Early Embryogenesis Flashcards
Ovulation is when
an oocyte gets released from the ovary and swept up by fimbriae. This then goes to the fallopian tube
By Day 7, what consists of the inner cell mass(embryoblast?)
epiblast and the hypoblast
Week two consists of
Doubling of everything, where the embryoblast forms two layers : the epiblast and the hypoblast,
The trophoblasts splits into the: cytotrophoblast and syncytiotrophoblast,
2 cavities form: aminotic and yolk sac cavities
the two mesodermal layers of the somatic and splanchnic layers
By day 7, what consists the make up of the zygote?
- Inner cell Mass
- Outer cell mass
- Blastocyst cavity
Splanchnic mesoderm vs. somatic mesoderm
Splanchnic is inner
What surrounds the oocyte for the sperm to get through for fertilization?
Zona pellucida
What needs to happen in order for implantation to occur
- Loss of Zona pellucida
2. Enter the uterus for proper implantation (no ectopic implantations)
What is the step after the morula called
Blastocyst, where the cells are arranged on the outside with a blastomere making up the blastocyst
What can cause conjoined twins?
splitting of the primitive node
When does gastrulation occur?
Week 3
What occurs around Day 13?
Implantation Bleeding, which happens from excess blood due to the sealing of the embryo within the endothelial wall of mom. The yolk sac is gone by this point
What does the chorionic cavity give rise to?
extra embryonic cavity that gets smaller as the amniotic sac gets larger.
What is Gastrulation
Epiblastic cells invaginate to create the three layers: ecto, meso, and endoderm. Another layer allows for the notocordal plate to form, then the notochord.
Cloacal membrane
Anus
Trophoblast function
Nutrition
Week three consists of
tri laminar formation, where the epiblast forms the ectoderm, mesoderm, and endoderm.
Where does the egg get fertilized?
Ampulla of the fallopian tube
What is the inner cell mass a precursor of?
the embryo
Where does the primitive streak grow?
on the midline, caudal to cranial toward the oropharyngeal membrane
Result of fertilization
Zygote is formed (2n).
Sex is determined
Cleavage of cell for dividing cellular material is initiated
What is at the 16 cell stage?
Morula, which has all totipotent cells. It takes 3 days to turn into this
Amniocentesis
baby drandruff water
How many hours does it take for the fertilized egg to divide to a zygote?
30 hrs
Advanced Morula
DAY 6: enters the lumen of the uterine cavity
What will the syncytiotrophoblast show as a sign of pregnancy
hCG secretions
How long do spermies chill in the ampulla for before receiving signal from the egg to speed over for fertilization
12-24 h
Teratogenesis seen in gastrulation
Holoprosencephaly, Cyclopia, sirenomelia, sacrococcygeal tumors
How much can sperm travel time vary from?
30 minutes to 6 days
What is the purpose of the notochordal plate, and then the notochord?
allows for communication between the epiblast area and the yolk sac. Notochord is what allows proper signaling of forming surrounding structures.
By Day 7, what consists of the outer cell mass?
Syncytiotrophoblast: multinucleated fused cytotrophoblasts
How many days post fertilization does the Blastocyst form?
~ 5 days
Week one consists of
fertilization and implantation of the zygote
What will the syncytiotrophoblast give rise to?
The placenta
