Editing Large intestine (section)

==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>