Placenta (Natalia) Flashcards
again, sorry for the long ass deck, she has 84 slides and there was no obvious way to pick out the important info
inner cell mass of the blastocyst becomes the ____
fetus
What is the origin of the placenta?
outercell mass of the blastocyst:
- villous cytotrophoblast cells → syncytiotrophoblast
- extravillous cytotrophoblast cells → invasive throphoblast
What mediates implantation of the blastocyst?
L-selectin system:
The human blastocyst expresses L-selectin, and ‘rolls’ on the endometrial surface. There is a weak interaction between the surface of the blastocyst with glycocalyx (on endometrial surface). This allows for enough time (?) for the hCG secreted from the blastocyst to induce trophin expression on the endometrium. Trophin has a domain that is the ligand for L-selectin. They bind and adhesion can occur.
What changes in the endometrial epithelium does attachment of the blastocyst to the endometrium initiate?
decidualisation: increased vascular permeability and secretary action of stromal cells
What signaling interactions occurs from the endometrium to the blastocyt for implantation?
progesterone and estrogen from the ovary/CL induces endometrial secretion of EGF and Leukemia inhibiting factor which induces blastocyst expression of MMPs and uPA (plasminogen activator)
does a women have to be pregnant to undergo a decidual reaction
NO it happens every menstrual cycle
Is decidualized endometrium suitable for implantation?
no, it does not allow trophoblast to be able to implant **this occurs at the end of the menstrual cycle ~day 23
what are the characteristic histo signs of the decidual reaction?
prominent spiral arteries
spindle shaped stromal cells → round cells (from Nichols’ lecture)
When in the menstrual cycle does the decidual reaction occur?
later part,~ day 23
Why does decidualisation occur?
efficient placentation = access to maternal blood
restricts trophoblast invasion
provides nutrients
**this “prepares the uterine lining for the presence of the invasive trophoblast but simultaneously closes the door to implantation”
But how can a nonreceptive decidualized endometrium be returned to a receptive nondecidualized endometrium if no pregnancy occurs?
menstruation
Within hours of attachment trophoblast destroys _____
epithelial cells
Some trophoblast cells fuse to form _____ others retain cellularity and form _____ .
Some trophoblast cells fuse to form syncytiotrophoblasts others retain cellularity and form cytotrophoblast
What invades the decidua to attack blood vessel walls? Why?
villi to release nutrients, eventually the villi are invaded by embryonic blood vessels
layer of mononuclear cells that forms new cells form into the syncytiotrophoblast
villous cytotrophoblast
What is the major source of placental hormone production, particularly hCG?
syncytiotrophoblast
what are the primary chorionic villi? when are they present?
villous extensions from cytotrophoblast
end of 2nd week
what are the multinucleated cells that invade the endometrial stroma
syncytiotrophoblast
primary chorionic villi originate from
cytotrophoblast
known as villous cytotrophoblast when they are present
By nine days the embryo is surrounded by ____
two layers of trophoblasts
Describe the trophoblast layers (~day 9)
inner mononuclear cytotrophoblast
outer multinucleated syncytiotrophoblast layer
What is the function/purpose of the trophoblast laysers
extract nutrients from mother and protects fetus/embryo from maternal immunologic attack
what is a proposed theory for the origination of the deciduation?
retrovirus
What mechanisms are present to facilitate immune tolerance of the mother?
cytotrophoblasts:
• decrease complement activity
alter Ag presentation (HLA-G)
syncytiotrophoblasts:
• regulate leukocyte traffic by cytokines and chemokines
• releases indolemanine 2,3-dioxygenase
ovaries: secrete progesterone (anti-inflammatory, regulates prostaglandin production)
what promotes angiogenesis in the endometrium surrounding the implanted embryo?
trophoblast (both layers) make VEGF
By what week are the anatomical arrangements necessary for physiological exchanges between the mother and her embryo are established
3rd
At what week is the complex vascular network established in the placenta (to facilitates maternal-embryonic exchanges of gases, nutrients, and metabolic waste products)?
4th
How are secondary chorionic villi formed?
made from primary villi that branch and then develop a core of mesenchymal tissue
what do the secondary chorionic villi cover?
entire surface of the chorionic sac
what happens as the chorionic sac grows (past the 8th week)?
villi assc with the decidua capsularis are compressed → reduced blood supply to them → they degenerate → bald areas/smooth chorion
Decidual vera =
decidua capsularis + decidua parietalis
does NOT incule decidua basalias
As the secondary villi disappear, those associated with the ______ rapidly increase in number, branch profusely, and enlarge
decidua basalis
As the villi disappear, those associated with the decidua basalis rapidly increase in number, branch profusely, and enlarge → forming the
villous chorion
*part of the chorionic sac
During early implantation, the maternal vessels are penetrated and become plugged up with
trophoblasts
T or F: you need an embryo present to develop the placenta
F: the fetus is a “by product” of the placenta forming
the ____ of the spiral arteries decreases to allow more blood to get to the fetus
resistance
During implantation the trophoblast differentiates into the
syncytiotrophoblastand the cytotrophoblast and the embryoblast
The______ begins to invade maternal
tissue, making contact with maternal vessels
syncytiotrophoblast
lacunae develop within the
syncytiotrophoblast
cytotrophoblastic cones grow into
the syncytiotrophoblast mass
First fetal capillaries appear within the
chorion plate
branching of the____ results in a trabecular tree
trophoblast
The trabecle contain
mesenchyme, fetal capillaries, and a single layer of cytotrophoblast cells
The _______ is built by a thin syncytiotrophoblast layer
barrier to the labyrinth
Maternal vessels are opened so that the ______ is filled with maternal blood
placental labyrinth
Blastocyst implantation occurs around day _____ post-conception
6-7
Forms a shell that ultimately anchors the conceptus to the endometrium
Cytotrophoblast
Cavity between the embryoblast and trophoblast forms the_______, lined by a membrane called the
primordial amnionic cavity lined by the amnion
what cells/tissues constitute the chorion?
Trophoblastic layers and extraembryonic somatic mesoderm
Basic structure of placenta formed ____ weeks gestation.
5
maternal and fetal circulations are seperated by
syncytiotrophoblast
The placenta is responsible for respiration and excretion in the growing fetus. Describe how this is accomplished.
Fetal blood flows through the blood vessels of the umbilical cord to the placenta, where fingerlike capillary nets (intermediate and terminal villi) are surrounded by pools of the mother’s blood. Here carbon dioxide and other metabolic wastes diffuse from fetus to mother, and oxygen and nutrients pass from mother to fetus.
The definitive placental disc is called the
chorion frondosum
The _____ contains fetal arteries and veins that connect the umbilical circulation to smaller branches of chorionic arteries and veins
chorionic plate (continuous with the bald chorion)
What is the inner shell of the conceptus? outer shell?
inner = amnion outer = chorion
___ is embryologically continuous with the epithelium of the umbilical cord and the baby’s skin
amnion
is the amnion vascularized?
no
Wharton’s jelly is
the connective tissue of the umbilical cord
protects the cord blood vessels from mechanical trauma
Wharton’s jelly
The maternal portion of the placenta arises from the_____ that is transformed into_____
endometrium → decidua
What hormone is the major driving force that transforms the endometrium into the decidua?
progesterone
WHat is the portion of the decidua at the base of the chorion frondosum (the implantation site)?
decidua basalis
WHat is the origin of the uteroplacental arteries
spiral arteries + trophoblast invasion (with remodeling)
What causes the uteroplacental arteries to dilate?
pressure due to increased uterine blood flow
How are the uteroplacental arteries structurally different than other arteries
the lack elastic or muscular layers (just fibrous)
a predominantly acellular zone that develops at the interface between the chorionic villi and the decidua in the decidua basalis.
Nitabuch’s fibrinoid layer
The intervillous space can also be thought out as part of the maternal component of the placenta. This space is filled by maternal blood provided by the
uteroplacental arteries
Fetal nutrient exchange occurs at the interface between the
intervillous space and the chorionic villi.
**TERMINAL VILLI
What regulates nutrient and gas exchange within the intervillous space
blood flow and placenta structure
how are Immunoglobulins transferred from maternal circulation to fetal circulation?
endocytosis (vesicular transport)
how are respiratory gases transferred from maternal circulation to fetal circulation?
lipophillic diffusion
how are hydrophillic molecules transferred from maternal circulation to fetal circulation?
paracellular diffusion (via watter filled channels/pores)
- ex: Na, Ca, K
- **larger proteins use transporters
Transporters mediating the transfer of amino acids, glucose (GLUTs), and fatty acids (FATPs) are expressed in both plasma membranes (apical and basolateral) of the ______
syncytiotrophoblast
describe the transfer of lipids from maternal circulation to fetal circulation
extracellular lipases release fatty acids from maternal lipoproteins and intracellular binding proteins (FABPs) guide the fatty acids within the cytosol of the syncytiotrophoblast.
_____ may interfere with amino acid transport through nutrient signal pathways
glc and lipid metabolism
what type of FA does the placenta preferentially pick up?
long chain poly-unsaturated FA
… are predicted to prevent accumulation of xenobiotics in the fetal circulation by limiting their entry into the placenta
Maternal facing apical/microvillous membrane ATP-binding cassette (ABC) family of transmembrane transporters
Accreta
placenta attached to the myometrium
Increta
placenta invades the myometrium
Percreta
placenta invades to or through the uterine serosa
Absence of the fibrinoid layer between the villi and decidua (Nitabuch’s layer)
placenta accreta (leads to the placenta beign directly attached to the myometrium)
implantation of the placenta in the lower uterine segment
placenta previa
complete vs partial vs marginal placenta previa
Complete—placenta covers entire internal cervical os
Partial—placenta covers a portion of the os
Marginal—placenta immediately adjacent to internal os
separation of a normally-implanted placenta before the birth of the fetus
abruption placentae
presentation of placental abruption
vaginal bleeding, abdominal pain, tender or rigid abdomen, hypercontracile uterine contraction pattern
What are risk factors for placental abruption
truama maternal HTN maternal cocaine use maternal cigarette smoking sudden uterine decompression
