Parturition Neonatal Adaptations Flashcards
(39 cards)
describe what occurs to the progesterone and oestradiol levels during pregnancy of cow
oestradiol levels; rise gradually in late pregnancy and reach peak before calving
prog levels; begin to decline & drop acutely before parturition
describe progesterone & oestradiol levels specifically in pregnancy of ewe
In ewes, progesterone rises considerably from about mid-pregnancy, and oestradiol remains low until a sudden peak just before parturition, accompanied by a sudden decline in progesterone
describe when and what happens to progesterone and oestradiol levels during pregnancy in the mare
oestrogens/oestradiol reach a peak in mid-pregnancy (2nd term), while progesterone declines to baseline when accessory CLs regress
name the 2 placental progestagens formed in mare placenta
when are they formed specifically
- 5a-dihydroprogesterone (DHP) & allopregnenolone
- maintain pregnancy after accessory CL’s have declined in 2nd and 3rd term of pregnancy
what happens to progestagen levels during mare pregnancy
begin to decline leading up to foaling (just like in ruminants)
what happens to levels of cortisol in mare pregnancy
rise abruptly in days leading up to parturition
all species appear to have a steroid hormone ratio change before parturition. what is this change?
all species also seem to have a rise in __________ in the 2 days before parturition
^ oestradiol : decrease in progesterone
cortisol rise
what does progesterone decline allow?
to allow myometrial activation and onset of labour –> parturition
where does cortisol production come from?
foetal adrenal glands (then travels to placenta)
describe the process of production of cortisol
foetal hypothalamus produces releasing factor CRF (corticotrope cell) which goes to the foetal anterior pituitary and releases ACTH hormone. this binds to the cortex of foetal adrenal gland which leads to release of cortisol
what occurs once the cortisol has been produced in the SHEEP
travels from fetus to placenta and induces steroid enzyme changes which allow production of oestradiol from progesterone precursors like pregnenolone
what does oestradiol do when progesterone levels get low? in sheep
induces contractility factors like oxytocin receptors and PGF2a which cause smooth muscle contractions in the myometrium
The rapid increase in oestradiol and decline in progesterone causes…
PGF2alpha synthesis in sheep placenta
cortisol rise–>???–>???
- ^ oestradiol & ^PGF2a –> uterus/smooth muscle contractions & cervix dilation
what is another important role of ^PGF2a
releases
name the 3 distinct stages of labour
- preparation stage
- expulsion of foetus
- placenta expulsion and first suckling/standing up
how long is each stage of labour?
- hours to days
- minutes when foetus is in birth canal
- hours
describe each stage of labour
- preparation
-fetus changes position within uterus and enters the birth canal
-only noticeable by behavioural and mammary gland changes
-in cows and mares, relaxation of ligaments around the tail
-the outer placental membrane (chorioallantois) bursts - expulsion of foetus
-abdominal contractions visible
-fetus delivered through the birth canal in the inner placental membrane (amnion), passes through the cervix and is then expelled - placenta expulsion & first suckling/standing up
-afterbirth is delivered
-onset of the postnatal period for neonates finding teats and suckling
-onset of the postpartum period for the dam with onset of lactation
what are some behavioural changes that occur in animal during stage 1 of labour which reflect PGF2alpha-induced myometrial contractions, and a prolactin increase
Restlessness
Vomiting (bitch)
Standing/Lying down
Sweating (pain: mare)
Raising tail
Nesting
Grumbling and licking other neonates (ewe)
external changes to animal’s body during stage 1 of labour is due to…
internal changes to animal’s body during stage 1 of labour are due to…
- hormone changes
- actions of PGF2a
list the external changes to an animals body that occur during stage 1 of labour
Mammary development - oedema
Waxing - dripping colostrum
Temperature drop (0.5°C)
Relaxation of pelvic ligaments
Expulsion of the cervical plug
list the internal changes to animals body that occur during stage 1 of labour
Progressive myometrial activity pushing the fetus towards internal os of cervix
Cervical dilation
Appearance of the (chorio)allantois
Rupture of the (chorio) allantois
what are some events that occur during stage 2 of labour
Escape of allantoic fluid
Further widening and softening of birth canal
Strong uterine contractions
strong abdominal contractions visible
widening and softening of birth canal during stage 2 of labour is due to what hormone?
relaxin
