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The meninges of the brain II

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
image



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
The meninges of the brain II The meninges of the brain II Reviewed by Radiology Madeeasy on August 04, 2010 Rating: 5
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