blood supply, meninges and CSF Flashcards
(23 cards)
what are the 3 layers of the meninges
dura mater
arachnoid mater
pia mater
describe dura mater
thick fibrinous layer
two indistinguishable layers within skull - outer = periosteal and inner = meningeal
separates to form 2 folds which course into fissures between areas of brain tissue - falx cerebri and tentorium cerebeli
pain sensitive - trigeminal
own blood supply
describe arachnid mater
- Thin transparent membrane
- Fibrous tissue forms a web-like structure
- Avascular, little innervation
- Closely associated with dura matter: subdural space = potential space
- Subarachnoid space contains CSF and blood vessels
describe pia mater
- Thin, delicate membrane
- Highly vascular and dense nerve innervation
- Tightly adherent to underlying tissue
- Follows blood vessels into tissue and merges with tunica adventitia
what is the epidural space filled with
fat and connective tissue
describe the development of the meninges
- Neural tube surrounded by mesenchymal tissue – meninges
- Axial mesoderm – mesenchyme – ectomeninx – dura mater
- Neural crest cells arise from ectoderm – mesenchyme – endomeninx – arachnoid and pia mater – spaces in mesenchyme coalesce – subrachnoid space
origin of the lateral ventricles
telencephalic vesicles
origin of the third ventricle
central cavity of telencephalon and diencephalon
origin of the mesencephalic aqueduct
mesencephalic vesicle
origin of the fourth ventricle
rhombencephalon
describe the development of the choroid plexi
- Tela choroidea = region of pia mater which adheres to underlying ependyma
- Twp projections of this tela choroidea invaginate into roof of 4th ventricle in the myelencephalon = choroid plexus
- Roof palate of cranial diencephalon invaginates into 3rd ventricle
- Grooves form in the ventromedial cerebral hemispheres = choroid fissures
- Pia matter covering these grooves invaginates into lateral ventricles
composition of CSF
cell free
protein free
low amino acid content
low and stable potassium content
low glucose content
functions of CSF
physical protection of CNS tissues
circulation of nutrients and neurotransmitters
stable environment
volume buffer
describe the blood;brain barrier
- maintains CSF in a steady state by reducing vascular permeability
- foot processes of astrocytes
- tight junctions between endothelial cells of capillaries
describe permeability of CSF
- Transporting ependymal cells covering the choroid plexi pump solutes into the CSF to draw water in by osmosis
- lipid soluble substances pass readily across CSF
- water soluble materials must be actively transported in CSF eg glucose
what is the main source of CSF
choroid plexi
describe circulation and drainage of CSF
- Circulates through subarachnoid space, ventricles of brain and central spinal canal
- Constant production and drainage, pressure gradient – helps circulation
- Ventricles and central canal lined by ependymal cells which possess cilia
- Small amount from ultrafiltate of pial blood
where to sample CSF
- Can be collected from the subarachnoid space at 2 separate locations:
- Cerebellumomedullary cistern – atlanto – occipital space
- Lumbar cistern (l5-6 lumbar space)
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what is the combination of arteries that supply the CNS
- Internal carotid, basilar artery, maxillary artery and vertebral artery
arterial supply to CNS in dog and horse
internal carotid and basilar arteries
arterial supply to CNS in sheep and cat
maxillary via rete mirabile
arterial supply to CNS in cow
maxillary and vertebral via 2 rete
spinal cord blood supply
branches of aorta and vertebral artery
