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ENRE > Placental and Fetal Membranes > Flashcards

Placental and Fetal Membranes Flashcards

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1
Q

What part of the blastocyst becomes extraembryonic tissue?

A

trophoblast

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2
Q

What occurs to the blastocyst when it implants?

A

embryoblast –> bilaminar embryonic disc

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3
Q

What are the extraembryonic structures present in the blastocyst?

A

amnion

umbilical vesicle

connecting stalk

chorionic sac

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4
Q

What are the 3 parts of the decidua?

A

decidua basalis: deep to conceptus, forms maternal part of the placenta

decidua capsularis: superficial and overlies conceptus (opposite side of implantation site, faces uterine cavity)

decidua parietalis: remaining parts

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5
Q

What does the decidua look like histologically?

A

pale-staining cells w/ glycogen and lipid accumulation

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6
Q

What is the decidual reaction?

A

cellular and vascular changes that occur as the blastocyst implants

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7
Q

When does implantation occur?

A

2nd week (6-10 days post fertilization)

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8
Q

What part of the endometrium is incorporated into the placenta?

A

functional layer

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9
Q

What does the trophoblast differentiate into once it contacts the endometrium?

A

cytotrophoblast = inner layer

syncytiotrophoblast (outer layer) –> invades and displaces decidua basalis; produces hCG

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10
Q

When does the zona pellucida degenerate?

A

day 5

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11
Q

When does the blastocyt adhere to the endometrial epithelium?

A

day 6

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12
Q

When does the trophoblast differentiate?

when does the syncytiotrophoblast erode endometrial tissue?

A

day 7

day 8

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13
Q

When do blood-filled lacunae apper in the syncytiotrophoblast?

When do the lacunar networks form?

A

day 9

days 10 and 11

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14
Q

When does the syncytiotrophoblast erode endo blood vessels to establish uteroplacental circulation?

When do primary chorionic villi develop?

A

days 11 and 12

days 13 and 14

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15
Q

What is the amnion?

How does it form?

A

thin, tough membrane that surrounds the embryo/fetus and amniotic fluid

amnio blasts separate from the epiblast –> enclose the developing amniotic cavity

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16
Q

What is an ectopic pregnancy and where do they most commonly occur?

A

implantation of plastocyst outside uterine cavity = 2% of all pregnancies

95-98% occur in oviduct, most commonly in ampulla and isthmus

produce hCG, but at slower rate than normal pregnancies

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17
Q

How does the amnion form?

A

amnioblasts separate from the epiblast –> enclose epiblast and space btw epiblast and amnion/amniotic sac = amniotic cavity

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18
Q

What occurs to the relative sizes of the amniotic and chorionic cavities as the embryo grows?

A

amniotic fluid increases and embryo grows –> amnion eventually goes out and bindw w/ chorionic sac = just chorion now

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19
Q

What forms the epithelial covering of umbilical cord?

A

amnion

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20
Q

What is the villous chorion?

A

initial villi growing out of chorion to surrounding uterus –> fetal part of placenta

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21
Q

What is the function of amniotic fluid?

A

cushions fetus inside uterus, provices space, regulates fetal body temp

derived from maternal tissue and IF

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22
Q

How often does the water of the amniotic fluid change itself?

A

every 3 hrs - exchange w/ fetal blood via umbilical cord

fluid also secreted by respiratory sys, GI tract, and urinary system

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23
Q

When does the fetal urinary sys excrete amniotic fluid?

A

11 wks

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24
Q

What are the amniotic fluid volumes throughout pregnancy?

A

10 wks - 30 mL

20 wks - 350 mL

37 wks - 700-1000 mL

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25
What is polyhydramnios?
excessive amniotic fluid genetic defect, fetal defect in CNS or GI blockage can cause
26
What is oligohydramnios?
too little amniotic fluid problem w/ fetal development (renal agenesis, pulmonary hypoplasia) placental abnormality or maternal HBP
27
What makes up the chorion?
extraembryonic mesoderm from hypoblast surrounds amnion and primary umbilical vesicle will separate and split mesoderm into 2 layers separated by extraembryonic coelom = fluid-filled cavity that surrounds amnion and umbilical vesicle
28
What are the 2 layers of chorion?
extraembryonic somatic mesoderm --\> lines trophoblast and covers amnion extraembryonic splanchnic mesoderm --\> surrounds umbilical vesicle
29
What does the connecting stalk do?
connects amnion and umbilical vesicle to the chorion
30
What defines the entire chorionic sac?
extraembryonic somatic mesoderm + cytotrophoblasts + syncytiotrophoblasts
31
What are the fetal and maternal parts of the placenta?
fetal = villous chorion, projects into intervillous space maternal = decidua basalis, almost entirely replaced by the fetal part of the placenta (4th month)
32
What is the cytotrophoplastic shell?
external layer of trophoblast cells on maternal surface that attach villi to decidua basalis
33
When do chorionic villi appear? Where are they initially and how do they change?
appear week 2 cover chorionic sac until 8th week --\> then degenerates part w/out villi = smooth chorion part w/ villi = villous chorion/chorion frondulum
34
What is the placental barrier?
cytotrophoblast and syncytiotrophoblast cells and supporting basal lamina endothelial cells and basal lamina of fetal blood capillaries
35
Primary villi
cytotrophoblast core covered by syncytiotrophoblast
36
secondary villi
extraembryonic mesoderm extends into primary villi (3rd week) mesenchyme core --\> cytotrophoblasts --\> syncytiotrophoblasts
37
tertiary villi
extraembryonic mesoderm --\> capillary and blood cells capillary core and mesenchyme--\> cytotrophoblast --\> syncytiotrophoblast
38
What are cotyledons?
rough surface of fetal part of placenta produced when villi erode --\> decidua makes placental septa --\> 2 main stem villi + multiple branch villi = a cotyledon
39
What are stem and branch villi?
stem villi = attach to maternal tissues through cytotrophoblastic shell branch villi = grow from sides of stem
40
What is the amniochorionic membrane and how does it form?
amniotic sac grows faster than chorion --\> fuses w/ capsularis --\> decidua capsularis degenerates 22-24 weeks --\> smooth chorion will merge with decidua parietalis = amniochorionic membrane
41
What is the timeline/character of the placental membrane?
**until 20th** week: syncytio, cyto, CT of villi, and fetal capillary endothelium **after 20th** week: **cytotrophoblasts** are essentially **lost**; vasculosyncytial placental membrane **3rd trimester**: nuclei in syncytio aggregate to form multinucleated protrusions = **syncytial knots** end of pregnancy: eosinophilic firin thickens
42
What is the vasculosyncytial placental membrane?
cyncytiotrophoblasts directly in condact w/ endothelium of fetal capillaries occurs after ~20th week of pregnancy
43
What things can cross the placental membrane?
hormones IgG waste products most drugs viruses nutrients for baby
44
What things can NOT cross the placental membrane?
protein hormones IgD, IgM, IgE, IgA drugs w/ structural similaries to AAs heparin bacteria
45
What is the trophoectoderm shell? What does it look like histologically?
cytotropho + outer syncytio cells in early placenta syncytiotrophoblast cells: fusion of many cells - have many nuclei/cell w/ no discernable lateral boundary cytotrophoblast cells: clearly demarcated w/ single, large nucleus and basophilic cytoplasm
46
What are hofbauer cells?
phagocytic cells predominant in early pregnancy
47
What are syncytial knots?
aggregates of syncytiotrophoblast nuclei in late placenta
48
What is a fibrin/oid?
amorphous eosinophilic substance commonly deposited in interillus space in older placenta clings to villus surface and may bind several villi together commonly used for placental stagin
49
What is contained in the umbilical cord?
2 umbilical arteries (baby--\> mom) 1 umbilical vein (mom --\> baby)
50
What are the 3 main circulatory shunts?
ductus venosus --\> skips liver ductus arteriosus and foramen ovale --\> skip lungs
51
What is placenta accreta (in general)?
abnormally strong and deep attachment of placenta to uterine wall due to previous uterine surgery or scare tissue from curettage incidence increases w/ increasing C-section rate
52
What are the 3 types of placental acretta?
placenta accreta: through uterine wall, but doesn't penetrate myometrium (75%) increta: through myometrium (15%) percreta: through serosa, commonly attaches to bladder/rectum (10%)
53
What are the 3 types of placental previa?
marginal: margin of placenta lies close to internal uterine os partial: edge of placenta extends across part of internal os total: placenta covers internal os
54
What is a hydatidiform mole?
replacement of normal villi by dilated or hydropic translucent vesicles caused by improper fertilization (polyspermy)
55
What are the 2 types of hydatidiform mole?
partial: triploid w/ one set of maternal chromosomes and 2 paternal; from meiotic nondisjunction or polyspermy; capillaries w/ blood seen in villi complete: of paternal origin, no recognizable fetus; blighted ovum fertilized by haploid sperm --\> reduplicates in egg; avascular villi w/ no blood in vessels
56
What is an invasive mole?
complete hydatidiform mole w/ increased local invasion persistent high hCG trophoblast deeply invades uterine wall and can cause hemorrhaging responsive to chemo
57
What is choriocarcinoma?
invasive, metastatic tumor that arises from gestational chorionic epithelium 50% of ppl with molar pregnancies increasing hCG w/ no uterine enlargement combination chemo is usually curative
58
What are the membranes like in dizygotic twins?
2 amnions and 2 chorions chorions and placentas may be fused if implantation occurs near each other
59
What happens if monozygotic twins are divided in the embryoblast stage?
one placenta one chorionic sac two amniotic sacs \*placental vessels may or may not anastomose
60
What happens if monozygotic twins separate in embryonic blastomere stage?
2 amnions 2 chorions 2 separate placentas (but can fuse if them implant closely)

ENRE (21 decks)

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