1:05:38right and left ones to where they kind
1:05:40of go like this
1:05:41so look at that now so now here you have
1:05:43that right into a cardio cushion there
1:05:45you still have that anterior cardio
1:05:47cushion indicator cushion there
1:05:50left endocardial cushion like this
1:05:53and then posterior endocardial cushion
1:05:55like that so again we'll kind of give
1:05:57you the
1:05:58diagram kind of anatomy here anterior
1:06:02posterior right left
1:06:06eventually what happens is remember what
1:06:09we said
1:06:10as you form that aortic pulmonary septum
1:06:13it
1:06:13rotates right so that corkscrew like
1:06:15structure that you form the aortic
1:06:16pulmonary septum
1:06:17we said it rotates and when it rotates
1:06:20and kind of forms these little
1:06:21invaginations it splits into two
1:06:24portions
1:06:25okay you're gonna get
1:06:28this posterior portion here
1:06:31okay and then you're going to get this
1:06:33anterior portion here
1:06:34now here's what i want you to think
1:06:35about
1:06:38you're going to still have this little
1:06:40piece
1:06:41right here from that posterior
1:06:43endocardial cushion
1:06:44right then a half let's actually kind of
1:06:47cut this in half here
1:06:49with a nice little distinguishable
1:06:51marker here with this one
1:06:54i'm going to cut this in half and cut
1:06:55this in half this portion will go here
1:06:58this portion will go here this will go
1:07:00here this will go here
1:07:02so now in this little like
1:07:05tube if you will this will become where
1:07:07the valve is this outflow tract
1:07:09this will have a posterior cardio
1:07:11cushion and then half of that right
1:07:14endocardial cushion and then half
1:07:18of that left endocardial cushion
1:07:22same thing here in the anterior portion
1:07:23you'll get a half
1:07:25of the left endocardial cushion you'll
1:07:28get a half
1:07:29of the right endocardial cushion and
1:07:31you'll get the whole
1:07:34anterior endocardial cushion this
1:07:37posterior structure this posterior
1:07:39outflow tract
1:07:41is going to be for the aorta so this
1:07:44will be the left ventricular outflow
1:07:46tract
1:07:47this one will be your right ventricular
1:07:50outflow tract
1:07:51the left ventricular outflow track will
1:07:53flow into the
1:07:54aorta and the right valine check of the
1:07:56outflow tract will allow for outflow
1:07:58into the
1:07:59pulmonary trunk and now
1:08:02what else have i formed here my valves
1:08:06these right here are my semi
1:08:09valves and then what would these be
1:08:13if we think about them respectively if
1:08:14this is at the left ventricular outflow
1:08:16tract level
1:08:17that's going to be for the aorta these
1:08:18are the aortic semilunar valves
1:08:21if this is for the right ventricular
1:08:22outflow tract and which is going to feed
1:08:24into the pulmonary trunk this is your
1:08:25pulmonary semilunar valve
1:08:27and then again not only did we have this
1:08:29invagination
1:08:31and splitting into two different types
1:08:33of outflow tracts
1:08:34what else happens rotation so remember
1:08:37how we have rotation at this point
1:08:39same thing is going to happen we have to
1:08:40have rotation
1:08:43and whenever we have this rotation
1:08:47it puts the aorta a little bit kind of
1:08:50more posterior and on the right side
1:08:53and the pulmonary trunk a little bit
1:08:55more interior into the left side
1:08:57because you know whenever you listen to
1:08:58heart sounds when you're listening to uh
1:09:00the pulmonary valve which side are you
1:09:02listening to
1:09:03you're listening to the patient's what
1:09:05to their left side
1:09:06and if you're listening for the aortic
1:09:07semilunar valve you're listening to the
1:09:09right side
1:09:11so now if i draw this here kind of
1:09:14continuing here i have my semilunar
1:09:16valves here and again
1:09:21right here
1:09:24and again this is going to be the aortic
1:09:27semilunar valve semilunar valves
1:09:31and the left ventricular outflow tract
1:09:34and again this is going to be on the
1:09:35right side i like to remember that
1:09:37because when i'm listening for heart
1:09:38sounds i listened
1:09:39to which side the right is like second
1:09:40intercausal space and an adult
1:09:43whereas over here you're going to get
1:09:45your pulmonary
1:09:48semilunar valve and the right
1:09:51ventricular outflow tract and that's
1:09:52going to be on your
1:09:54left okay i'm listening for on the adult
1:09:57the left
1:09:57second intercostal space so this
1:10:01is how i actually form these valves so
1:10:02now let me just take now that we've done
1:10:04this
1:10:05what do i got to do here here's my
1:10:07outflow tracks
1:10:08between the pulmonary what am i going to
1:10:10have right here
1:10:11pulmonary symmetry valves what am i
1:10:14going to have here
1:10:15aortic semilunar valves and then again
1:10:17we've already formed them here you can't
1:10:18see them but you already have your
1:10:19tricuspid
1:10:21and your mitral valves we have now
1:10:23formed the heart
1:10:26all right ninja nerds in this video
1:10:27today we talk about the development of
1:10:30the heart
1:10:31i hope it made sense i truly hope that
1:10:34you guys enjoyed it
1:10:35and if you did like it please continue
1:10:37to support us ninja nerds
1:10:39we can't do this without you ninja nerds
1:10:40we love you we thank you and as always
1:10:42until next time now that we've done that
1:10:45let's move to the next part and start
1:10:47going through what happens
1:10:48after we form this osteum secundum
1:10:50sounds like i'm naming transformers
1:10:52right like
1:10:53the ostium secondum roi the septum
1:10:56problem
1:10:57all right let's let's never mind let's
1:10:58get back to it
1:10:59[Laughter]
1:11:07i gotta do that then right like a
1:11:09british the ostian primum
1:11:14is it the austin problem in the ocean
1:11:16second or the english
1:11:18i don't know like like the mega megatron
1:11:21or something like that i don't know that
1:11:22was actually really good
1:11:24all right back down can i keep that yeah
1:11:27you can
1:11:29the austrian secunda man i'm going to do
1:11:31it again
1:11:33all right i promised the laugh that was
1:11:34pretty funny
1:11:37good yep all right so now we formed the
1:11:40ostium secondum within the septum prima
1:11:42what's the next thing that happens all
1:11:43right let's let's get into it right
1:11:45sounds like i'm naming transformers
1:11:46right now osteum secondum and the
1:11:48septum project all right let's get back
1:11:51into it
1:11:52so first thing that we have here is what
1:11:54do we do we formed the
1:11:56dang you robert dang
1:12:00you
1:12:04crikey cronky
1:12:12[Laughter]
1:12:15are we doing this again let's do it
1:12:17again we're good
1:12:19okay i'm gonna
1:12:25[Laughter]
1:12:28oh me
1:12:39[Music]
1:12:49you