Second Week of Development Flashcards
Trophoblast forms 2 layers
inner layer of cells- cytotrophoblast
outer layer- syncytiotrophoblast
Embryoblast differentiates to form a bilaminar embryonic disc of 2 layers
The epiblast (thicker) and the hypoblast
A small cavity appears in the epiblast that enlarges to form what?
the amniotic cavity
What does the amnion formed by amnioblasts do?
encloses the amniotic cavity
Days 9-10 the hypoblast now becomes what?
the exocoelomic cavity
The exocoelomic membrane and exocoelomic cavity are modified to form what?
the primitive yolk sac
When does the blastocyst become fully embedded in the endometrium?
Day 10, site closed by fibrin coagulum
When is uteroplacental circulation established?
Days 11-12
Formation of the primary villi
the cells of the cytotrophoblast proliferate and penetrate into syncytiotrophoblast forming cellular columns that are surrounded by syncytia
Where does the exchange of materials (oxygen and nutrients) between the blood of the mother and the embryo take place?
through the walls of branch chorionic villi
Where is the embryo, amniotic sac, and umbilical vesicles suspended?
the chorionic cavity
What does the syncytotrophoblat produce?
hCG which by the end of the 2nd week can be detected by a pregnancy test
Hydatidiform mole
trophoblast forms placental membranes but there is no embryonic development
Placenta previa
placenta bridges the internal os of the cervix causing severe, life-threatening bleeding in late pregnancy and during delivery
Placenta accreta
abnormal adherence of the placenta to the myometrium
