9. foetal growth and development (workbook) Flashcards
what does the foetus rely heavily upon maternal glucose for?
to drive glucose across the placenta and support foetal growth and development
when does foetal insulin secretion commence?
at week 10
can the foetus excrete bilirubin via its gut?
no
what effect does this have on foetal bilirubin? (can’t excrete via gut)
bilirubin is therefore not conjugated, and so passes across to the maternal circulation
as the neonate is not able to immediately able to deal with bilirubin, what condition is not uncommon?
neonate jaundice
what forms a major part of the amniotic fluid?
the foetal kidneys produce urine - forming major part of amniotic fluid
particularly late in gestation
what constantly happens to the amniotic fluid?
constantly swallowed, so the gut absorbs water and electrolytes, leaving debris to accumulate (together with debris from the developing gut)
where does debris from amniotic fluid and developing gut accumulate?
in the foetal large bowel
what is the debris accumulating in foetal large bowel known as?
meconium
when is meconium usually excreted?
ONLY excreted by a foetus in distress e.g. foetal hypoxia
what can amniotic fluid volume reach a maximum of?
1l around 38 weeks, but may fall as labour nears
where are cells within the amniotic fluid derived from?
the amnion and from the foetus
what is made by amniocentesis?
biochemical and cytological studies of the fluid are made by amniocentesis
what is amniocentesis?
amniotic fluid test
a small amount of amniotic fluid, which contains foetal tissues, is sampled from the amniotic sac
what is amniocentesis used to assess?
presence of neural tube defects, chromosomal abnormalities e.g. Down’s syndrome etc.
in early pregnancy, where is amniotic fluid likely to derive from?
by dialysis of foetal and maternal extracellular compartments with some exchange occuring across the foetal skin
later on in pregnancy, what contributes to the volume of amniotic fluid?
foetal urine (with functional maturation of the foetal kidney)
when the foetus swallows amniotic fluid, where is it then processed?
through the foetal gut and kidneys
how are amniotic fluid volumes assessed?
by ultrasound
what is an excess of amniotic fluid volumes known as?
polyhydramnios
what is polyhydramnios associated with?
oesophageal or duodenal atresia (no opening) and CNS abnormalities (coordinate the movements)
what is a low amniotic fluid volume known as?
oligohydramnios
what is oligohydramnios suggestive of?
poor / absent renal function
OR
reduced placental function e.g. in pre-eclampsia
when can withdrawal from pain be elicited?
at 15 weeks
when does thalamo-cortical projections reach maturity?
until week 29
when is completion of myelination in cortocospinal tract complete?
not until into the post-natal period
BUT MSK movements are essential for foetal growth
what does placenta progesterone promote?
foetal corticosteroid production especially near term
what is vital for foetal physiology?
placental steroid hormones (oestrogen and progesterone)
especially in CVS function
what is mediated via thyroid hormones active from week 12?
nervous system development
bone and hair growth
what does the liver store?
large amounts of glycogen
what is the large amounts of glycogen store reflected in?
changes in foetal abdominal circumference
what induces the neonate to take its first breath at birth?
a combination of physical trauma and cold temperatures
what does the neonate taking its first breath result in?
dramatic reduction in pulmonary vascular resistance and a dramatic rise in arterial pO2
what does a fall in pulmonary vascular resistance cause?
left atrial pressure to rise in respect to the right atrial pressure, so closing the foramen ovale
what happens to the foetal shunts after taking the first breath? why?
Smooth muscle sensitive to high pO2 in the wall of the ductus arteriosus
contracts to close the ductus (high pO2 closes shunt between pulmonary artery to aorta)
when are both shunts closed off completely?
within a few weeks
which duct remains open after birth?
ductus venosus variably remains open for several days after birth, but closes within two - three months
what happens to the ductus venosus to close?
a sphincter in the vessel constricts shortly after birth, re-directing all blood through the liver sinusoids
(this process is regulated by pO2 levels)
