Physiology of embryology Flashcards
What do you call it when a sperm and egg fuse?
They create a zygote
What are the zygotes called when they split?
2 cell phase
4 cell phase
8 cell stage
16 cell stage
What do you call it after a 16 cell stage?
Morula
(16+ cell stage until it becomes a blastocyst)
Describe what is formed after a morula.
A blastocyst is formed around day 6/7. There is a hollow ball with cells clumbed to one edge:
Inner cell mass and outer cell mass
At this point the blastocyst sheds the zona pelucida and implants in week 2(day 7)
Another name for outer cell layer of a blastocyst?
Trophoblast
Another name for inner cell layer of a blastocyst?
Embryoblast - contains stems cells
What do the trophoblasts become?
Cytotrophoblast cells - key for embedding the embryo into the uterus
Syncytiotrophoblast cells
How do syncitiotrophoblasts form?
Synctiotrophoblast forms from the proliferation of the cytotrophoblasts, the breakdown of their cell membranes. A syncitium of these cells. What stays is the nucleus of these cells and cytoplasm.
What are the two layers of the BILAMINAR embryonic disc?
Hypoblast - cuboidal cells
Epiblast - columnar cells
What are the two layers of the BILAMINAR embryonic disc? What type of cells do they contain? At which week is this formed? What is above and below?
By week 2, the embryoblast differentiates into:
Epiblast - columnar cells
Hypoblast - cuboidal cells
Above epiblast - amniotic cavity
Below hypoblast - York sac
Whta else happens on day 10 besides primitive yolk sac formation from the hypoblast?
Lacunae start froming on the synctiotrophoblast
By the end of day 10, what has happened?
The blastocyst has completed embedded in the endometrium.
What does the syncitiotrophoblast do?
Invades uterine bessles, ruptures maternal capillaries so there is a pool of blood in the lacunae.
This creates an INTERFACE between maternal blood and embryonic ECF, allowing passive exchange of substances.
What hormone does the syncitiotrophoblast produce?
beta-HcG - this maintains the corpus luteum to keep making progesterone, to maintain the endometrium (remember STB is all about blood and maintenance).
