Prenatal environment Flashcards
What are the 4 vascular shunts in place until birth?
Umbilical-placental circulation
Ductus venosus
Foramen ovale
Ductus arteriosus
How does the fetus survive at low PaO2?
Lower oxygen consumption in fetal tissues
Fetal haemoglobin has a greater affinity to O2
Increased blood volume (10-12%)
Circulation changes maintain oxygenated blood to brain
What is exchanged at the placenta?
Nutrients
Waste products
Respiratory gasses
What is fetal PaO2?
25-35mmHg
Double Bohr shift in pregnancy
Maternal blood shifts to the right (unload O2)
Fetal blood shifts to the left (take up O2)
Umbilical-placental circulation
Maternal blood pools surrounds fetal capillaries
Point of exchange
Ductus venosus
Bypasses liver
Foramen ovale
Conducts blood through the right atrium to the left atrium
Bypasses the lungs
Ductus arteriosus
Conducts blood from the pulmonary artery to the aorta
Bypasses the lungs
Which shunt allows fetal capillaries to be bathed by maternal blood pools?
Umbilical-placental circulation
Which shunt bypasses the liver from the placenta?
Ductus venosus
Which shunt bypasses the lungs by conducting blood from the right atrium to the left atrium?
Foramen ovale
Which shunt bypasses the lungs by conducting blood from the pulmonary artery to the aorta?
Ductus arteriosus
What factors are responsible for pulmonary vasodilation at birth?
Mechanical expansion of alveoli and transmural pressure gradient
Local stretch-induced PGI2 release
PO2 induced bradykinin, ATP and NO release
Local changes in PO2
What changes happen to the lungs at birth?
Reabsorption and removal of lung fluid
Production of surfactant to lower surface tension
Vasodilation and increase in pulmonary blood flow
