Editing Human brain (section)

====The blood–brain barrier====
The larger arteries throughout the brain supply blood to smaller [[capillaries]]. These smallest of [[blood vessel]]s in the brain, are lined with cells joined by [[tight junction]]s and so fluids do not seep in or leak out to the same degree as they do in other capillaries; this creates the [[blood–brain barrier]].{{sfn|Guyton & Hall|2011|pp=748–749}} [[Pericyte]]s play a major role in the formation of the tight junctions.<ref name="Daneman">{{cite journal |last1=Daneman |first1=R. |last2=Zhou |first2=L. |last3=Kebede |first3=A.A. |last4=Barres |first4=B.A. |title=Pericytes are required for blood-brain barrier integrity during embryogenesis |journal=Nature |date=November 25, 2010 |volume=468 |issue=7323 |pages=562–6 |pmid=20944625 |doi=10.1038/nature09513 |pmc=3241506|bibcode=2010Natur.468..562D }}</ref> The barrier is less permeable to larger molecules, but is still permeable to water, carbon dioxide, oxygen, and most fat-soluble substances (including [[anaesthetic]]s and alcohol).{{sfn|Guyton & Hall|2011|pp=748–749}} The blood-brain barrier is not present in the [[circumventricular organs]]{{Em dash}}which are structures in the brain that may need to respond to changes in body fluids{{Em dash}}such as the [[pineal gland]], [[area postrema]], and some areas of the [[hypothalamus]].{{sfn|Guyton & Hall|2011|pp=748–749}} There is a similar [[Choroid plexus#Function|blood–cerebrospinal fluid barrier]], which serves the same purpose as the blood–brain barrier, but facilitates the transport of different substances into the brain due to the distinct structural characteristics between the two barrier systems.{{sfn|Guyton & Hall|2011|pp=748–749}}<ref name="BCSF">{{cite book |last1=Laterra |first1=J. |last2=Keep |first2=R. |last3=Betz |first3=L.A. |title=Basic neurochemistry: molecular, cellular and medical aspects |date=1999 |publisher=Lippincott-Raven |location=Philadelphia |edition=6th |section-url=https://www.ncbi.nlm.nih.gov/books/NBK27998/ |section=Blood–cerebrospinal fluid barrier |display-authors=etal}}</ref>