Page 316 - Clinical Anatomy

ECA5 7/18/06 6:50 PM Page 301

The veins of the head and neck 301

The veins of the head and neck

The cerebral venous system

The venous drainage of the brain follows two pathways:
1◊◊the superficial structures, e.g. the cerebral and cerebellar cortices, drain
to the nearest available dural sinus (see below) by thin-walled veins;
2◊◊the deep structures drain through the internal cerebral vein on each side,
which is formed at the interventricular foramen by the junction of the
choroid vein (draining the choroid plexus of the lateral ventricle) with the
thalamostriate vein (draining the basal ganglia).
The two internal cerebral veins unite to form the great cerebral vein
(the vein of Galen) which emerges from under the splenium of the corpus
callosum to join the inferior sagittal sinus in the formation of the straight
sinus.

The venous sinuses of the dura (Fig. 214)

The venous sinuses lie between the layers of the dura. They receive the
venous drainage of the brain and of the skull (the diploic veins) and disgorge
ultimately into the internal jugular vein. They also communicate with the
veins of the scalp, face and neck via emissary veins which pass through a
number of the foramina in the skull.
The superior sagittal sinus lies along the attached edge of the falx cerebri
and ends posteriorly (usually) in the right transverse sinus. Connecting
with it are a number of venous lakes (lacunae laterales) into which project the
Pacchionian bodies of arachnoid, filtering cerebrospinal fluid (C.S.F.) back
into the blood.
The inferior sagittal sinus lies in the free margin of the falx cerebri and
opens into the straight sinus.
The straight sinus lies in the tentorium cerebelli along the attachment of
the falx cerebri. It is formed by the junction of the great cerebral vein of
Galen with the inferior sagittal sinus and runs backwards to open (usually)
into the left transverse sinus.
The transverse sinuses commence at the internal occipital protuberance
and run in the tentorium cerebelli on either side along its attached margin.
On reaching the mastoid part of the temporal bone each passes down-
wards, forwards and medially as the sigmoid sinus to emerge through the
jugular foramen as the internal jugular vein.
The cavernous sinuses (Fig. 215) lie one on either side of the body of the
sphenoid against the fibrous wall of the pituitary fossa and rest inferiorly
on the greater sphenoid wing. They communicate freely with each other via
the intercavernous sinuses.
Traversing the cavernous sinus are the carotid artery and the cranial
nerves III, IV, V (ophthalmic and maxillary divisions) and VI. Lying above
the cavernous sinus are three important structures — the optic tract, the