021815 parturition Flashcards
how do uterine contractions occur?
myometrial cells contract spontaneously (spontaneous action potential, so no hormonal or nervous input is needed)
uterine contractions-biochemical basis?
action potential causes Ca influx into myometrial cell. activates Ca calmodulin complex. activates myosin light chain kinase. phosphorylates myosin, ATP is hydrolyzed, myosin undergoes structural change, and myosin interacts with actin
labor phenotype
transition from quiescence phase to labor phase involves shift from progesterone dominance to estrogen dominance
uterine stretch and estrogen upregulate CONTRACTION ASSOCIATED PROTEINS in myometrium
how does estrogen dominance at the end of pregnancy help the uterus?
increases gap jxns btwn myometrial cells
increases oxytocin receptor and PG receptor expression in myometrium
(progesterone during pregnancy inhibits expression of contraction associated proteins)
contraction associated proteins-ex
gap jxn protein connexin
oxytocin receptor
corticotropin releasing hormone receptor
COX-2 enzyme
oxytocin’s role
increases PG and estrogen level in labor phenotype
stages of labor
first stage-latent phase and active phase. latent phase is contraction w slow cervical dilation. active phase is contractions with fast cervical dilation.
secondstage-complete dilation until delivery of fetus
third stage-post delivery to delivery of placenta
fourth stage-lasts one hr after delivery of placenta. constant myometrial contrac that limits blood loss
preterm labor–mechanism?
the same as normal labor, but what leads to the labor is likely different
risk factors for preterm labor
infections
smoking
genetics
cercial shortening/decreased uterine space
low pre-pregnancy weight, socioeconimic disadvantage
tx for stopping preterm labor
magnesium
calcium channel blockers
beta 2 adrenergic receptor agonist
PG synthesis inhibitors (indomethacin-COX inhibitor)
these primarily act by preventing intracellular Ca influx
what can be used to PREVENT preterm delivery?
progesterone
tx for inducing labor
dinoprostone
misopristol
oxytocin
atony
uterine relaxation during 4th stage of labor leading to excessive blood loss
how do you tx post partum hemorrhage
uterine massage
oxytocin, PGs, ergot alkaloid ergonovine
Sheehan syndrome
hypovolemia from obstetrical blood loss leads to pituitary infarction or necrosis
can hv amenorrhea for ex
