hey there hi everyone so today we're going to be talking about the neuroembryology it's an introductory leure we're not going to delve into any abnormalities we're going to talk about the high yield basic embryology of the nervous system or uh aka the neur relation so I hope you guys have a good time and uh get something useful out of this lecture so let's start so first of all when we are still an embryo before we develop into you know our full final version of ourselves with all those organs we are basically a tril laminer disc such as the one shown here in this diagram and then this trilaminar dis gets folded that way and becomes this cylindrical tube and then this tube provides us with all the parts of our body such as the skin the the organs all that stuff so this disc here this trilaminar disc is composed of an outer surface called the ectoderm the ectoderm provides us with the outer part of our body such as the skin and the nervous system and the part of the ectoderm that gives us the nervous system is called neuroectoderm okay then the mism provides us with the connective tissue of our body of the the bones the muscles the cartilage all that stuff and then the endoderm provides us with all of our internal organs such as the liver the gut Etc all right so during the third week the new relation starts and our body starts forming the nervous system so we we have something called a notocord it's misal in origin and the part of the ectoderm that provides us with the nervous system which is called the neuroectoderm or another name the neural plate and during the third week the notto cord gives off a transcription factor that causes the neuroectoderm to undergo certain morphologic changes to develop into our mature nervous system so the Sonic Hedgehog transcription Factor has a lot of other functions including the separation of the cerebral hemispheres into right and left cerebral hemispheres as we all know our cerebral hemispheres are composed into uh composed of a right and a left hemispheres and all those little bulges here called the gyri and all those little grooves here called the suai or the salai I don't know really I don't know how they pronounce it but I'm just going to call it suai okay so as we talked about the Noto cord provides the Sonic Hedgehog transcription factor and then this transcription Factor acts on the neuroectoderm and it causes neuroectoderm to cause this slight invagination that we see here and a little bit of thickening like we see here and so we end up with a neural Groove here and two neural folds here then an extra invagination starts happening and then the neural fold endings here form this Crest called the neural crest and then the invagination completes and now we have a closed tube and the neural crest separates like we see here and then the neural tube provides us with a lot of things and neural crust other things and the not cord other things so as for the neural tube provides us with the CNS neurons the endal cells endites asites and those cells we're going to be talking about them in other lectures the neural crest basically provides the peripheral nervous system uh and the Schwan cells melanocytes all those stuff we're going to be talking about that in later videos so basically the neur neural tube provides us with the CNS and the neural crest provides us for the pns for the sake of the of the argument and the Noto cord provides us with the nucleus pulposis okay what is the nucleus pulposis this is our spine okay these are the vertebrae between two vertebras we have the intervertebral disc it provides us with flexibility and it reduces friction between the adjacent vertebrae and it has a central part which called the nucleus pooses it's basically a gelatinous part that's 90% water and this part you know provides the the spinal cord with the flexibility mobility and we have an outer fibrocartilagenous part called the anulus fibrosis as we see here the notocord provides us with this central part called the nucleus pulposis whenever you hear patients saying they had a disc herniation what happens basically is this part right here the nucleus pooses gets herniated out of the anulus fibrosis into the spinal can canal and compresses the spinal cord over here here so Noto cord provides us with the nucleus pulposis so now that we talked about the closure of the neural tube we want to look at that neural tube from above and talk about how exactly does it close Okay so first of all this is the neural tube this is a da Vinci quality drawing I can already sense you guys saying that so what happens first is this middle part here closes like so this happens in day 23 and then the upper part closes and then the lower part closes okay so when the central port closes at day 23 that leaves us with two openings an anterior opening and a posterior opening the anterior opening is called the anterior neuropore or the cranial rostral neuropore or and the posterior opening is called the codal or posterior neuropore the anterior neuropore basically provides us with our brain um and the posterior neuropore basically provides us with the spine if they close if they don't close they'll provide us with problem they will provide us with problems in the brain and problems in the spine okay so first of all day 23 closure of the mid portion of the neural fold then day 25 the anterior portion closes and then day 27 everything closes and by week four the whole neural tube should be closed if this fails to happen then we have something called the neural tube defect which will be the topic of the next lectures so I hope you had a good time I hope you understood something from my ramblings in this lecture and I'll see you in the next one