Ventricles & Meninges.docx

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Western University
Anatomy and Cell Biology
Anatomy and Cell Biology 3319
Kem Rogers

Ventricles & Meninges Ventricles • Nervous system originates from a hallow, fluid-filled tube: neural tube • Cells of tube wall proliferate & differentiate forming cells of CNS • Enclosed fluid-filled space (neural canal) forms ventricular spaces of CNS • Expansion of the brain’s central cavity • Filled with cerebrospinal fluid • Lined by ependymal cells • Continuous & continuous with central canal of spinal cord • Some ependymal cells form cerebral spinal fluid & that circulates through ventricles & leaves ventricles & circulate around brain & spinal cord in arachnoid space • Paired lateral ventricles (first & second ventricles) o Lie in cerebral hemispheres – associated with forebrain o Horseshoe shape reflects bending of hemispheres o Anteriorly – 2 ventricles lie close together – separated by thin median membrane: septum pellucidum (transparent wall) • Third ventricle o Lies in diencephalon o Anteriorly connects to each lateral ventricle through interventricular foramen o Interthalamic adhesion creates hole • Cerebral aqueduct o In the midbrain o Thin tube-like central cavity o Connects third & forth ventricles o Runs between cerebral peduncles & tectum • Fourth ventricle o Lies in brain stem o Dorsal to the pons & superior half of the medulla oblongata o Three openings occur in the walls  Paired lateral apertures  Median aperture o Holes connect the ventricles with subarachnoid space – surrounds the whole CNS o Connection allows cerebrospinal fluid to fill both the ventricles & subarachnoid space o Fourth ventricle connects caudally to the central canal of the inferior medulla & spinal cord Protection of the Brain • Meninges o 3 connective tissue membranes just lie external to brain & spinal cord • Functions o Cover & protect the CNS o Enclose & protect blood vessels that supply the CNS o Contain cerebrospinal fluid • From external to internal o Dura mater o Arachnoid mater o Pia mater • Meninges extend around spinal cord & are continuous throughout the CNS • Dura & arachnoid mater surround the brain loosely – never dipping into sulci Meninges Meningeal Spaces Epidural (Extradural) Hematoma • Travels through dura, in grooves on lateral aspect of calvaria • Vulnerable to damage at pterion • Brie f loss of consciousness, followed by lucid interval • Drowsiness & coma due to compression of brain • Bones are very weak – can break & tear meningeal artery Intracranial Hemorrhage Dura Mater • Leathery • Strongest • Around the brain – two-layered sheet of dense fibrous connective tissue • Superficial layer: Periosteal Layer o Attaches to the internal surface of the skull bones (it is the periosteum) • Deeper layer: Meningeal Layer o From true external covering of the brain • 2 layers are fused together except where they separate to enclose blood-filled dural venous sinuses o Collect blood from the brain & conduct it to large internal jugular veins of neck o Largest dural sinus: superior sagittal sinus in superior midline • Meningeal dura mater extend inward to form flat partitions that subdivide cranial cavity & limit movement of the brain within the cranium • Partitions o Falx cerebri (A)  Large  Sickle-shaped  Vertical sheet  Lies in median plane in longitudinal fissure (between L & R hemispheres)  Attaches anteriorly to crista galli of ethmoid bone  Upper fixed margin  Lower free margin o Tentorium cerebelli (B)  Resembling a tent over cerebellum  Almost horizontal sheet  Lies in transverse fissure - separates cerebrum & cerebellum  Transverse sinus is enclosed by tentorium cerebelli  Falx ce
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