Pregnancy Flashcards
2 roles of placenta
- interface between maternal and fetal plasma
- protects fetus from attack by the maternal immune system
what 5 main hormones produced in placenta
Protein:
- human chorionic gonadotrophin (hCG)
- human placental lactogen (hPL)
- placental growth hormone (pGH)
Steroid:
- progesterone
- estrogens
what is hcg structually related to
LH
hCG production: 2 cell model?
cytotrophoblast produces GnRH
GnRH stimulates syncytiotrophoblast
which then produces hCG
what is role of hCG
signals pregnancy to maternal organism
- rescues corpus luteum!
- maintains progesterone production by placenta
used in pregnancy test
and a marker of foetal wellbeing (if too high then indicates more than one foetus)
where is progesterone produced
syncitiotrophoblasts
after 9th week (and so corpus luteum not needed after this point)
where does placenta get cholesterol to make the progesterone
mum
what is progesterone release regulated by
hCG
roles of progesterone
- maintains lining of uterus
- decreases prostaglandin = relaxes myometrium
- supresses t lymphocyte tissue rejection (immunological provelage)
- effects of peripheral smooth muscle
which estrogens are produced in placenta
all 3
estradiol
estriol
and estrone
which estrogen is made only via fetus
estriol
its precursor is made in fetal liver
why is estriol only made in week 9
This bit only happens from week 9 = 9 this is when maturation of steroid synthesis pathway occurs
role of estrogens in preganncy
- vasodilation and good uteroplacental blood flow
- regulates progesterone production in 3 trimester
- and mammary gland devleopment
how do we know pituitary growth hormone not needed for fetal growth
anencephalic fetuses and women with GHD both have normal growth
so only placental growth hormone affects it
how does pGH influence fetal growth
influences IGF-I production by maternal liver
which effects maternal metabolism
increase nutrients avialable for transport across placenta for foetus
- via gluconeogensis and lipolysis
effects of hPL
possible lactogenic activity
- regulates maternal metabolism via IGF-I
- and stimulates onset of maternal behaviour via neurogenesis
4 phases of preg
phase 0 = quiescence
phase 1 = activation
phase 2 = stimulation
phase 3 = involution
what inhibits activation thus keep pregnancy in phase 0
progesterone
and possbile hPL
what are the 3 activators
estrogen
prostaglandins
oxytocin
what are the contraction associated proteins
- prostaglandin and oxytocin receptors
- connexins
what does involution do
- Sustained contractions of uterus = contsricts arteries to prevent blood loss
Reduces enlarged uterus back to pre pregnancy state
possible triggers of partruition
- functional progesterone withdrawal (less potent receptor produced)
- increase in estrogens via increased fetal androgens
- placental CRH! (when activated early = preterm birth)
what happens once partruition is initiated
- increased prostaglandin synthesis
- increased oxytocin receptors
what age do milk ducts appear
at 4 weeks gestation in the baby
what stimulates growth of milk duct first
puberty = estrogen, growth hormone and adrenal steroids
during preganncy, what hormones cause increase in lobulo-alveolar growth
estrogen
progesterone
prolactin
possible hPL
what is milk production regulated by
prolactin from APG
(high all thoguhout pregnancy)
but
its actions are surpessed by high ateroid and hPL levels = dont lactate until after birth
what action maintains prolactin levels after birth and how
suckling
activates neural pathways that surpess dopamine
which is a negative regulator of prolactin
what is milk ejection stimulated by
oxytocin from APG
3 hromones that have slightly diff function in fetus than adult
- thyroid hromones
- adrenal hromones
- growht hormones
why is T3 low in fetus
low type 1 deiodinase
and
high type 3 deiodinase
what is thyroid hormone important for in baby
brain development
e.g. myelination, neurogenesis, neuronal and glial cell differentiation
what happens at birth with thyroid hormones
TSH, T3 and T4 rise rapidly
how is the adrenal coretex diff in fetus
the fetal zone of the crtex takes up most of the glands
what does fetal zone of cortex produce
DHEAs
which are converted to estriol in placenta
what does medulla in fetus release
adrenaline
function of adrenaline in neonate
not fully known but
- thermogenesis
- releasing surfactant to allow lung expansion
- blood pressure regulation
what is growth in fetus controlled by
- genetic factors
- placental nutrient uptake
- placental growth horomone
- insulin like growth factors (important cuz seen in knockout experiments)
