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




Table 3.11 - Rerouting of Circuits at Birth.

Structure(s)EventTimeCause
Umbilical Art'sclosure2 - 4 min. smooth muscle contraction (PO2 & cold); ligature
Umbilical Veinclosure2 - 4 min. same
Ductus Venosusclosurehrs. - daypassive mechanical; smooth muscle contraction?
Foramen Ovaleclosureminutespressure in LA exceeds that in RA
Pulm. Vasculature openingminutes smooth muscle relaxation (increased PO2); smooth muscle atrophy
Ductus Arteriosusclosurehrs. - day smooth muscle contraction with increased PO2



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