Later Development, Develop. Physiol., Dr. D. Penney

Table 3.09 - Hemodynamic Changes at Birth.

  1. Lungs inflated by first breath (A).

  2. Relaxation of the pulmonary precapillary vessels by high PO2.

  3. Increase in lung blood flow.

  4. Decrease in pulmonary artery pressure.

  5. Increased surge of blood to left atrium.

  6. Left atrial pressure rises above right atrial pressure.

  7. Foramen ovale functionally closes (B).

  8. Umbilical cord is tied off or naturally closes (C).

  9. Ductus venosus closes and resistance of systemic circuit rises.

  10. Venous return to heart decreased, decreasing both atrial pressures.

  11. Pulmonary pressure falls below aortic pressure.

  12. Flow through the ductus arteriosus is reversed (L --> R) (D).

  13. Pulmonary blood flow and pressure temporarily increases.

  14. Ductus arteriosus closes due to rising arterial O2 saturation, etc.

  15. Pulmonary vascular resistance continues to fall because of regression of pulmonary arteriolar smooth muscle.

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