Meninges,Cerebrospinal Fluid, and the Spinal Cord

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Meninges,Cerebrospinal Fluid, and the Spinal Cord

The Nervous System MENINGES CSF Introduction Protection of the brain Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood-brain barrier (astrocytes) The Meninges Series of membranes Cover and protect the CNS Anchor and cushion the brain Contain cerebrospinal fluid (CSF) The Meninges Three layers Dura mater Arachnoid mater Pia mater Skin of scalp Periosteum Bone of skull Periosteal Dura Meningeal mater Superior Arachnoid mater sagittal sinus Pia mater Subdural Arachnoid villus space Blood vessel Subarachnoid Falx cerebri space (in longitudinal fissure only) Figure 12.24 The Meninges Dura mater Strongest meninx Fibrous connective tissue Limit excessive movement of the brain Superior sagittal sinus Falx cerebri Straight sinus Crista galli of the Tentorium ethmoid cerebelli bone Falx Pituitary cerebelli gland (a) Dural septa Figure 12.25a The Meninges Arachnoid mater Middle layer with weblike extensions Separated from the dura mater by the subdural space Subarachnoid space contains CSF and blood vessels The Meninges Pia mater Layer of delicate vascularized connective tissue Clings tightly to the brain Meningitis Inflammation of meninges May be bacterial or viral Diagnosed by obtaining CSF sample via lumbar tap T12 Ligamentum flavum L5 Lumbar puncture needle entering subarachnoid space L4 Supra- spinous ligament L5 Filum terminale S1 Inter- Cauda equina vertebral Arachnoid Dura in subarachnoid disc matter mater space Figure 12.30 Cerebrospinal Fluid (CSF) Composition Watery solution Modified plasma Constant volume (about 150 ml) About 500 ml formed daily Replaced every 8 hours or so Cerebrospinal Fluid (CSF) Functions Gives buoyancy to the CNS organs Protects the CNS from blows & other trauma Nourishes the brain & carries chemical signals Cerebrospinal Fluid (CSF) Choroid plexuses Produce CSF at a constant rate Hang from the roof of each ventricle Clusters of capillaries enclosed by pia mater & a layer of ependymal cells Ependymal cells Capillary Section of choroid Connective plexus tissue of pia mater Wastes and Cavity of CSF forms as a filtrate unnecessary containing glucose, oxygen, solutes absorbed ventricle vitamins, and ions (Na+, Cl–, Mg2+, etc.) (b) CSF formation by choroid plexuses Figure 12.26b Superior sagittal sinus 4 Choroid plexus Arachnoid villus Interventricular foramen Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle 3 Third ventricle 1 CSF is produced by the Cerebral aqueduct choroid plexus of each Lateral aperture ventricle. Fourth ventricle 2 CSF flows through the ventricles and into the Median aperture 2 subarachnoid space via the Central canal median and lateral apertures. of spinal cord Some CSF flows through the central canal of the spinal cord. 3 CSF flows through the (a) CSF circulation subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi. Figure 12.26a Cerebrospinal Fluid (CSF) Hydrocephalus Due to blockage or overproduction of CSF Internal versus external hydrocephalus Infants versus adults Treatment .

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Why Do Bridging Veins Rupture Into the Virtual Subdural Space?
J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.47.2.121 on 1 February 1984. Downloaded from Journal of Neurology, Neurosurgery, and Psychiatry 1984;47:121-127 Why do bridging veins rupture into the virtual subdural space? T YAMASHIMA, RL FRIEDE From the Department ofNeuropathology, University of Gottingen, Gottingen, Federal Republic of Germany SUMMARY Electron microscopic data on human bridging veins show thin walls of variable thick- ness, circumferential arrangement of collagen fibres and a lack of outer reinforcement by arach- noid trabecules, all contributory to the subdural portion of the vein being more fragile than its subarachnoid portion. These features explain the laceration of veins and the subdural location of resultant haematomas. Most subdural haematomas due to venous bleeding walls are delicate, lacking muscle fibres, with only a have been attributed to lacerations in bridging veins. thin fibrous wall and a thin elastic lamina adjacent to These veins form short trunks passing directly from the endothelial layer. The conclusions of these two the brain to the dura mater, almost at right angles to authors, have gained wide acceptance, although guest. Protected by copyright. both. Between these two points, bridging veins take there was little evidence concerning the fragility of a straight course with no tortuosity to allow for the the vein walls. possible displacement of brain.' Trotter2 speculated The purpose of the present communication is to that subdural haematomas are invariably due to provide electron microscopic data on tissue fixed in trauma tearing large veins, an interpretation situ, which might throw some light on to the lacera- elaborated by Krauland.3 According to Leary,4 the tion mechanism of bridging veins and its relationship common sources of subdural haematomas are rup- to the development of subdural haematoma.
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