Endocrinology of early-mid pregnancy Flashcards
A successful pregnancy requires maintenance of high blood concentrations of?
Progesterone
What are the 2 sources of progesterone?
- The CL
- The placenta
In which 2 species does the placenta not take over from the CL?
Bitch
Sow
When does the placenta take over during a cows gestation?
Between 6-8months out of the 9 month gestation
How would you terminate a pregnancy?
If the pregnancy is dependant on progesterone from the CL then prostaglandin can be administered
Which hormone is also secreted by the placenta?
Oestrogen
When does oestrogen peak?
Shortly before parturition
In the initiation of parturition, what causes foetal stress?
Uterine crowning
How does foetal stress lead to an increase in foetal cortisol?
Foetal stress causes an increase in foetal ACTH (Adrenocorticotropic hormone) which then causes an increase in foetal cortisol
Which 2 major events are initiated by foetal cortisol?
- The synthesis of 3 enzymes that convert progesterone to oestradiol
- The placenta synthesises PGF2a
What are the 3 effects, at parturition, of the placenta synthesising PGF2a?
- Causes luteolysis, which facilitates the declining progesterone
- Stimulates myometrial contractions
- Relaxin is secreted
What is the effect of relaxin at parturition?
Causes pelvic ligament stretching and softening of the tissues of the cervix
What are the 2 effects following oestradiol release?
- Increased secretion of mucus into the tract to provide lubrication
- Increases myometrial contractions
Cervix is dilated & uterine contraction push the foetus & allantois into the vagina setting up 2 reflexes, what are they?
- Neuroendocrine releasing oxytocin (Ferguson’s reflex)
- Spinal: stimulating abdominal straining
Describe Ferguson’s reflex
- Big positive feedback loop
- Stretch sensitive cells in the cervix are activated by the descending foetus, causing the release of oxytocin
- Oxytocin and Prostaglandin act to increase uterine contractions
