Late Development and Parturition Flashcards
How does embryo-fetal nutrition occur?
- histotrophic
- haemotrophic
How does the placenta develop?
cytotrophoblasts —> chorionic villi —> infiltrate trophoblastic lacunae —> extra-villus trophoblasts —> open up spiral arteries
What are the fetal membranes?
- amnion
- chorion
- allantosis
What are the 3 stages of chorionic villi development?
- Primary —> outgrowth
- Secondary —> fetal mesoderm
- Tertiary —> umbilical a+v into villus
mesoderm
How is blood supplied to the endometrium?
ovarian + uterine artery —> arcuate —> radial —> basal —> spiral
What is spiral artery re-modelling?
infiltrated by endovascular EVT —> open up spiral artery —> low pressure, high capacity
Which 6 nutrients are exchanged across the placenta to the foetus?
- Oxygen
- Glucose
- Water
- Electrolytes
- Calcium
- Amino acids
What are the maternal changes that occur to facilitate maternal fetal oxygen exchange?
CO inc
PVR inc
Blood vol inc
Ventilation inc
What are the placenta and fetal changes that occur to facilitate maternal fetal oxygen exchange?
Placenta consumes most O2 and glucose
Fetal O2 sat similar to maternal
Embryonic and fetal Hb —> greater affinity
How does the fetal circulatory system mature?
gas exchange at placenta
ventricles act parallel not series
shunts bypass pulmonary and hepatic close as birth
How does the fetal respiratory system mature?
air sacs at 20 weeks, vasculature at 28 weeks
surfactants at 20 weeks
1-4hr/day rapid respiratory movements in REM sleep
How does the fetal gastrointestinal system mature?
endocrine pancreas start at 2T (insulin mid 2T)
liver glycogen deposited
amniotic fluid swallowed —> debris + bile salts to
meconium
How does the fetal nervous system mature?
movement late 1T —> detect from 14 weeks
stress from 18 weeks
thalamus-cortex connections from 24 weeks
always in slow-wave or REM sleep
What is fetal organ maturation driven by?
corticosteroids
What are the 4 phases of labour?
- Quiescent
- Activation —> prep
- Stimulation —> labour
- Involution —> recovery
What are the 3 stages of stimulation?
- First —> latent and active cervix dilation
- Second —> contractions
- Third —> placenta, fetal membrane out, repair
What are the 4 stages of cervical re-modelling?
- Softening
- Ripening
- Dilation
- Post-partum repair
How is labour initiated?
Fetal HPA —> CRH —> fetal ACTH + cortisol + DHEAS
—> placenta CRH
How does progesterone contribute to labour?
normally inhibits —> PR-A switch to PR-B/C —> not active —> ‘blinded’
How does oestrogen contribute to labour?
- inc oxytocin
- activate activates phospholipase A2 —> inc
arachidonic acid —> inc prostaglandin
How does oxytocin contribute to labour?
- syncytium
- membrane potential —> lower threshold
- inc Ca2+ release
Which 3 prostaglandins contribute to labour?
- PGE2 —> cervical remodelling (+NO, relaxin)
- PGF2α —> myometrial contractions
- PGI2 —> myometrium relax
How do hormones control labour?
- Fetal CRH —> cortisol
—> DHEAS - Cortisol —> placental CRH —> inc fetal CRH
- DHEAS —> maternal oestrogen —> oxytocin
How do myometrial contractions facilitate labour?
Contract fundus down
Brachystatic
—> pull uterus up
How does the fetus facilitate labour?
Chin to chest —> fetus rotates (belly to spine) —> head out
What happens after labour?
- uterus shrink —> placenta less contact with
endometrium —> fetal membranes fold - clamp umbilical cord —> stop fetal blood to placenta
- expel placenta and fetal membranes
- uterine vessel thrombosis —> involution
