Page 345 - Anatomy and Physiology of Farm Animals, 8th Edition

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compounded, and pulmonary conges- constriction as well. If the ductus veno-
VetBooks.ir tion may result. sus fails to close completely, blood
Other modifications of circulation out-
returning from the viscera via the
side of the heart and great vessels take
place at birth. One of the most obvious portal vein may find its way back to the
systemic circulation (specifically, the
changes is that the placenta loses its role caudal vena cava) without first being
as oxygenator and provider of nutrients. processed in the liver. This abnormality
The vasculature associated with it (umbil- constitutes a portosystemic shunt
ical arteries and veins) collapses and con- (sometimes called portocaval shunt)
verts into fibrous cords (round ligaments) and can produce abnormalities of
that are sometimes identifiable grossly in metabolism, growth, and neural
the adult. The ductus venosus undergoes function.