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17: Embryology - Weeks 1 & 2
Terms in this set (21)
Where does fertilization occur?
Ampullary region of fallopian tube
What are the 3 steps of fertilization?
1. Capacitation (sperm conditioning to enter zona radiata)
2. Acrosome Reaction (protein reaction after binding to zona pellucida)
3. Fusion (sperm + oocyte)
How can Pelvic Inflammatory Disease affect fertilization, and what can cause PID?
Pelvic Inflammatory Disease prevents successful migration (narrowed FT)
Caused by STDs (gonorrhea or chlamydia)
What's a morula and what is it made up of?
16 cells -- inner cells (embryo) plus outer cells (trophoblast)
What creates the blastocyst?
Fluid enters zona pellucida into intracellular spaces -- forms a "blastocele" cavity
Where does the blastocyst hatch and implant?
What are four examples of abnormal implantation?
1. Ectopic (tubal)
2. Cervix (placenta covers cervix)
4. Intra-abdominal (pouch of Douglas, mesentery)
What are the two layers that the trophoblast divides into during week 2?
What does the syncitiotrophoblast do?
1. Makes HCG
2. Erodes endometrium
What is HCG?
Human Chorionic Gonadotropin maintains corpus luteum to maintain progesterone production
What can go wrong with trophoblast growth?
Abnormal growth with high HCG -- little to no embryonic tissue.
Hydatiform mole (benign) or choriocarcinoma
What are the two layers that the embryoblast divides into in week 2?
epiblast (next to amniotic cavity) and hypoblast ("under" amniotic cavity)
What are the two cavities that form in week 2?
Chorionic cavity and amniotic cavity
What creates these two cavities?
Extraembryonic mesoderm splits
What are the two extraembryonic mesoderms that form?
somatopleuric and splachnopleuric mesoderm
Where is the somatopleuric mesoderm?
next to cytotrophoblast and amnion
Where is the splanchnopleuric mesoderm?
next to yolk sac
What is the space between the two mesoderms?
How is the secondary/definitive yolk sac (exocoelomic cavity) formed?
Hypoblast cells migrate along the inside of the exocoelomic membrane (Heuser's membrane)
What are exocoelomic cysts?
Portions of exocoelomic cavity pinch off during secondary yolk sac formation
What forms the connecting stalk?
Portions of the extraembryonic mesoderm traverse across the chorionic cavity
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