Transcript for:
Mappa del Destino durante la Gastrulazione

Hello! I am Dr Aizaz from medicovisual.com and  in today's visual lecture we will talk about fate   map during the gastrulation process. As we  have discussed previously in the lecture of   somatogenesis and changes in the intra-embryonic  mesoderm that if we peel off this ectodermal layer   of the embryo the intra-embryonic mesoderm will  be revealed. Now what we have discussed already   that this intra-embryonic mesoderm it is not  a single homogeneous undifferentiated layer   instead it consists of different parts and those  parts are here is the neural tube and notochord.   This neural tube of course is not the part of  intra embryonic mesoderm but just remember that it   is there and along with that this is the notochord  which is also called axial mesoderm and then we   have par axial mesoderm which runs parallel to  this axial mesoderm but slightly laterally and   more lateral to paraxial mesoderm the most lateral  structure is the lateral plate mesoderm and in   between the par axial and lateral plate mesoderm  is the intermediate mesoderm. So, what we have   observed is that intra-embryonic mesoderm consists  of different components. Now how these different   components of intra-embryonic mesoderm are formed  during the process of gastrulation? Here is the   ectoderm and here is the endoderm and here I have  made this ectoderm slightly transparent. So, you   can see what happens. So, during the process of  gastrulation in third week the cells that ingress   downward from this primitive node or henson's node  they will form the notochord and pre-chordal plate   and the cells that ingress downward from this  primitive streak they will form different   components of intra-embryonic mesoderm, they will  form all those components the paraxial mesoderm,   the intermediate mesoderm, the lateral plate  mesoderm and even some contribution towards   the extra embryonic mesoderm. Now let's see what  happens. So, here is the ectoderm, here is the   endoderm, the primitive node and primitive streak.  Let's make the endoderm transparent and now first   cells that go from this primitive node they will  form the the prechordal plate and the notochord   and now the cell that, that ingresses  downward from the cranial most part,   from the cranial most part of primitive streak  and some cordolateral part of the primitive node   these cells that ingress from this point they will  form the par axial mesoderm. Right, now the point   to understand here is that the fate of these  ingressing cells is determined by the location   from which they ingress downward. For example:  these cells that ingress downward from the cranial   part of the primitive streak they will form the  par axial mesoderm and then let's move forward   here are those cells which ingress from the  midstream, from the middle part of the primitive   streak these cells will form the intermediate  mesoderm and then those cells which ingress from   the caudal part of the primitive streak they  are going to form the lateral plate mesoderm   and finally the cells that ingresses from  the caudal most part of this primitive streak   they will contribute towards the extra embryonic  mesoderm. Now extra embryonic mesoderm it, it is   thought to be formed from the hypoblast cells  during third week of development but there is   also some contribution done by these ingressing  cells in that third, during the third week of   development. Now what you can understand from  this diagram is that the medial most component,   the medial most component of the intraembryonic  mesoderm that is notochord here it passes from the   cranial most part of the of the primitive streak  and primitive node and lateral most part of,   of this intra-embryonic mesoderm it is contributed  by those cells that ingress from the caudal most   part. For example; here you can see that the  lateral most part is the lateral plate mesoderm   and it is contributed by those cell which ingress  through the caudal most part of the primitive   streak. So, the primitive streak and primitive  node they are thought to be the real guiding   stars during this process of gastrulation. Now  by the way what is the extra embryonic mesoderm?   We have already talked about extra embryonic  mesoderm during the second week of development   but let's briefly reorient ourselves  with the extra embryonic mesoderm.   Now you must be aware of the fact that this  ectoderm it continues dorsally with the   amnion. Right? And this, this endoderm it  continues ventrally with another balloon-like   structure that is called yolk sac. So, the  embryo is provided with two balloons the amnion   and the yolk sac and these two balloons  along with this embryo whole the structure   it is plastered outside, it is surrounded  outside by the extra embryonic mesoderm. So,   this is the extra embryonic mesoderm. So,  extra embryonic mesoderm during it is formed   during the second week of development and it is  thought to be mainly formed by the hypoblast cell   but it is also contributed by the cells  that ingress from the caudal most part   of the primitive streak. These cells they also  contribute to the extra embryonic mesoderm. So,   this was about the fate map during gastrulation.  Thank you so much for watching this video.