Later Development, Develop. Physiol., Dr. D. Penney
Table 3.09 - Hemodynamic Changes at Birth.
- Lungs inflated by first breath (A).
- Relaxation of the pulmonary precapillary vessels by high PO2.
- Increase in lung blood flow.
- Decrease in pulmonary artery pressure.
- Increased surge of blood to left atrium.
- Left atrial pressure rises above right atrial pressure.
- Foramen ovale functionally closes (B).
- Umbilical cord is tied off or naturally closes (C).
- Ductus venosus closes and resistance of systemic circuit rises.
- Venous return to heart decreased, decreasing both atrial pressures.
- Pulmonary pressure falls below aortic pressure.
- Flow through the ductus arteriosus is reversed (L --> R) (D).
- Pulmonary blood flow and pressure temporarily increases.
- Ductus arteriosus closes due to rising arterial O2 saturation, etc.
- Pulmonary vascular resistance continues to fall because of regression of pulmonary arteriolar smooth muscle.
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