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The Meninges of Brain and Spinal Cord

The Meninges of Brain and Spinal Cord. DR. S. H. KHAN. The Meninges of Brain and Spinal Cord. The spinal cord and brain are surrounded by three membranes, the meninges. Named from the outside~ inward they are the dura mater , arachnoid , and pia mater. DURA MATER.

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The Meninges of Brain and Spinal Cord

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  1. The Meninges of Brain and Spinal Cord DR. S. H. KHAN

  2. The Meninges of Brain and Spinal Cord • The spinal cord and brain are surrounded by three membranes, the meninges. Named from the outside~ inward they are the dura mater, arachnoid, and pia mater. DURA MATER SUB-DURAL SPACE (filled with thin film of fluid) ARACHNOID MATER SUB-ARACHNOID SPACE (filled with CSF) PIA MATER

  3. The meninges of spinal cord • Spinal Dura mater • Spinal Arachnoid mater • Spinal Pia mater

  4. Spinal dura mater Characters • Dense, strong, fibrous membrane • Encloses the sp. Cord & cauda equina • Continuous above foramen magnum with the meningeal layer of Dura mater of brain • Below, becomes thinner & ends at lower border of S2 • invests filum terminale to attach at back of coccyx

  5. Epidural space • Position: lies between spinal dura mater and periosteum & ligaments of vertebral canal • Contents: loose connective tissue, semi liquid fat, spinal arteries, vertebral venous plexus, lymphatics and, the spinal nerves on each side pass through the epidural space which is applicable for block anesthesia Subdural space: potential space

  6. Spinal arachnoid mater Characters • A thin, delicate, tubular membrane loosely investing spinal cord • Above, it is continuous with cerebral arachnoid mater • Inferiorly extends as Dura ( lower border of S2)

  7. Subarachnoid space • Position: lies between pia and arachnoid maters containing cerebrospinal fluid. Extends upto low. Border of S2 • Terminal cistern : the largest part of subarachnoid space extending from termination of spinal cord (low. Border of L1) to level of S2, where it is occupied by nerves of cauda equina, so it is the best site for a lumbar puncture

  8. Lumbar puncture (spinal tap) Bet. L3 & L4 (adult), L4 & L5 (child)

  9. Spinal pia mater • A delicate vascular membrane that closely invests the spinal cord • Denticulate ligament: consist of 21 pairs triangular ligaments extending from spinal cord on each side between anterior and posterior roots of spinal nerves to spinal dura mater; these ligaments help to fix position of spinal cord. • Filum terminale: an extension of pia beyond conus medullaris

  10. The Meninges of Brain • Cerebral Dura mater (Pachymeninx) • Cerebral Arachnoid mater • Cerebral Pia mater Leptomeninges

  11. Cerebral Dura mater Characters • A thick and dense inelastic membrane • Composed of two layers, an inner - meningeal and outer - endosteal • Cranial venous sinuses lie between 2 layers

  12. Endosteal layer of Cerebral Dura mater • Lies just below the skull bone -Epidural Hge • Continuous outside at sutures & foramina with the periosteum of skull bones • Most strongly adherent to the bones over base of skull Meningeal layer of Cerebral Dura mater (Dura mater proper) • Dense, strong fibrous membrane • Continuous through the foramina magnum as Dura mater of Spinal cord • Forms 4 septa which divide the cranial cavity

  13. Four septa of Dura mater Proper • Falx cerebri － Lies in between the cerebral hemispheres. • Tentorium cerebri － Roof over the posterior cranial fossa. － covers the upper surface of cerebellum . • Falx cerebelli － Lies between the cerebellar hemispheres. • Diaphragma sellae － Forms roof of the sellar/ hypophyseal fossa

  14. Dural Artery Supply • ICA • Vertebral A. • ECA Maxillary a. Middle meningeal artery (clinically important -Epidural hge) Ascending pharyngeal a. Occipital a.

  15. Venous Sinuses of duramaterFunction: To receive blood from brain through cerebral veins To receive CSF from SA space through Arachnoid villi • Superior sagittal sinus • Inferior sagittal sinus • Straight sinus • Confluence of sinus

  16. Transverse sinus • Sigmoid sinus • Superior petrosal sinuses • inferior petrosal sinuses

  17. Cavernous sinus • Position: lies on each side of sella turcica (hypophyseal fossa) • Relations of cavernous sinus: • Internal carotid artery and abducent nerve run through the sinus • Oculomotor and trochlear nerves and ophthalmic & maxillary divisions of trigeminal nerve lie in the lateral wall of the sinus MCA Pituitary gland Occul n. Troch n. ICA Abducent n. Optha n. Maxil n. Sphenoid air sinus

  18. The flowing of the blood in dural sinus Sup. sagittal sinus Transverse sinus Inf. sagittal sinus Straight sinus Confluence of sinus Sup. petrosal sinus Sigmoid sinus Cavernous sinus Inf. petrosal sinus Internal jugular vein

  19. Cerebral Arachnoid mater Characters: • A delicate membrane covering brain loosely, • Passing over sulci and entering only cerebral longitudinal and transverse fissures. • Separated from Dura by potential Subdural space • Separated from Pia by the Subarachnoid space

  20. Arachnoid villi : • In certain areas arachnoid projects into venous sinuses to form arachnoid villi • Most numerous along the sup. Sagital sinus • serve as sites where CSF diffuses into bloodstream • Aggregations of arachnoid villi called archnoid granulations, • May give rise to Brain tumour (Meningioma)

  21. Cerebral pia mater • Thin vascular membrane • Closely invests brain surface, • Covers the gyri and descends into the sulci • Folds of Pia mater enclosing tufts of capillaries form the Telachoroidea. Such pia mater lined by secretory ependyma form the Choroid plexuses

  22. Tela choroidea and choroid plexus Capillaries Pia Ependyma

  23. Sub Arachnoid Space (SAS) • Interval between Arachnoid & Pia mater • Contains : － CSF, large blood vessels of brain & cranial nerves • Extension: － Along the olfactory n. to the mucoperiosteum of nose － Along the cerebral bl. Vessels, till they become an arteriole or venule － Beyond the lower end of spinal cord, ends between S2 & S3 • Around the base of the brain the SAS expands to form SA cisterns

  24. Subarachnoid cisterns • In certain situations the Arachnoid & Pia are widely separated to form the SA cisterns • Has free comunication with one another and with remainder SA Space • Cerebellomedullary cistern / Cisterna magna (Bet. Inf. Surface of cerebellum and the medulla) • Interpeduncular cistern (contain circle of Willi’s) • Pre Pontine cistern (contain vert. & basillar a.) • Quadrigaminal cistern / Cisterna ambiens (contain the great cerebral vein of Galen)

  25. Cerebellomedullary cistern CISTERNAL PUNCTURE

  26. Cerebrospinal fluid (CSF) • Clear colorless fluid, • Contained in the ventricular system & SA space • Replaces lymph in the CNS • Function: －Cushions & protects the CNS. －Nourishment of CNS. －Removes metabolites from CNS • Production: －By the choroids plexuses within the lateral ventricle mainly and, third and fourth ventricles also • Absorption: By arachnoid villi • Amount: 150ml • Rate of production: 0.5ml/min • Density of brain is slightly greater than that of CSF.

  27. Circulation of cerebrospinal fluid interventricular foramina third ventricle CSF drains from lateral ventricle mesencephalic aqueduct median and two lateral apertures fourth ventricle arachnoid granulations vein subarachnoid space superior sagittal sinus

  28. Ventricular System Lateral(L&R) Cerebral Aqueduct 3rd 4th

  29. The Blood vessels of Brain and Spinal Cord

  30. Arteries of brain Two sources • Internal carotid artery:suppliesanterior 2/3 of cerebral hemisphere and parts of diencephalon. Divides into ant. & mid. Cerebral arteries. • Vertebral artery:supplies posterior 1/3 of cerebral hemisphere and parts of diencephalon, brain stem and cerebellum At lower border of pons two VA join to form the basilar artery

  31. Internal carotid artery • Anterior cerebral artery • Middle cerebral artery • Anterior choroidal artery • Posterior communicating artery ICA ACA MCA AChA PComA

  32. Anterior cerebral artery • Terminal br. Of ICA • Joins the fellow of the opposite side by the anterior communicating artery • supply all medial surface of the cerebral cortex up to the parietooccipital sulcus ACA

  33. Middle cerebral artery • Largest br. Of ICA • Cortical branches: supply entire lateral surface of cerebral hemisphere, except occipital pole and inferolateral surface which is supplied by PCA • Central branches: supply lentiform and caudate nuclei, internal capsule

  34. Posterior communicating artery runs backward to join posterior cerebral artery

  35. Vertebral artery • Cranial branches • Anterior and posterior spinal arteries • Posterior inferior cerebellar artery • Branches of basilar artery • Anterior inferior cerebral artery • Labyrinthine artery • Pontine arteries • Superior cerebellar artery • Posterior cerebral artery

  36. Posterior cerebral artery • Cortical branches: supply medial and inferolateral surfaces of temporal lobe and lat. & medial surfaces of occipital lobe • Central branches: supply dorsal thalamus, midbrain, medial and lateral geniculate bodies,

  37. Cerebral arterial circle ( circle of Willis ) Concept: －Arterial anastomosis. －Distribute blood to any part of the cerebral hemisphere. －Equalizes pressure in the arteries of the two sides of brain. Position: －lies in the interpeduncular fossa at the base of the brain.

  38. Formation: Anteriorly:－Ant. communicating arteryPosteriorly:－Basilar artery that divides into posterior cerebral arteriesOn each side: －Anterior cerebral arteries, －Internal carotid arteries, －Posterior communicating arts, －Posterior cerebral arteries

  39. VENOUS DRAINAGE －very thin wall －no valves －lie in the subarachnoid space －drain into the cranial venous sinuses －ultimately drain into internal jugular vein 1.External cerebral veins 2.Internal cerebral veins

  40. Veins of brain External cerebral veins • Drain blood from cortex and subcortical medullary substance and empty into adjacent sinuses of dura mater

  41. Veins of brain • Internal cerebral veins: Two veins drain deeper parts of hemispheres, basal nuclei, internal capsule, diencephalon and choroid plexus, ultimately two ICV form great cerebral veinof Galen which enter straight sinus

  42. Blood vessels of spinal cord Arteries of spinal cord • Two sources • One Anterior and two posterior spinal arteries • Branches of segmental arteries: PSA ASA

  43. Blood vessels of spinal cord Post. Sp. A. Segmental sp. A. Spinal veins: drain into internal vertebral venous plexus Ant. Spinal artery

  44. Optic/visual pathway Light falling on the cornea. Traverse the refractive medias of the eye. Stimulates the rods and cones of retina. Optic nerve ( nasal & temporal fibers) Optic chaisma ( nasal fibers cross) Optic tract Lateral geniculate body Optic radiation Visual cortex

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