Zona Pellucida: Digested or Not?

[gracy]

My textbook says zona pellucida is digested at the time of fertilization but then it mentions that zona pellucida remains intact throughout the cleavage process to avoid /prevent implantation at abnormal places. If zona pellucida is digested at the time of fertilization then how it reappears during cleavage process?

 

[jim mcnamara]

I'm confused -- it appears you are missing an assumption but let's start with assuming we are talking about humans:

From Wikipedia

In humans, five days after the fertilization, the blastocyst performs zona hatching; the zona pellucida degenerates and decomposes, to be replaced by the underlying layer of trophoblastic cells.

Which is somewhat like what you are describing.

Check out this article and follow the links. Then come back with what did not make sense.
https://en.wikipedia.org/wiki/Zona_pellucida

I believe the Wiki article to be pretty good, and unless your textbook is using an older pure mouse model, we should all be on the same page now. Sometimes textbook authors simplify or gloss over something they think you should already know. But they seem not to notice they never have covered it. Upper level math books often are the worst case for this IMO. So, get used to it.

 

[Fervent Freyja]

It is probably only referring to the sperms actual point of entry being "digested".