Lecture 13: bilaminar embryo Flashcards
blastocyst composed of
inner cell mass and cavity
when does implantation usually begin
5-7 days after fertilization at the blastocyst stage
what does the inner cell mass turn into
epiblasts and hypoblasts
what is the amniontic cavity created from
the epiblasts create a cavity
what initially attaches to the endometrium
cytotrophoblasts
what does the blastocyst cavity become
the exoceolomic cavity (primary yolk sac)
what does the yolk sac endoderm give rise to
a layer of extraembryonic mesoderm which surrounds the yolk sac, bilaminar disc, and amniotic cavity
how is the secondary yolk sac formed
spaces form in the extraembryonic mesoderm and these come together to form the extraembryonic coelem. this pinches off part of the primary yolk sac forming the secondary yolk sac.
what is the function of the secondary yolk sac
early transfer of nutrients, early blood development, provides primordial germ cells
where does the prechordal plate develop
thickened circle of hypoblasts in a localized area of bilaminar embryo
what does the prechordal plate determine
the head region of the embryo (future site of the mouth)
what does the hypoblast become
endoderm of yolk sac which becomes extraembryonic mesoderm
what does the epiblast become
ectoderm of amnion, embryonic ectoderm, primitive streak
what does the primitive streak become
extraembryonic mesoderm, embryonic mesoderm, notochordal process, embryonic endoderm
when is the due date
40 weeks (280 days) after the first day of the last menstrual period
