Implantation And Formation Of Placenta 2 Flashcards
Expands into to decidua
Outer pole faces the endometrial cavity
Inner pole forms the placenta
Blastocyst
Aka leafy chorion
Forms when chorionic villi proliferates upon contact with decidua basalis
Chorionic frondosum
As growth of embryonic and extra embryonic tissues continues
Blood supply to the chorion facing the endometrial cavity is restricted
Aka smooth chorion
Portion of chorion that becomes the avascular fetal membrane that touches the decidua parietalis
Chorion laeve
Chorion laeve composed of cytotrophoblast and fetal mesodermal mesenchyme that survives in
Low oxygen atmosphere
Chorion laeve
Separated from the amnion by exocoelomic cavity
Near the end of 3rd month
Important sites of molecular transfer and metabolic activity
Chorion laeve
Amnion
More translucent than the amnion
Chorion laeve
Paracrine arm of the fetal maternal communication system
Amniochorion
Accumulate in decidua and are found in direct contact with trophoblast during first half of pregnancy
Decidua natural killer cells
Decidua natural killer cells
Lacks of cytotoxic functions and are able to
Dampen inflammatory TH17 cells
Inhibits NK cells killing during pregnancy
Decidual macrophages
Decidua natural killer cells
It expresses both
IL8 and
Interferon inducible protein 10
Decidua natural killer cells
Produce proangigenic factors that promotes vascular growth in the decidua
VEGF
Placental growth factor (PIGF)
Secrete specific chemokines that attract the dNK cells to the maternal fetal interface
Trophoblasts
They form cell columns that extend from the endometrium to the inner third of the myometrial
Extra villus trophoblast
Requires invasion of endometrium and spinal arteries
Process occurs under low oxygen conditions
Hemochorial placental development
Secrete proteolytic enzymes that digest extracellular matrix and activate proteinase already present in the endometrium
Invasive trophoblast
Invasive trophoblast produce urokinase type plasminogen activator which converts plasminogen into
Plasmin
Degrades matrix proteins and activates matrix metalloproteases
Plasmin
Appears to be critical for human trophoblast invasion
MMP-9
Ability to invade maternal tissue in early pregnancy compared with limited Invasiveness in late pregnancy is controlled by?
Autocrine factors
Paracrine trophoblastic factors
Endometrial factors
Secrete insulin like growth factor 2 acts in an Autocrine manner
Trophoblast
Secrete insulin like growth factor binding protein type 4 that block Autocrine loops
Decidual cells
Degree of trophoblast invasion is controlled by
Matrix degradation regulation
Factors that cause trophoblast migration
Low estradiol levels in the first trimester are critical
For trophoblast invasion and
Remodeling of spinal arteries
Occurs in the first half of pregnancy
Important to utero placental blood flow
Invasion of spiral arteries
Invasion of spinal arteries
Integral to pathological conditions such as
Pre eclampsia
Fetal growth restriction
Preterm birth
Invasion of spinal arteries
Carried out by two populations of extravillous trophoblast
Interstitial trophoblasts
Endo vascular trophoblast
Aggregate around the spiral arteries
Vessel preparation for endo vascular trophoblast invasion
Interstitial trophoblast
Enter to the spiral arteries lumens
Initially from cellular plugs
Endo vascular trophoblast
Endo vascular trophoblast
Destroy vascular endothelium via
Apoptosis
Invasion by trophoblast involves only the decidual spiral arteries
Not decidual veins
2 stages of utero placental vessel development
First wave - before 12 weeks, post fertilization
Second wave - between 12-16 weeks
Maternal blood enters the
Intervillous space
Blood is propelled outside of the maternal vessels and sweep over and directly bathes the
Syncytiotrophoblast
Placental growth and maturation
Placental growth is more rapid than fetus
First trimester
Placental growth and maturation
Placenta and fetal weights are equal
17 weeks AOG
Placental growth and maturation
Placenta weight is 1/6 of fetal weight
By term
Placental growth and maturation
Slightly elevated convex areas from the maternal surface
Lobes
Placental growth and maturation
Grossly visible lobes
Cotyledons
Placental maturation
Abundant loose intercellular matrix in early pregnancy
Villous stroma
Placental maturation
Fetal macrophages
Nearly round with vesicular, often eccenteric nuclei and very granular or vacuolated cytoplasm
Hofbauer cells
Fetal circulation
Deoxygenated blood flows to the placenta through the
Two umbilical arteries
Fetal circulation
Umbilical vessels branch repeatedly beneath the
Amnion and villi
Fetal circulation
Oxygenated blood returns from the placenta bia
Umbilical vein
Fetal circulation
Umbilical vessels that traverse along the fetal surface of the placenta in the chorionic plate.
Responsive to vasoactive substances
Placental surface
Chorionic vessels
Fetal circulation
65% of placentas, chorionic arteries form a fine network supplying the
Cotyledons
Fetal circulation
Perforating branches of the surface arteries that pass through chorionic plate.
Truncal arteries
Each truncal arteries supplies
One main stem villus
One cotyledon
Maternal circulation
Maternal blood enters through the ________ and is driven high up toward the ________ by arterial pressure.
Basal plate
Chorionic plate
Maternal circulation
After bathing the external micro villus surface of chrorionic villi, maternal blood drains back through__________ in the _______ and enter _________.
Venous orifice
Basal plate
Uterine veins
Maternal circulation
Maternal blood transverse the placenta randomly without
Performed channels
Maternal circulation
Trophoblast invasion of the spiral arteries creates low resistance vessels that accomodate massive increase in
Uterine perfusion during gestation.
Maternal circulation
Uterine wall
Spiral arteries are
Perpendicular to it
Maternal circulation
Uterine wall
Veins are
Parallel to it
Maternal circulation
Arterial openings into the Intervillous space becomes gradually reduced by
Cytotrophoblast invasion
Maternal circulation
Uterine wall
How many spiral arteries entries into the Intervillous space at term
120
Maternal circulation
Uterine wall
A prominent venous plexus separates the deciduas basalis from the myometrial and thus participates in providing a cleavage plane for placental separation
After the 30th week
Maternal circulation
Uterine wall
Increased during contraction
Placental lenght
Thickness
Surface area
Maternal circulation
Larger volume of blood is available for exchange even though the rate of flow is decreased.
During contractions
Maternal circulation
Principal factors regulating Intervillous space blood flow
Arterial blood pressure
Intrauterine pressure
Uterine contraction pattern
Factors acting on arterial walls
Immunological consideration of the Fetal Maternal Interface
With their inefficient cytotoxic abilities
Decidual natural killer cells
Immunological consideration of the Fetal Maternal Interface
Populate the deciduas
Invasive trophoblast
Immunological consideration of the Fetal Maternal Interface
Only fetal derived cells in direct contact with maternal tissues
Trophoblast
Immunological consideration of the Fetal Maternal Interface
Act to control the invasion of trophoblast, which have adapted to survive in an immunologically hostile environment
Maternal NK cells
Human analogue of the major histo compatibility complex
Human leukocyte antigen
MHC clas 1 and 2 antigens are absent
Villus trophoblasts
Express MHC class 1 molecules
Invasive extravillous cytotrophoblast
Trophoblast HLA class 1 expression
Encodes the major class I class Ia
ABC
Trophoblast HLA class 1 expression
Encodes major class Ib
EFG
Trophoblast HLA class 1 expression
Combined with unique expression of three specific HLA class I genes in extravillous cytotrophoblast
Uterine decidual natural killer cells
Trophoblast HLA class 1 expression
Expressed only in humans
Expression is restricted to extravillous cytotrophoblast adjacent to maternal tissues
HLa-G antigen
Trophoblast HLA class 1 expression
A solute major isoform which has increased levels during pregnancy
HLA G2
Distinctive lymphocytes originate in bone marrow and belong to the natural killer cell
Uterine Natural Killer Cells
Uterine Natural Killer Cells
Infiltration is increased by
Progesterone
Stromal cell production of IL15
Decidual prolactin
Uterine Natural Killer Cells
Secrete large amounts of _________ means that they are in an activated state
Granulocyte macrophage colony stimulating factor
Distributed over the entire periphery of the chorionic membrane
Villi