Week 3 Flashcards
describe the hormonal changes in parturition of the cow in pregnancy?
late pregnancy - oestradiol rises gradually to reach peak
progesterone begins to decline + drops before parturition (CLs still produce progesterone)
describe the hormonal changes in sheep during parturition?
progesterone rises considerably from mid=pregnancy
oestrdial remains low until peak before parturition.
describe the hormonal changes in mare during parturition?
oestragrens reach peak in mid-pregnancy while progesterone declines
CLs progesterone conc declines dramatically
what else occurs in mare during partursition with cortisol and myometrial activity?
a rise in cortisol occurs during days of parturition
Myometrial activity increase at night in peripoant mare, thus mares feed predominantly at night
why must progesterone decline for parturition?
reduces functions to occur - increased oestrdiol
decreased progesterone
leads to onset of labour
describe how the fetal hypothalamus has a effect on fetal cortisol levels rising?
fetal hypothalamus release CRF
fetal Ant. Pititaru release ACTH
Feta; adrenal glands release cortisol levels that rise and travel to placenta.
describe how sheep fetal cortisol crosses the mature placenta and causes oestradiol synthesis?
cortisol diffuses across mature placenta membrane via PGE2 - 17a hydrolase aromatase which causes pregnenolone to covert into oestrdiaol synthesis.
oestradiol induces contractility active proteins in the myometrium, such as PGF2a and oxytocin receptors
describe how cow fetal cortisol induces PGF2a and causes luteolysis?
fetal cortisol crosses membrane increases levels of oestradiol and PGF2a causes CL regression in ovary leading to lowered progesterone levels.
what else does PGF2a cause in parturition?
uterine contractions, cervical dilation and aids fetal expulsion via relaxin release and oxytocin responsiveness.
relaxin levels increase in mare/bitch.
how does cortisol achieve the increase in oestriaol and decline in progesterone which is essential for parturition?
in placenta?
placenta responsible for progesterone production at the end of pregnancy - fetal cortisol induces 17a Hydroxylase + aromatase in the placenta
leads to C21 steroids used as a precursor for oestrdiaol production
oestradiol rises and progetsone falls.
how does cortisol achieve the increase in oestriaol and decline in progesterone which is essential for parturition?
in CLs?
corpus luteum (or CLs) is responsible for progesterone production at the end of pregnancy
Fetal cortisol induces placental PGF2a synthesis -
Luteolysis of the CL -
Acute prepartal progesterone decline -
Placental oestradiol synthesis is increasing
describe labour stage 1?
preparation - fetus changes position in uterus + enters birth canal
mother becomes restless, vomiting, sweating
mammary gland changes - oedema in mammary gland
- dripping colostrum
- expulsion of cervial plug
describe labour stage 2?
expulsion of foetuses (mins)
abdominal contractions viable - foetus delivered though birth canal in the aminon.
escape of allantoic fluid, strong uterine contractions. amino may rupture
explain the Ferguson + Pudendal reflex?
1) vaginal = cervical stretching leads to oxytocin release causing smooth muscle contractions
2) N.pudendus reflexes: vaginal stretching leads to strong abdominal contractions
describe labour stage 3?
placenta expulsion of first ducklings/standing up
after birth delivered.
repute of umbilical cord
expulsion of fetal membrane 1-12 hours post partum
beginning of puerperium (post partum blood)
name the basic neonate adaptations?
cortisol rise thyroid T3 hormone rise Cord Clamping Cold shock neonate breathing fetal lung fluid secretion thermoregulation (non-shivering thermogenesis)
explain the cortisol rise before birth and what its functions for?
lung anatomical devopelment, maturation + sue faction synthesis
clearance of fetal lung fluid
matyrationof thyroid axis + more conversions of T4 - T3 leading to rise in thyroid hormone
what does increasing thyroid hormone T3 do afterbirth?
stimulates thermogenesis
regulates maturation of the repsiratory, nervous system
discuss what cord clamping is?
leads to catecholamine surge within minutes of delivery
the NA + A surge is a response to hypoxia leads to = large increase in B.P
thermogenesis from brown adipose tissue (lipolysis = heat)
these hormones place neonate into ‘Catabolic state’
glycolysis + lipolysis occur which elevate glucose + free FA depleted by 2-3hours
insulin rises after colostrum feed intake to ensure nutrient uptake
explain the stages of neonate breathing?
1) cleansing of fetel lung fluid - reversal of fluid secretion + reabsodprption
Areation of the alveoli + INNITAION OF O2 + CO2 exchange between pulmonary capillary blood + gas.
2) surfactant secretion - new alveolar lining layer on liquid hypophase
3) continuous breathing pattern devoplment ex-utero when umbilical cord is calmed to hypoxia leading and cold stimuli
describe fetel lung fluid secretion?
1) high secretion in late gestation
2) decline in airspace fluid volume during birth
3) sodium pump responsible for reabsorption of lung fluid into blood vessels + lymphatics
what occurs when new-born takes first breath?
air enters bronchi - alveoli move fluid into distal airspace where it is absorbed, O2 can now move in
alveolar fluid is absorbed through the intertsiutm.
O2 transports form alveoli to blood vessels - increasing pO2
in 3 breaths = 50% of the lungs become aerated.
what must happen when neonate lungs are breathing?
neonate lungs must allow gas exchange by surfactant production + function.
surfactant reduces inflation resistance + ensures alveoli do not collapse after expiration.
what considerations occur when the fetal circulation oxygen and flow occur?
left shift - causes loads of O2 to low O2 tension
High pulmonary vascular resistance in fetal lungs due to low oxygen tension
umbilical vein O2 saturation is 80% with some flow bypassing liver enters caudal vena cava via DUCTUS VENOSUS
