Placentation

Question 1

What are the most common complications in the second half of pregnancy?

Answer 1

Placental problems.

Question 2

When does development of the placenta begin? and when does its functionality end?

Answer 2

Begins and implantation, functionality ends up delivery

Question 3

What is the placenta for?

Answer 3

It is the site of nutrient and gas exchange, occurring b/w the blood streams of the mother and fetus.

Question 4

What is the purpose of complete separation of maternal and fetal circulation?

Answer 4

So that the fetal and maternal blood do not mix.

Question 5

The placenta and fetal membranes provide protection and hormone production. What is included in the “fetal membranes”?

Answer 5

Chorion, Amnion, Umbilical vesicle (aka yolk sac), and allantois.

Question 6

The hormone hCG is made by what?

What does it do?

Answer 6

made by the syncytiotrophoblast, causes the ovary to continue producting progesterone which maintains the endometrium. Progesterone also acts as an anti-inflammatory agent.

Question 7

Why does the implanting blastocyst prevent the production of prostaglandins?

Answer 7

Prostaglandins decrease progesterone production, which is needed to maintain the endometrium and progesterone also acts as an anti-inflammatory agent.

Question 8

The blastocysts initially receives nutrients from ____ while floating in the uterus. Growth increases its demands which will then be supplied by _____.

Answer 8

secretions from uterine glands;

early placental tissues.

Question 9

What is the decidual reaction?

Answer 9

Endometrial stroma cells surrounding implantation site become loaded w/ glycogen and lipids. These decidual cells undergo apoptosis, and the syncytiotrophoblast engulfs them, providing nutrients for the developing embryo.

Question 10

What is the dedicua?

Answer 10

The functional layer of the endometrium in a pregnant woman

Question 11

What are the 3 regions of the decidua?

Answer 11

1. Decidua basalis: endometrium deep to conceptus, forms maternal part of placenta
2. Decidua capsularis: superficial part of overlying conceptus
3. Decidua parietalis: all remaining parts of decidua

Question 12

At what day of post fert do chorionic villi begin to develop?

Answer 12

day 13

Question 13

What are primary chorionic villi?

Answer 13

outgrowths of CYTOTROPHOBLAST which invade SYNCYTIOTROPHOBLAST and crow into developing blood-filled lacunae

Question 14

When do secondary chorionic villi develop? How are they distinguished by primary chorionic villi??

Answer 14

15 or 16 days post fert. The growth of mesoderm nto the villi is the transforming factor, changing primary to secondary villi.

Question 15

When do tertiary chorionic villi devlop and how are they distinguished?

Answer 15

20-21 days post-fert. Mensenchymal cells differentiate into capillaries and blood cells.

Question 16

What happens by the end of the 4th week with respect to the vascular network?

Answer 16

A complex vascular network is established in the placenta

Question 17

What happens UNTIl the beginning of the 8th wk w/ respect to chorionic villi?

Answer 17

Chorionic villi cover the entire chorionic sac until the beginning of the 8th wk

Question 18

What is chorionic villus sampling (CVS) and when is it done?

How does it compare to amniocentesis?

Answer 18

CVS is a form of prenatal diagnosis to determine any fetal genetic disorders.

It is performed b/w 10 to 12 wks.

Amniocentesis is performed at 15 and 18 wks.

Question 19

What is another name for villous chorion?

What is another name for smooth chorion?

Answer 19

Chorion frondosum;

laeve

Question 20

Why is there a cobblestone appearance in the placenta?

Answer 20

It is due to the projection of the placental septa (aka decidua basalis) into convex cotyledons

Question 21

The villous chorion is associated with which decidua region?

Answer 21

decidua basalis

Question 22

The maternal blood will eventually fill the ____ becoming an important area of fetal/maternal exchange.

Answer 22

Intervillous space

Question 23

What are the fates of each region of the decidua?

Answer 23

1. Decidua basalis forms meternal part of placenta, forming placental septa
2. Decidua capsularis bulges and eventually fuses w/ the decidua parietalis, and obliterates the uterine cavity

Question 24

What happens as a result of the amniotic sac enlarging faster than the chorionic sac?

Answer 24

The 2 fuse and form the amniochorionic membrane. This membrane fuses w/ the decidua capsularis, and then after its disappearance, fuses w/ the decidua parietalis.

NOTE: when a women’s water breaks, it refers to the rupture of this membrane.

Question 25

The 2 circulations of maternal and fetus are separated by\_\_\_ such that they NEVER mix.

Answer 25

placental membrane.

Question 26

Deoxygenated blood leaves the fetus via _____ to the \_\_\_\_\_. Oxygenated blood returns to the fetus via \_\_\_\_\_.

Answer 26

2 umbilical arteries; placenta 1 umbilical vein

Question 27

Where does the main exchange of materials b/w fetal and maternal circulation take place?

Answer 27

The branch chorionic villi

Question 28

What is the single most important factor to the welfare of the embryo/fetus?

Answer 28

The adequate bathing of the branch villi w/ maternal blood

Question 29

What is the most common of the dangerous pregnancy complications? What is it?

Answer 29

Pre-eclampsia: a medical condition where hypertension arises in pregnancy in association w/ significant amts of protein in the urine.

Question 30

What are some things that are exchanged through the placental membrane?

Answer 30

Gases, hormones, electrolytes, antibodies, CO2, urea, uric acid, bilirubin.

Question 31

The main funciton of the placenta is the exchange of materials b/w maternal and fetal blood steams. What are 2 additional functions?

Answer 31

1. Synthesize glycogen, cholesterol, and Fatty Acids during early pregnancy. 2. Transfer of maternal antibodies.

Question 32

Which membrane ruptures during labor?

Answer 32

Amniochorionic membrane

Question 33

What is the amniotic fluid and what are its purposes?

Answer 33

clear watery fluid that is 99% water. It: 1. Permits normal lung development 2. Prevents amnion adhering to embryo 3. Cushions embryo 4. Enables fetus to move 5. Maintains homeostasis 6. Acts as a barrier to infection.

Question 34

When is the placenta usually expelled?

Answer 34

10 minutes after the baby

Question 35

What is placental accreta? What are the 3 forms?

Answer 35

abnormal superficial attachment of the placenta to the myometrium. 1. Accreta: invasion of myometrium that doesn't penetrate the entire thickness of the muscle (75% of all cases) 2. Increta: placenta further extends into myometrium 3. Percreta: penetrates entire myometrium (5-7% of cases and most severe)

Question 36

What is placenta previa?

Answer 36

When the blastocyst implants close to the internal os, overlying the cervix. Indicates C-section delivery

Question 37

Twins that originate from one zygote are:

Answer 37

Monozygotic

Question 38

Describe the timing of zygote splitting and their results for monozygotic twins.

Answer 38

Twins separate at:\_\_;Result is:\_\_ 2-8cell stage;twins w/ 2 amnions, 2 chorions, 2 placentas (diamniotic-dichorionic) at end of first wk;twins w/ 2 amniotic sacs, 1 chorionic sac, 1 placenta (monochorionic-diamniotic twin placenta) after 8 days;monochorionic-monoamniotic twins 1 placenta beyond day 12; conjoined twins