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There are two smaller projections of serous duraathe falx cerebelli
The falx cerebri
The falx cerebri projects down in the sagittal plane to separate partially
which forms a roof over the pituitary fossa and the pituitary gland.
the two cerebral hemispheres. It tapers to a point anteriorly but pos-
teriorly it is attached to the tentorium. The superior sagittal sinus between the two cerebellar hemispheres and the diaphragma sellae
(Fig. 68.2) is in its attached border and the inferior sagittal sinus is in its The cavernous sinus (Fig. 68.3)
free border. Veins from the cerebral hemispheres drain into the superior The cavernous sinus lies on either side of the pituitary fossa and the
sagittal sinus or into diverticula from it, the lacunae laterales. In places body of the sphenoid. Like the other venous sinuses, it is formed by a
the underlying arachnoid sends small outgrowths through the serous layer of serous dura lined by endothelium. In addition, a layer of serous
dura to project into the sinus. These are the arachnoid villi and they are dura from the posterior cranial fossa projects forwards into the side of
the site of absorption of cerebrospinal fluid into the bloodstream. In the cavernous sinus to form the cavum trigeminale.
later life they clump together to form arachnoid villi which make
indentations in the skull. Contents
• Internal carotid artery: see p. 133.
The tentorium cerebelli • Oculomotor nerve: see p. 127.
The tentorium cerebelli forms a roof over the posterior cranial fossa • Trochlear nerve: see p. 127.
and the cerebellum. Its free border is attached to the posterior clinoid • Abducent nerve: see p. 131.
processes and through the opening passes the brainstem. The trans- • Three divisions of the trigeminal nerve: see p. 129.
verse sinuses are in the attached border of the tentorium.

The cranial cavity 153