11. Placenta and Fetal Membranes (Dennis) Flashcards Preview

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Flashcards in 11. Placenta and Fetal Membranes (Dennis) Deck (40)
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1
Q

What changes between the tertiary chorionic villi between early and late pregnancy?

A

The cytotrophoblasts become “attenuated” and disappear.

2
Q

Why doesn’t the placenta wrap all the way around the amniotic sac?

A

Because the superficial direction of the chorion becomes compressed by its proximity to the decidua capsularis. This causes ischemia in the chorionic villi, which then disappear. Since they aren’t there to form into the placenta, the placenta only forms where the chorionic villi contact decidua basalis.

3
Q

What is amniotic fluid made of?

A

Organic compounds like proteins, carbs, fats, enzymes, and hormones.

Inorganic salts, ions, glycol phospholipids, and steroid hormones.

4
Q

What are the three layers of the decidua and thier relative locations?

Which part of the decidua is the maternal part of the placenta?

A

Decidua basalis: deep to the conceptus.

Decidua capsularis: superficial, and overlying the conceptus.

Decidua parietalis: the remaining part of the decidua.

5
Q

How is the intervillous space formed?

A

The chorionic villi invade the decidua basalis and erode the space out.

6
Q

What happens to the placental membrane around the twentieth week?

A

The cytotrophoblastic layer is essentially lost, causing a thinning of the membrane where the syncytiotrophoblasts are in direct contact with the endothelium of the fetal capillaries.

This is called the vasculosyncytial placental membrane.

7
Q

What gives rise to the amnion?

A

The epiblast.

8
Q

What is the fetal part of the placenta?

A

The chorionic sac.

9
Q

What are the four fetal membranes?

A

The chorion.

The amnion.

The umbilical vesicle.

The allantois.

10
Q

And what two stages of development can monozygotic twins form, and what implication does this have for the placenta, chorionic sac, and amniotic sac?

A

Monozygotic twins which separate in the two cell stage to the Morrill stage will have two separate chorionic sacs, two separate placentas, two separate amniotic sacs.

Monozygotic twins which separate in the embryoblast stage result in one placenta, one chorionic sac, but still two amniotic sacs.

11
Q

What is the clinical significance of oligohydramnios?

A

Leads to problems with fetal development such as renal a Genesis, pulmonary hypoplasia, and underdevelopment of the G.I. tract.

May be due to a placental abnormality or maternal high blood pressure.

12
Q

Explain the formation of the amnion.

A

The embryoblasts, in the stages before the bilaminar disc, develops a primordial amniotic cavity. Soon, angiogenic cells called amnioblasts develop finish the formation of the amniotic cavity.

13
Q

What is the difference between primary, secondary, and tertiary chorionic villi?

A

Primary chorionic villi have a cytotrophoblast core covered by syncytiotrophoblasts.

Secondary chorionic villi contain some mesoderm in the middle of a ring of cytotrophoblasts, which itself is in the middle of a ring of syncytiotrophoblasts.

Tertiary chorionic villi have true blood vessels inside of the ring of cytotrophoblasts inside of the ring of syncytiotrophoblasts.

14
Q

What makes up the fetal part of the placenta?

A

The villous chorion.

15
Q

What sorts of hormones can cross the placenta?

A

Nonprotein hormones, such as steroid hormones and thyroid hormones.

16
Q

What is at the core of the chorionic villi?

A

Mesenchymal connective tissue and fetal blood cells.

17
Q

What are the two basic causes of a hydatidiform mole?

A

Partial mole: meiotic nondisjunction or two haploid fertilizing sperm.

Complete mole: fertilization of a nonviable ovum by haploid sperm.

18
Q

What is placenta previa?

A

When the placenta attaches too close to, or over, the cervical opening.

Can be marginal, partial, or total.

19
Q

What are syncytial knots?

A

Aggregate – very eosinophilic – nuclei of syncytiotrophoblasts that are deposited at random, but often found on the surfaces of villi.

– These are markers of late stage pregnancy. –

20
Q

What is an anchoring villi?

A

A chorionic villus that attaches to the maternal tissues through the cytotrophoblastic shell.

21
Q

What is the primordial uteroplacental circulation?

A

The phenomenon by which oxygen and nutrients are passed into the developing embryo via diffusion through the liquor networks in the syncytiotrophoblasts (chorionic sac).

22
Q

What is contained within the umbilical cord?

A

Two umbilical arteries and one umbilical vein.

23
Q

Where does amniotic fluid come from?

A

Maternal tissue and interstitial fluid.

24
Q

What is bypassed by the ductus venosus?

A

The liver.

25
Q

The intervillous spaces between which two layers of the placenta?

A

Between the decidua basalis and the chorionic plate.

26
Q

Where does hCG come from before it enters maternal blood?

A

The syncytiotrophoblasts.

27
Q

What structures make up the chorionic sac?

A

The extraembryonic somatic mesoderm.

The cytotrophoblasts.

The syncytiotrophoblasts.

28
Q

What is the clinical significance of polyhydramnios?

A

May indicate a genetic defect in the fetus.

May indicate specifically a central nervous system defect in the fetus.

Or may indicate a blockage of the gastrointestinal tube.

Clinical signs include abdominal pain, swelling and bloating, or breathlessness.

29
Q

What sort of blood is carried within the umbilical vein?

A

80% oxygenated fetal blood from the placenta.

30
Q

What is the name of the macrophages found within the connective tissue core of the chorionic villi?

A

Hofbauer cells.

31
Q

What is placenta accreta/increta/percreta?

What are the three severities?

A

An abnormally strong and deep attachment of the placenta to the uterine wall.

Placenta accreta: placenta invades the uterine wall but does not penetrate the myometrium.

Placenta increta: placenta penetrates through the myometrium.

Placenta percreta: placenta penetrates through the myometrium and the uterine serosa, commonly attaches to the bladder and or rectum.

32
Q

What forms the placental barrier histologically speaking?

A

Cytotrophoblasts, syncytiotrophoblasts, and their supporting basal lamina.

The endothelial cells and the basal lamina of the fetal blood capillaries.

33
Q

What complication can arise from an undiagnosed hydatidiform mole?

A

Choriocarcinoma: highly invasive metastatic tumor arising from chorionic epithelium.

34
Q

What is a cotyledon?

A

A space in the decidua basalis which is separated by placental septa, and contains 2+ main stem villi and multiple branch villi.

35
Q

What sort of drugs can and can’t cross the placenta?

A

Most drugs can cross, such as alcohol, cocaine, heroin, labor-management drugs, etc.

Drugs with structural similarities to amino acids cannot cross – such as methyldopa and heparin.

36
Q

What is bypassed by the ductus arteriosus and foramen ovale in the fetus?

A

The lungs.

37
Q

What sort of infectious agents can and can’t cross the placenta?

A

As a general rule, bacteria cannot.

Most viruses can, as well as syphilis, toxoplasmosis and listeria.

38
Q

How is the interface for maternal blood flow established after implantation?

A

Syncytiotrophoblasts grow into the endometrium and contact the spiral arteries from the mother. Enzymes degrade the spiral arteries and blood rushes into the lacunae formed in the syncytiotrophoblasts.

39
Q

What is the decidua?

A

Decidua is the portion of the functional layer of the endometrium which separates from the remainder of the uterus after childbirth.

40
Q

Which antibodies can cross the placenta?

A

IgG only.