Physiology of CSF Flashcards
what is CSF
a clear, colourless liquid composed mostly of water
where is CSF produced
the secretory epithelium of the choroid plexus (in the ventricles)
what is the volume of CSF at one time (replaced every 3-4 days)
150 ml
what does the CSF circulate in
subarachnoid space
between the arachnoid and pia mater
what does the CSF supply/remove from the brain
supplies water, amino acids, ions
removes metabolites
what are the 3 main functions of CSF
- mechanical protection (shock absorbing medium that protects brain tissue)
- homeostatic function (pH of CSF affects pulmonary ventilation and cerebral blood flow - transports hormones
- circulation (minor exchange of nutrients and waste products between blood and brain tissue)
how is clinical CSF analysis obtained
lumbar puncture
aids the diagnosis of the brain, meninges and spinal cord
what does normal CSF look like
clear
colourless
contains little protein and little immunoglobulins
how many cells are there per 1 cml of CSF
1-5
what does the developing nervous system look like at 3 weeks
the neural canal/tube
what does the neural canal give rise to in the human brain
the ventricles and the central canal of the spinal cord
what does the choroid plexus develop from c
cells in the walls of the ventricles
what cells produce CSF
Choroidal cells (in the choroid plexus)
how is the choroid fissure formed
developing arteries press the roof of the ventricle inside out to produce the choroid fissure
this then develops into the choroid plexus
where is the choroid plexus found in the adult brain
the 3rd and 4th and lateral ventricles
what ions are transported across the epithelium from blood to CSF to allow CSF secretion
Na+
Cl-
HCO3-
transferred across the epithelium from blood to CSF
what is the circulation of CSF
choroid plexuses of the lateral ventricles
then to 3rd ventricle via the inerventricular foramen
more CSF is added by the choroid plexuses of the 3rd ventricle
then flows through aqueduct of midbrain (cerebral duct) into 4th ventricle
choroid plexus un 4th ventricle adds more CSF
then enters subarachnoid space via 4th ventricle - goes through the lateral apertures or the median aperture
circulated in the central canal of the spinal cord
how does CSF return to venous blood
through arachnoid granulation into the dural sinus
what restricts the blood supply to the majority of the brain
blood brain barrier
how does the brain interstitial fluid drain into the CSF
via the perivascular spaces
what makes up the blood brain barrier
endothelial cells in brain capillaries
tight junctions between brain endothelial cells prevent paracellular movement of molecules
what parts of the brain do not have a blood brain barrier
circumventricular organs
pineal gland
what does the BBB protect the brain from
bacterial infections and toxins
what pathology can affect the ventricles, choroid plexus and CSF
Tumours
Ventricular haemorrhage (accumulation of blood in the ventricles)
Hydrocephalus
Idiopathic intracranial hypertension
