Editing Large intestine

{{short description|Last part of the digestive system in vertebrates}}
{{Infobox anatomy
| Name        = Large intestine
| Latin       = colon or intestinum crassum
| Caption     = Front of [[abdomen]], showing the large intestine, with the [[stomach]] and [[small intestine]] in gray.
| Precursor   = 
| PartOf      = [[Gastrointestinal tract]]
| System      = [[Digestion|Digestive system]]
| Artery      = [[Superior mesenteric artery|Superior mesenteric]], [[Inferior mesenteric artery|inferior mesenteric]] and [[Internal iliac artery|iliac arteries]]
| Vein        = [[Superior mesenteric vein|Superior]] and [[inferior mesenteric vein]]
| Nerve       = 
| Lymph       = [[Inferior mesenteric lymph nodes]]
|Image=Tractus intestinalis intestinum crassum.svg|Width=200}}
{{Gastrointestinal tract sidebar}}
The '''large intestine''', also known as the '''large bowel''', is the last part of the [[gastrointestinal tract]] and of the [[Digestion|digestive system]] in [[tetrapod]]s. Water is absorbed here and the remaining waste material is stored in the [[rectum]] as [[feces]] before being removed by [[defecation]].<ref name="NCILargeIntestineDef">{{cite web |title=Small & Large Intestine {{!}} SEER Training |url=https://training.seer.cancer.gov/anatomy/digestive/regions/intestine.html |website=training.seer.cancer.gov |access-date=9 April 2025}}</ref> The [[Colon (anatomy)|colon]] (progressing from the [[ascending colon]] to the [[transverse colon|transverse]], the [[descending colon|descending]] and finally the [[sigmoid colon]]) is the longest portion of the large intestine, and the terms "large intestine" and "colon" are often used interchangeably, but most sources define the large intestine as the combination of the [[cecum]], colon, [[rectum]], and [[anal canal]].<ref name='NCILargeIntestineDef'/><ref name="Kapoor2011">{{cite web | url=http://emedicine.medscape.com/article/1948929-overview | title=Large Intestine Anatomy | publisher=WebMD LLC. | work=Medscape | date=13 Jul 2011 | access-date=2013-08-20 | author=Kapoor, Vinay Kumar | editor=Gest, Thomas R.}}</ref><ref name="GrayLargeIntestine">{{cite book | url=http://www.bartleby.com/107/ | title=Gray's Anatomy | publisher=Lea & Febiger | author=Gray, Henry | author-link=Henry Gray | year=1918 | location=Philadelphia}}</ref> Some other sources exclude the anal canal.<ref>{{Cite encyclopedia|title=large intestine|dictionary=Mosby's Medical Dictionary|year=2009|edition=8th|publisher=Elsevier|isbn=9780323052900|url-access=registration|url=https://archive.org/details/isbn_9780323052900}}</ref><ref>{{Cite encyclopedia | title=intestine | dictionary=Concise Medical Dictionary|year=2010|publisher=Oxford University Press|isbn=9780199557141}}</ref><ref>{{Cite encyclopedia | title=large intestine | dictionary=A Dictionary of Biology | year=2013 | publisher=Oxford University Press|isbn=9780199204625}}</ref>

In humans, the large intestine begins in the right [[iliac region]] of the [[pelvis]], just at or below the [[waist]], where it is joined to the end of the [[small intestine]] at the cecum, via the [[ileocecal valve]]. It then continues as the colon [[ascending colon|ascending]] the [[abdomen]], across the width of the [[abdominal cavity]] as the [[transverse colon]], and then [[descending colon|descending]] to the rectum and its endpoint at the  [[anal canal]].<ref>{{cite web|title=Large intestine|url=http://www.gesa.org.au/content.asp?id=100|access-date=2016-07-24|archive-url=https://archive.today/20150828202413/http://www.gesa.org.au/content.asp?id=100|archive-date=2015-08-28|url-status=dead}}</ref> Overall, in humans, the large intestine is about {{convert|1.5|m|ft|0}} long, which is about one-fifth of the whole length of the human gastrointestinal tract.<ref>{{Cite book | last1=Drake | first1=R.L. | last2=Vogl | first2=W. | last3=Mitchell | first3=A.W.M. | title=Gray's Anatomy for Students | date=2010|publisher=Churchill Livingstone|location=Philadelphia}}</ref>

==Structure==
[[File:Blausen 0604 LargeIntestine2.png|thumb|Illustration of the large intestine.]]
The '''colon''' of the large intestine is the last part of the [[Digestion|digestive system]]. It has a segmented appearance due to a series of saccules called [[haustra]].<ref>{{Cite journal|last1=Azzouz|first1=Laura|last2=Sharma|first2=Sandeep|title=Physiology, Large Intestine|url=https://www.ncbi.nlm.nih.gov/books/NBK507857/|website=[[NCBI Bookshelf]]|year=2020|pmid=29939634}}</ref> It extracts [[water]] and [[salt]] from [[feces|solid wastes]] before they are [[defecation|eliminated]] from the body and is the site in which the [[fermentation]] of unabsorbed material by the [[gut microbiota]] occurs. Unlike the [[small intestine]], the colon does not play a major role in absorption of foods and nutrients. About 1.5 litres or 45 ounces of water arrives in the colon each day.<ref name="Krogh2010">{{citation|author=David Krogh|title=Biology: A Guide to the Natural World|url=https://books.google.com/books?id=Ph7NSAAACAAJ|date=2010|publisher=Benjamin-Cummings Publishing Company|isbn=978-0-321-61655-5|page=597}}</ref>

The colon is the longest part of the large intestine and its average length in the adult human is 65 inches or 166&nbsp;cm (range of 80 to 313&nbsp;cm) for males, and 61 inches or 155&nbsp;cm (range of 80 to 214&nbsp;cm) for females.<ref name="Hounnou">{{cite journal |vauthors=Hounnou G, Destrieux C, Desmé J, Bertrand P, Velut S |title=Anatomical study of the length of the human intestine |journal=Surg Radiol Anat |volume=24 |issue=5 |pages=290–294 |year=2002 |pmid=12497219 |doi=10.1007/s00276-002-0057-y |s2cid=33366428 }}</ref>

===Sections===
[[File:Diameters of the large intestine.svg|thumb|Inner diameters of colon sections]]
In [[mammal]]s, the large intestine consists of the [[cecum]] (including the [[appendix (anatomy)|appendix]]), colon (the longest part), [[rectum]], and [[anal canal]].<ref name='NCILargeIntestineDef'/>

The four sections of the colon are: the [[ascending colon]], [[transverse colon]], [[descending colon]], and [[sigmoid colon]]. These sections turn at the [[colic flexures]].

The parts of the colon are either intraperitoneal or behind it in the [[retroperitoneum]]. Retroperitoneal organs, in general, do not have a complete covering of [[peritoneum]], so they are fixed in location. Intraperitoneal organs are completely surrounded by peritoneum and are therefore mobile.<ref>{{cite web |url=http://www.mananatomy.com/digestive-system/peritoneum |title=Peritoneum |publisher=Mananatomy.com |date=2013-01-18 |access-date=2013-02-07 |archive-date=2018-10-08 |archive-url=https://web.archive.org/web/20181008195347/http://www.mananatomy.com/digestive-system/peritoneum |url-status=dead }}</ref> Of the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the cecum, appendix, transverse colon and sigmoid colon are intraperitoneal.<ref>{{cite web|url=http://www.ucd.ie/vetanat/ga-subject/abdomen/ab13.html|title=Untitled}}</ref> This is important as it affects which organs can be easily accessed during surgery, such as a [[laparotomy]].

In terms of diameter, the cecum is the widest, averaging slightly less than 9&nbsp;cm in healthy individuals, and the transverse colon averages less than 6&nbsp;cm in diameter.<ref name=":0">{{Cite journal|last1=Horton|first1=K. M.|last2=Corl|first2=F. M.|last3=Fishman|first3=E. K.|date=March 2000|title=CT evaluation of the colon: inflammatory disease|journal=Radiographics |volume=20|issue=2|pages=399–418|doi=10.1148/radiographics.20.2.g00mc15399|issn=0271-5333|pmid=10715339|doi-access=}}</ref> The descending and sigmoid colon are slightly smaller, with the sigmoid colon averaging {{convert|4–5|cm|in|abbr=on}} in diameter.<ref name=":0" /><ref>{{Citation|last=Rossini|first=Francesco Paolo|chapter=The normal colon|date=1975|pages=46–55|editor-last=Rossini|editor-first=Francesco Paolo|publisher=Springer New York|doi=10.1007/978-1-4615-9650-9_12|isbn=9781461596509|title=Atlas of coloscopy}}</ref> Diameters larger than certain thresholds for each colonic section can be diagnostic for [[megacolon]].
[[File:3DPX-002736 Large intestine Nevit Dilmen.stl|thumb|3D file generated from [[computed tomography]] of large intestine]]

====Cecum and appendix====
{{Main|Cecum|Appendix (anatomy)}}
The [[cecum]] is the first section of the large intestine and is involved in digestion, while the [[appendix (anatomy)|appendix]] which develops embryologically from it, is not involved in digestion and is considered to be part of the [[gut-associated lymphoid tissue]]. The function of the appendix is uncertain, but some sources believe that it has a role in housing a sample of the [[gut microbiota]], and is able to help to repopulate the colon with microbiota if depleted during the course of an immune reaction. The appendix has also been shown to have a high concentration of lymphatic cells.

====Ascending colon====
{{Main|Ascending colon}}
The ascending colon is the first of four main sections of the large intestine. It is connected to the small intestine by a section of bowel called the cecum. The ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20&nbsp;cm).

One of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it. As the waste material exits the small intestine through the [[ileocecal valve]], it will move into the cecum and then to the ascending colon where this process of extraction starts. The waste material is pumped upwards toward the transverse colon by [[peristalsis]]. The ascending colon is sometimes attached to the [[appendix (anatomy)|appendix]] via [[Joseph von Gerlach|Gerlach's valve]]. In [[ruminants]], the ascending colon is known as the '''spiral colon'''.<ref>{{citation
| url = http://medical-dictionary.thefreedictionary.com/spiral+colon
| title = Medical dictionary}}</ref><ref>{{citation
| url = http://faculty.ucc.edu/biology-potter/Pig_Digestive_System/sld009.htm
| title = Spiral colon and caecum
| access-date = 2014-04-02
| archive-url = https://web.archive.org/web/20160304022928/http://faculty.ucc.edu/biology-potter/Pig_Digestive_System/sld009.htm
| archive-date = 2016-03-04
| url-status = dead
}}</ref><ref>{{cite web|url=http://www.answers.com/topic/colon-9|title=Answers – The Most Trusted Place for Answering Life's Questions|website=[[Answers.com]]}}</ref>
Taking into account all ages and sexes, colon cancer occurs here most often (41%).<ref name="Colorectal cancer statistics, 2017">{{cite journal|vauthors=Siegel RL, Miller KD, Fedewa SA, Ahnen DJ, Meester RG, Barzi A, Jemal A |title=Colorectal cancer statistics|journal=CA Cancer J. Clin.|volume=67|issue=3|pages=177–193|date=March 1, 2017|doi=10.3322/caac.21395|pmid=28248415|doi-access=free}}</ref>

====Transverse colon====
{{Main|Transverse colon}}
The transverse colon is the part of the colon from the [[Colic flexures|hepatic flexure]], also known as the right colic, (the turn of the colon by the [[liver]]) to the [[Colic flexures|splenic flexure]] also known as the left colic, (the turn of the colon by the [[spleen]]). The transverse colon hangs off the [[stomach]], attached to it by a large fold of [[peritoneum]]  called the [[greater omentum]]. On the posterior side, the transverse colon is connected to the posterior abdominal wall by a [[mesentery]] known as the [[transverse mesocolon]].

The transverse colon is encased in [[peritoneum]], and is therefore mobile (unlike the parts of the colon immediately before and after it).

The proximal two-thirds of the transverse colon is perfused by the [[middle colic artery]], a branch of the [[superior mesenteric artery]] (SMA), while the latter third is supplied by branches of the [[inferior mesenteric artery]] (IMA). The "watershed" area between these two blood supplies, which represents the embryologic division between the [[midgut]] and [[hindgut]], is an area sensitive to [[ischemia]].

====Descending colon====
{{Main|Descending colon}}
The descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon. One function of the descending colon in the digestive system is to store feces that will be emptied into the rectum. It is [[retroperitoneal]] in two-thirds of humans. In the other third, it has a (usually short) mesentery.<ref>{{Cite journal|last1=Smithivas|first1=T.|last2=Hyams|first2=P. J.|last3=Rahal|first3=J. J.|date=1971-12-01|title=Gentamicin and ampicillin in human bile|journal=The Journal of Infectious Diseases|volume=124 Suppl|pages=S106–108|issn=0022-1899|pmid=5126238|doi=10.1093/infdis/124.supplement_1.s106}}</ref> The arterial supply comes via the [[left colic artery]]. The descending colon is also called the ''distal gut'', as it is further along the gastrointestinal tract than the proximal gut. Gut flora are very dense in this region.

====Sigmoid colon====
{{Main|Sigmoid colon}}
The sigmoid colon is the part of the large intestine after the descending colon and before the rectum. The name ''sigmoid'' means S-shaped (see [[wiktionary:sigmoid|sigmoid]]; cf. [[sigmoid sinus]]). The walls of the sigmoid colon are muscular and contract to increase the pressure inside the colon, causing the [[feces|stool]] to move into the rectum.

The sigmoid colon is supplied with blood from several branches (usually between 2 and 6) of the [[sigmoid arteries]], a branch of the IMA. The IMA terminates as the [[superior rectal artery]].

[[Sigmoidoscopy]] is a common diagnostic technique used to examine the sigmoid colon.

====Rectum====
{{Main|Rectum}}
The [[rectum]] is the last section of the large intestine. It holds the formed feces awaiting elimination via defecation.
It is about 12&nbsp;cm long.<ref>{{Cite web|title=Anatomy of Colon and Rectum {{!}} SEER Training|url=https://training.seer.cancer.gov/colorectal/anatomy/|access-date=2021-04-14|website=training.seer.cancer.gov}}</ref>

===Appearance===
The [[cecum]] – the first part of the large intestine
* [[Taeniae coli]] – three bands of smooth muscle
* [[Haustra]] – bulges caused by contraction of taeniae coli
* [[Epiploic appendages]] – small fat accumulations on the viscera

The [[taenia coli]] run the length of the large intestine.  Because the taenia coli are shorter than the large bowel itself, the colon becomes ''[[:wikt:sacculated|sacculated]]'', forming the [[haustra]] of the colon which are the shelf-like intraluminal projections.<ref>Anatomy at a Glance by Omar Faiz and David Moffat</ref>

===Blood supply===
[[Artery|Arterial]] supply to the colon comes from branches of the [[superior mesenteric artery]] (SMA) and [[inferior mesenteric artery]] (IMA). Flow between these two systems communicates via the [[marginal artery of the colon]] that runs parallel to the colon for its entire length. Historically, a structure variously identified as the arc of Riolan or meandering mesenteric artery (of Moskowitz) was thought to connect the [[Anatomical terms of location#Proximal and distal|proximal]] SMA to the proximal IMA. This variably present structure would be important if either vessel were occluded. However, at least one review of the literature questions the existence of this vessel, with some experts calling for the abolition of these terms from future medical literature.<ref>{{cite journal |last1=Lange |first1=Johan F. |last2=Komen |first2=Niels |last3=Akkerman |first3=Germaine |last4=Nout |first4=Erik |last5=Horstmanshoff |first5=Herman |last6=Schlesinger |first6=Frans |last7=Bonjer |first7=Jaap |last8=Kleinrensink |first8=Gerrit-Jan |title=Riolan's arch: confusing, misnomer, and obsolete. A literature survey of the connection(s) between the superior and inferior mesenteric arteries |journal=Am J Surg |date=June 2007 |volume=193 |issue=6 |pages=742–748 |doi=10.1016/j.amjsurg.2006.10.022|pmid=17512289 }}</ref>

[[Vein|Venous]] drainage usually mirrors colonic arterial supply, with the [[inferior mesenteric vein]] draining into the [[splenic vein]], and the [[superior mesenteric vein]] joining the splenic vein to form the [[hepatic portal vein]] that then enters the [[liver]]. [[Middle rectal veins]] are an exception, delivering blood to [[inferior vena cava]] and bypassing the liver.<ref>{{cite journal |last1=van Hoogdalem |first1=Edward |last2=de Boer |first2=Albertus G. |last3=Breimer |first3=Douwe D. |title=Pharmacokinetics of rectal drug administration, Part I. General considerations and clinical applications of centrally acting drugs |journal=Clinical Pharmacokinetics |date=July 1991 |volume=21 |issue=1 |page=14 |doi=10.2165/00003088-199121010-00002 |pmid=1717195 |url=https://pubmed.ncbi.nlm.nih.gov/1717195/ |access-date=18 March 2024 |issn=0312-5963 |quote=The superior rectal vein, perfusing the upper part of the rectum, drains into the portal vein and subsequently into the liver On the other hand, the middle and inferior rectal veins drain the lower part of the rectum and venous blood is returned to the inferior vena cava.}}</ref>

===Lymphatic drainage===
[[Lymphatic system|Lymphatic drainage]] from the ascending colon and proximal two-thirds of the [[transverse colon]] is to the [[ileocolic lymph node]]s and the [[superior mesenteric lymph node]]s, which drain into the [[cisterna chyli]].<ref name="Little, Brown, and Company">{{cite book|last1=Snell|first1=Richard S.|title=Clinical Anatomy for Medical Students|date=1992|publisher=Little, Brown, and Company|location=Boston|pages=53–54|edition=4th}}</ref> The lymph from the distal one-third of the [[transverse colon]], the [[descending colon]], the sigmoid colon, and the upper [[rectum]] drain into the inferior mesenteric and colic lymph nodes.<ref name="Little, Brown, and Company"/> The lower rectum to the anal canal above the pectinate line drain to the internal ileocolic nodes.<ref name="First Aid for the USMLE Step 1">{{cite book|last1=Le|first1=Tao|title=First Aid for the USMLE Step 1|date=2014|publisher=McGraw-Hill Education|page=196|display-authors=etal}}</ref> The anal canal below the pectinate line drains into the superficial [[Groin|inguinal]] nodes.<ref name="First Aid for the USMLE Step 1"/> The [[pectinate line]] only roughly marks this transition.

===Nerve supply===
Sympathetic supply: superior & inferior mesenteric ganglia;
parasympathetic supply: vagus & sacral plexus (S2-S4){{citation needed|date=September 2024}}

===Development===
{{See also|Development of the digestive system}}
The endoderm, mesoderm and ectoderm are germ layers that develop in a process called gastrulation. Gastrulation occurs early in human development. The gastrointestinal tract is derived from these layers.<ref>{{Citation |last1=Wilson |first1=Danielle J. |title=Embryology, Bowel |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK545247/ |work=StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=31424831 |access-date=2022-05-27 |last2=Bordoni |first2=Bruno}}</ref>

===Variation===
One variation on the normal anatomy of the colon occurs when extra loops form, resulting in a colon that is up to five metres longer than normal. This condition, referred to as '''redundant colon''', typically has no direct major health consequences, though rarely [[volvulus]] occurs, resulting in obstruction and requiring immediate medical attention.<ref>{{cite web|url=http://www.mayoclinic.com/health/redundant-colon/AN00239/rss=1 |title=Redundant colon: A health concern? |access-date=2007-06-11 |date=2006-10-13 |author=Mayo Clinic Staff |work=Ask a Digestive System Specialist |publisher=MayoClinic.com |archive-url=https://web.archive.org/web/20070929110621/http://www.mayoclinic.com/health/redundant-colon/AN00239/rss%3D1 |archive-date=2007-09-29 |url-status=dead }}</ref><ref>{{cite web |url= http://www.riversideonline.com/health_reference/Questions-Answers/AN00239.cfm |title= Redundant colon: A health concern? (Above with active image links) |work= riversideonline.com |author= Mayo Clinic Staff |access-date= 8 November 2013 |archive-date= 9 November 2013 |archive-url= https://web.archive.org/web/20131109023215/http://www.riversideonline.com/health_reference/Questions-Answers/AN00239.cfm |url-status= dead }}</ref> A significant indirect health consequence is that use of a standard adult [[colonoscope]] is difficult and in some cases impossible when a redundant colon is present, though specialized variants on the instrument (including the pediatric variant) are useful in overcoming this problem.<ref>{{cite journal | last=Lichtenstein | first=Gary R. |author2=Peter D. Park |author3=William B. Long |author4=Gregory G. Ginsberg |author5=Michael L. Kochman  | title=Use of a Push Enteroscope Improves Ability to Perform Total Colonoscopy in Previously Unsuccessful Attempts at Colonoscopy in Adult Patients | journal=The American Journal of Gastroenterology | volume=94 | issue=1 | pages=187–190 | date=18 August 1998 | doi=10.1111/j.1572-0241.1999.00794.x | pmid=9934753 | s2cid=24536782 }} ''Note: single use PDF copy provided free by [[Blackwell Publishing]] for purposes of Wikipedia content enrichment.''</ref>

==Microanatomy==
{{Further|Gastrointestinal wall}}

===Colonic crypts===
[[File:Colonic crypts within four tissue sections.jpg|thumb|Colonic crypts ([[intestinal glands]]) within four tissue sections.  The cells have been [[staining|stained]] to show a brown-orange color if the cells produce the [[mitochondrion|mitochondrial]] protein [[cytochrome c oxidase subunit I]] (CCOI), and the [[Cell nucleus|nuclei]] of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with [[haematoxylin]]. Panels A, B were cut across the long axes of the crypts and panels C, D were cut parallel to the long axes of the crypts. In panel A the bar shows 100 μm and allows an estimate of the frequency of crypts in the colonic epithelium. Panel B includes three crypts in cross-section, each with one segment deficient for CCOI expression and at least one crypt, on the right side, undergoing fission into two crypts. Panel C shows, on the left side, a crypt fissioning into two crypts. Panel D shows typical small clusters of two and three CCOI deficient crypts (the bar shows 50 μm). The images were made from original photomicrographs, but panels A, B and D were also included in an article<ref name="Bernstein">{{cite journal |vauthors=Bernstein C, Facista A, Nguyen H, Zaitlin B, Hassounah N, Loustaunau C, Payne CM, Banerjee B, Goldschmid S, Tsikitis VL, Krouse R, Bernstein H |title=Cancer and age related colonic crypt deficiencies in cytochrome c oxidase I |journal=World J Gastrointest Oncol |volume=2 |issue=12 |pages=429–442 |year=2010 |pmid=21191537 |pmc=3011097 |doi=10.4251/wjgo.v2.i12.429 |doi-access=free }}</ref> and illustrations were published with Creative Commons Attribution-Noncommercial License allowing re-use.]]
The wall of the large intestine is lined with simple columnar [[intestinal epithelium|epithelium]] with [[invagination]]s.  The invaginations are called the [[intestinal gland]]s or colonic crypts.

<gallery mode="packed">
File:Micrograph of normal large intestinal crypts.jpg|Micrograph of normal large instestinal crypts.
File:Anatomy of normal large intestinal crypts.jpg|Anatomy of normal large intestinal crypts
</gallery>

The colon crypts are shaped like microscopic thick walled test tubes with a central hole down the length of the tube (the crypt [[Lumen (anatomy)|lumen]]). Four tissue sections are shown here, two cut across the long axes of the crypts and two cut parallel to the long axes.  In these images the cells have been stained by [[immunohistochemistry]] to show a brown-orange color if the cells produce a [[mitochondrion|mitochondrial]] protein called [[cytochrome c oxidase subunit I]] (CCOI).  The [[Cell nucleus|nuclei]] of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with [[haematoxylin]]. As seen in panels C and D, crypts are about 75 to about 110 cells long.  Baker et al.<ref name="Baker">{{cite journal |vauthors=Baker AM, Cereser B, Melton S, Fletcher AG, Rodriguez-Justo M, Tadrous PJ, Humphries A, Elia G, McDonald SA, Wright NA, Simons BD, Jansen M, Graham TA |title=Quantification of crypt and stem cell evolution in the normal and neoplastic human colon |journal=Cell Rep |volume=8 |issue=4 |pages=940–947 |year=2014 |pmid=25127143 |doi=10.1016/j.celrep.2014.07.019 |pmc=4471679}}</ref> found that the average crypt circumference is 23 cells.  Thus, by the images shown here, there are an average of about 1,725 to 2,530 cells per colonic crypt.  Nooteboom et al.<ref name="pmid19878146">{{cite journal |vauthors=Nooteboom M, Johnson R, Taylor RW, Wright NA, Lightowlers RN, Kirkwood TB, Mathers JC, Turnbull DM, Greaves LC |title=Age-associated mitochondrial DNA mutations lead to small but significant changes in cell proliferation and apoptosis in human colonic crypts |journal=Aging Cell |volume=9 |issue=1 |pages=96–99 |year=2010 |pmid=19878146 |pmc=2816353 |doi=10.1111/j.1474-9726.2009.00531.x }}</ref> measuring the number of cells in a small number of crypts reported a range of 1,500 to 4,900 cells per colonic crypt.  Cells are produced at the crypt base and migrate upward along the crypt axis before being shed into the colonic [[Lumen (anatomy)|lumen]] days later.<ref name=Baker />  There are 5 to 6 stem cells at the bases of the crypts.<ref name=Baker />

As estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium.<ref name="Nguyen">{{cite journal|vauthors=Nguyen H, Loustaunau C, Facista A, Ramsey L, Hassounah N, Taylor H, Krouse R, Payne CM, Tsikitis VL, Goldschmid S, Banerjee B, Perini RF, Bernstein C|year=2010|title=Deficient Pms2, ERCC1, Ku86, CcOI in field defects during progression to colon cancer|journal=J Vis Exp|issue=41|doi=10.3791/1931|pmc=3149991|pmid=20689513}}</ref>  Since the average length of the human colon is 160.5&nbsp;cm<ref name=Hounnou /> and the average inner circumference of the colon is 6.2&nbsp;cm,<ref name=Nguyen /> the inner surface epithelial area of the human colon has an average area of about 995&nbsp;cm<sup>2</sup>, which includes 9,950,000 (close to 10 million) crypts.

In the four tissue sections shown here, many of the intestinal glands have cells with a [[mitochondrial DNA]] mutation in the ''CCOI'' gene and appear mostly white, with their main color being the blue-gray staining of the nuclei.  As seen in panel B, a portion of the stem cells of three crypts appear to have a mutation in ''CCOI'', so that 40% to 50% of the cells arising from those stem cells form a white segment in the cross cut area.

Overall, the percent of crypts deficient for CCOI is less than 1% before age 40, but then increases linearly with age.<ref name=Bernstein /> Colonic crypts deficient for CCOI in women reaches, on average, 18% in women and 23% in men by 80–84 years of age.<ref name=Bernstein />

Crypts of the colon can reproduce by fission, as seen in panel C, where a crypt is fissioning to form two crypts, and in panel B where at least one crypt appears to be fissioning.  Most crypts deficient in CCOI are in clusters of crypts (clones of crypts) with two or more CCOI-deficient crypts adjacent to each other (see panel D).<ref name=Bernstein />

====Mucosa====
About 150 of the many thousands of [[Human genome#Coding sequences (protein-coding genes)|protein coding genes]] expressed in the large intestine, some are specific to the mucous membrane in different regions and include [[CEACAM7]].<ref>{{Cite journal|last1=Gremel|first1=Gabriela|last2=Wanders|first2=Alkwin|last3=Cedernaes|first3=Jonathan|last4=Fagerberg|first4=Linn|last5=Hallström|first5=Björn|last6=Edlund|first6=Karolina|last7=Sjöstedt|first7=Evelina|last8=Uhlén|first8=Mathias|last9=Pontén|first9=Fredrik|date=2015-01-01|title=The human gastrointestinal tract-specific transcriptome and proteome as defined by RNA sequencing and antibody-based profiling|journal=Journal of Gastroenterology|volume=50|issue=1|pages=46–57|doi=10.1007/s00535-014-0958-7|pmid=24789573|s2cid=21302849|issn=0944-1174}}</ref>

==Function==
[[File:Large intestine histology.jpg|thumb|Histological section.]]
The large intestine absorbs water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum. The colon absorbs vitamins that are created by the colonic bacteria, such as [[thiamine]], [[riboflavin]], and [[vitamin K]] (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate [[blood coagulation]]).<ref>{{Cite journal |last1=Sellers |first1=Rani S. |last2=Morton |first2=Daniel |date=2014 |title=The Colon: From Banal to Brilliant |journal=Toxicologic Pathology |volume=42 |issue=1 |pages=67–81 |doi=10.1177/0192623313505930 |pmid=24129758 |s2cid=20465985 }}</ref>{{Citation needed|date=May 2018}}<ref>{{Cite journal |last=Booth |first=Sarah |date=April 2012 |title=Vitamin K: Food Consumption and Dietary Intakes |url=https://foodandnutritionresearch.net/index.php/fnr/article/view/505 |journal=[[Food Nutrition Research]] |volume=56|doi=10.3402/fnr.v56i0.5505 |pmid=22489217 |pmc=3321250 }}</ref> It also compacts feces, and stores fecal matter in the rectum until it can be discharged via the [[anus]] in [[defecation]].

The large intestine also secretes K+ and Cl-. Chloride secretion increases in cystic fibrosis.
Recycling of various nutrients takes place in the colon. Examples include fermentation of carbohydrates, short chain fatty acids, and urea cycling.<ref>{{Cite news|url=http://www.news-medical.net/health/What-Does-the-Large-Intestine-Do.aspx|title=The Large Intestine (Human)|date=2009-11-17|work=News-Medical.net|access-date=2017-03-15}}</ref>{{Citation needed|date=March 2014}}

The [[appendix (anatomy)|appendix]] contains a small amount of [[mucosa-associated lymphoid tissue]] which gives the appendix an undetermined role in immunity. However, the appendix is known to be important in fetal life as it contains [[endocrine]] cells that release biogenic amines and peptide hormones important for [[homeostasis]] during early growth and development.<ref name="SAAppendix">{{cite journal | url=http://www.scientificamerican.com/article/what-is-the-function-of-t/ | title=What is the function of the human appendix? Did it once have a purpose that has since been lost? | journal=Scientific American | date=1999-10-21 | access-date=2014-03-03 | author=Martin, Loren G.}}</ref>

By the time the [[chyme]] has reached this tube, most [[nutrient]]s and 90% of the water have been absorbed by the body. Indeed, as demonstrated by the commonality of [[ileostomy]] procedures, it is possible for many people to live without large portions of their large intestine, or even without it completely. At this point only some [[electrolyte]]s like [[sodium]], [[magnesium]], and [[chloride]] are left as well as indigestible parts of ingested food (e.g., a large part of ingested [[amylose]], starch which has been shielded from digestion heretofore, and [[dietary fiber]], which is largely indigestible [[carbohydrate]] in either soluble or insoluble form). As the chyme moves through the large intestine, most of the remaining [[water]] is removed, while the chyme is mixed with [[mucus]] and [[bacteria]] (known as [[gut flora]]), and becomes feces. The [[ascending colon]] receives fecal material as a liquid. The muscles of the colon then move the watery waste material forward and slowly absorb all the excess water, causing the stools to gradually solidify as they move along into the [[descending colon]].<ref>[http://ccnt.hsc.usc.edu/colorectal/functioncolon.aspx La función de la] [http://www.hidroterapiadecolon.es/ hidroterapia de colon] Retrieved on 2010-01-21</ref>

The bacteria break down some of the [[fiber]] for their own nourishment and create [[acetate]], [[propionate]], and [[butyrate]] as waste products, which in turn are used by the cell lining of the colon for nourishment.<ref>{{cite journal |author1=Terry L. Miller |author2=Meyer J. Wolin |year=1996 |title=Pathways of Acetate, Propionate, and Butyrate Formation by the Human Fecal Microbial Flora |journal=[[Applied and Environmental Microbiology]] |volume=62 |issue=5 |pages=1589–1592 |url= |doi=10.1128/AEM.62.5.1589-1592.1996 |pmid=8633856 |pmc=167932 |bibcode=1996ApEnM..62.1589M }}</ref> No protein is made available. In humans, perhaps 10% of the undigested carbohydrate thus becomes available, though this may vary with diet;<ref>{{cite journal|last=McNeil|first=NI|title=The contribution of the large intestine to energy supplies in man|journal=The American Journal of Clinical Nutrition|year=1984|volume=39|issue=2|pages=338–342|pmid=6320630|doi=10.1093/ajcn/39.2.338}}</ref> in other animals, including other apes and primates, who have proportionally larger colons, more is made available, thus permitting a higher portion of plant material in the diet.  The large intestine<ref>{{Cite news|url=http://www.maglenia.com/what-side-is-your-appendix-located/|title=What Side is Your Appendix Located?|last=lorriben|date=2016-07-09|newspaper=Maglenia|access-date=2016-10-23|archive-url=https://web.archive.org/web/20161009115416/http://www.maglenia.com/what-side-is-your-appendix-located/|archive-date=2016-10-09|url-status=dead}}</ref> produces no digestive [[enzyme]]s — [[chemical digestion]] is completed in the [[small intestine]] before the chyme reaches the large intestine. The [[pH]] in the colon varies between 5.5 and 7 (slightly [[acid]]ic to neutral).<ref>[http://jamesallred.com/function-of-the-colon Function Of The Large Intestine] {{webarchive|url=https://web.archive.org/web/20131105044630/http://jamesallred.com/function-of-the-colon |date=2013-11-05 }} Retrieved on 2010-01-21</ref>

===Standing gradient osmosis===
Water absorption at the colon typically proceeds against a [[Route of administration#Application location|transmucosal]] [[osmotic pressure]] [[Osmosis#Osmotic gradient|gradient]]. The '''standing gradient osmosis''' is the reabsorption of water against the osmotic gradient in the intestines. Cells occupying the intestinal lining pump sodium ions into the intercellular space, raising the osmolarity of the intercellular fluid. This [[Tonicity|hypertonic]] fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via [[tight junction]]s and adjacent cells, which then in turn moves across the [[Basal lamina|basement membrane]] and into the [[Capillary|capillaries]], while more sodium ions are pumped again into the intercellular fluid.<ref>{{cite web | url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_water.html | title=Absorption of Water and Electrolytes}}</ref> Although water travels down an osmotic gradient in each individual step, overall, water usually travels against the osmotic gradient due to the pumping of sodium ions into the intercellular fluid. This allows the large intestine to absorb water despite the blood in capillaries being [[Tonicity|hypotonic]] compared to the fluid within the intestinal lumen.

===Gut flora===
{{main|Gut microbiota}}

The large intestine houses over 700 species of [[bacteria]] that perform a variety of functions, as well as [[fungi]], [[protozoa]], and [[archaea]]. Species diversity varies by geography and diet.<ref>{{cite journal | last1 = Yatsunenko | first1 = Tanya | display-authors = etal | year = 2012 | title = Human gut microbiome viewed across age and geography | journal = Nature | volume = 486 | issue = 7402| pages = 222–227 | pmc = 3376388 | pmid = 22699611 | doi = 10.1038/nature11053 | bibcode = 2012Natur.486..222Y }}</ref> The microbes in a human distal gut often number in the vicinity of 100 trillion, and can weigh around 200 grams (0.44 pounds). This mass of mostly symbiotic microbes has recently been called the latest human organ to be "discovered" or in other words, the "forgotten organ".<ref>{{cite journal | last1 = O'Hara | first1 = Ann M. | last2 = Shanahan | first2 = Fergus | year = 2006 | title = The gut flora as a forgotten organ | journal = EMBO Reports | volume = 7 | issue = 7| pages = 688–693 | doi=10.1038/sj.embor.7400731| pmid = 16819463 | pmc = 1500832 }}</ref>

The large intestine absorbs some of the products formed by the bacteria inhabiting this region. Undigested [[polysaccharides]] (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and absorbed by [[passive diffusion]]. The bicarbonate that the large intestine secretes helps to neutralize the increased acidity resulting from the formation of these fatty acids.<ref>{{Cite journal|title = The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism|journal = Journal of Lipid Research|date = 2013-09-01|issn = 0022-2275|pmc = 3735932|pmid = 23821742|pages = 2325–2340|volume = 54|issue = 9|doi = 10.1194/jlr.R036012 |doi-access=free |first1 = Gijs|last1 = den Besten|first2 = Karen|last2 = van Eunen|first3 = Albert K.|last3 = Groen|first4 = Koen|last4 = Venema|first5 = Dirk-Jan|last5 = Reijngoud|first6 = Barbara M.|last6 = Bakker}}</ref>

These bacteria also produce large amounts of [[vitamins]], especially [[vitamin K]] and [[biotin]] (a [[B vitamin]]), for absorption into the blood. Although this source of vitamins, in general, provides only a small part of the daily requirement, it makes a significant contribution when dietary vitamin intake is low. An individual who depends on absorption of vitamins formed by bacteria in the large intestine may become vitamin-deficient if treated with [[antibiotics]] that inhibit the vitamin producing species of bacteria as well as the intended disease-causing bacteria.<ref>{{Cite journal|title = Time to Recognize Our Fellow Travellers|journal = Journal of General Internal Medicine|date = 2012-12-01|issn = 0884-8734|pmc = 3509308|pmid = 22588826|pages = 1704–1706|volume = 27|issue = 12|doi = 10.1007/s11606-012-2105-6|first1 = Travis B.|last1 = Murdoch|first2 = Allan S.|last2 = Detsky}}</ref>

Other bacterial products include gas ([[flatulence|flatus]]), which is a mixture of [[nitrogen]] and [[carbon dioxide]], with small amounts of the gases [[hydrogen]], [[methane]], and [[hydrogen sulfide]]. Bacterial [[Fermentation (biochemistry)|fermentation]] of undigested [[polysaccharides]] produces these. Some of the fecal odor is due to [[indole]]s, metabolized from the amino acid tryptophan. The normal flora is also essential in the development of certain tissues, including the cecum and [[lymphatics]].{{Citation needed|date=March 2014}}

They are also involved in the production of cross-reactive antibodies. These are antibodies produced by the immune system against the normal flora, that are also effective against related pathogens, thereby preventing infection or invasion.

The two most prevalent phyla of the colon are [[Bacillota]] and [[Bacteroidota]]. The ratio between the two seems to vary widely as reported by the Human Microbiome Project.<ref name="Structure, function and diversity of the healthy human microbiome">{{cite journal|last1=Human Microbiome Project Consortium|title=Structure, function and diversity of the healthy human microbiome|journal=Nature|date=Jun 14, 2012|volume=486|issue=7402|pages=207–214|doi=10.1038/nature11234|pmid=22699609|pmc=3564958|bibcode=2012Natur.486..207T}}</ref> [[Bacteroides]] are implicated in the initiation of [[colitis]] and [[colon cancer]]. [[Bifidobacteria]] are also abundant, and are often described as 'friendly bacteria'.<ref>{{Cite journal|title = Commensal Bacteroides species induce colitis in host-genotype-specific fashion in a mouse model of inflammatory bowel disease|journal = Cell Host & Microbe|date = 2011-05-19|issn = 1931-3128|pmc = 3241010|pmid = 21575910|pages = 390–403|volume = 9|issue = 5|doi = 10.1016/j.chom.2011.04.009|first1 = Seth M.|last1 = Bloom|first2 = Vinieth N.|last2 = Bijanki|first3 = Gerardo M.|last3 = Nava|first4 = Lulu|last4 = Sun|first5 = Nicole P.|last5 = Malvin|first6 = David L.|last6 = Donermeyer|first7 = W. Michael|last7 = Dunne|first8 = Paul M.|last8 = Allen|first9 = Thaddeus S.|last9 = Stappenbeck}}</ref><ref>{{Cite journal|title = Diversity, ecology and intestinal function of bifidobacteria|journal = Microbial Cell Factories|date = 2014-08-29|issn = 1475-2859|pmc = 4155821|pmid = 25186128|pages = S4|volume = 13|issue = Suppl 1|doi = 10.1186/1475-2859-13-S1-S4|first1 = Francesca|last1 = Bottacini|first2 = Marco|last2 = Ventura|first3 = Douwe|last3 = van Sinderen|first4 = Mary|last4 = O'Connell Motherway | doi-access=free }}</ref>

A [[mucus]] layer protects the large intestine from attacks from colonic [[commensal bacteria]].<ref>{{Cite journal|title = The gastrointestinal mucus system in health and disease|journal = Nature Reviews. Gastroenterology & Hepatology|date = 2013-06-01|issn = 1759-5045|pmc = 3758667|pmid = 23478383|pages = 352–361|volume = 10|issue = 6|doi = 10.1038/nrgastro.2013.35|first1 = Malin E.V.|last1 = Johansson|first2 = Henrik|last2 = Sjövall|first3 = Gunnar C.|last3 = Hansson}}</ref>

==Clinical significance==

===Disease===
{{Main|Gastrointestinal disease}}
Following are the most common diseases or disorders of the colon:
{{columns-list|colwidth=17em|
* [[Angiodysplasia]] of the colon
* [[Appendicitis]]
* [[Chronic functional abdominal pain]]
* [[Colitis]]
* [[Colorectal cancer]]
* [[Colorectal polyp]]
* [[Constipation]]
* [[Crohn's disease]]
* [[Diarrhea]]
* [[Diverticulitis]]
* [[Diverticulosis]]
* [[Hirschsprung's disease]] (aganglionosis)
* [[Ileus]]
* [[Intussusception (medical disorder)|Intussusception]]
* [[Irritable bowel syndrome]]
* [[Pseudomembranous colitis]]
* [[Ulcerative colitis]] and [[toxic megacolon]]
}}

===Colonoscopy===
{{Main|Colonoscopy}}
[[File:Colonoscopy splenic flexure.jpg|thumb|Colonoscopy image, [[splenic flexure]],<br />normal [[mucosa]]. The [[spleen]] can be seen through it]]
[[Colonoscopy]] is the [[endoscopy|endoscopic]] examination of the large intestine and the [[Anatomical terms of location#Proximal and distal|distal]] part of the [[ileum|small bowel]] with a [[CCD camera]] or a [[fiber optic]] camera on a flexible tube passed through the [[Human anus|anus]]. It can provide a visual diagnosis (e.g. [[Peptic ulcer|ulceration]], [[Colorectal polyp|polyps]]) and grants the opportunity for [[biopsy]] or removal of suspected [[colorectal cancer]] lesions. Colonoscopy can remove polyps as small as one millimetre or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. It takes 15 years or fewer for a polyp to turn cancerous.

Colonoscopy is similar to [[sigmoidoscopy]]—the difference being related to which parts of the colon each can examine. A colonoscopy allows an examination of the entire colon (1200–1500&nbsp;mm in length). A sigmoidoscopy allows an examination of the distal portion (about 600&nbsp;mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.<ref name="Baxter09">{{cite journal|vauthors=Baxter NN, Goldwasser MA, Paszat LF, Saskin R, Urbach DR, Rabeneck L |title=Association of colonoscopy and death from colorectal cancer |journal=Ann. Intern. Med. |volume=150 |issue=1 |pages=1–8 |date=January 2009 |pmid=19075198 |doi=10.7326/0003-4819-150-1-200901060-00306 |s2cid=24130424 |doi-access= }} [http://www.media.dssimon.com/taperequest/acp50_study.pdf as PDF] {{webarchive|url=https://web.archive.org/web/20120118213536/http://www.media.dssimon.com/taperequest/acp50_study.pdf |date=2012-01-18 }}</ref><ref>{{cite journal |vauthors=Singh H, Nugent Z, Mahmud SM, Demers AA, Bernstein CN |title=Surgical resection of hepatic metastases from colorectal cancer: a systematic review of published studies |journal=Am J Gastroenterol |volume=105 |issue=3 |pages=663–673 |date=March 2010 |pmid=19904239 |doi=10.1038/ajg.2009.650 |s2cid=11145247 }}</ref><ref>{{cite journal |vauthors=Brenner H, Hoffmeister M, Arndt V, Stegmaier C, Alterhofen L, Haug U |title=Protection from right- and left-sided colorectal neoplasms after colonoscopy: population-based study |journal=J Natl Cancer Inst |volume= 102|issue= 2|pages=89–95 |date=January 2010 |pmid=20042716 |doi=10.1093/jnci/djp436 |s2cid=1887714 |doi-access=free }}</ref>

A sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a stool-based test such as a fecal occult blood test (FOBT), fecal immunochemical test (FIT), or multi-target stool DNA test (Cologuard) or blood-based test, SEPT9 DNA methylation test (Epi proColon).<ref>{{cite journal |last1=Tepus |first1=M |last2=Yau |first2=TO |title=Non-Invasive Colorectal Cancer Screening: An Overview |journal=Gastrointestinal Tumors |date=20 May 2020 |volume=7 |issue=3 |pages=62–73 |doi=10.1159/000507701|pmid=32903904 |pmc=7445682 |doi-access=free }}</ref> About 5% of these screened patients are referred to colonoscopy.<ref>{{cite journal|vauthors=Atkin WS, Edwards R, Kralj-Hans I, etal |title=Once-only flexible sigmoidoscopy screening in prevention of colorectal cancer: a multicentre randomised controlled trial |journal=Lancet |volume=375 |issue=9726 |pages=1624–33 |date=May 2010 |pmid=20430429 |doi=10.1016/S0140-6736(10)60551-X |s2cid=15194212 |doi-access=free }} [http://www.foroaps.org/blogevidencia/wp-content/uploads/2010/08/once_only_sigmoid.pdf as PDF] {{webarchive|url=https://web.archive.org/web/20120324041415/http://www.foroaps.org/blogevidencia/wp-content/uploads/2010/08/once_only_sigmoid.pdf |date=2012-03-24 }}</ref>

[[Virtual colonoscopy]], which uses 2D and 3D imagery reconstructed from [[computed tomography]] (CT) scans or from [[nuclear magnetic resonance]] (MR) scans, is also possible, as a totally [[non-invasive (medical)|non-invasive]] medical test, although it is not standard and still under investigation regarding its diagnostic abilities. Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5 millimeters.  If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed. Additionally, surgeons have lately been using the term [[pouchoscopy]] to refer to a colonoscopy of the [[ileo-anal pouch]].

==Other animals==
The large intestine is truly distinct only in [[tetrapod]]s, in which it is almost always separated from the small intestine by an [[ileocaecal valve]]. In most vertebrates, however, it is a relatively short structure running directly to the anus, although noticeably wider than the small intestine. Although the caecum is present in most [[amniote]]s, only in mammals does the remainder of the large intestine develop into a true colon.<ref name="VertebrateBody">{{cite book | title=The Vertebrate Body | publisher=Holt-Saunders International | author=Romer, Alfred Sherwood | author2=Parsons, Thomas S. | year=1977 | location=Philadelphia, PA | pages=351–354 | isbn=978-0-03-910284-5}}</ref>

In some small mammals, the colon is straight, as it is in other tetrapods, but, in the majority of mammalian species, it is divided into ascending and descending portions; a distinct transverse colon is typically present only in [[primates]]. However, the taeniae coli and accompanying haustra are not found in either [[carnivora]]ns or [[ruminant]]s. The rectum of mammals (other than [[monotreme]]s) is derived from the [[cloaca]] of other vertebrates, and is, therefore, not truly [[homology (biology)|homologous]] with the "rectum" found in these species.<ref name="VertebrateBody" />

In some fish, there is no true large intestine, but simply a short rectum connecting the end of the digestive part of the gut to the cloaca. In [[shark]]s, this includes a ''rectal gland'' that secretes salt to help the animal maintain [[osmosis|osmotic]] balance with the seawater. The gland somewhat resembles a caecum in structure but is not a homologous structure.<ref name="VertebrateBody" />

==Additional images==
<gallery>
 Image:illu_intestine.jpg|Intestines
 File:Slide12bek.JPG|Colon. Deep dissection. Anterior view.
</gallery>

==See also==
{{Anatomy-terms}}
* [[Colectomy]]
*[[Colonic ulcer]]
* [[Large intestine (Chinese medicine)]]

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

==External links==
{{Commons}}
{{Wiktionary}}
* {{MerckHome|09|118|h}}

{{Digestive tract}}

{{Authority control}}

{{Portal bar|Anatomy}}

[[Category:Large intestine| ]]
[[Category:Digestive system]]
[[Category:Organs (anatomy)]]