Fetal & Neonatal Physiology Flashcards
What vessels are involved in fetal circulation through the placenta?
Umbilical arteries, umbilical vein, fetal capillaries in chorionic villi, maternal uterine arteries and veins.
What increases the surface area for maternal-fetal exchange in the placenta?
Chorionic villi.
What is the role of the intervillous spaces?
Maternal blood pools here, allowing gas and nutrient exchange with fetal capillaries.
Where does gas exchange occur in the fetus?
At the placenta.
What physiological changes in the mother promote gas exchange at the placenta?
Maternal pCO₂ drops (hyperventilation), improving diffusion gradient.
What factors promote fetal oxygen uptake?
HbF, increased fetal hematocrit, maternal 2,3-DPG, and Bohr/Haldane effects.
How does the fetus respond to hypoxia?
Increased HbF, bradycardia, blood flow redistribution to vital organs.
What are the three major fetal shunts?
Ductus venosus, foramen ovale, ductus arteriosus.
What is the function of the ductus venosus?
Shunts oxygenated blood from umbilical vein to IVC, bypassing the liver.
How does the foramen ovale function?
Allows blood to flow from the right atrium to the left atrium due to higher RA pressure.
Why is the ductus arteriosus important?
Shunts blood from pulmonary trunk to aorta, bypassing the non-functional lungs.
In what stage do terminal sacs and pneumocytes develop?
Terminal sac stage (26 weeks – term).
What is the function of Type II pneumocytes?
Produce surfactant to reduce surface tension in alveoli.
What maternal treatment can enhance fetal surfactant production before preterm delivery?
Antenatal corticosteroids (betamethasone or dexamethasone).
Why are fetal lungs fluid-filled in utero?
Maintains lung expansion and pressure critical for normal development.
What is the result of Preterm Prelabour Rupture of Membranes (PPROM) before 20 weeks?
Pulmonary hypoplasia due to loss of lung fluid.
What causes Respiratory Distress Syndrome in preterm babies?
Insufficient surfactant production.
What are the four defects in Tetralogy of Fallot?
VSD, overriding aorta, RV outflow tract obstruction, RV hypertrophy.
What structural issue underlies Tetralogy of Fallot?
Defective conotruncal septum formation (neural crest origin).
What happens in Transposition of the Great Arteries (TGA)?
Aorta arises from RV and pulmonary trunk from LV, leading to cyanosis.
What causes an ostium secundum type ASD?
Excessive resorption of septum primum or underdevelopment of septum secundum.
