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  1. 1. Fetal Circulation Dr.(Mrs.)S.Valliammal Lecturer College of Nursing NIMHANS Bangalore
  2. 2. Anatomy and Physiology Fetal Circulation Umbilical cord  2 umbilical arteries: return de- oxygenated blood, fecal waste, CO2 to placenta  1umbilical vein: brings oxygenated blood and nutrients to the fetus
  3. 3. Special Structures in Fetal Circulation Placenta – Where gas exchange takes place during fetal .life Umbilical Arteries – Carry deoxygenated blood from the fetus to placenta Umbilical Vein – Brings oxygenated blood coming from the placenta to the fetus Foramen Ovale – Connects the left and right atrium. It pushes blood from the right atrium to the left atrium. Ductus Venosus - Carry oxygenated blood from umbilical vein to inferior vena cava, bypassing fetal liver Ductus Arteriosus - Carry oxygenated blood from pulmonary artery to aorta, bypassing fetal lungs.
  4. 4. Flow Chart of Fetal Circulation
  5. 5. 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
  6. 6. After reaching fetus theblood flows through theinferior vena cava
  7. 7. Fetal Circulation Blood continues to travel to the inferior vena cava from the ductus venosus Ductus Venosus  Small amount of blood routed to growing liver  Increased blood flow leads to large liver in newborns
  8. 8. 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
  9. 9. 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
  10. 10. Fetal Circulation From the right atrium, the blood goes to the right ventricle then to the pulmonary arteries Pulmonary arteries Small amount of blood goes to the maturing lungs Rest of blood is shunted away from lungs by ductous ateriosus back to aorta
  11. 11. 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
  12. 12. Why more blood flow directly to the Left atrium? Due to the higher pressure of the blood in the inferior vena cava, more blood flows from it directly into the left atrium via the foramen ovale. foramen ovale opens like a valve and can direct the blood stream that comes from below directly into the left atrium. the diameters of the inferior and superior vena cava are larger than that of the foramen ovale and therefore a small portion of the blood seeps into the right ventricle via the tricuspid valve. The heart is filled only with a mixed blood.
  13. 13. Fetal Circulation Low pressure system  Lungs are closed  Most oxygenated blood flows between the atria of the heart through the foramen ovale
  14. 14. 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
  15. 15. 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 Contd….
  16. 16. 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
  17. 17. Overview of Conversion Umbilical cord is clamped Loose placenta Closure of ductus venosus Blood is transported to liver and portal system Contd….
  18. 18. Loss of placenta also leads to : First breath Lungs expand and fluid is expelled Decreased pulmonary resistance Increased pressure in left atrium Closure of foramen ovale Contd….
  19. 19.  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 Contd….
  20. 20. Fetal vs. Infant Circulation Fetal  Infant Low pressure system  High pressure system Right to left shunting  Left to right blood flow Lungs non-functional  Lungs functional Increased pulmonary  Decreased pulmonary resistance resistance Decreased systemic  Increased systemic resistance resistance
  21. 21. Conclusion Oxygenated blood enters the umbilical vein from the placenta Enters ductus venosus Passes through inferior venacava Enters the right atrium Enters the foramen ovale Goes to the left atrium Passes through left ventricle Flows to ascending aorta to supply nourishment to the brain and upper extremities Contd….
  22. 22. . Enters superior vena cava  Goes to right atrium  Enters the right ventricle  Enters pulmonary artery with some blood going to the lungs to supply oxygen and nourishment  Flows to ductus arteriosus  Enters descending aorta ( some blood going to the lower extremeties)  Enters hypogastric arteries  Goes back to the placenta End