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65 Cards in this Set
- Front
- Back
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Meninges |
Special Protection of the brain & spinal cord |
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Special Protection of the brain and spinal cord tissue is provided by |
Cranial Vault Bony Vertebral Canal Dura Mater Arachnoid Mater Pia Mater |
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Dura Mater |
Outermost of the meninges |
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Characteristics of Dura Mater |
Outer Layer- Periosteal Layer Inner Layer- Meningeal Layer |
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Periosteal Layer |
Outermost layer of dura mater Adheres to the inner surface of the cranial bone Highly vasculated and innervated No Space between Cranium & Dura |
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Meningeal Layer |
Innermost layer of the dura mater Continuous with the dura of the spinal cord at the foramen magnum. Smooth & Avascular |
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Septa of the Dura |
Sheet like processes that are reflected inward and extend from the meningeal layer of the dura deep into the cranial cavity Provides Support and Protection for the brain Reduce or prevents displacement of the brain |
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4 Septa Locations in the Dura |
1.) Falx Cerebri 2.) Tentorium Cerebelli 3.) Falx Cerebelli 4.) Diaphragma sellae |
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Falx Cerebri |
Largest septum Located in the longitudinally fissure between the two hemispheres Sickle-like form Attached to the superior & inferior sagittal sinus |
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Tentorium Cerebelli |
Extends horizontally between the occipital lobes and the cerebellum and attached dorsally to the falx cerebri in the midline. Divides the brain transversely Forms the roof of the cerebellum Anterior portion has tentorial notch through which the midbrain runs. Supra and infra tentorial lesions (space-occupying lesions) are above and below the tentorium cerebelli respectively. |
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Falx Cerebelli |
Vertically oriented triangular projection into the posterior fossa (below the tentorium-infratentorial space) Dural fold between the folds of the cerebellum in the posterior fossa Analogous to the Falx cerebri |
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Diaphargma sellae |
Located on the ventral aspect of the brain Contains a small hole to accommodate the infundibulum (pituitary stalk) which connects the hypothalamus and the hypophysis (pituitary gland) |
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Venous Sinuses |
Endothelial lined channels formed between the 2 layers of the cranial dura which allows venous drainage from the brain. Provide for the venous drainage of blood from the brain mainly to the internal jugular vein Provide a route by which CSF is returned to the general systemic circulation |
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Venous Sinuses of the Dura |
1.) Superior Sagittal Sinus 2.) Inferior Sagittal Sinus 3.) Straight Sinus 4.) Transverse (Lateral) Sinus 5.) Sigmoid Sinus 6.) Confluence of Sinuses 7.) Cavernous Sinus |
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Superior Sagittal Sinus |
Located within the attached borders of the falx cerebri and then deviates to posteriorly as the right transverse (lateral) sinus Receives branches from the superior cerebral vein and veins from the meninges, scalp, and nose thus provides a route for the spread of infections to the CNS CSF is returned to the general systemic circulation |
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Inferior Sagittal Sinus |
Extends along the inferior margin of the falx cerebri Drains blood predominantly from the medial aspect of the brain |
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Straight Sinus |
Posterior continuation of the inferior sagittal sinus -Empties in the transverse (lateral) sinus (usually the left) -The Great Cerebral Vein of Galen (which collects venous blood from the internal cerebral veins) joins with the straight sinus Supratentorial space- occupying lesions can cause this vein to be compressed and impede the venous outflow of blood from the brain |
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Transverse Sinus |
Continuation of the straight sinus around the lateral aspect of the hemispheres |
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Sigmoid sinus |
Continuation of the transcerse or lateral sinuses anteriorly |
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Confluence of sinuses |
Dilatation of the venous channels posteriorly where the superior sagittal, straight, and the two transcerse (lateral) sinuses converge. |
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Cavernous Sinus |
At the base of the brain and close to the interanl carotid artery Receives blood from veins of the face, pharynx, nose and thus providing a route for CNS infection |
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Anterior Meningeal Arteries |
Supplies the Anterior Part of the Dura |
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Branches of the Vertebral and Occpital Lobes Supply the |
Posterior Part of the Dura |
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Middle Meningeal Artery/Branches Supply the |
Lateral Cranial Dura |
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Arachnoid Mater |
Delicate (spider-like) avascular membrane enveloping the brain and spinal cord (medulla spinalis) Lies between the pia mater internally and the dura mater externally Follows closely the meningeal layer of the cranial dura and is separated from it by a narrow (or potential) space called the Subdural Space Separated from the pia mater by the subarachnoid cavity, which is filled with CSF. |
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Subarachnoid Space |
Has a network of connective tissue or traveculae which bridges the arachonoid and pia membranes Has CSF which bathes the brain and helps distribute and equalize pressure within the skull All major blood vessels of the brain are located here. |
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CNS Cisterns |
are where pools of CSF form |
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Types of Cisterns |
1.) Cerebellomedullary Cistern (Cistern Magna) 2.) Pontine Cistern 3.) Chiasmatic Cistern 4.) Interpeduncular Cistern 5.) Lumbar Cistern |
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Cerebellomedullary Cistern (Cistern Magna) |
Spans the space over the cerebellum and medulla. It is the largest cistern |
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Pontine Cistern |
Lies over the pons |
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Chiasmatic Cistern |
Adjacent to the Optic Chiasm |
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Interpeduncular Cistern |
Lies over the interpeduncular fossa |
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Lumbar Cistern |
Extends from the L1 to S2 of the vertebral column Advantages of this area include lumbar punctures, spinal taps, Administer of drugs, etc. |
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Arachnoid Villi (Granulation) |
At the sinuses, minute pieces of arachnoid penetrate through aperturees int he meningeal layer and protrude into the venous sinuses Main passageway for the CSF in the general systemic circulation If dura sinus pressure s higher, the blood cant flow into the subarachnoid space because arachnoid villi tubules collapse. |
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Pia Mater |
Innermost meningeal layer Thin vascular membrane that adheres closely to the surface of the brain and spinal cord some internal structures (ventricles) also covered by pia Cannot be removed and gives brain shiny appearance |
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Brain Ventricular System |
4 cavities (ventricles) are located in the brain 2 lateral ventricles 1- 3rd ventricle 1- 4th ventricle |
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2 Lateral Ventricles |
Correspond to the shape of the hemisphere in which it is located and consists of 4 parts 1.) Anterior (frontal) horn in the frontal lobe 2.) Body- Parietal Lobe 3.) Posterior (occipital lobe) horn- occipital lobe 4.) Inferior horn- more ventrally in the temporal lobe Lateral Ventricles are connected to the 3rd ventricle via 2 short channels called the interventricular foramen (Monroe) |
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3rd ventricle |
Forms the medial surface of the thalamus and hypothalamus Organum Vasculosum Lamina Terminalis (OVLT) forms the anterior end of the 3rd ventricle It is connected to the 4th ventricle via the cerebral aqueduct (Aqueduct of Sylvius) |
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4th ventricle |
Is located posterior to the pons and the upper half of the medulla and ventral too the cerebellum Communicates with the subarachnoid space via 2 lateral aperatures- Foramina of Luschka (1) Foramina of Magendie (1) (median) End of the 4th ventricle, a small central canal extends through the spinal cord
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Choroid Plexus |
Present in each ventricle and produces CSF In the lateral ventricles, the choroid plexus is in the medial wall and extends from the tip of the inferior orn to the interventricular foramen In the 3rd and 4th ventricles it is in the roof |
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Layers of Chorid Plexus |
3 layers of membranes - An endothelial layer of the choroidal capillary wall which is fenestrated (openings) -A pia membrane -A layer of choroidal epithelial cells that contain numerous mitochondria and have many basal in folding and microvilli on the surface facing the ventricles |
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CSF Formation |
70% of the CSF in the brain and spinal cord is produced by the choroid plexus 30% is secreted by the parenchymal cell of the brain crosses the ependyma and enters the ventricles CSF production is active and involves the enzyme carbonic anhydrase and specific transport mechanisms Involves fenestration of blood through endothelial cells however movement of larger molecules into the filtrate is prevented by tight junctions |
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CSF & Active Transport |
Active transport is required to transport sodium and magnesium ions into the CSF and remove potassium and calcium ions. Water flows across the endothelium to maintain osmotic pressure |
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CSF rate of formation |
Average of 500 mL/day |
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CSF Circulation |
Movement of CSF is due predominantly to pulsations of the arteries of the arteries in the subarachnoid space. Flows from each lateral ventricles through the interventricular foramen (Monroe) then to the 3rd ventricle, then through the cerebral aqueduct into the 4th ventricle then fluid travels from the ventricular system via Foramen of Luschka and Magendie to enter the cerebellomedullary cistern. CSF will travel over the cerebral hemispheres where it enters the arachnoid villi to the dural venous sinuses into the cistern magna. From the cistern magna, CSF also flows downward into the spinal subarachnoid space and then ascends along the ventral surface of the spinal cord into the basal part of the brain where it courses dorsally to empty into the dural sinuses. |
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CSF Function |
Reduction of traction exerted on the nerves and blood vessels with the CNS Cushioning of the CNS and dampens effects of trauma Vehicle for the removal of metabolites Provides a stable ionic envionment |
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Clinical CSF color changes |
Pink/Red= blood in CSF due to rupture or bleeding from aneurysm Yellow= increased protein content sometimes due to tumors Xanthrochromia- hours are subarachnoid hemorrhage hemoglobin from lyzed RBC gets broken down into bilirubin; increase gamma globulin Cloudy or white- increase in the number of white blood cells which signals an infection (meningitis) Glucose levels- low bacterial/fungal infections of CNS Normal- Viral infections |
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Blood Brain Barrier |
Large molecules cannot pass from the blood into the interstitial fluid due to the existence of the blood brain barrier Located in the interface between capillary wall and brain tissue which consists of -endothelial cells lining the capillary wall with tight junctions between them -processes of astrocytes abutting on the capillaries -A capillary basement membrane Prevents entry of blood borne foreign substances in to the brain tissue Prevents drug delivery into the CNS |
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Blood CSF barrier |
Prevents large molecules from passing into the CSF from the blood Tight junctions don't exit between neighboring capillary endothelial cells in the choroid plexus. The cells are fenestrated and allow passage of large molecules. Outermost layer of epithelial cells with tight junctions, large molecules cant enter the CSF |
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7 circumventricular organ) sturctures without BBB / permit the passage of large molecules |
- Area posterma -Pineal body -Subcommissural organ - Organum vasculosum lamina terminalis (OVLT) -Neurohypophysis -Medial eminence -Subfornical organ
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Hydrocephalus |
dilation of the ventricles ensure when circulation of CSF is blocked or absorption is impeded. Leads to increase in ventricular pressure and thus dilation Can lead to impairment of structures such as the corticobulbar and corticospinal tracts with a progressive loss of motor functions Hydrocephalus can occur before birth and usually noted during the first few months |
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Types of Hydrocephalus |
1.) Non-communicating = fluid flow out of one or more of the ventricles is blocked Most common blockage is of the cerebral aqueduct in the 4th ventricle 2.) Communicating= Over production of CSF and movement into the dural venous sinuses are obstructed usually at the level of the arachnoid villi Often seen in newborns where there is more fluid made than reabsorbed Choroid plexus are sometimes destroyed |
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Non-Communicating Hydrocephalus Malformations |
Dandy-Walker= cyst formation near the internal base of the skull partial or complete absence of the area of the brain between the two cerebellar hemisphere and an enlargement of the fourth ventricle Arnold-Chiari malformation= indented bony space at the lower rear of the skull is smaller than normal and pushed and elongates of the brainstem and cerebellum. If not corrected, brain damage and/or herniation and death can occur. |
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Meningitis |
Can be viral, bacerial, or fungal induced and life threatening. Most common in infants and children. Commonly involves leptomeningitis Bacterial meningitis is the most serous and needs prompt treatment Increase number of WBC count, CSF pressure, protein level Treatment= antibiotic, corticosteroid, acetaminophen and anticonvulsant |
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Herniation |
After skull sutures have closed, herniation occurs if there is a space-occupying lesion oin the cranial valut. |
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Types of Herniation (2 for exam) |
Uncal herniation & Tonsillar herniation |
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Uncal Hernation |
The uncus (tiny structure of the medial temporal lobe) herniates into the tentorial notch and puts pressure on the midbrain.
Causes decrease consciousness and eventually death Dilation of the pupil on the side of the herniation. If the herniation is bilateral both pupil will be dilated If pressure not relieved, uncal herniation may advance to the central herniation. |
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Tonsillar Herniation |
The tonsil ( a tiny structure medial to the cerebellum) herniates into the foremen magnum Causes rapid decrease in consciousness, abnormalities in heart rate and breathing If pressure not relieved, it will lead to death |
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Hemorrhage |
Usually fractures to the base of the skull which increases the risk of CSF from the nose, bleeding from auditory canal, meningeal bleeding and infections |
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Types of Hemmorages |
Intracerebral hemorrhage (ICH) Extra/Epidural Hemorrhage Subdural hemorrhage Dementia Pugilistica |
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Intracerebral Hemorrhage (ICH) |
Occurs with brain tissue May occur during child birth |
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Extra/Epidural Hemorrhage |
Occurs between the periosteal and meningeal layers of the cranial dura Occur when arteries tear (usually meningeal arteries) with skull fracture Herniation and death can occur if hematoma is not addressed |
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Subdural hemorrhage |
Bleeding in the potential space between dura and arachnoid membranes Most commonly results from the tearing of the superior cerebral vein Usually sudden blow to the front of the head ( anterior/posterior displacement) |
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Dementia Pulgilistica |
Common syndrome affecting professional boxers Generalized brain damage Severe global cerebral atrophy Develop thinking/memory loss and personality issues |
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Intracranial Pressure |
Occurs due to an increase in size or volume of any of the consitutients which can be caused by - Volume increase due to cerebral edema -Intracranial hemorrhage or tumors -Obstruction in CSF flow -Increase blood volume in brain tissue due to venous obstruction Symptoms may include: Headaches Nausea/Vomiting Bradychardia Increase in systemic pressure Loss of Consciousness Elevation and Blurring of the optic disc margin |
