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Blood supply, meninges & CSF (CSF (Communicates with ISF of neural…
Blood supply, meninges & CSF
Meninges - Membrane
3 layers
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Dura mater
2 indistinguishable layers within skull:
- Outer = endosteal (confluent with endosteum of skull)
- Inner = Meningeal
Separates to form two folds which course into fissures between areas of the brain tissue:
- Falx cerebri (cerebral fold)
- Tentorium cerebelli (between cerebrum and cerebellum)
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Physical protection, facilitate flow of CSF, provide framework for blood vessels to supply CNS tissues
3 layers go all way down spinal cord. Dura separates from endosteum within vertebral canal, creates epidural space
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CSF
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Cell-free, protein-free, low amino-acid content, low and stable K+ content, relatively low glucose content
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Nourishment, volume buffer, facillitates neurotransmitter flow, maintains stable enviro for neurones, shock absorber
Circulates through: Subarachnoid space, ventricles of brain and central spinal canal
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Blood:brain barrier maintains CSF in steady state (in healthy) - Tight junctions, thick basement membrane, foot processes of astrocytes
Transporting ependymal cells covering plexi. They pump solutes into CSF drawing in water by osmosis,
Lipid soluble pass readily into CSF, water soluble must be actively transported
CSF sampling - Subarachnoid spaces from atlantoocipital junction (cerebellomedullary cistern), lumbar cistern.
Arterial supply
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5 pairs of arteries from circle:
- Rostral cerebral arteries
- Middle cerebral arteries
- Caudal cerebral arteries
- Rostral cerebellar arteries
- Caudal cerebellar arteries
How circle is fed varies in different species:
- Dog/horse - Blood from internal carotid and basilar arteries
- Sheep and cat - Blood from maxillary artery via rete mirabile
- Ox - Blood from maxillary artery and vertebral artery via 2 rete
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Spinal cord blood supply
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Branches split into dorsal branch and ventral branch, supply respective aspect. Ventral also forms ventral spinal artery
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