1. Fetal Circulation

2. Objectives Discuss anatomy and physiology of fetal circulation
Compare and contrast fetal circulation to infant circulation
Define specialized structures of fetal circulation

3. Anatomy and Physiology Fetal Circulation
Umbilical cord
2 umbilical arteries: return non-oxygenated blood, fecal waste, CO2 to placenta
1umbilical vein: brings oxygenated blood and nutrients to the fetus

4. Anatomy and Physiology
Fetus depends on placenta to meet O2 needs while organs continue formation
Oxygenated blood flows from the placenta
To the fetus via the umbilical vein
After reaching fetus the blood flows through the inferior vena cava

5. A/P Fetal Circulation
Blood continues to travel from the inferior vena cava to the ductus venosis
Ductus Venosis
Small amount of blood routed to growing liver
Increased blood flow leads to large liver in newborns

6. A/P Fetal Circulation
Blood continues to travel up the inferior vena cava
Empties into the right atrium of the heart
The blood then passes to the left atrium through the foramen ovale

7. A/P Fetal Circulation Foramen ovale
Small opening in the septum of the heart
Completely bypasses the non-functioning lungs
Blood continues journey to the left ventricle blood is then pumped into the aorta
Blood is circulated to the upper extremities
Blood then returns to the right atrium

8. A/P Fetal Circulation
From the right atrium, the blood goes to the right ventricle then to the pulmonary arteries
Pulmonary arteries
Small amount goes to the maturing lungs
Rest of blood is shunted away from lungs by ductous ateriosus back to aorta

9. A/P Fetal Circulation
Blood travels back from aorta to the two umbilical arteries to the placenta
The placenta will re-supply the blood with oxygen
Fetal circulation is a low-pressure system

10. A/P Fetal Circulation Low pressure system Lungs are closed
Most oxygenated blood flows between the atria of the heart through the foramen ovale
This oxygen rich blood flows to the brain through the ductus arteriosus

11. Conversion of Fetal to Infant Circulation
At birth
Clamping the cord shuts down low-pressure system
Increased atmospheric pressure(increased systemic vascular resistance) causes lungs to inflate with oxygen
Lungs now become a low-pressure system
Pressure from increased blood flow

12. Conversion: Fetal to Infant Circulation
In the left side of the heart causes the foramen ovale to close
More heavily oxygenated blood passing by the ductus arteriosus causes it constrict
Functional closure of the foramen ovale and ductus arteriosus occurs soon after birth
Overall anatomic changes are not complete for weeks

13. Conversion (cont)
What happens to these special structures after birth?
Umbilical arteries atrophy
Umbilical vein becomes part of the fibrous support ligament for the liver
The foramen ovale, ductus arteriosus, ductus venosus atrophy and become fibrous ligaments

14. Overview of Conversion
Umbilical cord is clamped
Loose placenta
Closure of ductus venosus
Blood is transported to liver and portal system
Loss of placenta also leads to

15. Overview of Conversion
First breath
Lungs expand and fluid is expelled
Decreased pulmonary resistance
Increased pressure in left atrium
Closure of foramen ovale

16. Overview of Conversion
Loss of placenta
Increased systemic resistance
Pressure in right atrium decreased
Change from right to left shunting to left to right blood flow
Increased O2 levels in pulmonary circulation
Closure of the ductus arteriosus

17. Fetal vs. Infant Circulation
Low pressure system
Right to left shunting
Lungs non-functional
Increased pulmonary resistance
Decreased systemic resistance
Infant
High pressure system
Left to right blood flow
Lungs functional
Decreased pulmonary resistance
Increased systemic resistance

18. Summary Reviewed anatomy and physiology of fetal circulation
Discussed conversion from fetal to infant circulation
Compared fetal to infant circulation
Determined outcome of special features associated with fetal circulation after birth