Dla After Lecture 10: Fetal And Neonatal Circulation

Question 1

What are the 4 fetal shunts?

Answer 1

1. Umbilical/Placenta
2. Ductus venosus
3. Formen ovale (FO)
4. Ductus arteriosus
   (DA)

Question 2

Contrast the blood flow pattern in the fetus with that of a normal neonate.

Answer 2

Fetus Blood Flow:
Mom –> Placenta –> Right atrium –> Parent foramen ovale –> left atrium –> left ventricle –> Body

Neonatal (Newborn) Blood Flow:
Right atrium –> Right ventricle –> Lungs –> Left atrium –> Left ventricle –> Body or DA

Question 3

Describe the function of the ductus venosus, foramen ovale and ductus arteriosus. Explain the mechanisms causing their closure at birth.

Answer 3

Ductus Venosus
-Closes 2-3 months, remnant

Foramen Ovale:
-Allows oxygen rich blood right atrium –> left atrium –> left ventricle –> aorta

-Closes in pressure reversal causes flap over foramen
ovale to close

Ductus arteriosus:

• Right to left shunt:
• Channel between pulmonary artery and fetus that bypasses lungs
• Sends the oxygen poor blood to the organs in the lower half of the fetal body
• Closes w decrease PGE1 (Prostaglandin) generated in response to hypoxia in newborns, pressure difference –> Muscular wall vasocontricts

Question 4

Discuss the relative differences in oxygen saturation and pressure in the fetus and how these values change at birth

Answer 4

Fetus:
1) Pulmonary pressure –> high
O2 sat –> Not as high

Birth:
Pressure –> Reversed, decrease
O2 sat: Increase O2 (Bc closure of DA)

Question 5

Explain the consequences of failure of the ductus arteriosus to close

Answer 5

• Can happen in premature infants
• Left atrium and Left ventricle become overloaded w blood, LV dilates

Results:

1) Left side heart failure
2) tachycardia

Syms:
2-3 days after birth
1) Murmur
2) Hypoperfusion
3) Edema
4) Hemorrhage
5)  bronchopulmonary
dysplasia

Question 6

Explain the consequences of failure of the foramen ovale to close?

Answer 6

Formane ovale:

• Persistent Left to right shunting
• Can have ischemic stroke
• Cryptogenic stroke –> Stroke in absence of vessel source (causes ischemic strokes)

Question 7

Explain the consequences if pulmonary vascular resistance fails to decrease (Hypertension)

Answer 7

• Persistent right to left shunting
• Hypoxia develops

Sym:

• cyanosis
• Respiratory distress
• Loud 2nd heart sound/murmur
• Systemic hypotension
• Shock
• Poor cardiac function/perfusion