I an engineer so what we're gonna do in this video is we're gonna continue we left off talking about what happened during the gastrulation process and the development of the notochord what we're gonna do is we're gonna take it from that point of where we left off right with our node accord our trilemma Nordisk and how we're going to completely develop the nervous system it's gonna be awesome let's go and get started all right guys so we started off last we ended off last when we talked about the trilemma Nordisk right so we talked about how we formed the ectoderm mesoderm endoderm and then we finished lastly with how what happened is remember we said that whenever the cells are moving through that primitive pit right and we can't echo you can call those cells that are moving through there well they actually are kind of like Mesa dermal derived cells they form the nodal cord right now what happens is usually to kind of keep up we were at the end of the second week if you really want to be particularly we might be close to about day 15 anywhere from day 15 to day 17 it's about where we're at right now now what happens is is the body is so cool that no decor that good old notochord it starts releasing certain types of growth factors right so this new d'accord starts secreting a bunch of different types of growth factors and when it does this it tells the ectodermal cells start proliferating so again first step here notochord is gonna release chemicals and what's this whole process this whole first event gonna be it's gonna be causing ectodermal proliferation baby and that ectodermal proliferation is going to occur and occur and occur and guess what starts to form in the ectoderm okay so that notochord was releasing a lot of those growth factors many different types it might be a part of you know growth factors like such as fibroblasts it might be transforming growth factor beta there can also be parts of like the wynt pathway the nodal path there's so many different types of pathways that are involved in this not necessarily the most crucial thing what I do want you to know is as the ectoderm starts proliferating and thickening it forms a specific type of plate right which we call the neural plate so again octo dermal proliferation will lead to this kind of like this big thickening of the ectoderm which is going to be called the neural pleat now as we get this thickening of the neural plate what starts happening is the embryo will actually begin to start allowing for this plate to begin to kind of involute right so imagine in like this way here's the plate imagine I'm pulling in this the central line right what's dividing in this into two pieces imagine I'm tugging on that from the bottom right in the center it's gonna pull the center of this plate downwards right at the same time the edges of this neural plate are gonna start working towards one another they're gonna come towards the center right so again central part of the neural plate pull that down edges of the neural plate start rolling towards one another right so that's gonna begin this kind of folding our involution process as that begins to occur look what we get next look at that so now remember that that part I said was here at the bottom imagine here's like that line that we had there right and that's spanning all the way down here from the part of where we had that primitive pit if you guys remember all the way up to the actual pro chordal plate now what's happening is from that part it's pulling down it's in veloute and then the edges of that actual plate are starting to move towards one another now what happens is is you get this part here you see how it's kind of like folding it's getting ready to fold this is going to be called our neural folds and then here this little like u shape or half a circle are almost a complete circle almost a complete tube this is actually going to be called the neural groove right now what happens is some cells start to actually specialize and differentiate right some of those ectodermal so I'll start to proliferate differentiate and become specialized cells you see these orange cells these orange cells are what we call neural crest cells and they kind of form towards the around the edges of neural folds so the neural folds is the edges of the neural plate the neural groove is going to dip down make this little kind of like canal and then the neural crest cells are gonna be kind of right around the edges of the neural folds so again what are these orange cells here called they're called neural crest cells these are important because they're gonna differentiate into a lot of different structures that are important for our peripheral nervous system okay so again neural folds neural groove is going to begin to happen right well what day do we start to see the neural plate right so when does this notochord start releasing certain types of cytokines and growth factors that trigger the neural plate usually approximately day 17 is when we start to see it so you start seeing the formation of the neural plate approximately around day 17 okay somewhere around that now neural folds with the neural groove and the neural crest cells they start kind of growing approximately around day 18 so the next day so you'll see this around day 18 now here's where it gets really good all right the neural folds the edges of the neural folds fuse with one another right the neural groove it completely in volutes and then you form a complete tube right that tube comes underneath the ectoderm and then we form this neural tube look at that look at that little guy right there that's our neural tube so right here we're gonna have the neural tube and remember what do we say we had the neural folds right so remember it's kind of coming in the neural folds are fusing with one another and then right up on top of them you have your neural crest cells well look where they're for me right there where the neural folds fuse together so cool right so again that's our neural crest cells still so neural crest cells and then again what's here below it the notochord right so you sir have the notochord and then the ectoderm is gonna be there right now what's important is we need to look at this from two different views it's nice to look at it like this but it's also nice to look at it from an actual kind of a larger view right so I kind of like a more of a dorsal view so now let's take we had this year where the actual neural folds fused right you get your complete neural tube with the neural crest cells just above it and then no decor below it but look at this view it's the same view instead of us looking at it and the tube kind of straight on now we're looking at kind of a dorsal view all right now our top up view here is going to be the cranial portion okay so up here let's mark this in purple this is the cranial portion of the neural tube and this is going to be the caudal portion of the neural tube now there's a part here of the neural tube right which we call the posterior neuro poor in other words if you imagine kind of like this here's a tube here's the other end of the tube right this tube hasn't completely closed off right so it's open it's kind of like a like a vessel basically let's say that this part appears the cranial this part here is the caudal this is going to be what they called the anterior oh poor and this one here on the bottom is going to be the post here neuro poor now around approximately day we'd say around day 21 you completely form the neural tube my pink marker there it is so around day 21 you completely form the actual neural tube okay but the neuro pores are still open around day 21 okay as the cells continue to proliferate eventually they close up that cranial end and that caudal end or what we call the again what do we call this area here interior neuro poor and post here your neuro poor why am i mentioning this why am i spending so much time line the reason why is in order for this anterior neuro porn post here neuro port to close your cells need a specific type of fuel right and that is called folate folate is so important in order to be able to allow for the cells to synthesize DNA and replicate so with the lack of folate what do you think would happen to the anterior neuro porn post your narrow board do you think it'll close no if it doesn't close guess what can happen you can get defects within the spinal cord so for example things that can happen whenever the anterior or poor doesn't close you can get things like anencephaly you can get things like an encephalocele right what about a post here normal pull where that sucker doesn't close didn't get spina bifida which has the different types right so you know you have spina bifida cystic ax and spina bifida occulta and then there can be complications or associations with that such as arnold-chiari type 2 malformation Gandy Walker syndrome tethered cord syndrome so there can be terrible things even with the anterior neural port and we talked about I said in cephalus field that can actually lead to what's called Mekel Gruber syndrome which can be terrible where they have a cystic renal dysplasia they have polydactyly and they have a part of the brain and meningeal tissue that are coming out in the occipital part right so these are very very important things and for folate usually during pregnancy you need anywhere from about 3 to 5 milligrams per day to be able to maintain this actual proliferative process okay so Foley it is absolutely necessary for the neuro poor closure okay around what day approximately do we see the anterior up or closes and your nope or generally closes approximately around day 24 so around day 24 the anterior neuro poor closes and that's a good thing we don't want that bad boy to be open again if it is it can lead to anencephaly can lead to an ACEF Allah seal right around day 26 approximately the post here no report should close so that should be the posterior no rapport should close all right now once the post Tierney rapport has closed and the anterior no rapport is closed then what can happen is we can take this nice little spinal tube right or basically are what we're gonna lead to the development of the entire central nervous system so this neural tube that we formed is in lead to the development of the entire central nervous system it's unbelievable so we're gonna see how that happens so to make it simple for you what I'm gonna do is imagine I take here right so you're gonna have two anterior or posterior nerve or cranial or cephalic and caudal and all I'm gonna do is take this and just imagine you have a simple tube all right top part here bottom part here it's a phallic end here caudal in here cranial end here caudal in here it's the same thing for all of them and see what happens when we take this little tube and we develop all these different structures it's so darn cool alright so again so what have we covered throughout this entire process all the way from where we started with our trilemma Nordisk all the way until we formed our neural tube that was the process of nourishing alright so again just remember that this is near ulation very simple process nothing crazy to it it's just basically a step of knowing right ectothermic proliferation neural plate narrow groove with the neural folds neural crest cells forming on the edges of those neural folds completely closing up forming the neural tube and then after that anterior oh poor closure at one at 24 post your neuro poor closure at 26 which requires folic acid are fully around approximately 3 to 5 milligrams alright so what we're gonna do now is we're gonna take this tube that we formed to the process of Mary elation right and what we're doing is kind of just pulling it out of this structure that we formed over there right now what we need to do is take this neural tube form of the central nervous system so we have to go through a process called vesicular Sheen so what happens is there's neural tube towards the actual what does this end we got to make sure that we know our end this end up here is going to be V cranial or cephalic in whichever one you prefer it doesn't matter Cottle and we're just gonna be the tail end right towards the cranial end we're gonna form three vesicles it's kind of kind of bulge out those three vesicles are going to be these from cranial to caudal accordingly first one is called the pros and Cephalon okay the second one which is going to be the actual purple one there's gonna be called the mesencephalon and this is basically going to become the midbrain the pros and Cephalon will separate into two other vesicles in a second and the green one here is actually going to be the rhombencephalon and some hako some names for these in the past right but again accordingly rhombencephalon mieze and Cephalon and pros in Cephalon and again what are these structures that we form first this is going to be the primary vesicles so primary vesicles now what happens is these vesicles they even develop even more so they proliferate they start specializing they start curving in different ways and they form some more vesicles now remember we had the pros in Cephalon what I want you to remember is that splits into two parts okay it splits into this top one right the kind of looks like your telescopes this is gonna be called the Teelin Cephalon so the telencephalon is this top one now the pros and Cephalon forms the telencephalon and it forms this kind of like maroonish one which we call the diencephalon the diencephalon and then this purple one you guys should already remember we already covered it it stays the same it's the Me's encephalon that's gonna become the midbrain so this is still the Me's in Cephalon then the rhombencephalon is actually going to break up into a couple different pieces right I saw this green structure here is going to be the mat ten Cephalon all right now the men Cephalon is going to be basically become the ponds but there's another structure that's a part of the mat and Cephalon you see these little like peanuts that are coming off the edge over here these little guys here are going to be forming a part of there's still a part of the mat and Cephalon but they're going to become a part of the cerebellum they're going to become the cerebellum then you've got these orange structures here right so then you've got this next one and this is going to be the myelin Cephalon and that's going to become the medulla so pros and Cephalon becomes the telencephalon which is gonna be your cerebral hemispheres and the diencephalon which is gonna be your thalamus your hypothalamus your epithalamus your sub thalamus mammillary bottles bodies all those good jazz Me's and stuff alone will stay the same it's the midbrain the rhombencephalon will form the Metzen Cephalon right which is going to become the pons and the cerebellum and then the myelin Cephalon is going to become the medulla and then guess what the remaining part here is the spinal cord and we'll talk about how that develops in a little bit so again this last part here is going to be the Kombi spinal cord alright so to finish our all off now telencephalon is going to become this structure right and this is going to become the cerebrum so we're gonna have the cerebrum which has your different lobes you guys know frontal lobe parietal lobe occipital lobe okay even the fifth mini lobe which is the insula temporal lobe then inside of that cerebrum you're have little gray matter structure sprinkled in there and remember I told you that's a part of the diencephalon so a couple of those structures are gonna be your thalamus right you're gonna have the sub thalamus what else are you gonna have you also have the hypothalamus we're not gonna show that here and you'll also have the epithalamus or the part of the pineal gland right so we'll have over here that's gonna be a part of the epithalamus or the pineal gland which is going to also consist of other structures as well so that's gonna be your diencephalon right and again it's gonna consist of thalamus epithalamus hypothalamus sub thalamus and even a part of the mammillary bodies then you have your Emmys and stuff along what did I say that's gonna become the midbrain so mid brain and then the meting Cephalon is going to become two structures right we said that that's going to become what - this green one here is going to become the pons and then the dark green is going to be the cerebellum and then we also have the orange here which is going to be the midbrain I'm sorry medulla medulla oblongata and then lastly again we'll have the spinal cord so it's amazing to see how from a little tube you get your primary vesicles frozen Cephalon B's and Cephalon rhombencephalon frozen Cephalon Meiktila Cephalon diencephalon musing Cephalon stays the same rhombencephalon makes the Metin Cephalon and myelin Cephalon Jilin Cephalon gonna form your cerebrum right all the different lobes diencephalon is gonna be the thalamus sub thalamus epithalamus mammillary bodies hypothalamus measly Cephalon is gonna be technically the midbrain men Cephalon is gonna be the pons and a part of the cerebellum and then the mile and Cephalon is the medulla and then we'll have our spinal cord and we'll talk about all the structures within that part of the spinal cord so it's an amazing process that can happen here which is this process of the circulation okay so what is this process that we basically covered here going all the way for the development of the the brain the brain stem the cerebellum and we'll get into more detail in spinal cord this was the process of vesicular Sheen right so the sick you layin now we got to keep going right so we took that that tube there right that neural tube when we formed these structures but remember there were some cells that were right on the kind of surrounding that neural to remember that we talked about the neural crest cells these little suckers are so darn cool so we have to talk about in this part here is I want us to discuss the neural crest cell differentiation because these little buggers they can they just do a bunch of things they turn into a bunch of different structures so what do these little guys do well they move all over the place they're just moving right and they become multiple different types of structures where all over the place so what are some of the things that they can become well you know your skin cells your Milano sites that are within the the stratum Visalli right of the skin the epidermis they're gonna be become those they're gonna become the melanocytes the melanocytes what are they important for they produce pigment that allows for us to be white or brown or black all the different types of colors so again they're going to become Milano sites what else they can migrate to these little structures that are sitting on top of our kidneys where they can become what's called the enteric Ramah fence also just the chromaffin cells that secrete epinephrine and norepinephrine that I'm important within the actual catecholamine surge for our stress response what is this they can actually come down here and form and become a part of the adrenal medulla and again this is a part of the sympathetic nervous system right so again you know the sympathetic nervous system you have pre ganglionic axons that come out into this adrenal medulla and those are gonna be long they come and they sign apps on these little postganglionic motor neurons which are very short and they release lots of epinephrine and norepinephrine so again remember these are important because they make epinephrine and they also make norepinephrine and if your member is 80/20 pretty cool stuff right all right next thing they also can and they can actually develop not to the actual structures of our gut right because that's the that's the part of the endo derm but they can derive into the nerves that are important and surrounding that structure if you remember the submucosal nerve plexus right we also call it the meissner's plexus or if you guys remember the my enteric plexus or the arbok plexus they're important with what structure the enteric nervous system and they're all within that submucosa and what else muscularis externa so what are these structures here these darn things are important right because they help to involve structures for the enteric nervous system enteric nervous system and again what are some of the structures of the enteric nervous system in case you might have forgot remember you had the submucosal plexus and then another one is going to be the my enteric plexus and if you like the old school name you can also remember sub mucosal also known as meissner's don't know how to spell it not going to my enteric plexus is our box plexus so that's pretty cool right that helps to regulate our GI T all right what else they can also migrate just outside of the spinal cord into these neurons the pseudo unipolar neurons that are located outside of the spinal cord what are these little guys well if you remember a lot of the sensory information comes in to these little pseudo unipolar neurons which has a peripheral process picking up information from the periphery and a central process which is going into the actual spinal cord that's our dorsal root ganglion so the dorsal root ganglion should be here so here's the dorsal root ganglion so they're important also for making that but guess what else not just that let's let's amp it up but let's involve the sympathetic ganglia this is gonna be where the what you know how you have the lateral gray horn right the lateral gray horn which is particularly within t12 l2 right which is for the sympathetic ganglia the preganglionic the preganglionic sympathetic fibers are supposed to be short there's only supposed to go a small distance where they go into these little Chang ganglia or the pre vertebral right so you have pair of vertebral right or chain right and then over here you have pre vertebral or collateral it's whichever one you like but what's important is that the preganglionic fibers are going into where these cell bodies are and then those axons move out guess what these are again let's write them down jeez my market a little bit here we go so this one is actually going to be the chain ganglia and this one is going to be your collateral ganglia this is basically all part of the sympathetic nervous system ganglia sympathetic chain paravertebral pre vertebral collateral ganglia they also can develop into these so cool all right what else my narrow crest cells can also develop into these layers of the brain you know you have the brain right any of the spinal cord and then surrounding that you have the first layer which is clinging to the brain and spinal cord that a little pink layer what does that guy called that's called the Pia mater so this is the Pia mater and then what's just outside of that which is going to be forming this spider-like layer with where the subarachnoid space is or there's a lots of cerebrospinal fluid this is the arachnoid mater now together these two modders make up what's called the lepto meninges okay so the leptomeninges are also going to be made by the neural crest cells pretty darn cool right now the neural crest cells also help with formation of a lot of the muscles and bones and different types of structures that have formed the head and the neck right as well as the nerves that are going to be supplying parts of those ferengi alar ch's right so you have friends you larches we're not going to go into that right now in another video we will but the head in the neck and then you're gonna have nerves which is applying the fringe of arches what are some of the nerves that supply the French arches well the first one first French arch you should remember is going to be cranial nerve five and a trigeminal nerve so that's going to be one there are crest cells help to be able to form those also cranial nerve seven which is the facial nerve that's going to be a part of the actual French Alaris and nine and ten the some books will also say that three and eight some of three and eight can also be a part what the neural crest cells can differentiate but for right now we're just gonna say five seven nine and ten these are helpful because these are gonna be nerves of the Ferengi alar chah's all right now not only does it help for the formation of five seven nine and ten cranial nerves but also again for the structures of the head and neck so let's also remember structures of the head and neck muscles the bones different things like that it's also important for okay and if you really want to remember something else you get little bones in the ear right the little bones in the middle ear the ossicles right malleus incus tabes it also can develop into those structures too if you really want to remember that Southall's are pretty cool so again this is going to be the neural crest cells differentiation so we cover with the top cranial part of the neural tube forms we covered what the neural crest cells becomes now we got to cover what the bottom part of the actual neural tube develops in again remember what we said here don't matter how you remember just remember your orientation cranial or cephalic I like cranial because it's easier to spell and claudel okay head tale we covered this part we cover the neural crest cells now let's cover the caudal portion what I want to do though to make it easier for ourselves is to see how it actually derives from the inside-out so what I'm going to do now is I'm going to take a cross-section so what I'm do is I'm going to go right there because generally all of the upper structures right brain brain stem that's all going to be formed up here I want to see how the spinal cord develops down here so I'm gonna take a cross-section and look on it from the okay now we haven't formed the spinal cord yet but we do have is the neural tube and I want to look at the neural tube so imagine I'm cutting it and I'm holding it like this now and I'm looking down the neural tube well you know the neural tube it might just look like this thin thing but it's actually made up of three layers okay we're not going to go into crazy detail on everything in these layers but I what I want you to know is that these three layers are going to be consisting of the green layer the outermost layer which is called the marginal zone this is generally where the neurons are going to start actually forming so the neurons and their axons right here is going to be the mantle zone in the mantle zone is going to be where you have your neuro blasts okay and then inside here is the most inner layer and this is going to be the neuro epithelial layer neuro epithelial zone and what's happening is is these cells are proliferating and they're becoming neuroblasts and then these neural blasts are becoming neurons and they're starting to develop and move their way outward from this central neural tube so what I wanted to do now is we take this whole tube like we had here you just imagine it as this little circle again okay so imagine this circle contains all of these layers the marginal zone the mantle zone and the nura epithelial zone and as it's replicating right going from the neuropathy lleol zone to the mantle zone to the marginal zone it's making structures that are gonna be extending out from that at that point right what are those things well the first thing that's gonna happen here is this gonna make like these little bunny ears that come out here right it's gonna make these little bunny ears that extend out here so the cells again from the neuro epithelial zone you're going to get again mantle marginal and the cells are going to start working their way out and making these bunny ears that are extending towards the actual posterior part so if you imagine the spinal cord if I'm taking a cross-section this is the dorsal surface or the posterior surface and this is going to be the ventral or the anterior surface of that spinal cord right now what happens is this neural tube form structures that are going to be working its way post here towards the dorsum and then it's gonna have some other structures that it's actually going to work its way let's do this and let's do this color that's gonna work its way anteriorly look at this and these two things are specific structures they have specific names right so here the top part the little ears I want you remember like a little bunny ears these are going to be called your this is your owl or plate okay so that's your owl or plate your owl or plate is going to be forming these little bunny ears that are extending their way dorsally from the actual neural tube and that's going to be imagine you have a point of symmetry here so imagine here we have a sulcus and then a fissure right so imagine here you're gonna have a point of symmetry bilateral symmetry from here working its way out like posterior Li and laterally you're gonna form these outer plates and then ventrally and laterally you're going to form your basal plates why is this important because what eventually happens is is your outer plate it's gonna start looking like something very very similar what is this thing here well if you guys remember this is going to be called the posterior gray horn so all this is the posterior horn extending from that neural tube then extending eventually and laterally is going to be the aunt hair gray horn now our plate right we said this is going to make again this is gonna be our ventral gray horn and then the our plate is going to make the posterior or dorsal gray Horn what kind of neurons are the posterior horn are they sensory or they motor they're sensory so these are going to be where your sensory neurons are and what kind of neurons are going to be forming here on the ventral gray horn or the anterior horn these are going to be motor and then again guess what little that the remnants of that actual neural tube is leaving a nice little spinal canal what's in that spinal canal nice little cerebrospinal fluid so inside of this you're gonna have cerebrospinal fluid now that should cover everything that you need to know for the development of the neural tube and the neural crest cells iron engineer so in this video we covered a decent amount of information I hope it made sense I hope you guys really did enjoy it I really hope it helped that's the whole point that's what we want to make happen is for you guys to be able to understand this stuff I know it can't be complicated but I hope we were able to help we're gonna continue this embryology series and what we're gonna do next is we're gonna move into the next process which is taking that saito trophoblast and since is your trophoblast and seeing how it implants and makes the placenta that'll be our next process that we're going to attack but I hope this video made sense I hope you guys did enjoy it if you guys did please hit that like button comment down the comment section and please subscribe also if you guys could go down to the description box go check out our Facebook or Instagram our patreon account and also our GoFundMe page if you guys could donate any money we would really appreciate it it would help us to continue to make videos for you guys enjoyment but I love you guys ninja nerds you guys are the best fans ever and as always until next time [Music]