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*GIGU I > 39. Placenta and Fetal Membranes > Flashcards

39. Placenta and Fetal Membranes Flashcards

1
Q

What are the 4 fetal membranes?

A

Chorion
Amnion
Umbilical vesicle
Allantois

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2
Q

What separates the fetus from the endometrium?

A

The placenta + 4 fetal membranes

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3
Q

Describe the stem cell ability of the zygote

A

Totipotent

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4
Q

Expression of cell lineage specific factors begins in the blastocyst:

The ______ becomes the embryo

The _____ becomes the extra-embryonic tissue (i.e., the fetal membranes)

A

Embryoblast

Trophoblast

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5
Q

What are the 2 parts of the trophoblast layer?

A

Polar (in direct contact with embryoblast)

Mural (surrounding blastocyst cavity)

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6
Q

In what week of development does blastocyst implantation occur

A

2nd week

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7
Q

When implantation occurs during the second week of development, the embryoblast becomes the ________, composed of the _______ + _________, the former is what forms the primary germ layers

A

Bilaminar embryonic disc; epiblast + hypoblast

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8
Q

As implantation takes place, the trophoblast contacts the endometrium, at which time it differentiates into an inner layer called the _____ and an outer layer called the ____ which is what invades and displaces the _____ cells of the endometrium

A

Cytotrophoblast; syncytiotrophoblast; decidual

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9
Q

The syncytiotrophoblast produces _____, which enters maternal circulation via the _______ network

A

hCG; lacunar

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10
Q

95-98% of ectopic pregnancies occur in the ____ or _____ of the uterine tube

A

Ampulla; isthmus

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11
Q

Signs/symptoms of ectopic pregnancy

A

Abdominal pain
Amenorrhea
Vaginal bleeding
Rupture of oviduct wall

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12
Q

Do ectopic pregnancies produce hCG?

A

Yes, but at a slower rate than normal pregnancies

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13
Q

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

A

Amnion

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14
Q

The amniotic sac forms when amnioblasts separate from the _____ and enclose the developing amniotic cavity; the amnion is then considered continuous with cells of the layer from which it was derived

A

Epiblast

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15
Q

With development of the amnion, there is development of ______ _____ circulation, supplying O2 and nutritive substances via diffusion through lacunar networks

A

Primordial uteroplacental

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16
Q

The amnion itself will grow into and eventually obliterate the _____________, as well as form the epithelial covering of the ______

A

Chorionic cavity; umbilical cord

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17
Q

What is the function of amniotic fluid

A

Cushions fetus inside uterus, provides space for fetal movement, regulates fetal body temp

[made up of organic proteins, carbs, fats,enzymes, and hormones, as well as inorganic salts, ions, glycophospholipids, steroid hormones]

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18
Q

What is amniotic fluid derived from

A

Maternal tissue

Interstitial fluid

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19
Q

What are volumes of amniotic fluid like from 10 weeks — 20 weeks — 37 weeks?

A 
10w = 30 mL
20w = 350 mL
37w = 700-1000 mL

[water content changes every 3 hrs, exchange with fetal blood via umbilical cord — ‘dialysis’; fluid secretion from respiratory and GI tracts, as well as fetal urinary system at 11 wks]

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20
Q

Excessive amniotic fluid characterized by abdominal pain, significant swelling/bloating, and breathlessness

A

Hydramnios

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21
Q

Insufficient amniotic fluid (<400 mL) in which decreased fluid does not provide enough cushion to fetus and umbilical cord — leads to defects in lung dev’t, clubbed extremities, etc.

A

Oligohydramnios

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22
Q

What causes hydramnios vs. oligohydramnios?

A

Hydramnios = genetic defect, fetal defect in CNS, or blockage of GI tube

Oligohydramnios = problem with fetal development (renal agenesis, pulmonary hypoplasia), placental abnormality, or maternal HTN

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23
Q

The amnion forms from epiblast. The chorionic sac forms from ___________, which is from __________

A

Extraembryonic mesoderm; hypoblast

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24
Q

In the formation of the ________, the extraembryonic mesoderm from the hypoblast surrounds the amnion and primary umbilical vesicle (yolk sac), later separating and splitting the mesoderm into 2 layers. These are separated by the __________, a fluid-filled cavity that surrounds the amnion and umbilical vesicle.

A

Chorionic sac; extraembryonic coelom

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25
Q

For the chorionic sac, ________ ________ _____ lines the trophoblast and covers the amnion while _____ _____ _____ surrounds the umbilical vesicle

A

Extraembryonic somatic mesoderm; extraembryonic splanchnic mesoderm

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26
Q

During formation of the chorionic sac, the amnion and umbilical vesicle are attached to the chorion via the _____ _____. Also around this time, the primary vesicle will pinch off, thus forming the secondary umbilical vesicle which is now known as the _____ ____

A

Connecting stalk; yolk sac

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27
Q

Overall, the chorionic sac is composed for what 3 parts?

A

Extraembryonic somatic mesoderm

Cytotrophoblasts

Syncytiotrophoblasts

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28
Q

The chorionic villus originates from the chorionic plate and derives from a ____ ____, giving rise to villous branches

Fetal vessels are spearated from the maternal blood in the intervillous space by the ____ ______, made up of cytotrophoblast and syncytiotrophoblast cells and supporting basal lamina, as well as endothelial cells and basal lamina of fetal blood capillaries

A

Stem villus

Placental barrier

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29
Q

Each chorionic villus has a core of _______ CT and fetal ____ ____

A

Mesenchymal; blood vessels

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30
Q

During what week of development do chorionic villi first appear?

A

Appear by end of 2nd week

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31
Q

Chorionic villi consist of chorionic processes that form vascular syncytial columns. These will grow into ______, likely induced by _________

A

Syncytiotrophoblasts; extraembryonic somatic mesoderm

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32
Q

Chorionic villi projections form the primary chorionic villi in the first stage of placental development. They will cover the entire chorionic sac until the ____ week

A

8th

33
Q

Functional layer of the endometrium that separates from the remainder of the uterus after parturition

A

Decidua

34
Q

What are the 3 parts of the decidua

A

Decidua basalis — deep to the conceptus, forms the maternal part of the placenta

Decidua capsularis — superficial and overlies conceptus

Decidua parietalis — remaining parts of the decidua

35
Q

How does the decidua appear on histological slides?

A

Pale-staining cells with glycogen and lipid accumulation

36
Q

Fetomaternal organ responsible for protection, nutrition, respiration, excretion of waste, and hormone production

A

Placenta

37
Q

Compare/contrast the fetal part vs. the maternal part of the placenta

A

Fetal part = formed by the villous chorion, which projects into the intervillous spcae containing maternal blood

Maternal part = formed by decidua basalis, almost entirely replaced by the fetal part by 4th month

38
Q

Primary chorionic villi cover the entire chorionic sac until the 8th week. With growth, the villi associated with the ____ ____ become compressed, blood supply is reduced, and these villi with degenerate, leaving an avascular bare area known as the ____ ____

A

Decidua capsularis; smooth chorion

39
Q

While the villi associated with the decidua capsularis degenerate, those associated with the ___ ____ rapidly increase, branching profusely, and enlarging to form the bushy area of the chorionic sac known as the ____ ____

A

Decidua basalis; villous chorion

40
Q

The chorionic villi invade the decidua basalis and erode the decidual tissues, forming the _____ _____

This erosion produces the ____ ____ which divide the fetal part of the placenta into irregular convex areas called _______

A

Intervillous space

Placental septa; cotyledons

41
Q

Cotyledons consist of what components?

A

2+ main stem villi and multiple branch villi

42
Q

What is the difference between stem villi and branch villi?

A

Stem villi = attach to maternal tissues through cytotrophoblastic shell

Branch villi = grow from sides of stem villi — participate in gas exchange

43
Q

What layer of the decidua bulges into the uterine cavity and forms the capsule covering the surface of the chorionic sac as the embryo/fetus enlarges?

A

Decidua capsularis

44
Q

The decidua capsularis forms the capsule covering the surface of the chorionic sac as the embryo enlarges. The capsularis thins and fuses with the ______ on the opposite wall, eventually obliterating the ______ _____

A

Decidua parietalis; uterine cavity

45
Q

The decidua capsularis degenerates around 22-24 weeks, then the ______ _____ will fuse with the decidua parietalis, obliterating the uterine cavity

A

Smooth chorion

46
Q

The amniotic sac grows faster than the chorionic sac, so these eventually fuse forming the ________ _____

What is the fate of this structure?

A

Amniochorionic membrane

This membrane will fuse with the decidua capsularis and adhere to the parietalis

47
Q

Primary villi form at the end of the 2nd week; cytotrophoblast cells proliferate due to extraembryonic mesoderm and extend forming villi. The core of the cytotrophoblast cells is covered by the syncytiotrophoblast.

The secondary villi form when the _____ ______ extends into the primary villi during the 3rd week.

What are the 3 layers of the secondary villi?

A

Extraembryonic mesoderm

[core of extraembryonic mesoderm, middle cytotrophoblast layer, outer syncytiotrophoblast layer]

48
Q

Tertiary villi develop when extraembryonic mesoderm differentiates into ____ and _____ cells

What are the 3 layers of tertiary villi?

A

Capillary; blood

Core of extraembryonic mesoderm + CAPILLARIES, middle cytotrophoblast layer, outer syncytiotrophoblast layer

49
Q

What is the primary difference between secondary and tertiary villi?

A

Secondary villi DO NOT have capillaries but tertiary DO

50
Q

What condition can occur with reduced development of the branches of the chorionic villus tree?

A

Preeclampsia

51
Q

______ chorionic villi are bathed in maternal blood and are the site of main exchange

They provide a large surface area for materials exchange across the _______ membrane, which is a composite structure consisting of extra-fetal tissues separating maternal and fetal blood

A

Branch

Placental

52
Q

What is the difference in placental membrane structure until the 20th week, and after the 20th week?

A

Up until the 20th week, composed of syncytiotrophoblast, cytotrophoblast, connective tissue of villi, and endothelium of fetal capillaries

After 20th week, composed for syncytiotrophoblast, connective tissue of the villi, and endothelium of fetal capillaries — cytotrophoblasts are essentially lost, membrane can be markedly thin

53
Q

After the 20th week, the syncytiotrophoblast of the placental membrane is in direct contact with the endothelium of fetal capillaries, forming the ____ _____ membrane

A

Vasculosyncytial placental

54
Q

In the 3rd trimester, nuclei in the placenta - in the syncytiotrophoblast - aggregate to form multinucleated ____ ___

A

Syncytial knots

55
Q

Toward the end of pregnancy, eosinophilic ________ thickens on surface of villi

A

Fibrin/oid

56
Q

Compare/contast histology of the placenta on fetal side vs. maternal side

A

Fetal side = smooth and associated with amnion

Maternal side = partially subdivided into 10+ lobes by decidual septa; each lobe contains 10+ stem villi and its branches

57
Q

In the early placenta, the _______ shell is comprised of inner cytotrophoblast and outer syncytiotrophoblast cells

Describe these cell populations in terms of histology

A

Trophectoderm

Cytotrophoblast cells = clearly demarcated, with single large nucleus and basophilic cytoplasm forming complete ring around each villus

Syncytiotrophoblasts = result from fusion of many cells and have many nuclei/cell with no discernable lateral boundaries

58
Q

In the early placenta, the core of villus is comprised of mesenchymal cells (fibroblasts) and fetal blood vessels.

______ cells are phagocytic cells predominant in early pregnancy

Fetal RBCs are in early stages of _______, so they can still have nuclei

A

Hofbauer

Hematopoiesis

59
Q

In the late placenta, multinucleate syncytiotrophoblast cells form trophectoderm shell (after 4th month of pregnancy, cytotrophoblast cells decrease/essentially non-existent)

What 3 structures distinguish the late placenta from the early?

A

Hofbauer cells = macrophage like cells found within CT core

Syncytial knots = aggregates of syncytiotrophoblast nuclei

Fibrinoid = amorphous eosinophilic substance commonly deposited in intervillous space in older placenta — clings to villus surface and may bind several villi together, frequently used for placental staging

60
Q

The umbilical cord contains 2 ______ and 1 ________

What is the oxygenation of these vessels?

A

Umbilical arteries; umbilical vein

Vein carries 80% oxygenated fetal blood

Arteries return deoxygenated fetal blood to placenta

61
Q

What are the 2-3 main fetal circulatory shunts?

A

Ductus venosus (bypasses the liver)

Ductus arteriosus and foramen ovale (bypasses the lungs)

62
Q

Condition characterized by abnormally strong and deep attachment of the placenta to uterine wall — can be d/t previous uterine surgery or scar tissue following uterine curettage

A

Placental accreta

63
Q

What are the 3 forms of placental accreta?

A

[based on how deeply the myometrium is penetrated]

Placenta accreta = placenta invades uterine wall but does not penetrate the myometrium (~75% of cases)

Placenta increta = placenta penetrates through myometrium (~15% of cases)

Placenta percreta = placenta extends through uterine wall and pierces uterine serosa, commonly attaches to bladder and/or rectum (~10% of cases)

64
Q

Abnormal extension of placenta over or close to internal opening of cervical canal

A

Placental previa

65
Q

3 types of placenta previa

A

Marginal = margin of placenta lies close to internal cervical os

Partial = edge of placenta extends across part of internal ostium

Total = placenta covers internal cervical ostium

66
Q

What is the primary complication associated with placenta previa?

A

Spontaneous painless bleeding, resulting from partial separation of placenta from uterus

67
Q

Gestational trophoblastic disease in which replacement of normal villi by dilated or hydropic (edematous) translucent vesicles occurs

A

Hydatiform mole

68
Q

Describe partial hydatiform mole

A

Fetus commonly found, usually 69,XXY: one haploid set of maternal chromosomes (23,X) and 2 haploid sets of paternal chromosomes (46,XY)

Arises from meiotic nondisjunction or from 2 haploid fertilizing sperm

Capillaries containing blood can be seen in the villi

69
Q

Describe complete hydatidiform mole

A

Of paternal origin (androgenetic), no recognizable fetus

Fertilization of a blighted ovum by a haploid sperm, reduplicates within egg

Frequent karyotype = 46,XX or 46,YY

Avascular villi with no blood present in remnant vessels

70
Q

Describe an invasive hydatidiform mole

A

Complete mole with increased local invasion

Diagnosed by persistent high blood levels of hCG

Trophoblast deeply invades uterine wall and can cause hemorrhage

Responsive to chemo

71
Q

Highly invasive, metastatic tumor that arises from gestational chorionic epithelium, observed in about 50% of patients with molar pregnancies; increasing hCG titer w/o uterine enlargement

Tx with combined chemotherapy is usually curative

A

Choriocarcinoma

72
Q

Fetal membranes and placentas vary according to origin of twins

_______ twins always have 2 amnions and 2 chorions, but chorions and placentas may be fused

In ______ twins, the type of placenta and membranes formed depends on when the twinning process occurs — division of ______ vs. ________ (2-8 cell stage)

A

Dizygotic

Monozygotic; embryoblast; embryonic blastomeres

73
Q

What nutrients cross the placenta?

A 
Water
Glucose
Electrolytes
Amino acids
Vitamins
74
Q

What hormones cross placenta?

A

Testosterone
Progestins
Thyroxin
Triiodothyronine

75
Q

Which of the following cross the placenta?

IgG, IgM, IgA, IgD, IgE

A

IgG ONLY!

76
Q

What waste products cross the placenta?

A

Urea
Uric acid
Conjugated bilirubin

77
Q

T/F: most drugs cross the placenta including alcohol, cocaine, and heroine

A

True

78
Q

What infectious agents cross the placenta?

A

CMV, Rubella, Coxsackiviruses

Variola, measles, herpes

Treponema pallidum (syphilis); toxoplasma gondii, listeria monocytogenes

*GIGU I (67 decks)

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