Later Development, Develop. Physiol., Dr. D. Penney
Table 3.15 - Perinatal Changes in the Circulation.
- Loss of low resistance placental circulation.
- Decrease pulmonary vascular resistance in response to rising PO2.
- Rising systemic vascular resistance and pressure.
- Transformation of heart from two pumps in parallel to a series arrangement.
- Closure of umbilical vessels, ductus venosus, ductus arteriosus and foramen ovale.
- Gradual decrease in thickness of RV wall relative to LV, due to more rapid growth of the latter.
- Gradual changeover from fetal type to adult type hemoglobin (HbF to HbA).
- Increase in arterial PO2 & % Hb saturation.
- Hemoconcentration if cord is clamped late
- Gradual decrease in cardiac output & O2 consumption on a per g. body wt. basis.
- Loss of O2 carrying capacity (Hb) after birth, "postnatal anemia".
- Decrease in ratio of heart weight to body weight (greater in some animals than in others).
- Decrease in heart rate to 60 - 70 bpm.
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