15.1
Dural venous sinuses – Sinus durae matris
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The dural venous sinuses are enclosed between the two original sheets of the ectomeninx. The wall of a sinus is formed by endothelium and a sheet of the dura mater, which replaces the media and adventitia. The sinuses are not typical veins – they lack valves and are not able to collapse when they are damaged. The sinuses have numerous tributaries from the brain, meninges, and cranial bones. They also establish connection with the extracranial veins (emissary veins).
• 1 Confluence of sinuses (confluens sinuum)
– the confluence is located near the internal occipital protuberance – is formed by connection of the superior sagittal, straight, and occipital sinus 1.1 1.1 Superior sagittal sinus (sinus sagittalis superior) – passes in the midline within the superior margin of the falx cerebri 1.2.1 – originates in front of the crista galli and terminates 1.2 in front of the internal occipital protuberance, 4.2 where it opens into the confluence of the sinuses 1 – arachnoid granulations of Pacchioni are projections 4 2 which bulge into the sinuses and by which 4.3 2.1 cerebrospinal fluid is absorbed into the venous system 1.2 Straight sinus (sinus rectus) 1.3 – is located at the junction of the falx cerebri and tentorium cerebelli – originates as a confluence of the inferior sagittal sinus and great cerebral vein 1.2.1 Inferior sagittal sinus (sinus sagittalis inferior) – passes within the inferior margin of the falx cerebri – opens into the straight sinus in the site of the falx cerebri insertion into the tentorium cerebelli 1.3 Occipital sinus (sinus occipitalis) – originates near the foramen magnum – passes upwards in front of the internal occipital crest and opens into the confluence of the sinuses or the terminal segment of the transverse sinus 4.1 1.4 Marginal sinus (sinus marginalis) – a paired sinus passing around the foramen magnum 4 3 – caudally it is connected with the internal vertebral 4.3 venous plexuses, dorsally with the occipital sinus, 4.2 and ventraly with the basilar plexus 1.4 2 Transverse sinus (sinus transverus) 2.1 – a paired sinus located in the groove for the transverse sinus – laterally it continues as the sigmoid sinus 1.3 2.1 Sigmoid sinus (sinus sigmoideus) 1.1 2 – a paired sinus, a continuation of the transverse sinus – the superior bulb of the internal jugular vein originates as a confluence of the sigmoid and inferior petrosal sinus Venous sinuses at the cranial base, anterior view at the level of the jugular foramen 3 Basilar plexus (plexus basilaris) – a venous sinus located on the clivus of the occipital bone – interconnects the cavernous and both inferior petrosal sinuses – communicates with the system of the internal vertebral venous sinuses 4 Cavernous sinus (sinus cavernosus) 1.1 – passes from the superior orbital fissure to the apex of the petrous bone – the internal carotid artery passes within the cavernous sinus together 1.2.1 with the oculomotor, trochlear, abducens, ophthalmic, and maxillary nerve – the superior ophthalmic vein empties into the sinus – the right and left sinus are interconnected by the anterior and posterior 4 intercavernous sinus (sinus intercavernosus anterior et posterior) 4.1 Sphenoparietal sinus (sinus sphenoparietalis) 4.1 3 – medially drains into the cavernous sinus 1.2 – courses along the posterior margin of the lesser wing of the sphenoid bone 4.3 4.2 Superior petrosal sinus (sinus petrosus superior) 2 4.2 – interconnects the cavernous and sigmoid sinus 2.1 1 – coursing along the superior margin of the petrous bone 1.4 4.3 Inferior petrosal sinus (sinus petrosus inferior) 1.3 – a connection of the cavernous sinus to the jugular foramen Scheme of the venous sinuses, – gives an origin to the internal jugular vein left view from behind by a confluence with the sigmoid sinus
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