Cardiology - Foetal Circulation Flashcards
Why are shunts needed?
Blood goes to placenta to collect oxygen and nutrients
Foetal lungs are not developed or functional, no need for blood to pass through pulmonary circulation
Shunts allow blood to bypass pulmonary system
What are the two key waste products disposed in the blood at the placenta?
Carbon dioxide
Lactate
What are the 3 foetal shunts and what do they bypass?
Ductus venosus
Bypasses liver
Connects umbilical vein to IVC
Foramen ovale
Bypasses RV and pulmonary circulation
Connects RA with the LA
Ductus arteriosus
Bypasses pulmonary circulation
Connects pulmonary artery with the aorta
Why does the foramen ovale close?
During first breaths, the alveoli expand
This decreases pulmonary vascular resistance
Decrease in pulmonary vascular resistance causes a fall in RA pressure
LA pressure > RA pressure, atrial septum is squashed shut, becomes sealed after a few weeks
What is the name of foramen ovale after it has been sealed?
Fossa ovalis
Why does ductus arteriosus close?
Prostaglandins are needed to keep it open
Increased blood oxygenation causes a drop in circulating prostaglandins, causing ductus arteriosus to close
What is ductus arteriosus called after it is forced shut?
Ligamentum arteriosum
Why does ductus venosus stop functioning?
Umbilical cord is clamped and no flow in umbilical veins
Ductus venosus structurally closes a few days later
What does the ductus venosus form after birth?
Ligamentum venosum
