Thurber RS 2- 1st 4 Weeks of Development Flashcards
What is a zygote called when it reaches the 32 cell stage? What is it called after further mitotic divisions?
32-cell stage–> morula
Morula eventually becomes a blastocyst, which gives rise to the trophoblast and embryoblast
When does the blastocyst implant?
Day 7, although this can vary between 6-10 days
Where is the most common place for an ectopic pregnancy?
Ampulla
What might happen if the blastocyst implants over the internal os?
This can cause a condition called placenta previa, where the placenta covers the uterus, leading to bleeding during childbirth
What might happen if the placenta attaches inappropriately to the uterine wall?
3 conditions can occur, due to improper implantation
Placenta accreta: Placenta is attached to the myometrium
Placenta increta: Placenta is embedded in the myometrium
Placenta perceta: Placenta passes through the entire wall of the uterus
What is the difference between the secondary and tertiary chorionic villi?
Tertiary villi develop blood vessels (villous capillaries), forming connections with the embryo’s developing circulatory system
What are the components of the placenta?
The placenta is made up of a fetal and maternal part
Fetal part: Chorionic plate and villi
Maternal part: Decidua basalis
What structures are found within the umbilical cord?
Two umbilical arteries and one umbilical vein
How is the primitive streak organized as to what parts derive from it?
The cranial end becomes the paraxial mesoderm
The intermediate streak becomes the intermediate mesoderm
Caudal end of the streak becomes the lateral plate mesoderm
Where does the primitive yolk sac develop from? How does the primitive yolk sac develop?
Hypoblast cells migrate along the internal surface of the cytotrophoblast layer to give rise to Heuser’s membrane. This membrane gives rise to the primitive yolk sac, which replaces the blastocyst cavity.
What is the difference between a complete molar and partial molar pregnancy? What hormonal changes may occur with both of these? What may these appear as on an ultrasound?
A complete molar pregnancy is when there is the fertilization of an empty egg by two sperm, while a partial molar pregnancy is the fertilization of an egg by two sperm resulting in a 69xxx, 69xxy, or 69xyy karyotype.
Hormonally, these result in higher than normal hCG levels.
On an ultrasound, they appear as a snowstorm
