physiology of the eye 1 Flashcards
what is cerebrospinal fluid produced by?
secretory epithelium of choroid plexus
where is CSF formed?
in ventricles and circulates in subarachnoid space then absorbed into venous circulation
what does CSF supply?
water
amino acids
ions
what does CSF remove?
metabolites/waste
what are the 3 major functions of CSF?
mechanical protection
homeostatic function
circulation
what is the mechanical protection?
shock-absorbing that protects brain tissue, brain floats inside cavity
what is the homeostatic function?
pH of CSF affects pulmonary ventilation and cerebral spinal blood flow
transports hormones
what is the circulatory function?
medium for minor exchange of nutrients and waste products between blood and brain tissue
what is clinical CSF obtained by and why?
lumbar puncture
aids in diagnosis of brain, meninges and spinal chord
what can conditions that cause accumulation of CSF cause?
serious neurological defects
how many ventricles are in the brain?
4
where are the ventricles of the brain located?
2 lateral -> in cerebrum, one of each side (at front)
3rd -> in diencephalon in the middle of the brain
4th -> in hindbrain, at the back of pons in the middle of medulla oblongata
during embryonic development of the brain what dies the NS consist of at 3 weeks?
tube - neural canal
what does the cavity of the neural canal give rise to in adult brain’s and the spinal cord?
brain - ventricles
SC - central canal
where does the choroid plexus develop?
cells in walls of ventricles
choroid cells are specialized in secreting cells that produce what?
CSF
how is the choroid fissure formes?
developing arteries invaginate the roof of the ventricle
how is the choroid plexus formed?
involuted ependymal cells along with vessels enlarge into villi
what is the choroid plexus of each lateral ventricle responsible for?
CSF production
in the adult brain, where is the choroid plexus found?
3rd
4th
lateral ventricles
what cells line the ventricles?
ependymal cells
CSF secretion involves transport of which ions across what?
Na+Cl- and HCO3-
sodium chloride and bicarb
across epithelium from blood to CSF
where is the basolateral membrane closest to?
arteries
where is the apical membrane closest to?
veins
is production of CSF active or passive?
active
what is the intraventricular foramina (of Monroe)?
lateral ventricles to 3r ventricle
what is the cerebral aqueduct (of Sylvius)?
3rd ventricle to 4th
what is the foramen of megendie?
median aperture - 4th ventricle to subarachnoid space
what is the foramina of Luschka?
lateral apertures - 4th ventricle to subarachnoid space
explain CSF circulation.
CSF formed in choroid plexuses of each lateral ventricle and flows to 3rd ventricle through 2 openings - IV foramina
more CSF added by choroid plexus in roof of 3rd ventricle
flows through aqueduct of midbrain
into 4th ventricle
another choroid plexus in 4th ventricle adds more CSF
CSF enters subarachnoid space through openings in roof of 4th ventricle (1 med, 2 lat apertures)
circulates in central canal of SC
500ml produced and absorbed every day - constant
directional flow through ventricular system into subarachoid space between which mater?
pia and dura mater
what does CSF return to venous blood through?
arachnoid granulations into superior sagittal sinus (SSS)
what restricts blood supply to majority of the brain?
blood-brain barrier
what does the brain interstitial fluid do?
makes up final portion of CSF and drains to CSF through perivascular spaces
what cells in brain capillaries are at site of BBB?
endothelial cells
what parts of the brain do not have BBB?
circumventricular organs and pineal gland
what is the role of BBB?
protects against infection and toxins
main obstacle for drug delivery
what are some pathologies of ventricles, choroid plexus and CSF?
tumours
ventricular haemorrhage
hydrocephalus
IIH/pseudotumor cerebri
what types of tumours can you get?
colloid cyst (found at IV foramen)
ependymomas (ependymal cells lining ventricles)
choroid plexus tumours
what is ventricular haemorrhage and what are the types?
accumulation of blood in ventricles
epidural -> arterial bleed between skull and dura
subdural -> venous bleed between dura and arachnoid
subarachnoid haemorrhage
what is hydrocephalus?
accumulation of CSF in ventricular system or around brain (obstruction or overproduction)
enlargement of one or more ventricles and increase CSF pressure
what is papilloedema?
optic disc swelling due to increased intracranial pressure transmitted to subarachnoic space urrounding optic nerve
