Midterm 3 - Lecture 28 Flashcards
What are the 3 stages of parturition?
- Stage 1: initiation of myometrial contractions
- removal of P4 Block caused by fetal signaling - Stage 2: expulsion of fetus
- strong contractions of the myometrium - Stage 3: expulsion of fetal membranes
5 hormones of parturition
- Adrenal Corticotropin (ACTH)
- Estrogens
- Prostaglandin F2a (PGF2a)
- Relaxin
- Oxytocin
What triggers the secretion of Adrenal Corticotropin (ACTH)?
- as fetal mass approaches the space limitations of uterus the fetus is brought under stress
- under stress the fetal anterior pituitary will secrete ACTH
What does Adrenal Corticotropin (ACTH) do?
- stimulates the fetal adrenal gland to produce the corticosteroid- cortisol
- fetal cortisol passes into the maternal circulations and abolishes the “P4 Block”
What does fetal cortisol abolishing the P4 block promote?
- promotes the conversion of P4 to E2
- promotes PGF2a synthesis by the placenta
Who triggers the onset of parturition?
- the fetus; but both the fetal and maternal system must be prepared
- if a pregnant mother is put under stress, her cortisol will degrade the P4 = premature birth or late-term abortion
What happens when once the fetus occupies most of the available space?
- stressed
- fetal ACTH
- fetal cortisol
- P4 converted to E2
- PGF2a release = luteolysis and relaxin release
What are the effects of Estradiol (E2) on the female tract?
- increases secretions of cervix and vagina; mucus acts as a lubricant
- stimulates contractions of the myometrium; pushes fetus into the cervical canal
What stimulates PGF2a production? What does PGF2a do?
- cortisol stimulates placenta to produce PGF2a
- initiates regression of CL = reducing P4 production and helping to eliminate the “P4 Block”
- stimulates a surge of relaxin
What stimulates a surge of relaxin?
PGF2a
What is relaxin produced BY? What does it do?
- peptide hormone produced by the CL and/or placenta during gestation (depending on the species)
- softens connective tissue of the cervix & promotes elasticity of pelvic ligaments
- prepares birth canal for expulsion of the fetus
What is oxytocin secreted by?
- neuropeptide secreted by the posterior pituitary
What signals the release of oxytocin?
- pressure on the cervix from the fetus activates pressure sensitive neurons that signal the posterior pituitary to release oxytocin
What does oxytocin do?
- augments the myometrial contractions initiated by E2 to a level that allows for expulsion of the fetus and eventually the fetal membranes
What is dystocia?
- difficult or abnormal birthing process resulting in a extended duration of the parturition
- can result in serious consequences for the fetus and dam
What are 4 potential causes of dystocia?
- fetal size (too large)
- dam condition (too fat or thin)
- improper fetal positioning
- multiple births in monotocous species (cows, mares)
What is “normal” fetal presentation for cows?
- cranial longitudinal aka head positioned btw both feet
What are calf “pullers”? How are they used?
- straps/chains attached to the front feet
- must work with the dam so you don’t damage her tract
- can use body wt to pull or a mechanical puller
What is “reaching” for piglets?
- if the sow is in trouble while farrowing, we “reach”
- go in through the vagina and feel for a mummified fetus, piglet in the crossway etc.
- find the piglet and pull by the leg or jaw
What is puerperium?
the period btw parturition and return to “normal ovarian and uterine activity (ie estrous cycle)
What are the 4 major events of puerperium?
- myometrial contractions and expulsion of remaining tissues, blood & mucus
- endometrial repair (involution)
- resumption of ovarian fxn
- elimination of bacterial contamination from the repro tract
What happens during uterine involution?
- decrease uterine size (length and diameter)
- decrease uterine volume
- expulsion of lochia
- endometrial repair
