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