Session 9- The fetus Flashcards
how does the mother compensate for the low partial pressure of oxygen
progesterone causes physiological hyperventilation which results in the mother developing a physiological respiratory alkalosis- this also means there will be a lower conc of aCo2 in maternal blood setting up a gradient for gas exchange
increased maternal dpg to reduce materal affinity for o2
what is HbF comprised of
2 alpha
2 gamma
why does HbF have a higher affinity for o2
it doesnt bind 2,3 BPG as maternal Hb does
what is the double Bohr effect
as co2 passes into the intervillous blood the pH will decrease causing decreased affinity for oxyen for the mother
the fetus will be giving up Co2 dur to the gradient of transfer causing increased pH which results in increased affinty for oxygen
what is the double haldene effect
as maternal Hb gives up o2 it can accept increasing amounts of Co2
the fetal Hb gives up more Co2 as o2 is accepted
why causes fetal distress
a possible fetal response to hypoxia is bradycardia via vagal stimulation to try and reduce he o2 demand required by the heart
how can smoking affect blood oxygen levels
can cause chronic hypoxaemia which could lead to intruterine growth restriction
where does ductus venosus shunt and why
blood from umbilical vein to IVC to prevent blood going to the liver to maintain a high level of o2 in circulation that will be arriving to the brain
where does foramen ocale shunt
allows most of the blood to travel from right atrium to left atrium and a small amount goes to right ventricle mixing with blood from SVC
what hormones are neccesary for fetal growth
insulin
IGFI- nutrient infependant dominates in T1
IGFII - nutrient dependant dominated in T2 T3
leptin
What is the dominat cell growth mechanism in 0-20 weeks
hyperplasia
what is the dominant cell growth mechanims in 20-28 weeks
hyperplasia and hypertrophy
what is the dominant cell growth mechnaism in 28-term
hypertrophy
where does amniotic flid come from
fetal urinary tract
fetal lungs
fetal GI tract
how is bilirubin metablised
during gestation clearnance of fetal bilirubin is handled efficiently by the placents
fetus cannot conjugate bilirubin
physiological jaundice is common
where does the ductus arteriosus shunt
pulmonary trunk and aorta
why does blood enter the RV
due to teh crista dividens to prevent the RV atrophying and allows a small amount of blood to enter the lungs to promote its devlopment