Wherever the cranial and
meningeal zones separate, a cleft is created within the thickness of the
dural sheet. Cells facing the lumen become epithelialized, forming
a mesothelial lining, and the cleft becomes a dural venous sinus.
sinuses receive the venous drainage of the brain and convey it to
extracranial veins whence it returns to the right heart. Most of the
dural sinuses leave grooves on the inner surface of the prepared skull.
Two, however, have no relation to the skull itself but lie within dural
folds: the inferior sagittal sinus runs in the free lower border of the
falx cerebri; the straight sinus runs in the intersection between
tentorium cerebelli, falx cerebri, and falx cerebelli.
The figure on the left shows a groove (marked with black dots) formed by
the left transverse and sigmoid sinuses (FM indicates the foramen
magnum) in the wall of the left posterior cranial fossa.
The intracranial system of dural
venous sinuses (blue vessel in animation below) is continuous with the right and left internal jugular
veins through the jugular foramina. This is the principal route of
drainage, but there are also communications with veins of the face
around the margins of the orbits as well as direct and indirect
communications with extracranial veins of the scalp and upper neck.
Emissary veins pass directly through emissary foramina in the
skull, while other veins link the dural sinuses to veins in the diploë
that drain through the outer table into veins of the scalp. The
bilayer dura is represented by the orange and green layers in the
The bones of the living skull receive much if not most
of their blood supply through fine branches of the numerous so-called
“meningeal” arteries (red vessel in the animation below), which are derived from internal carotid,
external carotid, and vertebral systems. As a rule, these vessels lie
against the inner table of the skull, and their adventitia blends with
the endocranium. When the dura is stripped from the skull, the meningeal
vessels come away with it, leaving grooves in the surface of the bone
(black arrow, below).
Animation showing the disposition of the dura and its
relationship to certain intracranial veins.
Impressions on the inner surface of the skull made by meningeal vessels.
Animation courtesy of
T. Van Houten, PhD. ©2008