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Blood supply, meninges, CSF (CSF (Communicates with ISF of neural tissue…
Blood supply, meninges, CSF
Meninges
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3 layers:
- Dura mater - Tought mother
- Arachnoid membrane
- Pia mater - Soft mother
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Dura mater
2 indistinguishable layers withing skull:
- Outer = endosteal (confluent with endosteum)
- Inner = Meningeal
Separates to form 2 folds, course into fissures between areas of brain tissue:
- Falx cerebri - Cerebral fold
- Tentorium cerebelli - Between cerebrum and cerebellum
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Spinal cord meninges
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Dura separates from endosteum within vertebral canal, creates epidural space
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CSF
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Cell-free, protein-free, amino acid content low, low and stable K+ content and relatively low glucose content.
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Volume buffer (can increase drainage when pressure increased), facilitates neurotransmitter flow, maintains stable enviro for neurones, shock absorber, nourishment.
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 the plexi, pump solutes into CSF, draw water in by osmosis
Lipid soluble substances pass readily across CSF, water soluble must be actively transported into CSF (e.g. glucose)
CSF sampling - Subarachnoid spaces from atlantoocipital junction (cerebellomedullary cistern), lumbar cistern
Arterial blood supply
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How circle is fed varies in species:
- Dog and horse - Internal carotid and basilar arteries
Sheep and cat - Mainly maxillary artery via rete mirabile
- Ox - Maxillary artery and vertebral artery via 2 rete mirabile
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Functional end arteries - Few inter-arterial anastomoses and little collateral circulation in the CNS
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Venous drainage of brain
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Cavernous sinus - Behind nasal cavity. Drains into 2 petrosal sinuses. Dorsal drains in transverse sinus. Ventral drains into basilar sinus which then drains to internal vertebral plexus
Transverse sinuses go sideways (transverse), go to either side of brain (left and right)
Confluence of sinuses is where straight, dorsal sagittal and transverse sinuses all drain into
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