Fetal Development Flashcards
what is the ductus venosus
fetal blood shunt which bypasses the liver
why is the ductus venosus important
the liver is very metabolically active so will use up the oxygen in the umbilical veins on the way to the heart
what is the ductus arteriosus
fetal blood shunt causing blood to move from the pulmonary trunk into the aorta
why is the ductus arteriosus important
to bypass the lungs as these are not functional
what is the foramen ovale
fetal blood shunt, moving blood from the RA to LA
why is the foramen ovale important
to bypass the lungs and RV
what factors allow for an increase in the pO2 gradient between the mother and fetus
- increase in maternal pO2 through hyperventilation
- increase in maternal 2,3-BPG
- fetal haemoglobin
- double Bohr effect
how does a increase in maternal 2,3-BPG increase the pO2 gradient
it means at the placenta there is a loss of affinity of Hb for oxygen so more is given up, producing a high pO2 in maternal blood
how does fetal haemoglobin produce an increase in the pO2 gradient
it has a higher affinity for oxygen so there will be less oxygen in the fetal blood, keeping the pO2 lower
describe the double Bohr effect
- the CO2 from the fetus causes a decrease of pH in the mother, this causes a loss of affinity of the Hb for oxygen
- in the fetus the loss of CO2 increases the pH which causes an increase in affinity of the Hb to oxygen
what happens to the heart rate in fetal hypoxia
it slows down
what is normal fetal heart rate
110-160 bpm
what are the 2 types of growth restriction
asymmetrical and symmetrical
what is symmetrical growth restriction
where the baby is smaller but the body is proportionally smaller
what is asymmetrical growth restriction
where the head/abdomen may be bigger or smaller resulting in not normal proportions
why does physiological jaundice occur at birth
as the liver must mature to conjugate and excrete the bilirubin as the mother did this previously
what birth weight does growth restriction class as
under 2500g
what is it known as when the birth weight is above 4500g
macrosomia
give a cause of macrosomia
gestational/maternal diabetes
give some ways of assessing ante-natal development
- 20 weeks fetal movement can be detected
- symphsis-fetal height
- ultra sound
- doppler ultra sound (see placental flow)
- crown rump length
- femur length
- biparietal circumference
- abdominal circumference
how is the amniotic fluid produced after 9 weeks
through the urine production by the fetal kidneys
how is amniotic fluid recycled
- inhaled by the fetus
- swallowed by fetus
what does inhaling the amniotic fluid result in
development of the lungs
allows the lung muscles to start moving preventing atrophy
what happens to the swallowed amniotic fluid
it is absorbed through the GI tract
what happens to the amniotic fluid which is not absorbed by the GI
it is combined with the secreted fetal bile to form meconium
what happens to the meconium in fetal stress
it is prematurely released
what part of the primitive gut tube does the respiratory system develop from
foregut
what separates the GI tract and the respiratory tract
tracheoesphageal septum
what is fetal bradycardia associated with
hypoxia
what is it called when there is too little amniotic fluid
oliohydramnios
what is it called when there is too much amniotic fluid
polyhydramnios
give some reasons for oligohydramnios
placental insufficiency, maternal hypertension, bladder outlet obstruction
give some reasons for polyhydramnios
CNS problems with swallowing, blind ended oesophagus, poor positioning of the tracheoesphageal septum
when does myelination of the brain begin
after birth
how can premature birth cause respiratory distress syndrome
not enough surfactant may be produced
when is the majority of surfactant produced
week 34
when do the alveoli appear (terminal stage f respiratory development)
26 weeks
