Parturition and Lactation Flashcards
Parurition
Childbirth
What are the main hormones involved in maternal changes during parturition?
Progesterone Estrogen Prostaglandins Oxytocin Relaxin
Main action of Progesterone on the mother?
Blocks myometrial contractions and promotes its relaxation during pregnancy
Progesterone antagonists can induce?
Labor/contractions at any stage of pregnancy!
How do uterine cells overcome the actions of progesterone (myometrial relaxation)?
Desensitization of the uterine cells to progesterone
= leads to an INCREASE in estrogen receptors
Main action of Estrogen after uterine cell desensitization to progesterone?
Increases myometrial contractibility and cervical dilation
How does Estrogen oppose the actions of progesterone?
Increases uterine cell responsiveness to oxytocin and prostaglandins
- increase oxytocin receptors on uterine cells
- increase prostaglandin release from fetal membranes
Main action of Prostaglandins?
Stimulate strong myometrial contractions
Prostaglandin synthesis is stimulated by?
Estrogen, oxytocin and uterine stretch
Which prostaglandins can induce myometrial contractions at any stage of pregnancy?
PGF2alpha and PGE2
Which hormones can stimulate the formation of gap junctions?
Estrogen and Prostaglandins
Estrogen can increase what hormone receptor on uterine cells?
Oxytocin
Prostaglandin effect on the cervix?
Promotes effacement (thinning and softening) early in labor
Main function of oxytocin?
Stimulates uterine contractions that sustain labor
Describe the release frequency of oxytocin during labor
Released in bursts that increase in frequency as labor progresses
What is the primary stimulus for oxytocin release?
DISTENTION OF THE CERVIX
What is the positive feedback loop that enhances labor?
Ferguson reflex
Describe the Ferguson reflex
- Estrogen increases oxytocin receptors on uterine cells
- DISTENTION OF THE CERVIX
- Release of oxytocin
- Oxytocin stimulates uterine contractions and prostaglandin release from placenta
- Prostaglandin stimulates more uterine contractions
- Uterine contractions feedback to activate more oxytocin release
The uterus is insensitive to ____ for around 20 weeks gestation
Oxytocin
Main action of Relaxin
Keeps uterus quiet during pregnancy
Relaxin is structurally similar to?
Insulin
When are concentrations of Relaxin at their peak and what does this cause?
Relaxin amounts are at their peak at the END of pregnancy
- Causes cervical relaxation and dilation
If there are increased levels of _____ around 30 weeks, premature birth may occur
Relaxin
What are the mechanical changes of the mother during parturition?
Uterine size
Cervical remodeling