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 downwards, 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
uncus of the temporal lobe of the cerebrum and the internal carotid artery, which first pierces the roof of the sinus then doubles back to lie against it.
The ophthalmic veins drain into the anterior aspect of the cavernous sinus which also links up, through these veins, with the pterygoid venous plexus and the anterior facial vein. The cavernous sinus also receives venous drainage from the brain (the superficial middle cerebral vein) and from the dura (the sphenoparietal sinus).
Posteriorly, the superior and inferior petrosal sinuses drain the cavernous sinus into the sigmoid sinus and into the commencement of the internal jugular vein respectively.
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