Physiology of the Placenta

Question 1

Placenta comes from the Greek term for ___________.

Answer 1

flat cake

Question 2

The lining of the cavity that the fetus is in (between the fetus and the uterus) is the ___________.

Answer 2

amnion

Question 3

What is the division between the fetus and the placenta?

Answer 3

The chorionic plate

Question 4

One of the difficulties of placental research is _______________.

Answer 4

that no animal has a perfectly analogous placental system (the placenta is not a perfectly conserved organ)

Question 5

Implantation occurs _________.

Answer 5

during day 6-8

Question 6

The arteriocapillary network begins to form during the _________ stage.

Answer 6

tertiary villi

Question 7

The majority of placental mass is _____________.

Answer 7

floating villi, where nutrient and waste exchange occur

Question 8

Which cells are in the deepest part of chorionic invasion?

Answer 8

Cytotrophoblasts

Question 9

The ____________ invade and make contact with the maternal circulation.

Answer 9

syncytiotrophoblasts

Question 10

Describe the three kinds of transport across the placenta and give an example of each.

Answer 10

• Passive diffusion: H2O, gases
• Facilitated diffusion: glucose
• Active transport: amino acids

Note: passive diffusion is perfusion-limited and active diffusion is membrane-limited

Question 11

hCG levels correlate with _______________ during the late first trimester.

Answer 11

morning sickness

Question 12

Which endocrine hormone suppresses uterine contractions?

Answer 12

Progesterone

Question 13

3-beta hydroxysteroid dehydrogenase converts ______________.

Answer 13

pregnenolone to progesterone (and DHEA to estradiol)

Question 14

Two vaccinations are recommended during pregnancy for the immune benefit of the fetus: ______________.

Answer 14

TDaP and influenza

Question 15

What is the volume of the amniotic fluid over the pregnancy?

Answer 15

• 250 mL at 16 weeks

* 1 liter at birth

Question 16

What three things can cause polyhydramnios?

Answer 16

• Gestational diabetes
• Neural tube defects (anencephaly)
• Esophageal atresia

Question 17

Maternal blood comes in direct contact with _____________.

Answer 17

trophoblasts

Question 18

From day 9 to day 12, the syncytiotrophoblasts form trabeculae. Between these are ______________.

Answer 18

vacuolized lacunae which holds blood (this is the intervillous space)

Question 19

From day 13 to day 18, the primary villi form. What two cells make up the villi?

Answer 19

During this stage, called the villous stage, cytotrophoblasts invade the trabeculae which are made of syncytiotrophoblasts. These become the villi. (Thus, primary villi are made of syncytiotrophoblasts around cytotrophoblast cores.)

Question 20

What’s the difference between an anchoring villus and a floating villus?

Answer 20

Anchoring villi connect to the decidua of the maternal uterus. Floating villi dangle off of the anchoring to bolster fluid contact.

Question 21

There are two umbilical ___________ and one umbilical _________.

Answer 21

arteries; veins

Question 22

The umbilical arteries carry deoxygenated blood from the fetus to the ___________ of the placenta.

Answer 22

capillary network within the tertiary villi

Question 23

The term placenta is roughly _______ the weight of the term fetus.

Answer 23

1/6

Question 24

What drugs can cause oligohydramnios?

Answer 24

Those that decrease GFR: COX inhibitors and ACE inhibitors

Question 25

The trophoblasts invade up to the _____________ of the uterus.

Answer 25

most superficial 1/3

Note: the cytotrophoblasts invade the spiral arteries.

Question 26

hCG peaks around __________.

Answer 26

10 weeks

Question 27

Women with elevated hCGs may have _____________.

Answer 27

choriocarcinoma (if extremely elevated) or a baby with trisomy 21 (if moderately elevated)

Question 28

What does hPL do?

Answer 28

Human placental lactogen makes the maternal system switch to fatty acid metabolism and increases insulin resistance to provide sugar to the fetus.

Question 29

what maintains the corpus luteum and progesterone production until the placenta takes over?

Answer 29

hCG until week 8

Question 30

what regulated cytotrophoblast differentiation into syncytiotrophoblasts?

Answer 30

hCG

Question 31

does estrogen production require both maternal and fetal placental tissue?

Answer 31

yes, estrogen synthesis intermediates are shuttled back and forth across the placenta because each part has needed enzymes that the other part lacks.

• placenta lacks P450c17 and 16-a-hydroxylase
• fetus lacks P450 aromatase and 3-B-hydroxysteroid dehydrogenase