Editing Spleen

{{Short description|Immune organ that filters blood}}
{{Other uses}}
{{Anatomy-terms}}
{{Infobox anatomy
| Name        = Spleen
| Latin       = splen, lien
| Greek      = σπλήν
| Image       = Diagram showing the position of the spleen CRUK 417.svg
| Caption     = Position of the human spleen
| Width       = 
| Image2      = 
| Caption2    = 
| Precursor   = 
| System      = [[Immune system]] ([[lymphatic system]])
| Artery      = [[Splenic artery]]
| Vein        = [[Splenic vein]]
| Nerve       = [[Splenic plexus]]
| Lymph       = 
}}
[[File:3D Medical Animation Spleen Anatomy.jpg|alt=3D medical animation still showing structure of as well as location of the spleen in human body|thumb|A 3D medical animation still of spleen structure and exact location]]

The '''spleen''' ({{etymology|xno|espleen}}, {{tooltip|ult.|ultimately}} from [[Ancient Greek]] '' σπλήν'', splḗn)<ref name="σπλήν">{{Cite encyclopedia |last1=Liddell |first1=Henry George |last2=Scott |first2=Robert |editor1-last=Jones |editor1-first=Henry Stuart |editor2-last=McKenzie |editor2-first=Roderick |year=1940 |entry=σπλήν |entry-url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=splh/n |encyclopedia=A Greek-English Lexicon |edition=New (9th) |volume=2: ''λ–φώδης'' |location=Oxford |publisher=Clarendon Press |page=1628 |oclc=13606128 |via=Perseus Digital Library}}</ref> is an [[organ (biology)|organ]] found in almost all [[vertebrate]]s. Similar in structure to a large [[lymph node]], it acts primarily as a [[blood]] filter.

The spleen plays important roles in regard to [[red blood cell]]s (erythrocytes) and the [[immune system]].<ref>{{Citation |last1=Kapila |first1=Vaishali |title=Physiology, Spleen |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK537307/ |work=StatPearls |place=Treasure Island, FL |publisher=StatPearls Publishing |pmid=30725992 |access-date=2022-12-04 |last2=Wehrle |first2=Chase J. |last3=Tuma |first3=Faiz}}</ref> It removes old red blood cells and holds a reserve of blood, which can be valuable in case of [[Shock (circulatory)|hemorrhagic shock]], and also [[Human iron metabolism|recycles iron]]. As a part of the [[mononuclear phagocyte system]], it metabolizes [[hemoglobin]] removed from [[senescent]] red blood cells. The [[globin]] portion of hemoglobin is degraded to its constitutive [[amino acid]]s, and the [[heme]] portion is metabolized to [[bilirubin]], which is removed in the [[liver]].<ref name="Mebius">{{Cite journal |pmid=16056254 |year=2005 |last1=Mebius |first1=RE |last2=Kraal |first2=G |title=Structure and function of the spleen |volume=5 |issue=8 |pages=606–16 |doi=10.1038/nri1669 |journal=Nature Reviews. Immunology |s2cid=3258595}}</ref><ref name="autogenerated1">{{cite journal |last1=Sahin |first1=NE |last2=Oner |first2=Z |last3=Oner |first3=S |last4=Turan |first4=MK |title=A study on the correlation between spleen volume estimated via cavalieri principle on computed tomography images with basic hemogram and biochemical blood parameters |journal=Anatomy & Cell Biology |date=10 January 2022 |volume=55 |issue=1 |pages=40–47 |doi=10.5115/acb.21.177 |pmid=35000931 |pmc=8968228 }}</ref>

The spleen houses [[antibody]]-producing lymphocytes in its [[white pulp]] and [[monocytes]] which remove antibody-coated bacteria and antibody-coated blood cells by way of blood and [[lymph node]] circulation. These monocytes, upon moving to injured tissue (such as the [[heart]] after [[myocardial infarction]]), turn into [[dendritic cell]]s and [[macrophage]]s while promoting tissue healing.<ref name="Swirski" /><ref name="Jia">{{Cite journal |pmid=19644100 |year=2009 |last1=Jia |first1=T |last2=Pamer |first2=EG |title=Immunology: Dispensable but not irrelevant |volume=325 |issue=5940|pages=549–50 |doi=10.1126/science.1178329 |pmc=2917045 |journal=Science |bibcode=2009Sci...325..549J}}</ref><ref>[https://www.nytimes.com/2009/08/04/science/04angier.html "Finally, the Spleen Gets Some Respect"] By Natalie Angier, ''The New York Times'', August 3, 2009</ref> The spleen is a center of activity of the [[mononuclear phagocyte system]] and is analogous to a large lymph node, as its absence causes a predisposition to certain [[infection]]s.<ref name="certain-infec">{{cite journal
  | last = Brender
  | first = Erin
  | others = Illustrated by Allison Burke
  | editor = Richard M. Glass
  | title = Spleen Patient Page
  | journal = [[Journal of the American Medical Association]]
  | volume = 294
  | issue = 20
  | page = 2660
  | date = 2005-11-23
  | pmid=16304080
  | doi = 10.1001/jama.294.20.2660| doi-access = free
  }}</ref><ref name="autogenerated1"/>

In humans, the spleen is purple in color and is in the [[quadrant (anatomy)|left upper quadrant]] of the [[abdomen]].<ref name="Mebius" /><ref>{{cite book|author1=Loscalzo, Joseph |author2=Fauci, Anthony S. |author3=Braunwald, Eugene |author4=Dennis L. Kasper |author5=Hauser, Stephen L |author6=Longo, Dan L. |title=Harrison's principles of internal medicine |publisher=McGraw-Hill Medical |year=2008 |isbn=978-0-07-146633-2 }}</ref> The surgical process to remove the spleen is known as a [[splenectomy]].

== Structure ==
In humans, the spleen is underneath the left part of the [[Thoracic diaphragm|diaphragm]], and has a smooth, convex surface that faces the diaphragm. It is underneath the ninth, tenth, and eleventh ribs. The other side of the spleen is divided by a ridge into two regions: an anterior gastric portion, and a posterior [[renal]] portion. The gastric surface is directed forward, upward, and toward the middle, is broad and concave, and is in contact with the posterior wall of the [[stomach]]. Below this it is in contact with the tail of the [[pancreas]]. The renal surface is directed medialward and downward. It is somewhat flattened, considerably narrower than the gastric surface, and is in relation with the upper part of the anterior surface of the left kidney and occasionally with the left [[adrenal gland]].

There are four ligaments attached to the spleen: [[gastrosplenic ligament]], [[splenorenal ligament]], [[colicosplenic ligament]], and [[phrenocolic ligament]].<ref>{{Cite journal |last1=Ostermann |first1=P. A. W. |last2=Schreiber |first2=H. W. |last3=Lierse |first3=W. |date=September 1987 |title=Der Bandapparat der Milz und seine Bedeutung bei chirurgischen Eingriffen |url=http://link.springer.com/10.1007/BF01259432 |journal=Langenbeck's Archiv für Chirurgie |language=de |volume=371 |issue=3 |pages=207–216 |doi=10.1007/BF01259432 |pmid=3683035 |s2cid=35213355 |issn=0023-8236}}</ref>

=== Measurements ===
{| class="wikitable" style="float:right;"
|+ 90% [[confidence interval]] of spleen length by [[abdominal ultrasonography]] by height of the person<ref name="ChowLuxembourg2016">{{cite journal|last1=Chow|first1=Kai Uwe|last2=Luxembourg|first2=Beate|last3=Seifried|first3=Erhard|last4=Bonig|first4=Halvard|title=Spleen Size Is Significantly Influenced by Body Height and Sex: Establishment of Normal Values for Spleen Size at US with a Cohort of 1200 Healthy Individuals|journal=Radiology|volume=279|issue=1|year=2016|pages=306–13|issn=0033-8419|doi=10.1148/radiol.2015150887|pmid=26509293|doi-access=}}</ref>
|-
!rowspan=2| Height !!colspan=2| Spleen length
|-
! Women !! Men
|-
| 155–159&nbsp;cm || 6.4–12&nbsp;cm || 
|-
| 160–164&nbsp;cm || 7.4–12.2&nbsp;cm || 8.9–11.3&nbsp;cm
|-
| 165–169&nbsp;cm || 7.5–11.9&nbsp;cm || 8.5–12.5&nbsp;cm
|-
| 170–174&nbsp;cm || 8.3–13.0&nbsp;cm || 8.6–13.1&nbsp;cm
|-
| 175–179&nbsp;cm || 8.1–12.3&nbsp;cm || 8.6–13.4&nbsp;cm
|-
| 180–184&nbsp;cm ||  || 9.3–13.4&nbsp;cm
|-
| 185–189&nbsp;cm ||  || 9.3–13.6&nbsp;cm
|-
| 190–194&nbsp;cm ||  || 9.7–14.3&nbsp;cm
|-
| 195–199&nbsp;cm ||  || 10.2–14.4&nbsp;cm
|}

The spleen, in healthy adult humans, is approximately {{convert|7|to|14|cm|in|frac=2}} in length. It weighs between {{cvt|1|oz|g}} and {{cvt|8|oz|g}} (standard [[reference range]]),<ref name="MolinaDiMaio2012">{{cite journal|last1=Molina|first1=D. Kimberley|last2=DiMaio|first2=Vincent J.M.|title=Normal Organ Weights in Men|journal=The American Journal of Forensic Medicine and Pathology|volume=33|issue=4|year=2012|pages=368–372|issn=0195-7910|doi=10.1097/PAF.0b013e31823d29ad|pmid=22182984|s2cid=32174574}}</ref> correlating mainly to height, body weight and degree of acute congestion but not to sex or age.<ref name="Sprogøe-JakobsenSprogøe-Jakobsen1997">{{cite journal|last1=Sprogøe-Jakobsen|first1=Susan|last2=Sprogøe-Jakobsen|first2=Ulrik|title=The weight of the normal spleen|journal=Forensic Science International|volume=88|issue=3|year=1997|pages=215–223|issn=0379-0738|doi=10.1016/S0379-0738(97)00103-5|pmid=9291593}}</ref>

<gallery>
File:Spleen ultrasound.jpg|Spleen seen on [[abdominal ultrasonography]]
File:Maximum length of spleen on ultrasonography.jpg|Maximum length of spleen on [[abdominal ultrasonography]]
File:Gray1226.png|Back of lumbar region, showing surface markings for kidneys, ureters, and spleen
File:Gray1217.png|Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green)
</gallery>

=== Blood supply ===
[[File:Gray1188.png|200px|thumb|Visceral surface of the spleen]]
Near the middle of the spleen is a long fissure, the [[hilum (anatomy)|hilum]], which is the point of attachment for the [[gastrosplenic ligament]] and the point of insertion for the [[splenic artery]] and [[splenic vein]]. There are other openings present for [[lymphatic vessel]]s and [[nerve]]s. In addition to the splenic artery, collateral blood supply is provided by the adjacent short gastric arteries.<ref>{{cite journal | url=https://pubmed.ncbi.nlm.nih.gov/6730702/|title=The collateral arterial network of the spleen following ligation of the splenic artery in traumatic rupture of the spleen; an arteriographic study|date=1984 |pmid=6730702 |last1=Keramidas |first1=D. C. |last2=Kelekis |first2=D. |last3=Dolatzas |first3=T. |last4=Aivazoglou |first4=T. |last5=Voyatzis |first5=N. |journal=Zeitschrift für Kinderchirurgie |volume=39 |issue=1 |pages=50–51 |doi=10.1055/s-2008-1044169 |s2cid=29302459 }}</ref>

Like the [[thymus]], the spleen possesses only [[efferent lymphatic vessels]]. The spleen is part of the [[lymphatic system]]. Both the [[short gastric arteries]] and the splenic artery supply it with blood.<ref>{{Cite book
| publisher = Lippincott Williams & Wilkins
| isbn = 978-0-7817-7076-7
| last = Blackbourne
| first = Lorne H
| title = Surgical recall
| year = 2008
| page = [https://archive.org/details/surgicalrecall00blac/page/259 259]
| url-access = registration
| url = https://archive.org/details/surgicalrecall00blac/page/259
}}</ref>

The [[germinal center]]s are supplied by [[arteriole]]s called ''penicilliary radicles''.<ref>{{cite web|url=http://medical-dictionary.thefreedictionary.com/penicilliary+radicles |title=Penicilliary radicles |publisher=Medical-dictionary.thefreedictionary.com |access-date=2011-04-03}}</ref>

=== Nerve supply ===
The spleen is innervated by the [[splenic plexus]], which connects a branch of the [[celiac ganglia]] to the [[vagus nerve]].

The underlying [[Central nervous system|central nervous]] processes coordinating the spleen's function seem to be embedded into the [[Hypothalamic–pituitary–adrenal axis|hypothalamic-pituitary-adrenal-axis]], and the [[brainstem]], especially the [[subfornical organ]].<ref>{{Cite journal|last1=Lori|first1=Andrea|last2=Perrotta|first2=Marialuisa|last3=Lembo|first3=Giuseppe|last4=Carnevale|first4=Daniela|date=2017-06-07|title=The Spleen: A Hub Connecting Nervous and Immune Systems in Cardiovascular and Metabolic Diseases|journal=International Journal of Molecular Sciences|volume=18|issue=6|page=1216|doi=10.3390/ijms18061216|issn=1422-0067|pmc=5486039|pmid=28590409|doi-access=free}}</ref>

=== Development ===
The spleen is unique in respect to its development within the [[Human gastrointestinal tract|gut]]. While most of the gut [[organ (anatomy)|organs]] are [[endodermally]] derived, the spleen is derived from [[Mesenchyme|mesenchymal tissue]].<ref>{{cite journal | last= Vellguth | first=Swantje |author2=Brita von Gaudecker |author3=Hans-Konrad Müller-Hermelink | title=The development of the human spleen | journal=[[Cell and Tissue Research]] | volume=242 | issue=3 | pages=579–92 | doi=10.1007/BF00225424 | pmid=4075378 | year= 1985 | s2cid=19864892 }}</ref> Specifically, the spleen forms within, and from, the [[dorsal mesentery]]. However, it still shares the same blood supply—the [[celiac trunk]]—as the [[foregut]] organs.

== Function ==

=== Pulp ===
[[File:Spleen hyaloserositis - low mag.jpg|thumb|right|[[Micrograph]] of splenic tissue showing the red pulp (red), white pulp (blue nuclei in lighter background) and a [[hyaloserositis|thickened inflamed capsule]] (mostly pink – top of image). [[H&E stain]].]]

[[File:Red Pulp and White Pulp of the Spleen.jpg|thumb|right|The spleen contains two different tissues, white pulp (A) and red pulp (B). The white pulp functions in producing and growing immune and blood cells. The red pulp functions in filtering blood of antigens, microorganisms, and defective or worn-out red blood cells.]]

{| class="wikitable"
|-
! Area !! Function !! Composition
 |-
 | [[red pulp]] || Mechanical filtration of [[red blood cell]]s. In mice: Reserve of [[monocyte]]s<ref name="Swirski"/>||
* "[[Sinus (anatomy)|sinuses]]" (or "[[Sinusoid (blood vessel)|sinusoid]]s"), which are filled with blood
* "[[splenic cords]]" of [[reticular fiber]]s
* "[[marginal zone]]" bordering on white pulp
 |-
 | [[white pulp]] || Active immune response through humoral and cell-mediated pathways. || Composed of nodules, called [[White pulp|Malpighian corpuscle]]s. These are composed of:
* "[[lymphoid follicles]]" (or "follicles"), rich in [[B cell|B-lymphocytes]]
* "[[periarteriolar lymphoid sheaths]]" (PALS), rich in [[T cell|T-lymphocytes]]
|}

=== Other ===
Other functions of the spleen are less prominent, especially in the healthy adult:
*Spleen produces all types of blood cells during fetal life
* Production of [[opsonin]]s, [[properdin]], and [[tuftsin]].
* Release of [[neutrophil]]s following myocardial infarction.<ref>{{cite web|url=https://academic.oup.com/cardiovascres/advance-article/doi/10.1093/cvr/cvac012/6522118 |title=Rapid neutrophil mobilization by VCAM-1+ endothelial cell-derived extracellular vesicles &#124; Cardiovascular Research &#124; Oxford Academic |publisher=Academic.oup.com |date= |accessdate=2022-02-15}}</ref>
* Creation of [[red blood cell]]s. While the [[bone marrow]] is the primary site of [[hematopoiesis]] in the adult, the spleen has important hematopoietic functions up until the fifth month of gestation. After birth, [[Erythropoiesis|erythropoietic]] functions cease, except in some hematologic disorders. As a major lymphoid organ and a central player in the [[reticuloendothelial system]], the spleen retains the ability to produce lymphocytes and, as such, remains a hematopoietic organ.
* Storage of [[red blood cell]]s, [[lymphocyte]]s and other formed elements. The spleen of horses stores roughly 30 percent of the red blood cells and can release them when needed.<ref name="MSNBC2006-Carey">{{cite news | first=Bjorn | last=Carey | url=http://www.nbcnews.com/id/12648465 | archive-url=https://web.archive.org/web/20150415114535/http://www.nbcnews.com/id/12648465/ | url-status=dead | archive-date=April 15, 2015 | title=Horse science: What makes a Derby winner – Spleen acts as a 'natural blood doper,' scientist says | publisher=NBC News | date=May 5, 2006  | access-date=2006-05-09}}</ref> In humans, up to a cup (240 ml) of red blood cells is held within the spleen and released in cases of [[hypovolemia]]<ref name="Spleen: Information, Surgery and Functions">{{cite web |url=https://chp.edu/CHP/organs+spleen+functions |title=Spleen: Information, Surgery and Functions |publisher=Children's Hospital of Pittsburgh |website= Chp.edu |date=2010-11-17 |access-date=2011-04-03 |url-status=dead |archive-url=https://web.archive.org/web/20110926085253/http://www.chp.edu/CHP/organs+spleen+functions |archive-date=2011-09-26 }}</ref> and [[hypoxia (medical)|hypoxia]].<ref>{{cite journal|last1=Lodin-Sundström|first1=Angelica|last2=Schagatay|first2=Erika|title=Spleen contraction during 20 min normobaric hypoxia and 2 min apnea in humans|journal=Aviation, Space, and Environmental Medicine|date=June 2010|volume=8|issue=6|pages=545–49|doi=10.3357/ASEM.2682.2010|pmid=20540444}}</ref>  It can store [[platelets]] in case of an emergency and also clears old platelets from the circulation. Up to a quarter of [[lymphocytes]] are stored in the spleen at any one time.

== Clinical significance ==
[[File:Spleen after spleenectomy.jpg|alt=Surgically removed spleen of a child with thalassemia. It is about 15 times larger than normal.|thumb|[[Thalassemia]]-enlarged spleen taken after [[splenectomy]]]]

=== Enlarged spleen ===
{{Main|Splenomegaly}}

Enlargement of the spleen is known as [[splenomegaly]]. It may be caused by [[sickle cell anemia]], [[sarcoidosis]], [[malaria]], [[bacterial endocarditis]], [[leukemia]], [[polycythemia vera]], [[pernicious anemia]], [[Gaucher's disease]], [[leishmaniasis]], [[Hodgkin's disease]], [[Banti's syndrome|Banti's disease]], [[hereditary spherocytosis]], [[cyst]]s, glandular fever (including [[Infectious mononucleosis|mononucleosis]] or 'Mono' caused by the [[Epstein–Barr virus]] and infection from [[Human betaherpesvirus 5|cytomegalovirus]]), and [[tumour]]s. Primary tumors of the spleen include [[hemangioma]]s and [[hemangiosarcoma]]s. Marked splenomegaly may result in the spleen occupying a large portion of the left side of the abdomen.

The spleen is the largest collection of [[lymphoid tissue]] in the body. It is normally palpable in preterm infants, in 30% of normal, full-term [[neonates]], and in 5% to 10% of infants and toddlers. A spleen easily palpable below the [[costal margin]] in any child over the age of three to four years should be considered abnormal until proven otherwise.

Splenomegaly can result from antigenic stimulation (e.g., infection), obstruction of blood flow (e.g., portal vein obstruction), underlying functional abnormality (e.g., [[hemolytic anemia]]), or infiltration (e.g., [[leukemia]] or storage disease, such as [[Gaucher's disease]]). The most common cause of acute splenomegaly in children is viral infection, which is transient and usually moderate. Basic work-up for acute splenomegaly includes a [[complete blood count]] with differential, platelet count, and [[reticulocyte]] and atypical lymphocyte counts to exclude hemolytic anemia and leukemia. Assessment of [[IgM]] antibodies to viral capsid antigen (a rising [[titer]]) is indicated to confirm Epstein–Barr virus or [[Human betaherpesvirus 5|cytomegalovirus]]. Other infections should be excluded if these tests are negative.

Calculators have been developed for measurements of spleen size based on [[CT scan|CT]], [[Ultrasound|US]], and [[Magnetic resonance imaging|MRI]] findings.

=== Splenic injury ===
{{Main|Splenic injury}}
[[trauma (medicine)|Trauma]], such as a [[traffic collision|road traffic collision]], can cause [[ruptured spleen|rupture of the spleen]], which is a situation requiring immediate medical attention.

=== Asplenia ===
{{Main|Asplenia}}

[[Asplenia]] refers to a non-functioning spleen, which may be [[genetic disorder|congenital]], or caused by traumatic injury, surgical resection ([[splenectomy]]) or a disease such as [[Sickle cell disease|sickle cell anaemia]]. Hyposplenia refers to a partially functioning spleen. These conditions may cause<ref name="Jia"/> a modest increase in circulating [[white blood cell]]s and [[platelet]]s, a diminished response to some [[vaccine]]s, and an increased susceptibility to infection. In particular, there is an increased risk of [[sepsis]] from [[polysaccharide encapsulated bacteria]]. Encapsulated bacteria inhibit binding of complement or prevent complement assembled on the capsule from interacting with macrophage receptors. Phagocytosis needs natural antibodies, which are immunoglobulins that facilitate phagocytosis either directly or by complement deposition on the capsule. They are produced by [[immunoglobulin M|IgM]] [[memory B cell]]s (a subtype of [[B cell]]s) in the [[marginal zone]] of the spleen.<ref>{{cite journal|last=Di Sabatino|first=A|author2=Carsetti, R |author3=Corazza, GR |title=Post-splenectomy and hyposplenic states|journal=Lancet|date=Jul 2, 2011|volume=378|issue=9785|pages=86–97|pmid=21474172|doi=10.1016/S0140-6736(10)61493-6|s2cid=30554953}}</ref><ref>{{cite journal|last=Carsetti|first=R|author2=Rosado, MM |author3=Wardmann, H |title=Peripheral development of B cells in mouse and man|journal=Immunological Reviews|date=February 2004|volume=197|pages=179–91|pmid=14962195|doi=10.1111/j.0105-2896.2004.0109.x|s2cid=20654498}}</ref>

A [[splenectomy]] (removal of the spleen) results in a greatly diminished frequency of memory B cells.<ref>{{cite journal|last=Kruetzmann|first=S |author2=Rosado, MM |author3=Weber, H |author4=Germing, U |author5=Tournilhac, O |author6=Peter, HH |author7=Berner, R |author8=Peters, A |author9=Boehm, T |author10=Plebani, A |author11=Quinti, I |author12=Carsetti, R|title=Human immunoglobulin M memory B cells controlling Streptococcus pneumoniae infections are generated in the spleen|journal=The Journal of Experimental Medicine|date=Apr 7, 2003|volume=197|issue=7|pages=939–45|pmid=12682112|doi=10.1084/jem.20022020|pmc=2193885}}</ref> A 28-year follow-up of 740 [[World War II]] veterans whose spleens were removed on the battlefield showed a significant increase in the usual death rate from [[pneumonia]] (6 rather than the expected 1.3) and an increase in the death rate from [[ischemic heart disease]] (41 rather than the expected 30), but not from other conditions.<ref>{{Cite journal|pmid=69206|doi=10.1016/S0140-6736(77)90132-5|title=Splenectomy and Subsequent Mortality in Veterans of the 1939–45 War|year=1977|last1=Dennis Robinette|first1=C.|last2=Fraumeni|first2=Josephf.|journal=The Lancet|volume=310|issue=8029|pages=127–29|s2cid=38605411}}</ref>

=== Accessory spleen ===
An [[accessory spleen]] is a small splenic nodule extra to the spleen usually formed in early [[human embryogenesis|embryogenesis]]. Accessory spleens are found in approximately 10 percent of the population<ref name=klmoore>{{cite book | last = Moore | first = Keith L. | author-link = Keith L. Moore | title = Clinically Oriented Anatomy | edition = 3rd | year = 1992 | publisher = Williams & Wilkins | location = Baltimore | isbn = 978-0-683-06133-8 | page = 187}}</ref> and are typically around 1 centimeter in diameter. ''[[Splenosis]]'' is a condition where displaced pieces of splenic tissue (often following [[physical trauma|trauma]] or splenectomy) [[autotransplantation|autotransplant]] in the abdominal cavity as accessory spleens.<ref>{{cite journal | author = Abu Hilal M |author2=Harb A|author3=Zeidan B|author4=Steadman B|author5=Primrose JN|author6= Pearce NW | date = January 5, 2009 | title = Hepatic splenosis mimicking HCC in a patient with hepatitis C liver cirrhosis and mildly raised alpha feto protein; the important role of explorative laparoscopy | journal = World Journal of Surgical Oncology | volume = 7 | issue = 1 | pmid = 19123935 | pmc = 2630926 | doi = 10.1186/1477-7819-7-1
| page = 1 |doi-access=free }}</ref>

[[Polysplenia]] is a congenital disease manifested by multiple small accessory spleens,<ref>{{DorlandsDict|seven/000085247|polysplenia}}</ref> rather than a single, full-sized, normal spleen.  Polysplenia sometimes occurs alone, but it is often accompanied by other developmental abnormalities such as [[intestinal malrotation]] or [[biliary atresia]], or cardiac abnormalities, such as [[dextrocardia]]. These accessory spleens are non-functional.

=== Infarction ===
{{Main|Splenic infarction}}

[[Splenic infarction]] is a condition in which blood flow supply to the spleen is compromised,<ref name="Chapman Bhimji 2018 p.">{{citation | last1=Chapman | first1=J | last2=Bhimji | first2=SS | title=Splenic Infarcts | chapter=article-29380 | publisher=StatPearls Publishing | location=Treasure Island (FL) | year=2018 | pmid=28613652 | url=http://www.ncbi.nlm.nih.gov/books/NBK430902/ | access-date=2019-02-27 }}</ref> leading to partial or complete [[infarction]] (tissue death due to oxygen shortage) in the organ.<ref name="pmid3764696">{{cite journal |vauthors=Jaroch MT, Broughan TA, Hermann RE |title=The natural history of splenic infarction |journal=Surgery |volume=100 |issue=4 |pages=743–50 |date=October 1986 |pmid=3764696 }}</ref>

Splenic infarction occurs when the [[splenic artery]] or one of its branches are occluded, for example by a [[blood clot]]. Although it can occur [[asymptomatic]]ally, the typical symptom is severe [[abdominal pain|pain]] in the [[left upper quadrant (abdomen)|left upper quadrant of the abdomen]], sometimes radiating to the left shoulder. Fever and chills develop in some cases.<ref>{{Cite journal |last1=Nores |first1=M1 |last2=Phillips |first2=EH |last3=Morgenstern |first3=L |last4=Hiatt |first4=JR |date=February 1998 |title=The Clinical Spectrum of Splenic Infarction |journal=[[The American Surgeon]] |volume=64 |issue=2 |pages=182–88 |pmid=9486895}}</ref> It has to be differentiated from other causes of [[acute abdomen]].

=== Hyaloserositis ===
The spleen may be affected by [[hyaloserositis]], in which it is coated with [[fibrosis|fibrous]] [[hyaline]].<ref name=omd>[http://cancerweb.ncl.ac.uk/cgi-bin/omd?hyaloserositis "Hyaloserositis"]. ''Online Medical Dictionary''. Accessed on: June 21, 2008.</ref><ref>{{cite web |url=https://www.drugs.com/dict/sugar-coated-spleen.html |title=Sugar-coated spleen |publisher=Drugs.com }}</ref>

== Society and culture ==
There has been a long and varied history of misconceptions regarding the physiological role of the spleen, and it has often been seen as a reservoir for juices closely linked to digestion.<ref name=Riva2019>{{cite journal |vauthors=Riva MA, Ferraina F, Paleari A, Lenti MV, Di Sabatino A |title=From sadness to stiffness: the spleen's progress |journal=Internal and Emergency Medicine |volume=14 |issue=5 |pages=739–743 |date=2019 |pmid=31152307 |doi=10.1007/s11739-019-02115-2 |s2cid=172137672 |url=}}</ref> In various cultures, the organ has been linked to [[melancholia]], due to the influence of [[ancient Greek medicine]] and the associated doctrine of [[humourism]], in which the spleen was believed to be a reservoir for an elusive fluid known as "black bile" (one of the four humours).<ref name=Riva2019/> The spleen also plays an important role in [[traditional Chinese medicine]], where it is considered to be [[Zang-fu|a key organ]] that displays the [[Yin and yang|Yin]] aspect of [[Earth (wuxing)|the Earth element]] (its Yang counterpart is the stomach).  In contrast, the [[Talmud]] (tractate Berachoth 61b) refers to the spleen as the organ of [[laughter]] while possibly suggesting a link with the humoral view of the organ.

Etymologically, ''spleen'' comes from the [[Ancient Greek]] {{lang|grc|σπλήν}} (''splḗn''), where it was the idiomatic equivalent of [[Heart (symbolism)|the heart]] in modern English. [[Persius]], in his satires, associated ''spleen'' with immoderate laughter.<ref name="Stanley2002"/> The native [[Old English]] word for it is '''{{wikt-lang|en|milt}}''', now primarily used for animals; a [[loanword]] from [[Latin]] is {{wikt-lang|en|lien}}.

In English, [[William Shakespeare]] frequently used the word ''spleen'' to signify [[Depression (mood)|melancholy]], but also [[wikt:caprice|caprice]] and merriment.<ref name="Stanley2002"/> In ''[[Julius Caesar (play)|Julius Caesar]]'', he uses the spleen to describe Cassius's irritable nature:

<blockquote><poem>Must I observe you? must I stand and crouch
Under your testy humour? By the gods
You shall digest the venom of your spleen,
Though it do split you; for, from this day forth,
I'll use you for my mirth, yea, for my laughter,
When you are waspish.<ref>''Julius Caesar'' by William Shakespeare Act 4:1</ref></poem></blockquote>

The spleen, as a byword for melancholy, has also been considered an actual disease.<ref name=Bynum2002>{{cite journal |vauthors=Bynum B |title=The spleen |journal=Lancet |volume=359 |page=1624 |date=2002 |issue=9317 |pmid=12048004 |doi=10.1016/S0140-6736(02)08479-9 |s2cid=33529100 |url=https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(02)08479-9/fulltext |url-access=registration}}</ref> In the early 18th century, the physician [[Richard Blackmore]] considered it to be one of the two most prevalent diseases in England (along with [[Tuberculosis|consumption]]).<ref name=Bynum2002/> In 1701, [[Anne Finch, Countess of Winchilsea|Anne Finch]] (later, Countess of Winchilsea) had published a [[Ode|Pindaric ode]], ''The Spleen'', drawing on her first-hand experiences of an affliction which, at the time, also had a reputation of being a fashionably [[upper-class]] disease of the English.<ref name="Rogers1989">{{cite journal |last1=Rogers KM |title=Finch's "Candid Account" vs. Eighteenth–Century Theories of the Spleen |journal=Mosaic: A Journal for the Interdisciplinary Study of Literature |date=1989 |volume=22 |issue=1 |pages=17–27 |jstor=24780450 |issn=0027-1276}}</ref>  Both Blackmore and [[George Cheyne (physician)|George Cheyne]] treated this malady as the male equivalent of "[[Vapours (disease)|the vapours]]", while preferring the more [[Learned medicine|learned]] terms "[[hypochondriasis]]" and "[[hysteria]]".<ref name=Bynum2002/><ref>[[George Cheyne (physician)|Cheyne, George]]: ''The English Malady; or, A Treatise of Nervous Diseases of All Kinds, as Spleen, Vapours, Lowness of Spirits, Hypochondriacal and Hysterical Distempers with the Author's Own Case at Large'', Dublin, 1733. Facsimile ed., ed. Eric T. Carlson, M.D., 1976, Scholars' Facsimiles & Reprints, {{ISBN|978-0-8201-1281-7}}</ref><ref>[[Richard Blackmore|Blackmore, Richard]]: ''Treatise of the spleen and vapors''. London, 1725</ref> In the late 18th century, the [[German language|German]] word ''Spleen'' came to denote [[Eccentricity (behavior)|eccentric]] and hypochondriac tendencies that were thought to be characteristic of English people.<ref name="Stanley2002">{{cite book |author=Stanley Eric | authorlink=Eric Stanley |editor=Coleman J, McDermott A |title=Historical dictionaries and historical Dictionary Research: Papers from the international conference on historical lexicography and lexicology, at the University of Leicester, 2002 |date=2002 |publisher=Walter de Gruyter |location=Germany |isbn=978-3-11-091260-9 |pages=170–171 |url= |language=en |chapter=Polysemy and synomyny and how these concepts were understood from the eighteenth century onwards in treatises, and applied dictionaries of English}}</ref>

In [[French language|French]], "splénétique" refers to a state of pensive sadness or melancholy. This usage was popularised by the poems of [[Charles Baudelaire]] (1821–1867) and his collection ''[[Le Spleen de Paris]]'', but it was also present in earlier [[French Romanticism|19th-century Romantic literature]].

=== Food ===
The spleen is one of the many organs that may be included in [[offal]]. It is not widely eaten as a principal ingredient, but cow spleen sandwiches are eaten in [[Sicily|Sicilian]] cuisine.<ref>{{cite web|url=https://www.theatlantic.com/health/archive/2010/05/spleen-sandwiches-an-italian-tradition/39761/|publisher=The Atlantic|access-date=2022-01-03|date=2010-05-03|first=Tejal|last=Rao|title=Spleen Sandwiches: An Italian Tradition}}</ref> Chicken spleen is one of the main ingredients of [[Jerusalem mixed grill]].<ref>{{cite news |url=http://www.haaretz.com/culture/arts-leisure/dining-out-mixed-jerusalem-grill-in-tel-aviv-1.216305 |title=Dining Out / Mixed Jerusalem grill in Tel Aviv |first=Daniel|last=Rogov |publisher=Haaretz |date=2007-03-22 |access-date=2022-01-03}}</ref>

== Other animals ==
[[File:Horse_spleen_laparoscopic.jpg|thumb|[[Laparoscopic surgery|Laparoscopic]] view of a horse's spleen (the purple and grey mottled organ)]]

In [[cartilaginous fish|cartilaginous]] and [[ray-finned fish]], the spleen consists primarily of red pulp and is normally somewhat elongated, as it lies inside the [[serosa]]l lining of the [[intestine]]. In many [[amphibian]]s, especially [[frog]]s, it has the more rounded form and there is often a greater quantity of white pulp.<ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia |pages= 410–11|isbn= 978-0-03-910284-5}}</ref>

In [[reptile]]s, birds, and [[mammal]]s, white pulp is always relatively plentiful, and in birds and some mammals the spleen is typically rounded, but it adjusts its shape somewhat to the arrangement of the surrounding organs.  In most vertebrates, the spleen continues to produce red blood cells throughout life; only in mammals this function is lost in middle-aged adults. Many mammals have tiny spleen-like structures known as [[haemal nodes]] throughout the body that are presumed to have the same function as the spleen.<ref name=VB/> The spleens of aquatic mammals differ in some ways from those of fully land-dwelling mammals; in general they are bluish in colour. In [[cetacean]]s and [[manatee]]s, they tend to be quite small, but in deep diving [[pinniped]]s, they can be massive, due to their function of storing red blood cells.

Marsupials have y-shaped spleens, and it develops postnatally.<ref> {{cite journal |vauthors= Old JM, Selwood L, Deane EM | title= Development of the lymphoid tissues of the stripe-faced dunnart (''Sminthopsis macroura''). |journal=Cells Tissues Organs|year=2002| volume=175|issue=4|pages=192-201|doi=10.1111/j.0021-8782.2004.00310.x |pmc=1571326}}</ref><ref> {{cite journal |vauthors= Old JM, Selwood L, Deane EM | title= A developmental investigation of the liver, bone marrow and spleen of the stripe-faced dunnart  (''Sminthopsis macroura''). |journal=Developmental and Comparative Immunology. |year=2004| volume=28|issue=4|pages=347-355|doi=10.1016/j.dci.2003.08.004  }}</ref><ref> {{cite journal |vauthors= Old JM, Selwood L, Deane EM | title= The appearance and distribution of mature T and B cells in the developing immune tissues of the stripe-faced dunnart  (''Sminthopsis macroura''). |journal=Journal of Anatomy|year=2004| volume=205|issue=1|pages=25-33|doi=10.1111/j.0021-8782.2004.00310.x  |pmc=1571326}}</ref><ref> {{cite journal |vauthors= Old JM, Deane EM | title= The detection of mature T and B-cells during development of the lymphoid tissues of the tammar wallaby (''Macropus eugenii''). |journal=Cells Tissues Organs|year=2003| volume=203|issue=1|pages=123-131|doi=10.1046/j.1469-7580.2003.00207.x  |pmc=1571143}}</ref>

The only vertebrates lacking a spleen are the [[lamprey]]s and [[hagfish]]es (the early-branching [[Cyclostomata]], or [[jawless fishes]]). Even in these animals, there is a diffuse layer of haematopoeitic tissue within the gut wall, which has a similar structure to red pulp and is presumed [[homology (biology)|homologous]] with the spleen of higher vertebrates.<ref name=VB/>

In mice, the spleen stores half the body's [[monocyte]]s so that, upon injury, they can migrate to the injured tissue and transform into [[dendritic cell]]s and [[macrophage]]s to assist [[wound healing]].<ref name="Swirski">{{Cite journal|pmid=19644120|year=2009|last1=Swirski|first1=FK|last2=Nahrendorf|first2=M|last3=Etzrodt|first3=M|last4=Wildgruber|first4=M|last5=Cortez-Retamozo|first5=V|last6=Panizzi|first6=P|last7=Figueiredo|first7=JL|last8=Kohler|first8=RH|last9=Chudnovskiy|first9=A|last10=Waterman|first10=P|last11=Aikawa|first11=E|last12=Mempel|first12=TR|last13=Libby|first13=P|last14=Weissleder|first14=R|last15=Pittet|first15=MJ|title=Identification of splenic reservoir monocytes and their deployment to inflammatory sites|volume=325|issue=5940|pages=612–16|doi=10.1126/science.1175202|pmc=2803111|journal=Science|bibcode=2009Sci...325..612S}}</ref>

== Additional images ==
<gallery>
File:Gray1189.png|Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries
File:Slide2ii.JPG|Spleen
File:Spleen.jpg|Laparoscopic view of human spleen
</gallery>

== See also ==
* {{annotated link|Asplenia with cardiovascular anomalies}}
* {{annotated link|Spleen transplantation}}
* {{annotated link|Splenic aspiration}}

== References ==
{{reflist|30em}}

== External links ==
{{Wiktionary|spleen}}
{{Commons|Spleen}}
* {{SUNYAnatomyFigs|38|03|01}} – "The visceral surface of the spleen."
* {{SUNYAnatomyImage|7|8|81}}
* [http://www.britannica.com/eb/article-9069185/spleen "spleen"] from ''[[Encyclopædia Britannica Online]]''
* [https://kidshealth.org/en/parents/spleen.html "The Spleen (for Parents)"], from KidsHealth.org
* [https://www.nlm.nih.gov/medlineplus/spleendiseases.html "Spleen Diseases"] from [[MedlinePlus]]
* [https://www.nytimes.com/2009/08/04/science/04angier.html "Finally, the Spleen Gets Some Respect"] – ''The New York Times''
* [https://radiology-universe.org/calculator/pediatric-spleen-sizes/calculator.php Normal range of spleen size for a given age in children]

{{Spleen}}
{{Lymphoid system}}
{{Authority control}}

[[Category:Spleen (anatomy)| ]]
[[Category:Abdomen]]
[[Category:Glands]]
[[Category:Immune system]]
[[Category:Lymphatic system]]
[[Category:Lymphatics of the torso]]
[[Category:Lymphoid organ]]
[[Category:Organs (anatomy)]]