Editing Choroid plexus

{{Short description|Structure in the ventricles of the brain}}
{{Infobox brain
| Name            = Choroid plexus
| Latin           = plexus choroideus
| Image           = Gray708.png     
| Caption         = Choroid plexus shown in the fourth ventricle
| Image2          = Gray723.png
| Caption2        = [[Coronal plane|Coronal section]] of [[lateral ventricle|lateral]] and [[third ventricle]]s.
| IsPartOf        =
| Components      =
| Artery          =
| Vein        =
}}

The '''choroid plexus''', or '''plica choroidea''',  is a [[plexus]] of [[cell (biology)|cells]] that arises from the [[tela choroidea]] in each of the [[ventricular system|ventricles of the brain]].<ref name="Langmans">{{cite book|last1=Sadler|first1=T.|title=Langman's medical embryology|date=2010|publisher=Lippincott William & Wilkins|location=Philadelphia|isbn=978-0-7817-9069-7|page=305|edition=11th}}</ref> Regions of the choroid plexus produce and secrete most of the [[cerebrospinal fluid]] (CSF) of the [[central nervous system]].<ref name="Damkier">{{cite journal |last1=Damkier |first1=HH |last2=Brown |first2=PD |last3=Praetorius |first3=J |title=Cerebrospinal fluid secretion by the choroid plexus. |journal=Physiological Reviews |date=October 2013 |volume=93 |issue=4 |pages=1847–92 |doi=10.1152/physrev.00004.2013 |pmid=24137023|s2cid=11473603 |url=http://physrev.physiology.org/content/93/4/1847.full.pdf }}</ref><ref name="Lun">{{cite journal |last1=Lun |first1=MP |last2=Monuki |first2=ES |last3=Lehtinen |first3=MK |title=Development and functions of the choroid plexus-cerebrospinal fluid system. |journal=Nature Reviews. Neuroscience |date=August 2015 |volume=16 |issue=8 |pages=445–57 |doi=10.1038/nrn3921 |pmid=26174708|pmc=4629451 }}</ref> The choroid plexus consists of modified [[ependymal cells]] surrounding a core of [[capillary|capillaries]] and [[Stroma (tissue)#Types|loose connective tissue]].<ref name="Lun"/> Multiple [[cilia]] on the ependymal cells move to circulate the cerebrospinal fluid.<ref name="Takeda1">{{cite journal |last1=Takeda |first1=S |last2=Narita |first2=K |title=Structure and function of vertebrate cilia, towards a new taxonomy. |journal=Differentiation; Research in Biological Diversity |date=February 2012 |volume=83 |issue=2 |pages=S4-11 |doi=10.1016/j.diff.2011.11.002 |pmid=22118931}}</ref>

== Structure ==

=== Location ===
[[File:Gray708.svg|thumb| Scheme of roof of [[fourth ventricle]]. The arrow is in the [[median aperture]].<br>1: [[Inferior medullary velum]]<br>2: Choroid plexus<br> 3: [[Cisterna magna]] of [[subarachnoid space]]<br>4: [[Central canal]]<br>5: [[Corpora quadrigemina]]<br>6: [[Cerebral peduncle]]<br>7: [[Superior medullary velum]]<br>8: [[Ependymal]] lining of [[ventricular system|ventricle]]<br>9: [[Pontine cistern]] of [[subarachnoid space]]]]
There is a choroid plexus in each of the four [[ventricular system|ventricles]]. In the [[lateral ventricles]], it is found in the [[Body of the lateral ventricle|body]], and continued in an enlarged amount in the [[Trigone of the lateral ventricle|atrium]]. There is no choroid plexus in the [[Anterior horn of lateral ventricle|anterior horn]]. In the [[third ventricle]], there is a small amount in the roof that is continuous with that in the body, via the [[Interventricular foramina (neuroanatomy)|interventricular foramina]], the channels that connect the lateral ventricles with the third ventricle. A choroid plexus is in part of the roof of the [[fourth ventricle]].{{cn|date=March 2025}}

=== Microanatomy ===
The choroid plexus consists of a layer of [[cuboidal epithelium|cuboidal epithelial cells]] surrounding a core of [[capillary|capillaries]] and [[Stroma (tissue)#Types|loose connective tissue]].<ref name="Lun"/> The [[epithelium]] of the choroid plexus is continuous with the [[ependymal cell]] layer (ventricular layer) that lines the ventricular system.<ref>{{cite book|vauthors=Javed K, Reddy V, Lui F |title= Neuroanatomy, Choroid Plexus|publisher= StatPearls|date=1 January 2022|pmid= 30844183|url= https://www.ncbi.nlm.nih.gov/books/NBK538156/}}</ref> Progenitor ependymal cells are monociliated but they [[Cellular differentiation|differentiate]] into multiciliated ependymal cells.<ref name="Delgehyr">{{cite book |last1=Delgehyr |first1=N |last2=Meunier |first2=A |last3=Faucourt |first3=M |last4=Bosch Grau |first4=M |last5=Strehl |first5=L |last6=Janke |first6=C |last7=Spassky |first7=N |chapter=Ependymal cell differentiation, from monociliated to multiciliated cells |title=Methods in Cilia & Flagella |series=Methods in Cell Biology |date=2015 |volume=127 |pages=19–35 |doi=10.1016/bs.mcb.2015.01.004 |pmid=25837384|isbn=9780128024515 }}</ref><ref name="pmid29437557">{{cite journal | vauthors = van Leeuwen LM, Evans RJ, Jim KK, Verboom T, Fang X, Bojarczuk A, Malicki J, Johnston SA, van der Sar AM | title = A transgenic zebrafish model for the in vivo study of the blood and choroid plexus brain barriers using claudin 5 | journal = Biology Open | volume = 7 | issue = 2 | pages = bio030494| date = February 2018 | pmid = 29437557 | pmc = 5861362 | doi = 10.1242/bio.030494 }}</ref> Unlike the ependyma, the choroid plexus epithelial layer has [[tight junctions]]<ref name="Hall">{{cite book|title=Guyton and Hall textbook of medical physiology|date=2011|publisher=Saunders/Elsevier|isbn=978-1-4160-4574-8|edition=12th|location=Philadelphia, Pa.|page=749|last1=Hall|first1=John}}</ref> between the cells on the side facing the ventricle (apical surface). These tight junctions prevent the majority of substances from crossing the cell layer into the cerebrospinal fluid (CSF); thus the choroid plexus acts as a blood–CSF barrier. The choroid plexus folds into many villi around each capillary, creating frond-like processes that project into the ventricles. The villi, along with a brush border of microvilli, greatly increase the surface area of the choroid plexus.{{citation needed|date=April 2017}} CSF is formed as plasma is filtered from the blood through the epithelial cells. Choroid plexus epithelial cells actively transport sodium ions into the ventricles and water follows the resulting osmotic gradient.<ref name=GUYTONHALL2005p764>{{cite book |first1=Arthur C. |last1=Guyton |first2=John Edward |last2=Hall | name-list-style = vanc |title=Textbook of medical physiology |year=2005 |publisher=W.B. Saunders |location=Philadelphia |isbn=978-0-7216-0240-0 |edition=11th |pages=764–7}}</ref>

The choroid plexus consists of many capillaries, separated from the ventricles by choroid epithelial cells. Fluid filters through these cells from blood to become cerebrospinal fluid. There is also much [[active transport]] of substances into, and out of, the CSF as it is made.{{cn|date=March 2025}}

==Function==
[[File:CSF circulation.png|thumb|upright=1.8|CSF circulation]]
The choroid plexus regulates the production and composition of [[cerebrospinal fluid]] (CSF), that provides the protective buoyancy for the brain.<ref name="Damkier"/><ref name="pmid29195051"/> CSF acts as a medium for the [[glymphatic system|glymphatic filtration system]] that facilitates the removal of metabolic waste from the brain, and the exchange of [[biomolecules]] and [[xenobiotics]] into and out of the brain.<ref name="pmid29195051">{{cite journal | vauthors = Plog BA, Nedergaard M | title = The Glymphatic System in Central Nervous System Health and Disease: Past, Present, and Future | journal = Annual Review of Pathology | volume = 13 | pages = 379–394 | date = January 2018 | pmid = 29195051 | pmc = 5803388 | doi = 10.1146/annurev-pathol-051217-111018 }}</ref><ref name="pmid29428972">{{cite journal | vauthors = Abbott NJ, Pizzo ME, Preston JE, Janigro D, Thorne RG | title = The role of brain barriers in fluid movement in the CNS: is there a 'glymphatic' system? | journal = Acta Neuropathologica | volume = 135 | issue = 3 | pages = 387–407 | date = March 2018 | pmid = 29428972 | doi = 10.1007/s00401-018-1812-4 | doi-access = free }}</ref> In this way the choroid plexus has a very important role in helping to maintain the delicate extracellular environment required by the brain to function optimally.{{cn|date=March 2025}}

The choroid plexus is also a major source of [[transferrin]] secretion that plays a part in [[Human iron metabolism|iron homeostasis]] in the brain.<ref name="Moos">{{cite journal |last1=Moos |first1=T |title=Brain iron homeostasis |journal=Danish Medical Bulletin |date=November 2002 |volume=49 |issue=4 |pages=279–301 |pmid=12553165}}</ref><ref name="Moos2">{{cite journal |last1=Moos |first1=T |last2=Rosengren Nielsen |first2=T |last3=Skjørringe |first3=T |last4=Morgan |first4=EH |title=Iron trafficking inside the brain |journal=Journal of Neurochemistry |date=December 2007 |volume=103 |issue=5 |pages=1730–40 |doi=10.1111/j.1471-4159.2007.04976.x |pmid=17953660|doi-access=free }}</ref>

===Blood–cerebrospinal fluid barrier===
{{See also|Glymphatic system}}
The '''blood–cerebrospinal fluid barrier'''<!--This term redirects here and is bolded per MOS:BOLD--> (BCSFB) is a fluid–brain barrier that is composed of a pair of membranes that separate blood from CSF at the capillary level and CSF from brain tissue.<ref name="BCSF" /> The blood–CSF boundary at the choroid plexus is a membrane composed of [[epithelial cells]] and [[tight junction]]s that link them.<ref name="BCSF" /> There is a CSF-brain barrier at the level of the pia mater, but only in the embryo.<ref>{{Cite journal|last1=Saunders|first1=Norman R.|last2=Habgood|first2=Mark D.|last3=Møllgård|first3=Kjeld|last4=Dziegielewska|first4=Katarzyna M.|date=2016-03-10|title=The biological significance of brain barrier mechanisms: help or hindrance in drug delivery to the central nervous system?|journal=F1000Research|volume=5|pages=313|doi=10.12688/f1000research.7378.1|issn=2046-1402|pmc=4786902|pmid=26998242|quote=The embryonic CSF-brain barrier, shown in Figure 1(f). In the ventricular zone is a temporary barrier between the CSF and brain parenchyma. In early brain development, strap junctions are present between adjacent neuroepithelial cells; these form a physical barrier restricting the movement of larger molecules, such as proteins, but not smaller molecules. At later stages of development and in the adult brain, these strap junctions are no longer present when this interface becomes ependyma. |doi-access=free }}</ref>

Similar to the [[blood–brain barrier]], the blood–CSF barrier functions to prevent the passage of most blood-borne substances into the brain, while selectively permitting the passage of specific substances (such as nutrients) into the brain and facilitating the removal of brain metabolites and metabolic products into the blood.<ref name="BCSF" /><ref name="BBB and BCSFB review">{{cite journal | vauthors = Ueno M, Chiba Y, Murakami R, Matsumoto K, Kawauchi M, Fujihara R | s2cid = 22154007 | title = Blood-brain barrier and blood-cerebrospinal fluid barrier in normal and pathological conditions | journal = Brain Tumor Pathology | volume = 33 | issue = 2 | pages = 89–96 | date = April 2016 | pmid = 26920424 | doi = 10.1007/s10014-016-0255-7}}</ref> Despite the similar function between the BBB and BCSFB, each facilitates the transport of different substances into the brain due to the distinctive structural characteristics of each of the two barrier systems.<ref name="BCSF">{{cite book|vauthors=Laterra J, Keep R, Betz LA |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> For a number of substances, the BCSFB is the primary site of entry into brain tissue.<ref name="BCSF" />

The blood–cerebrospinal fluid barrier has also been shown to modulate the entry of leukocytes from the blood to the central nervous system. The choroid plexus cells secrete [[cytokine]]s that recruit [[macrophage|monocyte-derived macrophages]], among other cells, to the brain. This cellular trafficking has implications both in normal brain homeostasis and in [[neuroimmune system|neuroinflammatory processes]].<ref>{{cite journal | vauthors = Schwartz M, Baruch K | title = The resolution of neuroinflammation in neurodegeneration: leukocyte recruitment via the choroid plexus | journal = The EMBO Journal | volume = 33 | issue = 1 | pages = 7–22 | date = January 2014 | pmid = 24357543 | pmc = 3990679 | doi = 10.1002/embj.201386609 }}</ref>

==Clinical significance==

===Choroid plexus cysts===
{{Main|Choroid plexus cysts}}
{{See also|Triple test}}
During [[fetal development]], some [[choroid plexus cysts]] may form. These fluid-filled cysts can be detected by a detailed [[Obstetric ultrasonography#Second and third trimester|second trimester ultrasound]]. The finding is relatively common, with a prevalence of ~1%. Choroid plexus cysts are usually an isolated finding.<ref name="pmid10607945" /> The cysts typically disappear later during pregnancy, and are usually harmless. They have no effect on infant and early childhood development.<ref name="pmid9241291">{{cite journal | vauthors = Digiovanni LM, Quinlan MP, Verp MS | s2cid = 40130437 | title = Choroid plexus cysts: infant and early childhood developmental outcome | journal = Obstetrics and Gynecology | volume = 90 | issue = 2 | pages = 191–4 | date = August 1997 | pmid = 9241291 | doi = 10.1016/S0029-7844(97)00251-2 }}</ref>

Choroid plexus cysts are associated with a 1% risk of fetal [[aneuploidy]].<ref name="pmid9678699">{{cite journal | vauthors = Peleg D, Yankowitz J | title = Choroid plexus cysts and aneuploidy | journal = Journal of Medical Genetics | volume = 35 | issue = 7 | pages = 554–7 | date = July 1998 | pmid = 9678699 | pmc = 1051365 | doi =  10.1136/jmg.35.7.554}}</ref> The risk of aneuploidy increases to 10.5-12% if other risk factors or ultrasound findings are noted. Size, location, disappearance or progression, and whether the cysts are found on both sides or not do not affect the risk of aneuploidy. 44-50% of [[Edwards syndrome]] (trisomy 18) cases will present with choroid plexus cysts, as well 1.4% of [[Down syndrome]] (trisomy 21) cases.  ~75% of abnormal karyotypes associated with choroid plexus cysts are trisomy 18, while the remainder are trisomy 21.<ref name="pmid10607945">{{cite journal | vauthors = Drugan A, Johnson MP, Evans MI | title = Ultrasound screening for fetal chromosome anomalies | journal = American Journal of Medical Genetics | volume = 90 | issue = 2 | pages = 98–107 | date = January 2000 | pmid = 10607945 | doi =  10.1002/(SICI)1096-8628(20000117)90:2<98::AID-AJMG2>3.0.CO;2-H}}</ref>

===Other===

There are three [[WHO classification of the tumors of the central nervous system|graded]] types of [[choroid plexus tumor]] that mainly affect young children. These types of [[cancer]] are rare.{{cn|date=March 2025}}

==Etymology==
Choroid plexus translates from the Latin {{lang|la|plexus chorioides}},<ref name="Suzuki1936">Suzuki, S., Katsumata, T., Ura, R. Fujita, T., Niizima, M. & Suzuki, H. (1936). Über die Nomina Anatomica Nova. ''Folia Anatomica Japonica, 14'', 507-536.</ref> which mirrors [[Ancient Greek]] {{lang|grc|χοριοειδές πλέγμα}}.<ref name="Liddell & Scott">{{cite book | vauthors = Liddell HG, Scott R | date = 1940 | title = A Greek-English Lexicon | url = https://archive.org/details/b31364949_0001 | location = Oxford | publisher = Clarendon Press }}</ref> The word ''chorion'' was used by [[Galen]] to refer to the outer membrane enclosing the fetus. Both meanings of the word plexus are given as pleating, or braiding.<ref name="Liddell & Scott"/> As often happens language changes and the use of both ''choroid'' or ''chorioid'' is both accepted. [[Nomina Anatomica]] (now [[Terminologia Anatomica]]) reflected this dual usage.{{cn|date=July 2024}}

==Additional images==
<gallery>
File:Gray749.png|Coronal section of inferior horn of lateral ventricle.
File:Choroid Plexus Histology 40x.png|Choroid plexus histology 40x
File:Slide2ff.JPG|Choroid plexus
File:Slide3oo.JPG|Choroid plexus
File:Choroid plexus.jpg|Choroid plexus
</gallery>

== See also ==
{{Anatomy-terms}}
* [[Choroid plexus papilloma]]
* [[Tela choroidea]]

== References ==
{{Gray's}}
{{Reflist|30em}}

== Sources ==
{{refbegin}}
* {{cite journal | vauthors = Brodbelt A, Stoodley M | s2cid = 6901013 | title = CSF pathways: a review | journal = British Journal of Neurosurgery | volume = 21 | issue = 5 | pages = 510–20 | date = October 2007 | pmid = 17922324 | doi = 10.1080/02688690701447420 }}
* {{cite journal | vauthors = Strazielle N, Ghersi-Egea JF | title = Choroid plexus in the central nervous system: biology and physiopathology | journal = Journal of Neuropathology and Experimental Neurology | volume = 59 | issue = 7 | pages = 561–74 | date = July 2000 | pmid = 10901227 | doi = 10.1093/jnen/59.7.561 | doi-access =  }}
{{refend}}

== External links ==
{{Commons category|Choroid plexus}}
* [https://web.archive.org/web/20010429022540/http://biocfarm.unibo.it/aunsnc/3dobjc10.html 3-Dimensional images of choroid plexus (marked red)]
* {{cite web|url=http://www.tk.de/rochelexikon/pics/s13048.000-3.html|title=Anatomy diagram: 13048.000-3|website=Roche Lexicon - illustrated navigator|publisher=Elsevier|archive-url=https://web.archive.org/web/20120722052451/http://www.tk.de/rochelexikon/pics/s13048.000-3.html|archive-date=2012-07-22|url-status=dead}}
* [https://web.archive.org/web/20070927220301/http://rad.usuhs.edu/medpix/medpix.html?mode=image_finder&action=search&srchstr=choroid%20plexus&srch_type=all#top MedPix] Images of Choroid Plexus
* More info at [https://web.archive.org/web/20100713033508/http://braininfo.rprc.washington.edu/centraldirectory.aspx?ID=1377 BrainInfo]

{{Meninges}}
{{Authority control}}

{{DEFAULTSORT:Choroid Plexus}}
[[Category:Meninges]]
[[Category:Ventricular system]]