Midterm 3 - Lecture 28 Flashcards
1
Q
What are the 3 stages of parturition?
A
- 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
2
Q
5 hormones of parturition
A
- Adrenal Corticotropin (ACTH)
- Estrogens
- Prostaglandin F2a (PGF2a)
- Relaxin
- Oxytocin
3
Q
What triggers the secretion of Adrenal Corticotropin (ACTH)?
A
- as fetal mass approaches the space limitations of uterus the fetus is brought under stress
- under stress the fetal anterior pituitary will secrete ACTH
4
Q
What does Adrenal Corticotropin (ACTH) do?
A
- stimulates the fetal adrenal gland to produce the corticosteroid- cortisol
- fetal cortisol passes into the maternal circulations and abolishes the “P4 Block”
5
Q
What does fetal cortisol abolishing the P4 block promote?
A
- promotes the conversion of P4 to E2
- promotes PGF2a synthesis by the placenta
6
Q
Who triggers the onset of parturition?
A
- 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
7
Q
What happens when once the fetus occupies most of the available space?
A
- stressed
- fetal ACTH
- fetal cortisol
- P4 converted to E2
- PGF2a release = luteolysis and relaxin release
8
Q
What are the effects of Estradiol (E2) on the female tract?
A
- increases secretions of cervix and vagina; mucus acts as a lubricant
- stimulates contractions of the myometrium; pushes fetus into the cervical canal
9
Q
What stimulates PGF2a production? What does PGF2a do?
A
- 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
10
Q
What stimulates a surge of relaxin?
A
PGF2a
11
Q
What is relaxin produced BY? What does it do?
A
- 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
12
Q
What is oxytocin secreted by?
A
- neuropeptide secreted by the posterior pituitary
13
Q
What signals the release of oxytocin?
A
- pressure on the cervix from the fetus activates pressure sensitive neurons that signal the posterior pituitary to release oxytocin
14
Q
What does oxytocin do?
A
- augments the myometrial contractions initiated by E2 to a level that allows for expulsion of the fetus and eventually the fetal membranes
15
Q
What is dystocia?
A
- difficult or abnormal birthing process resulting in a extended duration of the parturition
- can result in serious consequences for the fetus and dam
