6 Fetal Membranes And Placenta Flashcards
What happens to the placental barrier throughout pregnancy?
It becomes thinner
What gives rise to the placenta?
Trophoblast
Function of fetal membranes
Protection
Functions of the placenta (3)
Metabolism
Exchange of metabolic and gaseous products between maternal and fetal bloodstreams
Production of hormones
Metabolism
Synthesis of glycogen, cholesterol and fatty acids which provide nutrition for the endometrium
Exchange of metabolic and gaseous products between maternal and fetal bloodstreams including :
Nutrients and electrolytes
• Oxygen, CO2, and CO
• Maternal immunoglobulin G( passive immunity from the mother )
Production of hormones :
Human chorionic gonadotrophin
Progesterone
Estriol
Somatomammotropin (develops the mammary glands of the mother)
Fetal membranes include
Amnion
Chorion
Yolk sac
Allantois ( connective stalk - came from extraembyrionic mesoderm)
Fetal membranes develop from
zygote
True or false. The amnion and chorion participate in the formation of the embryo or fetus
False. The amnion and chorion do not participate in the formation of the embryo or fetus
What are essential for fetal development?
Amnion and amniotic fluid
The amnion and chorion do not participate in the formation of the embryo or fetus. Why?
Because they come from the extraembyrionic mesoderm
The yolk sac is incorporate as ..
primordium of the gut
When does transfer of nutrients occur between yolk sac and embryo?
2nd to 3rd week of development
When do blood cells develop in yolk sac wall?
3rd - 6th week of development
When do primordial germ cells appear in the yolk sac wall?
3rd week of development
Allantois forms _______ in fetus and _________________ in the adult
urachus
median umbilical ligament
When do blood cells develop in the wall of the allantois?
3rd-5th week of development
The allantois’ blood vessels persist as
Umbilical veins and arteries
When does the placenta start to develop?
As soon as implantation occurs
Placenta is a _________ organ
Fetomaternal
What does fetomaternal mean?
Has a fetal and maternal component
Fetal part develops from …
Chorionic sac
Maternal part derived from
Endometrium ( source of the blood vessels)
In humans the placenta is of hemochorial Type. What does that mean?
no mixing of blood
What type of placenta is present in humans?
hemochorial Type
What invades the endometrium?
Syncytiotrophoblast
Fetal membranes and placenta weeks to remember
5th-22
Decidua
The functional layer of the endometrium in a pregnant woman
What happens to the decidua after childbirth?
separates from the remainder of the uterus after childbirth.
The three regions of the decidua are named according to
their relation to the implantation site
What forms the maternal part of the placenta?
decidua basalis
What overlies the conceptus?
decidua capsularis
The__________ is all the remaining parts of the decidua
decidua parietalis
What pops when the mother is about to give birth?
The mucous plug
Gravid uterus at 4 weeks shows ..
relation of the membranes to each other and to the decidua and embryo
What is the chorionic plate?
It is a layer of the extraembyrionic mesoderm that marks the fetal part of the placenta
___________ fills up with blood vessels.
Extraembryonic mesoderm
Why do the villi decrease in size?
Decrease in size to allow for gas exchange
Why do the villi differentiate?
The villi differentiate to decrease the size of the barrier
Structure of full term placenta
Discoid structure with a diameter of 15-25 cm
Thickness of full term placenta
3 cm
Weight of full term placenta
500-600g
When is the placenta expelled?
Expelled 30 minutes after birth
Maternal side exhibits
15-20 cotyledons separated by decidual septa
What is the decidual septa?
spaces between the villi
Fetal surface is covered by the _____________, which is covered by the
________
chorionic plate
amnion
Attachment of the umbilical cord is usually ___________ and occasionally __________
eccentric ( near the middle)
Marginal ( to the side)
Whats on the fetal surface?
Amnion
Umbilical cord
Chorionic plate
Chorionic vessels
Whats on the maternal surface?
Cotyledon covered by decidua basalis
What are the structural features of the placenta?
Decidual septum , amnion, spiral artery, chorionic plate, decidual plate, endometrial veins,umbilical vessels, chorionix vessels
What leaves the embryo and goes into the maternal blood? ( general)
Waste products and other substances
What waste products leave the embryo and enter maternal circulation?
Carbon dioxide
Water
Urea
Uric acid
Bilirubin
What other substances leave the embryo and enter the maternal circulation?
RBC antigens
Hormones
What leaves the maternal circulation and goes into the embryo?
Oxygen and nutrients
Harmful substances
Other substances
What oxygen and nutrients leave maternal circulation and enter embryo?
Water
carbohydrates
amino acids
Lipids
Electrolytes
Hormones
Vitamins
Iron
Trace elements
What harmful substances leave maternal circulation and enter the embryo?
Drugs ( eg alcohol poisons and carbon monoxide)
Viruses ( rubella and cytomega)
Strontium-90
Toxoplasma gondii
What other substances leave the maternal circulation and enter the embryo?
Antibodies IgG and vitamins
What are nontransferabble substances that cant enter embryo through maternal circulation?
Bacteria
Heparin
Transferrin
IgS and IgM
How do substances leave and enter the embryo?
Leave embryo through umbilical arteries
Enter embryo through umbilical vein
How do substances leave and enter the maternal circulation?
Enter maternal circulation through endometrial veins
Leave maternal circulation through endometrial spiral arteries
The fetus is floating in _____________, and it ______ it while also _______ it at the same time. This is made possible due to …….
aminiotic fluid
Ingests
Secreting
the cleansing of the blood by the maternal blood vessels, which rids it of all harmful substances
Monozygotic twins and a common placenta
Come from same oocyte
Have one placenta , one chorionic sac, two amniotic sacs
Dizygotic twins and a fused placenta
came from two different oocytes
Has fused placenta, fused chorionic sacs, two amnions
What causes Dizygotic twins and a fused placenta ?
happens due to continuous AMH hormone secretion
Or because both ovaries ovulated and released eggs at the same time
Dizygotic twins and two placentae
Two oocytes
Two chorionic sacs
Two amnions
Two placentae
Placental abnormalities
Placenta percreta
Placenta accreta
Placenta previa
Chance of survival for Placenta percreta and placenta previa
No chance of survival
Chance of survival for placenta accreta
Variable chance of survival
Enlargement of Amnion
Starts happening from week 3 to about week 20 happens medially
Significance of amniotic fluid:
Permits symmetrical growth of the embryo and fetus
Acts as a barrier to infection
Prevents adherence of amnion to the embryo and fetus
Permits normal fetal lung development
Cushions the embryo and fetus
Enables movement of the fetus aiding in muscular development
Maintains homeostasis of fluid and electrolytes
Oligohydramnios
Refers to when there is a shortage of aminiotic fluid, it can cause the baby to be born with severe abnormalities including underdeveloped lungs
Polyhydramnios
 Refers to when there is an excess of aminiotic fluid, it can cause the baby to be born with severe abnormalities including anencephaly
