The meninges of the brain II

Dural venous sinus Description Superior sagittal sinus Along the upper fix border of the falx cere...

Dural venous sinus	Description
Superior sagittal sinus	Along the upper fix border of the falx cerebri Begins anteriorly at the foramen caecum At internal occipital protuberance it deviates to right  Continue with the right transverse sinus Many arachnoid villi & granulations are present along the course Sinus communicates with venous lacunae on either side Receives blood from superior cerebral veins  At internal occipital protuberance it dilates to form the confluence of the sinuses
Inferior sagittal sinus	Along the free margin of the falx cerebri It’s joined by the greater cerebral vein to form the straight sinus
Straight sinus	Along the line of junction of the falx cerebri with the tentorium cerebelli Formed by the union of inferior sagittal sinus & great cerebral vein Ends by turning to left to form the left transverse sinus
Transverse sinuses	Paired (Right & left) RTS continues with superior sagittal sinus LTS continues with the straight sinus Begins at the internal occipital protuberance Receives blood from   : Superior petrosal sinus, Inferior cerebral veins,  Cerebellar veins & Diploic veins Ends by turning down as the sigmoid sinus
Sigmoid sinus	It’s the direct continuation o the transverse sinus It becomes continuous with the internal jugular vein
Occipital sinus	Small Communicates with the vertebral veins Drains into confluence of sinuses
Cavernous sinus	Situated in the middle cranial fossa on either side of the body of the sphenoid bone Extends from the superior orbital fissure (In front) to the apex of the petrous part of the temporal bone (Behind) Structures passing through medially Internal carotid artery & sympathetic nerve plexus Abducent nerve (Below & lateral to the ICA)  Structures passing through laterally Occulomotor nerve Trochlear nerve Ophthalmic division of the TGN Maxillary division of the TGN Venous connections Superior & inferior ophthalmic veins Inferior cerebral veins Sphenoparietal sinus Central vein of the retina Sinus drains Posteriorly    : Superior & inferior petrosal sinuses Inferiorly       : Pterygoid venous plexus Right & left cavernous sinuses communicate with each other via anterior & posterior inter cavernous sinuses Each sinus communicates with the facial vein via superior ophthalmic vein (Infections can spread from facial skin to the cavernous sinuses)
Superior & inferior petrosal sinuses	Small sinuses SPS drains the cavernous sinus into the transverse sinus IPS drains the cavernous sinus into the internal jugular vein

The cross section of the cavernous sinuses




B.The arachnoid mater


1) Impermeable

2) It lies between the dura mater (Externally) & pia mater (Internally)

3) It’s separated from the dura by the subdural space (Filled with a film of fluid)

4) It’s separated from the pia by the subarachnoid space (Filled with CSF)

1. Cerebral arteries, veins & cranial nerves lie in this space
2. Arachnoid fuses with the cranial nerve at the point of exit from the skull, but the SAS extends around the optic nerve as far as the eyeball

5) The arachnoid projects into the venous sinuses to form the arachnoid villi

1. Arachnoid villi are most numerous along the superior sagittal sinus
2. Aggregations of arachnoid villi are called arachnoid granulation
3. CSF diffuses into blood stream at arachnoid villi

C.Pia mater



1) It’s a vascular membrane that closely covers the brain

2) Extends along all the cranial nerves

3) Cerebral arteries entering the brain substance carry a sheath of pia mater




Meninges of the spinal cord

Dura mater	Encloses the spinal cord & the cauda equina Extension Superiorly           : Continues through the foramen magnum with the meningeal layer of the dura covering the brain Inferiorly             : Ends on filum terminale at the level of S2 vertebrae   Separated from the wall of the vertebral canal by extra dural space Extra dural space contains internal vertebral venous plexus Extends along each nerve root
Arachnoid mater	Impermeable Separated from pia by the SAS (Contains CSF) Extends along each nerve root
Pia mater	Vascular membrane that closely covers the spinal cord Extends along each nerve root Forms ligamentum denticulatum