Placentation Flashcards
What are the most common complications in the second half of pregnancy?
Placental problems.
When does development of the placenta begin? and when does its functionality end?
Begins and implantation, functionality ends up delivery
What is the placenta for?
It is the site of nutrient and gas exchange, occurring b/w the blood streams of the mother and fetus.
What is the purpose of complete separation of maternal and fetal circulation?
So that the fetal and maternal blood do not mix.
The placenta and fetal membranes provide protection and hormone production. What is included in the “fetal membranes”?
Chorion, Amnion, Umbilical vesicle (aka yolk sac), and allantois.
The hormone hCG is made by what?
What does it do?
made by the syncytiotrophoblast, causes the ovary to continue producting progesterone which maintains the endometrium. Progesterone also acts as an anti-inflammatory agent.
Why does the implanting blastocyst prevent the production of prostaglandins?
Prostaglandins decrease progesterone production, which is needed to maintain the endometrium and progesterone also acts as an anti-inflammatory agent.
The blastocysts initially receives nutrients from ____ while floating in the uterus. Growth increases its demands which will then be supplied by _____.
secretions from uterine glands;
early placental tissues.
What is the decidual reaction?
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.
What is the dedicua?
The functional layer of the endometrium in a pregnant woman
What are the 3 regions of the decidua?
- Decidua basalis: endometrium deep to conceptus, forms maternal part of placenta
- Decidua capsularis: superficial part of overlying conceptus
- Decidua parietalis: all remaining parts of decidua
At what day of post fert do chorionic villi begin to develop?
day 13
What are primary chorionic villi?
outgrowths of CYTOTROPHOBLAST which invade SYNCYTIOTROPHOBLAST and crow into developing blood-filled lacunae
When do secondary chorionic villi develop? How are they distinguished by primary chorionic villi??
15 or 16 days post fert. The growth of mesoderm nto the villi is the transforming factor, changing primary to secondary villi.
When do tertiary chorionic villi devlop and how are they distinguished?
20-21 days post-fert. Mensenchymal cells differentiate into capillaries and blood cells.
What happens by the end of the 4th week with respect to the vascular network?
A complex vascular network is established in the placenta
What happens UNTIl the beginning of the 8th wk w/ respect to chorionic villi?
Chorionic villi cover the entire chorionic sac until the beginning of the 8th wk
What is chorionic villus sampling (CVS) and when is it done?
How does it compare to amniocentesis?
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.
What is another name for villous chorion?
What is another name for smooth chorion?
Chorion frondosum;
laeve
Why is there a cobblestone appearance in the placenta?
It is due to the projection of the placental septa (aka decidua basalis) into convex cotyledons
The villous chorion is associated with which decidua region?
decidua basalis
The maternal blood will eventually fill the ____ becoming an important area of fetal/maternal exchange.
Intervillous space
What are the fates of each region of the decidua?
- Decidua basalis forms meternal part of placenta, forming placental septa
- Decidua capsularis bulges and eventually fuses w/ the decidua parietalis, and obliterates the uterine cavity
What happens as a result of the amniotic sac enlarging faster than the chorionic sac?
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.
The 2 circulations of maternal and fetus are separated by___ such that they NEVER mix.
placental membrane.
Deoxygenated blood leaves the fetus via _____ to the _____.
Oxygenated blood returns to the fetus via _____.
2 umbilical arteries; placenta
1 umbilical vein
Where does the main exchange of materials b/w fetal and maternal circulation take place?
The branch chorionic villi
What is the single most important factor to the welfare of the embryo/fetus?
The adequate bathing of the branch villi w/ maternal blood
What is the most common of the dangerous pregnancy complications? What is it?
Pre-eclampsia: a medical condition where hypertension arises in pregnancy in association w/ significant amts of protein in the urine.
What are some things that are exchanged through the placental membrane?
Gases, hormones, electrolytes, antibodies, CO2, urea, uric acid, bilirubin.
The main funciton of the placenta is the exchange of materials b/w maternal and fetal blood steams. What are 2 additional functions?
- Synthesize glycogen, cholesterol, and Fatty Acids during early pregnancy.
- Transfer of maternal antibodies.
Which membrane ruptures during labor?
Amniochorionic membrane
What is the amniotic fluid and what are its purposes?
clear watery fluid that is 99% water. It:
- Permits normal lung development
- Prevents amnion adhering to embryo
- Cushions embryo
- Enables fetus to move
- Maintains homeostasis
- Acts as a barrier to infection.
When is the placenta usually expelled?
10 minutes after the baby
What is placental accreta?
What are the 3 forms?
abnormal superficial attachment of the placenta to the myometrium.
- Accreta: invasion of myometrium that doesn’t penetrate the entire thickness of the muscle (75% of all cases)
- Increta: placenta further extends into myometrium
- Percreta: penetrates entire myometrium (5-7% of cases and most severe)
What is placenta previa?
When the blastocyst implants close to the internal os, overlying the cervix. Indicates C-section delivery
Twins that originate from one zygote are:
Monozygotic
Describe the timing of zygote splitting and their results for monozygotic twins.
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
