Editing Cerebrospinal fluid (section)

===Contents===
CSF is derived from [[blood plasma]] and is largely similar to it, except that CSF is nearly protein-free compared with plasma and has some different [[electrolyte]] levels. Due to the way it is produced, CSF has a lower [[chloride]] level than plasma, and a higher [[sodium]] level.<ref name=GH2005/><ref name=SALADIN2012 />

CSF contains approximately 0.59% plasma proteins, or approximately 15 to 40&nbsp;mg/dL, depending on sampling site.<ref name="pmid4456012">{{cite journal | vauthors = Felgenhauer K | title = Protein size and cerebrospinal fluid composition | journal = Klinische Wochenschrift | volume = 52 | issue = 24 | pages = 1158–64 | date = December 1974 | pmid = 4456012 | doi = 10.1007/BF01466734 | s2cid = 19776406 }}</ref> In general, globular proteins and albumin are in lower concentration in ventricular CSF compared to lumbar or cisternal fluid.<ref>{{cite journal | vauthors = Merril CR, Goldman D, Sedman SA, Ebert MH | title = Ultrasensitive stain for proteins in polyacrylamide gels shows regional variation in cerebrospinal fluid proteins | journal = Science | volume = 211 | issue = 4489 | pages = 1437–8 | date = March 1981 | pmid = 6162199 | doi = 10.1126/science.6162199 | bibcode = 1981Sci...211.1437M }}</ref> {{anchor|IgG index}} This continuous flow into the [[venous system]] dilutes the concentration of larger, lipid-insoluble molecules penetrating the brain and CSF.<ref name="pmid10027064">{{cite journal | vauthors = Saunders NR, Habgood MD, Dziegielewska KM | title = Barrier mechanisms in the brain, I. Adult brain | journal = Clinical and Experimental Pharmacology & Physiology | volume = 26 | issue = 1 | pages = 11–9 | date = January 1999 | pmid = 10027064 | doi = 10.1046/j.1440-1681.1999.02986.x | s2cid = 34773752 | doi-access =  }}</ref> CSF is normally free of [[red blood cell]]s and at most contains fewer than 5 [[white blood cell]]s per mm<sup>3</sup> (if the white [[cell counting|cell count]] is higher than this it constitutes [[pleocytosis]] and can indicate inflammation or infection).<ref>{{cite book| vauthors  = Jurado R, Walker HK |title=Clinical Methods: The History, Physical, and Laboratory Examinations|date=1990|publisher=Butterworths|isbn=978-0409900774|edition=3rd|chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK398/|chapter=Cerebrospinal Fluid|pmid=21250239}}</ref>