Placenta and Fetal Membranes

Question 1

what do the fetal membranes include?

Answer 1

chorion, amnion, umbilical vesicle, and the allantois

Question 2

what is the fetal part of the placenta?

Answer 2

the chorionic sac (outermost fetal membrane)

Question 3

what is the maternal part of the placenta?

Answer 3

derivative from endometrium

Question 4

what connects the placental circulation with the fetal circulation?

Answer 4

vessels in the umbilical cord

Question 5

What is the decidua?

Answer 5

the functional layers of the endometrium that separates from the remainder of the uterus after childbirth

Question 6

what are the three parts of the decidua?

Answer 6

decidua basalis, decidua capsularis, decidua parietalis

Question 7

what area of the decidua forms the maternal part of the placenta?

Answer 7

decidua basalis

Question 8

what can the decidua capsularis be thought of as?

Answer 8

the chorion

Question 9

what can the decidua parietalis be thought of as?

Answer 9

“walls” of the uterus

Question 10

when does implantation typically occur?

Answer 10

late 2nd week (~ 10 days post-fertilization)

Question 11

how do the trophoblast differentiation when implanting?

Answer 11

they differentiate into cytotrophblasts and syncytiotrophoblasts

Question 12

which new layer of the blastocyst is responsible for invading and displacing the decimal cells of the endometrium?

Answer 12

the syncytiotrophoblasts

Question 13

what eventually appears in the syncytiotrophoblast layer that allows for blood and uterine secretions to wash and bathe over the implanting embryo?

Answer 13

lacunae

Question 14

what forms when adjacent lacunae fuse together?

Answer 14

lacunar networks

Question 15

what is the primordial uteroplacental circulation?

Answer 15

it is where O2 and nutritive substances pass to the embryo via diffusion through lacunar networks

Question 16

what is the chorionic sac made up of?

Answer 16

extra embryonic somatic mesoderm, cytotrophoblasts, and syncytiotrophoblasts

Question 17

what is the thin tough membrane that surrounds the embryo/fetus and the amniotic fluid?

Answer 17

the amnion

Question 18

how did the amnion develop?

Answer 18

from a population of cells known as amnioblasts (these separate from the epiblast and enclose the amniotic cavity)

Question 19

what is the umbilical cord covered with?

Answer 19

the amnion forms an epithelial covering over the umbilical cord

Question 20

what is amniotic fluid initially derived from?

Answer 20

maternal tissue and interstitial fluid; later fetal urinary, respiratory, and GI systems will also contribute

Question 21

what is (poly)hydramnios?

Answer 21

excessive amniotic fluid; too much produced or not removed effectively

Question 22

what could cause (poly)hydramnios?

Answer 22

genetic and/or CNS anomalies or blockage of the GI tube

Question 23

what are the clinical signs of (poly)hydramnios?

Answer 23

abdominal pain, significant swelling or bloating, and breathlessness

Question 24

what is a potential risk associated with (poly) hydramnios?

Answer 24

PROM (pre-mature rupture of membranes)

Question 25

what is oligohydramnios?

Answer 25

insufficient amniotic fluid

Question 26

what results from oligohydramnios?

Answer 26

renal agenesis, pulmonary hypoplasia, club footing; placental abnormality or maternal high blood pressure

Question 27

what two things are critical for establishing the placenta?

Answer 27

formation of the villous chorion and the chorionic villi from the chorionic sac

Question 28

where do the cytotrophobasts proliferate?

Answer 28

at the chorionic plate

Question 29

after proliferating at the chorionic plate, what do the cytotrophoblasts do?

Answer 29

they extend through the syncytiotrophoblasts to attach to the decidua basalis

Question 30

when extending through the syncytiotrophoblasts, where is the boundary for where the cytotrophoblasts will stop extending?

Answer 30

the cytotrophoblastic shell (surrounding the chorionic sac)

Question 31

what does the extension of the cytotrophoblast/ cytotrophoblastic shell create and enclose?

Answer 31

the intervillous space (created from the lacunar networks)

Question 32

what does decimal erosion produce?

Answer 32

placental septa

Question 33

what does the placental septa divide the villous chorion into?

Answer 33

irregular convex areas known as cotyledons

Question 34

when do the intervillous spaces start containing maternal blood?

Answer 34

11-14th week

Question 35

when do the cytotrophoblasts grow into the syncytiotrophoblast layer?

Answer 35

end of week 2

Question 36

when do the cytotrophoblasts form syncytial columns? (like little branches all along the chorionic sac)

Answer 36

through week 8

Question 37

where would you expect to find the villi with the branches?

Answer 37

with the decidua basalis- form bushy area of the chorionic sac, the villous chorion

Question 38

what is the smooth chorion?

Answer 38

the villi associated with the decidua capsularis become compressed and then degenerate

Question 39

what is the structure of the primary villi?

Answer 39

cytotrophoblastic core covered by syncytiotrophoblasts

Question 40

what is a secondary villi and when do you get it?

Answer 40

the extra embryonic mesoderm grows into the primary villi - 3rd week

Question 41

what makes up the secondary villi?

Answer 41

extra embryonic mesoderm (core), cytotrophoblasts, and syncytiotrophoblasts

Question 42

how do you get a tertiary villi?

Answer 42

the extra embryonic mesoderm differentiates into capillary and blood cells

Question 43

what is the outer layer of the tertiary villi?

Answer 43

syncytiotrophoblasts

Question 44

what is the middle layer of the tertiary villi?

Answer 44

cytotrophoblasts

Question 45

what is the core of the tertiary villi?

Answer 45

capillaries and extra embryonic mesoderm

Question 46

what are the two subpopulations of tertiary chorionic villi?

Answer 46

early and late (late tertiary chorionic villi start to lose the cytotrophoblastic layer

Question 47

what is the main stem villi extending from?

Answer 47

the chorionic plate

Question 48

what are the branch villi extending from?

Answer 48

the main stem villus

Question 49

what is the anchoring villi?

Answer 49

villi that attaches to the maternal tissues through the cytotrophoblastic shell

Question 50

what do cotyledons contain?

Answer 50

2 main stem villi and multiple branch villi

Question 51

where does the main exchange between mother and fetus occur?

Answer 51

via the branch villi

Question 52

what happens to the decidua capsularis are the embryo//fetus grows?

Answer 52

the capsularis will degenerate

Question 53

what happens once the capsularis degenerates?

Answer 53

the amnion and the chorion will fuse

Question 54

what do you get when you fuse the amnion and the chorion?

Answer 54

the amniochorionic membrane

Question 55

what does the amniochorionic membrane fuse with on the opposite wall?

Answer 55

the decidua parietalis (it can now span the internal uterine os)

Question 56

what things cannot cross the placenta?

Answer 56

protein hormones (pituitary hormones), bacteria, and drugs with amino-acid-like structures

Question 57

what kind of tissue comprises the umbilical cord?

Answer 57

mucous tissue (Wharton's jelly)

Question 58

what are the contents of the umbilical cord?

Answer 58

two umbilical arteries and one umbilical vein, allantois

Question 59

what do the umbilical arteries carry?

Answer 59

deoxygenated blood

Question 60

what do the umbilical veins carry?

Answer 60

oxygenated blood

Question 61

what is one of the most common umbilical cord anomalies?

Answer 61

absences of one umbilical artery

Question 62

who is at risk for absence of one umbilical artery?

Answer 62

fetuses with chromosomal and fetal anomalies

Question 63

what is the risk of absence of one umbilical artery?

Answer 63

it can impact perinatal and 3rd stage labor outcomes

Question 64

what is placenta previa?

Answer 64

a condition where the placenta implants in the lower uterine segment or cervix

Question 65

what does placenta previa often lead to?

Answer 65

serious 3rd trimester bleeding

Question 66

what is placenta accrete/a?

Answer 66

partial or complete absence of the decidua--> so the villous chorion adheres directly to the myometrium

Question 67

what is the result of placenta accrete/a?

Answer 67

failure of placental separation at birth

Question 68

what is a hydatidiform mole?

Answer 68

a placental anomaly because of faulty fertilization; there is replacement of normal villi by dilated or hydronic (edematous) translucent vesicles

Question 69

what are the two types of hydatidiform moles?

Answer 69

partial mole or complete mole

Question 70

which mole does not have any fetal tissue?

Answer 70

compete mole

Question 71

what happens in a case of a partial mole?

Answer 71

a normal ovum is fertilized with two sperm

Question 72

what would the karyotype of a partial mole be?

Answer 72

triploid or tetraploid

Question 73

what happens in a case of a complete mole?

Answer 73

there is fertilization of a blighted movum- all DNA is paternal; it is either fertilized by two sperm or there is duplication of a single sperm

Question 74

what would the karytype of a complete mole be?

Answer 74

46 XX or 46XY

Question 75

what is gestational trophoblastic disease?

Answer 75

a placental anomaly due to issues with invasion

Question 76

what are invasive moles?

Answer 76

complete moles that penetrate or perforate the uterine wall

Question 77

how are invasive moles diagnosed?

Answer 77

by persistent high blood levels of hCG

Question 78

what are invasive moles responsive to?

Answer 78

chemotherapy

Question 79

what is a gestational choriocarcinoma?

Answer 79

a highly invasive metastatic tumor that arises from trophoblast cells

Question 80

what do monozygotic twins originate from?

Answer 80

one zygote

Question 81

what are the membranes in monozygotic twins dependent upon?

Answer 81

timing of the division

Question 82

if there is cleavage in the 2-8 cell stage (0-72 hours), what is the nature of the membranes?

Answer 82

diamniotic and dichorionic

Question 83

if there is cleavage in the blastocyst stage (4-8 days) what is the nature of the membranes?

Answer 83

diamniotic and monochorionic

Question 84

if there is cleavage in the implanted stage (9-12 days) what is the nature of the membranes?

Answer 84

mono amniotic and monochorionic

Question 85

the earlier the split the...?

Answer 85

the more separate the membranes and the placenta will be

Question 86

what do dizygotic twins originate from?

Answer 86

two zygotes

Question 87

what do you get when you have separate implantation of 2 zygotes?

Answer 87

2 chorions and 2 amnions

Question 88

what do you get when you have adjacent implantation of 2 zygotes?

Answer 88

2 amnions, 2 fused chorions, and 2 placentas