Circulatory changes at birth

Question 1

What 3 shunts are present in fetal circulation?

Answer 1

foramen ovale, ductus arteriosus and ductus venosus

Question 2

What does the foramen ovale do?

Answer 2

allows flow from right atrium to left atrium

Question 3

What does the ductus arteriosus do?

Answer 3

carries blood from pulmonary artery to the descending aorta

Question 4

What does the ductus venosus do?

Answer 4

allows blood from the placenta to bypass the liver

Question 5

How does the ductus arteriosus work?

Answer 5

• pulmonary constriction (mediated by hypoxia) reduces blood flow to lungs which increases right atrial pressure (keeps foramen ovale open)

Question 6

When does the foramen ovale close after birth?

Answer 6

• within several minutes after birth

- anatomically closes after 1 year to leave fossa ovalis

Question 7

When does the ductus srteriosus close?

Answer 7

• within 10-96 hours after birth

- anatomically 2-3 weeks after to leave ligamentum arteriosum

Question 8

When does the ductus venosus close?

Answer 8

• several minutes after birth

- anatomically 3-7 days after to eave ligamentum venosum

Question 9

What is PDA?

Answer 9

• patent ductus arteriosus
• machine-like murmur
• more intense of systole

Question 10

What happens after the first breath?

Answer 10

partial pressure of oxygen increase which causes pulmonary vasodilation

Question 11

How does the foramen ovale close after birth?

Answer 11

as the lungs become an area of low resistance, the right atrial pressure decreases and the left atrial pressure increases so the foramen ovale closes

Question 12

What happens when placental circulation stops?

Answer 12

it becomes an area of high resistance so flow in the ductus venosus stops and left heart pressure increases

Question 13

What is right atrial streaming?

Answer 13

IVC blood (oxygenated) mainly flows through the foramen ovale to the left atrium and to the descending aorta
SVC blood (deoxygenated) mainly flows into the right ventricle and then onto the lower limbs

Question 14

Why is the ductus arteriosus important?

Answer 14

it prevents deoxygenated blood from going to the brain

Question 15

What happens when the foramen ovale closes?

Answer 15

venous blood travels through pulmonary artery to the lungs

Question 16

How does the right atrial dynamics change after birth?

Answer 16

blood from IVC which is now deoxygenated joins blood from the SVC and floows into right ventricle and then goes to the lungs to be oxygenated

Question 17

How does the ductus arteriosus remain open during pregnancy?

Answer 17

maintained by prostaglandin E2

Question 18

What produces the murmur in PDA?

Answer 18

turbulent flow from the aorta to the pulmonary artery