Flashcards in Week 2 (Days 8-14) - HY Deck (38):
To what 2 cell layers does the embryoblast differentiate?
1. The dorsal epiblast
2. The ventral hypoblast
What do the epiblast and the hypoblast together form?
A flat, ovoid-shaped disk known as the bilaminar embryonic disk.
What is formed within the epiblast?
Clefts develop and eventually coalesce to form the amniotic cavity.
Where do hypoblast migrate and what do they form?
Migrate and line the inner surface of the cytotrophoblast and eventually delimit a space called the definitive yolk sac.
What do the epiblast and hypoblast form by their fusion and what does ti mark?
Form the prochordal plate, which marks the future site of the mouth.
At the same time, what is the course of the syncytiotrophoblast?
Continues its growth into the endometrium to make contact with endometrial blood vessels and glands.
Does the syncytiotrophoblast divide mitotically?
NO - The cytotrophoblast does --> adding to the growth of the syncytiotrophoblast.
What does the syncytiotrophoblast produce?
What forms the primary chorionic villi and where do they protrude?
Formed by the cytotrophoblast and protrude into the syncytiotrophoblast.
From where does the extraembryonic mesoderm derive?
It is a new layer of cells derived from the epiblast.
What is the role of the extraembryonic somatic mesoderm (somatopleuric mesoderm)?
1. Lines the cytotrophoblast
2. Forms the connecting stalk
3. Covers the amnion
What suspends the conceptus within the chorionic cavity?
The connecting stalk.
How do we call the wall of chorionic cavity?
What are the 3 components of the wall of chorionic cavity?
1. Extraembryonic somatic mesoderm
What cell layer covers the yolk sac?
Extraembryonic visceral mesoderm (splanchnopleuric mesoderm).
What is the role of the hCG?
a GLYCOPROTEIN produced by the syncytiotrophoblast that stimulates the production of progesterone by the corpus luteum of the ovary (i.e. maintains corpus luteum function).
Why is the production of progesterone by the corpus luteum clinically important?
Because this progesterone is essential for the maintenance of pregnancy until week 8. --> then, the placenta takes over progesterone production.
At what time can hCG be assayed in maternal blood or maternal urine?
At day 8 in maternal blood and at day 10 in maternal urine.
--> The basis of pregnancy testing.
True or false? hCG is detectable throughout the pregnancy.
What may low hCG values predict?
A spontaneous abortion or indicate an ECTOPIC pregnancy.
What may high levels of hCG indicate?
1. Multiple pregnancy
2. Hydatidiform mole
3. Gestational trophoblastic neoplasia (GTN) --> Such as choriocarcinoma.
What is the RU-486?
What is the function of the RU-486?
Will initiate menstruation when taken within 8-10 weeks of the start of the last menstrual period.
--> If implantation of a conceptus has occured, the conceptus will be sloughed along with the endometrium.
What is the pharmacologically the RU-486?
A progesterone-receptor antagonist.
With what is RU-486 used in conjunction?
With misoprostol (Cytotec; a PGE1 analog) --> 96% effective at terminating pregnancy.
To what event does a blighted blastocyst (blastocyst growth is prevented) lead to?
Death of the embryo followed by hyperplastic proliferation of the trophoblast.
What does an hydatidiform mole represent?
An abnormal placenta characterized by marked enlargement of the chorionic villi.
What is the karyotype of a complete mole?
Usually has a normal karyotype (46XX), BUT both nuclear chromosomes are of PATERNAL origin.
How does a complete mole result?
From fertilization of an "empty egg" (absent or inactivated maternal chromosomes) by a haploid sperm that then duplicates (46, YY moles do not occur, because this karyotype is lethal).
What is the karyotype of a partial mole?
Usually triploid (69 XXX, 69XXY) due to the fertilization of an ovum (one set of haploid maternal chromosomes) by two sperm (two sets of haploid paternal chromosomes).
How is a complete mole distinguished from a partial mole?
By the amount of chorionic villous involvement.
In complete or in partial mole is an embryo present?
In a partial mole.
What are the hallmarks of a complete mole?
1. Gross, generalized edema of chorionic villi forming grape-like, transparent vesicles.
2. Hyperplastic proliferation of surrounding trophoblastic cells.
3. Absence of an embryo/fetus.
What are the clinical signs (diagnostic) of a complete mole?
1. Preeclampsia during the 1st trimester.
2. Elevated hCG.
3. Enlarged uterus with bleeding.
Why are follow-up visits after a mole essential?
Because 3-5% of moles develop into GTN.
What is basically a GTN?
A malignant tumor of the trophoblast that may occur following a normal or ectopic pregnancy, abortion, or a hydatidiform mole.
What is diagnostic of GTN?
With high degree of suspicion, elevated hCG levels are diagnostic.