Foetal Circulation

Question 1

What is the foramen ovale?

Answer 1

opening in atrial septum - flap on left atrium side - allows oxygenated blood to enter left atrium

Question 2

Why is there a greater CO to the lungs after birth?

Answer 2

decreased pulmonary vascular resistance

Question 3

What is the ductus arteriosus?

Answer 3

connects pulmonary bifurcation to descending aorta - little CO to lungs - patency maintained by placental prostaglandin E2

Question 4

What is the ductus venous?

Answer 4

connects umbilical vein to IVC - placental blood bypasses portal circulation

Question 5

Why does the foramen ovale close after birth?

Answer 5

decreased pulmonary vascular resistance and increased systemic vascular resistance - LA pressure > RA pressure - flap pushed closed

Question 6

Why does duct constriction occur after birth?

Answer 6

decreased pulmonary vascular resistance - decreased flow, increased lung metabolism - decreased prostaglandin E2, ends up as fibrous ligament - ligamentum arteriosum