Early Development, Devel. Physiol., Dr. D. Penney

Table 2.08 - Six Unique Fetal Vascular Channels:

  • Umbilical arteries (2) - carry blood to placenta; low HbO2 content (higher O2 saturation), low PO2

  • Umbilical vein - carries blood of higher O2 saturation & PO2 from placenta to fetus

  • Ductus venosus - arises from the umbilical recess; low resistance bypass of liver to heart; little smooth muscle in wall; carries 50% of blood from placenta

  • Cirsta dividens a) & Foramen ovale b) -
    a) directs blood to RA or LA
    via sinistra - path to upper body and head
    via dextra - path to descending aorta

    b) oval window; valve; flow rate through this structure less to LA than that to RA, thus tissue mass of latter greater; cross-sectional area 1/2 that of inferior vena cava

  • Ductus arteriosus - short shunt; distal portion of 6th left aortic arch; responsive to PO2, contracting above 50 - 60 mm Hg O2 tension.

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