The internal vascular system of vertebral bodies was investigated
in
17–24 wk human fetuses by acrylic dye
injection and by corrosion casting/scanning electron microscopy. The
regions
of intervertebral spaces did
not contain blood vessels. The radial metaphyseal vessels were at the stage
of centripetal ingrowth into the
vertebral body cartilage and their terminal, blindly ending segments had
a
form of cuff-like capillary
plexuses. The anterolateral equatorial arteries communicating with the
vessels
of the ossification centre were
only rarely found. The centre was usually supplied by 2 posterior (nutrient)
arteries which branched into
an arcade-like array of arterioles equipped with occasional sphincters
and
giving origin to a dense network
of peripherally located capillaries. Numerous blind capillary buds formed
the advancing border of the
ossification centre. The veins usually accompanied the arteries. In the
ossification centre the venous
compartment consisted of sinuses drained by larger posterior veins. In
the
17 wk fetus, an axial avascular
area was observed in the place of notochord localisation, indicating the
formation of a ring-shaped
ossification centre around the notochord remnants at earlier stages of
fetal
development.