development question

[biology_06er]

Hi there......

I was doing an old exam paper and I am unsure what this question is asking...can someone please help me..i just wanna know what they want by the lineages...are they talking about the trophoblast/inner cell mass??

QUESTION:
Describe the formation of the first 2 cell lineages in the preimplantaion mammalian embryo

Thanks in advance
biology_06er

[MrMistery]

They are probably reffering to the formation of the embryo proper and the extraembryonic membranes(basically, inner cell mass formes the embryo, the trophoblast formes the membranes). But the question is pretty basic..