Placenta & Fetal Membranes Flashcards
The placenta is the primary site of what?
Nutrients and gas exchange between the mother and fetus
The placenta is what kind of organ
Fetomaternal
What are the two components of the fetomaternal organ or placenta
1) A fetal part that develops from the chorionic sac
2) A maternal part that is derived from the endometrium
What constitute the fetal membranes?
The chorion, amnion, yolk sac and allantois
The fetal membranes delvelop from what?
The zygote
The fetal membranes do not participate in the formation of what? Except for which parts?
The embryo or fetus.
Except for parts of the yolk sac and allantois
Part of the yolk sac is incorporated into what? As what?
Into the embryo as the primordium of the gut
The allantois forms what?
A fibrous cord
What is the fibrous cord (formed by the allantois) called in a fetus?
Urachus
What is the fibrous cord (formed by the allantois) called in an adult?
Median umbilical ligament
The fibrous cord extends from what to what?
From the apex of the urinary bladder to the umbilicus
What separates the fetus from the endometrium of the uterus
The fetal part of the placenta and the fetal membranes
The interchange of what occurs between the maternal and fetal blood streams through what?
Nutrients & oxygen occurs
The placenta
The vessels in the umbilical cord connect what?
The placental circulation with the fetal circulation
The placenta and fetal membranes perform what functions and activities?
- Protection
- Nutrition
- Respiration
- Excretion
- Hormone production
Decidua refers to what?
The gravid endometrium
What is the gravid endometrium?
The functional layer of the endometrium in a pregnant woman
What are the 3 regions of the decidua (named according to their relation to the implantation site)?
The decidua basalis
The decidua capsularis
The decidua parietalis
The decidua basalis is what part of the decidua?
Deep to the conceptus that forms the maternal part of the placenta
The decidua capsularis is what part of the decidua?
The superficial part overlying the conceptus
The decidua parietalis is what part of the decidua?
All the remaining parts of the decidua
In response to increasing progesterone levels in the maternal blood, the connective tissue cells of the decidua do what?
Enlarge to form pale-staining decidual cells
Decidual cells enlarge as what accumulates in their cytoplasm
Glycogen and Lipid
The cellular and vascular changes occurring in the what as the blastocyst implants constitute the decidual reaction
endometrium
Decidual regions, clearly recognizable during ultrasonography, are important in what?
Diagnosing early pregnancy
When are the anatomical arrangements necessary for physiological exchanges between the mother and her embryo established
By the end of the third week
A complex vascular network is established in the placenta when, which facilitates what?
by the end of the fourth week
maternal-embryonic exchanges of gases, nutrients, and metabolic waste products
Chorionic villi covers what until when?
the entire chorionic sac
the beginning of the eighth week
As this sac grows, the villi associated with the decidua capsularis are what?
Compressed, reducing the blood supply to them.
These villi soon degenerate, producing a relatively what?
Avascular bare area, the smooth chorion.
As the villi disappear, those associated with the decidua basalis rapidly what?
Increase in number, branch profusely, and enlarge
The bushy part of the chorionic sac is what?
The villous chorion
Growth in the size and thickness of the placenta continues rapidly until when?
The fetus is about 18 weeks old (20 weeks’ gestation)
The fully developed placenta covers how much of the decidua and weighs about how much?
15 to 30%
One-sixth that of the fetus
Name the 2 parts of the placenta
- The fetal part
2. The maternal part
The fetal part of the placenta is formed by?
Villous chorion
The chorionic villi that arise from the villous chorion is projected into what?
Intervillous space containing maternal blood
The maternal part of the placenta is formed by?
the decidua basalis, the part of the decidua related to the fetal component of the placenta
By the end of the fourth month, the decidua basalis is almost entirely replaced by what?
the fetal part of the placenta
Cytotrophoblastic shell
the external layer of trophoblastic cells on the maternal surface of the placenta
The fetal part of the placenta (villous chorion) is attached to the maternal part of the placenta (decidua basalis) by what?
The cytotrophoblastic shell
The what attach firmly to the decidua basalis through the what and anchor the chorionic sac to the decidua basalis?
Chorionic villi
Cytotrophoblastic shell
Endometrial arteries and veins pass freely through what and open into the what?
Gaps in the cytotrophoblastic shell
Intervillous space
Poorly oxygenated blood leaves the fetus and passes through what to the placenta
the two umbilical arteries
These arteries divide into several radially disposed chorionic arteries that branch freely in the chorionic plate before entering the chorionic villi where
At the site of attachment of the cord to the placenta
The blood vessels form an extensive arterio-capillary-venous system within the chorionic villi, which brings what and where
The fetal blood extremely close to the maternal blood
There is normally no intermingling of what?
Fetal and maternal blood
However, very small amounts of fetal blood may enter the maternal circulation when what?
Minute defects develop in the placental membrane
The well-oxygenated fetal blood in the fetal capillaries passes into what that follow the chorionic arteries to the site of what?
thin-walled veins
attachment of the umbilical cord
The fetal veins converge to form what?
One umbilical vein
This large vessel carries oxygen-rich blood to the fetus
Umbilical vein
