Placenta Flashcards
Human placenta is hemochorial, which means-
Maternal blood comes in direct contact with the chorion
What is the fetal and maternal component of the placenta?
fetal- villous chorion
Maternal- decidua basalis
The fetal surface of the placenta is characterized by
vascular chorionic plate covered by amnion; appears smooth and grayish
The umbilical cord contains
2 umbilical arteries and 1 umbilical vein
What are the umbilical arteries and vein surrounded by?
Wharton’s jelly (mucous connective tissue)
Since umbilical vessels are longer than the cord, they twist around each other and bend forming
false knots
What is the decidua
endometrium of the uterus in a pregnant woman
What are the 3 regions of the decidua
Decidua basalis- part deep to the conceptus that forms the maternal part of placenta
Decidua capsularis- superficial part overlying conceptus
Decidua parietalis- all the reamining parts
Maternal side of the placenta has 15-20 compartments called
cotyledons separated by placental septa
Fetal component of the placenta is derived from the
trophoblast and extraembryonic mesoderm, forming the villous chorion
What are the 3 stages of chorionic villi development
primary villi, secondary villi, and tertiary villi
Cytotrophoblast cells penetrate through the synctiotrophoblast and reach the decade and form
the cytotrophoblast shell
What does the cytotrophoblast shell do
firmly attaches chorion to the endometrium.
What are villi that extend from the chorionic plate to the decidua basalis
Stem (anchoring) villi
What branches from the sides of the stem villi and represent sites where nutrient and gas exchange will occur?
Terminal (free; branch) villi
What is the placental membrane?
It separates the maternal blood from fetal blood
By month 4, what are the 4 layers of the placental membrane
Synctiotrophoblast, cytotrophoblast, extraembryonic mesoderm, and fetal endothelium
At the beginning of month 4, the cytotrophoblast degenerates leaving what 2 layers
Synctiotrophoblast and fetal endothelium
In the 3rd trimester, what becomes very thin
syncytiotrophoblast
What covers the surface of the chorion prior to week 8
Villi
As pregnancy progresses, the villi proliferate to form the
chorionic frondosum (bushy chorion)
Chorionic villi on the ab-embryonic pole degenerate and form __ by the end of month 3.
smooth chorionic laeve
When can you conduct chorionic villus sampling
10-12 weeks
What cells spread and form the lining of the amnion
epiblast cells
The amnion encloses the entire embryo by
week 8
The amnion becomes continuous with the skin at the attachment of the umbilical cord to the fetus to
cover the umbilical cord and placenta
What are the functions of the amniotic fluid?
allows for fetal movements; Prevents adherence between amnion and embryo; shock absorber; barrier to infection; promotes lung development.
What is the amniotic fluid volume at 10 weeks vs term
10 weeks- 30mL
37 weeks- 1000 mL
What is the “water-bag” that breaks prior to delivery of the baby?
amnio-chorionic membrane
How is the amnio-chorionic cavity formed?
The amnion pushes against the chorion and the chorionic cavity is obliterated so the amnion lies against the chorionic laeve
What is an amniocentesis
hollow needle is inserted through the mothers abdomen into the uterus and amniotic fluid is drawn for analysis
What is amniotic band syndrome
There are tears in the amnion that may result in amniotic bands that encircle fetal limbs or digits resulting in deformations
What is polyhydramnios and what is it correlated with
excess amniotic fluid; maternal diabetes and disorders of the central nervous system and GI tract that prevents fetus from swallowing.
What is oligohydramnios and what is it linked to
too little amniotic fluid; may result from failure of the kidneys to form.
What is oligohydramnios a risk factor of
lung hypoplasia (lung underdevelopment)
What are the functions of the placenta?
Acts as an organ of exchange between maternal and fetal tissues; Produces hormones (progesterone, hCG, human placental lactogen=somatomammotropin) Serves as an immunological barrier
What beneficial substances can cross the placenta?
Oxygen and CO2 glucose, amino acids, etc. Water, ions, etc. Urea, uric acid, bilirubin Maternal serum proteins unconjugated steroid hormones IgG, IgA
What harmful substances can cross the placenta?
Viruses (rubella, CMV, herpes simplex type 2, measles, polio), toxoplasma gondii, and troponema pallidum (only bacteria that can cross).
Category X drugs (absolute contraindication in pregnancy; thalidomide, coumadin, alcohol, etc.)
Category D drugs (definite risk to fetus; tetracycline, valium, etc.)
Carbon monoxide, mercury, lead, cocaine, heroin, rubella virus vaccine, anti Rh antibodies)
What substances do not cross the placenta
Maternally derived cholesterol, triglycerides, phospholipids.
Protein hormones- insulin
IgD, IgE, IgM
Umbilical arteries and veins carry what
arteries: deoxygenated blood toward placenta
Vein: oxygenated blood toward fetus
What is a newborns blood volume?
300 cc/mL
The inner sac is the __ and outer sac is the __
amnion; chorion
After 10 weeks amnion pushes out and
fuses with chorion
What is delivery en caul?
sac is intact
What are the metabolic functions of the placenta?
glycogen for fetus and cholesterol
When is Rh disease a problem
Rh - mom and Rh + baby
How to prevent Rh disease?
Give rhogam at 28 weeks, after baby is born if its Rh +, and after any bleeding in pregnancy
Up to how many hours does rhogam work after bleeding?
72 hours
What can cause postpartum hemorrhage?
leaving cotyledons behind after delivery
What does marginal insertion (battledore) placenta cause
fetus may be small
What occurs in membranous or velamentous insertion
cells can be kink, may result in non reassuring fetal heart tracing
What is vasa previa
accessory placental lobe has vessels running across the internal opening of the cervix
Why should you deliver vasa prevue babies early
If water breaks, vessels may rupture and baby can rapidly exsanguinate
What is placenta previa?
Whole placenta is covering the opening of the cervix
What is placenta accreta
placenta attaches too strongly to uterine muscle, or myometrium
What is placenta increta
placenta invades into myometrium
What is placenta percreta
placenta invades through myometrium to bowel, bladder
What is abruption
Premature separation; babys oxygenation ceases and blood lost is fetal blood
What causes abruption
cocaine, high BP, trauma
Cleavage of morula in days 1-3 results in
dichorionic/diamniotic
Cleavage of blastocyst in days 4-8
monochorionic/diamniotic
Cleavage of implanted blastocyst in days 8-13
Monochorionic/monoamniotic
Cleavage of formed embryonic disc in days 13-15
conjoined twins
What is twin-twin transfusion syndrome?
if monochorionic, artery of one fetus can connect to vein of other, and blood from one baby flows to the other
What happens to the fetuses in twin-twin transfusion
Donor: growth restricted, minimal fluid
Recipient: fluid overload
