First and Second Week of Development Flashcards
What is an autoradiography? How is it conducted?
A way to identify the specific chromosomes.
The cell is cultivated in the presence of timidin, which is labeled by radioactivity.
When does compaction happen?
On day 3.
What is compaction?
Individual outer blastomere tightly adhere through E cadherins and gap junctions.
How do different cells develop?
The inside-outside hypothesis: depending on the position of the cells, this will determine its fate. If it’s in the outer position, then it will become the trophoblast. While if it’s in the core, it will become the inner cell mass.
The cell polarity model: different fates for cells depend on the plane that drives the type of differentiation.
What happens on day 4-5 of gestation?
Cavitation occurs, this is caused by the accumulation of Na+ (Na/K pump) and H2O among inner blastomeres.
Differentiation of the cells into the trophoblast and the inner cell mass also occurs.
When does the blastocyst attach to the lining epithelium of the endometrium?
On day 6.
When is a blastocyst formed?
A blastocyst is formed when cavitation has occured, at approximately day 5.
What is an ectopic pregnancy?
This is where the egg implants anywhere beside the normal area in the epithelial lining of the endometrium in the uterus.
Describe how the blastocyst cells differentiate.
The cells in the outer area will become the trophoblast, the envelope of the embryo. While the cells inside will give rise to the inner cell mass.
How does the blastocyst implant into the uterine wall?
When the embryo is implanting, there is a layer of surrounding trophoblast cells which mediate implantation.
They form protrusions (microvilli) and are initially single mononucleated, but start fusing together to form syncytiotrophoblast cells that mediate implantation.
These cells stimulate apoptosis of the maternal cells, which is important for the release of nutrients. The cells destroyed released molecules which are used by the syncytiotrophoblast cells to nourish the embryo.
What is the decidual reaction?
The endometrial connective tissue cells undergo a transformation, the decidual reaction.
After the cells swell because of the accumulation of glycogen and lipid in their cytoplasm, they are known as decidual cells.
This enlargement of the cell is important for its nourishment, as there is no endogenous system at the moment to guarantee oxygen and nutrients.
What is cavitation? How does it happen?
Cavitation is when a cavity is formed inside the morula.
Accumulation of Na+ (Na/K pump) and H2O among inner blastomeres causes ‘cavitation’.
What do trophoblasts differentiate into when in contact with the endometrium?
Into syncytiotrophoblasts and cytotrophoblasts.
What does the inner cell mass differentiate into?
Into hypoblasts and epiblasts.
How is the excocoelomic membrane (Heusser’s) formed?
When the hypoblast cells proliferate and covers the blasto cell cavity, also transforming into a primitive yolk sac.
