Embryo ? about Prim Streak

[jakstat33]

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i don't have my Sadler handy (it's in the med bookstore), SO:

in FA 2003 (pg. 81) it says that the epiblast invaginates to form the primitive streak which gives rise to cells that form both intraembryonic mesoderm and endoderm... however, in a QBank explanation it writes that the prim streak gives rise to mesoderm and notochord (and specifically excludes endoderm)

which is accurate?

thanks

 

[babinski bob]

i don't have my Sadler handy (it's in the med bookstore), SO:

in FA 2003 (pg. 81) it says that the epiblast invaginates to form the primitive streak which gives rise to cells that form both intraembryonic mesoderm and endoderm... however, in a QBank explanation it writes that the prim streak gives rise to mesoderm and notochord (and specifically excludes endoderm)

which is accurate?

thanks

As I understand it, the epiblast cells which migrate into the primitive streak become the mesoderm and endoderm. Those epiblast cells which don't migrate will become the ectoderm, neuroectoderm, and neural crest cells. Following epiblast migration, I think the primitive streak then becomes the notochord which as you know is important in neurulation.

 

[Idiopathic]

As I understand it, the epiblast cells which migrate into the primitive streak become the mesoderm and endoderm. Those epiblast cells which don't migrate will become the ectoderm, neuroectoderm, and neural crest cells. Following epiblast migration, I think the primitive streak then becomes the notochord which as you know is important in neurulation.

This is all true.

 

[mpsheeha]

Yep, all is true. This reply might not be needed but just to solidify the things already said. You start out with essentially a "solid sheet" of cells. Involution at the primative streak gives you a three layered embryo with the classic endoderm (inner layer), mesoderm (middle layer), and ectoder (outer layer). The way this was explained to me was that the involuting cells that move first become endoderm and those that follow become mesoderm. The cells that remain on the surface become ectoderm (and thus neuroectoderm and neural crest). Importantly, the notocord is of mesoderm origin and induces the overlying ectoderm to differentiate into neuroectoderm.

Hopefully the three of us have helped to answer your question. Note: don't take the term involute too specifically. I use it here simply to mean that the cells move in at the primative streak. If I am remembering correctly there are a ton of very specific terms used to describe the exact method of movement, ie, single cell migration, movement in sheets, ect..... Things that are not important right know I am sure🙂

Good luck.