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70 Cards in this Set

  • Front
  • Back
what are the functions of the placenta
1) oxygen, carbon dioxide, nutrients
2) protection from infection
3) endocrine organ
4) maintains maternal recognition of pregnancy
5) secretes amniotic fluid
which form of transport across placenta for urea
simple diffusino
which form of transport across placenta for amino acids
active transport
which form of transport across placenta for bilirubin
diffusion
which form of transport across placenta for non conjugated steroids
diffusion
which form of transport across placenta for fatty acids
diffusion
which form of transport across placenta for water soluble vitamins
active transport
which form of transport across placenta for glucose
active transport
which form of transport across placenta for calcium
active transport
which form of transport across placenta for cholesterol
active transport
which form of transport across placenta for iron
receptor mediated trancytosis via transferrin receptors
which form of transport across placenta for IgG
receptor mediated transcytosis via Fc receptors
what is the concentration of iron in maternal blood compared to fetal
2-3x greater in maternal blood
what 2 layers must nutrients travel in the mature placenta to get across it?
syncytiotrophoblast
endothelium of spiral artery
describe the growth of the placenta and fetus in the first trimester
fetus very small
placenta larger in comparison
describe the growth of the placenta and fetus in the second and third trimester
weight of fetus increasing massively from 24 - 1000g
weight of placenta increases but not as much, from 300 - 800 grams
in 3rd trimester a lot of the growth is an increase in fetal vessels
what does the full term placenta look like on the fetal side?
chorionic plate with umbilical vessels
what does the full term placenta look like on the maternal side
bloody, cotyledons
how does the baby contribute to vascularisation of the placenta
vessels from umbilical artery and vein
umbilical artery carries deoxygenated blood to the placenta
umbilical vein carries oxygenated blood away from the placenta
what is the effect of being able to plug the spiral arteries
can stop fetus being dislodged by spurt of blood
allows slowing of blood flow for increased exchange
how does the mother have contorl of her circulatory contribution to the palcenta?
the arteries are sympathetically innervated by only in the myometrial course
what 2 things can cause chronic reductions in perfusion of the placenta
anxiety, smoking
how much does the cardiac ouput increase in pregnancy?
25%
how much of cardiac output goes to the full term placenta?
10%
describe how aborization of chorionic villi occurs in the 2nd trimester
tertiary villi mesh and change
stem villi are the villi which anchor the placenta to the decidua
develop intermediate villi from buds on the stem villus
describe a stem villu
has large amount of mesoderm
act as conduit vessels
thick walled
small diameter
describe intermediate villi
exchange vessels
large diameter
closer to walls of villus
also have proliferative buds of trophoblasts
what are the 2 types of villi involved in aborization in the 2nd trimester/
stem
intermediate
what 2 factors influence vessel identity?
VEGF and angiopoeitn 1
what is meant by vessel identity
whether they differntiate into an artery or a vein
what genes are switched on to get an artery?
notch, sonic hedgehog
what genes are switched on to get a vein?
COUP - TII
what does angiopoietin do?
restricts angiogenesis
also responsible for pericyte and smooth muscle wrapping of endotherlium
what is the role of VEGF specifically ?
may help in maturation of junctions i.e. endothelial-endothelial contacts
what do VEGF and Ang P 1 do together
control vessel identity and vascular pruning
what development of chorionic vili occurs in the 3rd trimester?
development of terminal villi and terminal villous capillaries
what causes a second wave of angiogenesis in the fetus
fetal growth
how do terminal villous loop capillaries develop?
existing vessels grow and elongate in restricted space
causes them to loop and coil
bulge out to form terminal villi
where is materno-fetal exchange at maximum in the chorionic villi
in the terminal villi
why are terminal villi so good for exchnage?
proximitity to maternal blood
dilated lumen
syncytium abuts with endothelium - i.e. no cytotrophoblast in between
what is the term for monozygotic twins' placenta/s
monochorial
may be diamniotic
what is the term for dizygotic twins placenta/s
dichorial
what is twin twin perfusion syndrome?
unbalanced blood flow through monochoria diamniotic sac
smaller twin does not get enough blood
what is the maternofetal barrier formed of?
syncytium
endothelium
what cell junctions are in the syncytial part of the materno-fetal barrier?
none
what cell juncitons are in the endothelial part of the maternofetal barrier?
adherens and tight junctions form defined paracellular compartments
what molecules cannot travel throgh paracellular clefts?
molecules >65kDa
where do molecules of >65kDa go to cross materno/fetal barrier?
trasncellularly thorugh endothelial cell
does IgG take a transcellular or paracellular route through the materno/fetal barrier?
transcellular
what is the materno/fetal barrier freely permeable to?
drugs, alcohol
how can inflammation affect the materno/fetal barrier?
phosphorylation of junctional molcules can disrupt junctions and cause loss of barrier functions
which disease can lead to a loss of materno/fetal barrier function?
diabetes
what are the two main ways of providing efficient exchange across the materno/fetal barrier
large surface area
small diffusion distance
how does the materno/fetal barrier have a large surface area?
extensive branching of chorionic villous and capillaries
development of microvilli on syncytiotrophoblasts
how does the maternofetal barrier have a small diffusion distance
capillaries very dilated
close apposition of capillaries to syncytium
- dispersal of cytotrophoblast in between
elongation and thinning of syncytiotrophoblast
extrusion of excess nuclei in syncytial knots
how do syncytiotrophoblasts contribute to a large surface area of the materno/fetal barrier
have microvilli
how are syncytial knots formed and what are they?
excess nuclei from syncytiotrophoblasts
pinched off in apoptosis, enter maternal blood stream
where are syncytial knots phagocytosed
macrophages in the lungs
what is the clinical significance of syncytial knots/
incorrect packagaing or necrosis instead of apoptosis may result in preeclampsia
can be used for karyotyping
what are the possible causes of preecplampsia?
reduced invasion of spiral arteries by EVCTs
reduced invasion by invasive trophoblasts due to defective integrin switch
in preeclampsia with IUGR, what may occur
increased fetal vascular resistance
reduced angiogenesis of placenta, reduced villous branching and reduced microvilli
what can be the result of diabetes mellitus in pregnancy?
increased placental angiogenesis and villous growth
thickned basement membrane
abnormal microvilli
leaky blood vessels, loss of adhesion molecules, protein leakage, impaired placental barrier
hyperglycaemia of mother leads to increased transplacental transport, this can lead to dysregulation of glucose transporters and insulin receptors
fetal hyperglycaemia and hyperinsulaemia can result
what kind of baby can result from diabetic preganncy
large baby (macrosomia), increased risk of malformations
can be postnatal hypoglyacemia as still has high insulin levels
may have high blood pressure
altered insulin sensitivity
what are the affects of diabetes on fetal programming?
developmental origins of cardiovascular disease in later life due to epigenetic modulation of endotherlial genes
specifically what can occur in the syncytiotrophoblast in diabetes?
increased chorionic villous branching
increased tissue VEGF
disturbed nutrient uptake
what can occur in endothelium of fetal vessels due to diabetes?
increased VEGF
junctional disruption / phosphorylation
oxidative stress
angiogenesis
what is oligohydramnios
insufficient amniotic fluid
what are the causes of oligohydramnios?
renal agenesis
what is polyhydramnios and what causes it?
too much amniotic fluid
oesophageal atresia result in no swallowing
when is alphafetoprotein elevated ?
neural tube deficiency, spina bifida