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ENRE > Placental and Fetal Membranes > Flashcards

Placental and Fetal Membranes Flashcards

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
Q

What is polyhydramnios?

A

excessive amniotic fluid

genetic defect, fetal defect in CNS or GI blockage can cause

26
Q

What is oligohydramnios?

A

too little amniotic fluid

problem w/ fetal development (renal agenesis, pulmonary hypoplasia)

placental abnormality or maternal HBP

27
Q

What makes up the chorion?

A

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
Q

What are the 2 layers of chorion?

A

extraembryonic somatic mesoderm –> lines trophoblast and covers amnion

extraembryonic splanchnic mesoderm –> surrounds umbilical vesicle

29
Q

What does the connecting stalk do?

A

connects amnion and umbilical vesicle to the chorion

30
Q

What defines the entire chorionic sac?

A

extraembryonic somatic mesoderm + cytotrophoblasts + syncytiotrophoblasts

31
Q

What are the fetal and maternal parts of the placenta?

A

fetal = villous chorion, projects into intervillous space

maternal = decidua basalis, almost entirely replaced by the fetal part of the placenta (4th month)

32
Q

What is the cytotrophoplastic shell?

A

external layer of trophoblast cells on maternal surface that attach villi to decidua basalis

33
Q

When do chorionic villi appear?

Where are they initially and how do they change?

A

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
Q

What is the placental barrier?

A

cytotrophoblast and syncytiotrophoblast cells and supporting basal lamina

endothelial cells and basal lamina of fetal blood capillaries

35
Q

Primary villi

A

cytotrophoblast core covered by syncytiotrophoblast

36
Q

secondary villi

A

extraembryonic mesoderm extends into primary villi (3rd week)

mesenchyme core –> cytotrophoblasts –> syncytiotrophoblasts

37
Q

tertiary villi

A

extraembryonic mesoderm –> capillary and blood cells

capillary core and mesenchyme–> cytotrophoblast –> syncytiotrophoblast

38
Q

What are cotyledons?

A

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
Q

What are stem and branch villi?

A

stem villi = attach to maternal tissues through cytotrophoblastic shell

branch villi = grow from sides of stem

40
Q

What is the amniochorionic membrane and how does it form?

A

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
Q

What is the timeline/character of the placental membrane?

A

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
Q

What is the vasculosyncytial placental membrane?

A

cyncytiotrophoblasts directly in condact w/ endothelium of fetal capillaries

occurs after ~20th week of pregnancy

43
Q

What things can cross the placental membrane?

A

hormones

IgG

waste products

most drugs

viruses

nutrients for baby

44
Q

What things can NOT cross the placental membrane?

A

protein hormones

IgD, IgM, IgE, IgA

drugs w/ structural similaries to AAs

heparin

bacteria

45
Q

What is the trophoectoderm shell?

What does it look like histologically?

A

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
Q

What are hofbauer cells?

A

phagocytic cells predominant in early pregnancy

47
Q

What are syncytial knots?

A

aggregates of syncytiotrophoblast nuclei

in late placenta

48
Q

What is a fibrin/oid?

A

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
Q

What is contained in the umbilical cord?

A

2 umbilical arteries (baby–> mom)

1 umbilical vein (mom –> baby)

50
Q

What are the 3 main circulatory shunts?

A

ductus venosus –> skips liver

ductus arteriosus and foramen ovale –> skip lungs

51
Q

What is placenta accreta (in general)?

A

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
Q

What are the 3 types of placental acretta?

A

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
Q

What are the 3 types of placental previa?

A

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
Q

What is a hydatidiform mole?

A

replacement of normal villi by dilated or hydropic translucent vesicles

caused by improper fertilization (polyspermy)

55
Q

What are the 2 types of hydatidiform mole?

A

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
Q

What is an invasive mole?

A

complete hydatidiform mole w/ increased local invasion

persistent high hCG

trophoblast deeply invades uterine wall and can cause hemorrhaging

responsive to chemo

57
Q

What is choriocarcinoma?

A

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
Q

What are the membranes like in dizygotic twins?

A

2 amnions and 2 chorions

chorions and placentas may be fused if implantation occurs near each other

59
Q

What happens if monozygotic twins are divided in the embryoblast stage?

A

one placenta

one chorionic sac

two amniotic sacs

*placental vessels may or may not anastomose

60
Q

What happens if monozygotic twins separate in embryonic blastomere stage?

A

2 amnions

2 chorions

2 separate placentas (but can fuse if them implant closely)

ENRE (21 decks)

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