Fetal Circulation

Question 1

fetal circulation

Answer 1

Question 2

How is pulmonary artery pressure bigger than arterial pressure in fetal circulation?

Answer 2

alveoli in fetal lungs are filled with fluids - not much O2 → hypoxic pulmonary vasoconstriction → high resistance

Question 3

hypoxic pulmonary vasoconstriction

Answer 3

alveoli constricts arteriole vessels → increased resistance in arteriole

Question 4

what makes blood to travel back to placenta easily than other branches?

Answer 4

placenta has low resistance

Question 5

Foramen ovale?

Answer 5

blood to flow from right atrium to left atrium

Question 6

Ductus arteriosus in fetus?

Answer 6

blood to flow from pulmonary artery to aorta

Question 7

Wharton’s jelly?

Answer 7

jelly-like connective tissue in the umbilical cord

Question 8

when umbilical cord is cut, wharton’s jelly close off. how?

Answer 8

by sensing decrease in temp right after birth

Question 9

how does closing of wharton’s jelly affect the resistance of umbilical vein and artery?

Answer 9

increases resistance

Question 10

What happens to the lungs at birth?

Answer 10

Lungs fill with air + fetal lung fluid is pushed into pulmonary capillaries and lymphatic

Question 11

What effect does increased alveolar O₂ have on pulmonary arterioles?

Answer 11

Increased O₂ → pulmonary arteriolar vasodilation→ lower pulmonary vascular R

Question 12

What causes functional closure of the foramen ovale?

Answer 12

Left atrial pressure becomes higher than right atrial pressure due to increase in pulmonary blood flow

Question 13

What triggers ductus arteriosus constriction after birth?

Answer 13

Increased arterial O₂ tension and decreased prostaglandins

Question 14

What role does the placenta play in ductus arteriosus patency?

Answer 14

placenta produces prostaglandins that keep the ductus arteriosus open

Question 15

Why does removal of the placenta promote ductus arteriosus closure?

Answer 15

Loss of placental prostaglandins allows the ductus arteriosus to constrict

Question 16

What happens to the umbilical arteries after birth?

Answer 16

constrict and close, stopping blood flow to the placenta.