colon
American Heritage Dictionary:
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co·lon2
(kō'lən) 
n., pl., -lons, or -la (-lə).
The section of the large intestine extending from the cecum to the rectum.
n., pl., -lons, or -la (-lə).
The section of the large intestine extending from the cecum to the rectum.
[Middle English, from Latin, from Greek kolon, large intestine.]
colonic co·lon'ic (kə-lŏn'ĭk) adj.
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Segment that makes up most of the large intestine. Though the two terms are often used interchangeably, the colon technically excludes the cecum (a pouch at the beginning of the large intestine), rectum, and anal canal. It runs up the right side of the abdomen (ascending colon), across it (transverse colon), and down the left side (descending colon); its last section (sigmoid colon) joins the rectum. It has no digestive function but lubricates waste products, absorbs remaining fluids and salts, and stores waste products until excretion. Problems involving the colon include ulcerative colitis, constipation and diarrhea, gas discomfort, megacolon (enlarged colon), and cancer.
For more information on colon, visit Britannica.com.
The portion of the intestine that runs from the cecum to the rectum; in some mammals, it may be separated from the small intestine by an ileocecal valve. It is also known as the large intestine. The colon is usually divided into ascending, transverse, and descending portions. In the human a fourth section, the sigmoid, is found. The colon is longer in herbivores and shorter in carnivores, and is about 4 to 6 ft (1.2 to 1.8 m) long in humans. No digestive enzymes are secreted in the colon. Much digestion (for example, all breakdown of cellulose) occurs by bacteria, of which Escherichia coli is the most common. Most of the fluid added to the food during digestion is reabsorbed into the body in the colon. All digestive action, water absorption, and so on, is completed before the food materials pass out of the colon into the rectum. See also Digestive system.
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Also known as the large intestine or bowel, consisting of three anatomical regions: the ascending, the transverse, and the descending colon. The colon normally has a considerable population of bacteria, while it is rare to find a significant bacterial population in the small intestine. The colon terminates at the rectum, where faeces are compacted and stored before voiding. See also gastro-intestinal tract.
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Also known as the large intestine, or sometimes the large bowel, because it is wider, although much shorter, than the small intestine, which leads into it via the caecum. There are three components: ascending, from the lower right side of the abdominal cavity; transverse, crossing to the left; and descending, to the lower left where it leads into the rectum. Its main function is the absorption of water, changing the liquid contents received from the ileum into the normally semi-solid faeces.
— Stuart Judge
See alimentary system.
The main part of the large intestine. Its main function is to absorb large amounts of water and electrolytes from undigested food passing through the colon from the small intestine to the rectum.
Saunders Veterinary Dictionary:
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colonic
Pertaining to or arising from the colon.
- c. aganglionosis — see colonic aganglionosis.
- c. atony — see megacolon.
- c. atresia — affected neonates appear normal at birth but develop abdominal distention quickly. No feces are passed and death occurs at about one week unless surgical repair is effected. The defect occurs sporadically in most species. In horses and cattle it can be inherited, in cattle it can result from over-vigorous palpation of the fetus between 35 and 41 days gestation at pregnancy diagnosis, but the cause is not determined in most cases.
- c. bands — see tenia coli.
- c. constriction — due to contraction of peritoneal adhesions in horses; causes chronic or intermittent colic.
- c. contraction — permanent inability of colon to dilate due to congenital aganglionosis.
- c. crypt — straight tubular glands in the colonic mucosa.
- c. entrapment — see left colonic displacement (below).
- c. foreign body — foreign bodies, e.g. halter shanks, are found in the colon in horses, having passed the gastric sphincter and the ileocecal valve; quickly encrusted with salts.
- c. impaction — intractable constipation occurs in dogs and cats, primarily with obstruction by foreign material and secondarily when there is an obstruction to the normal passage of feces, including retention because of pain at defecation. See also colon impaction colic of horses.
- c. infarction — see thromboembolic colic.
- c. ischemia — deprivation of blood supply to all or part of the colon. See also intestinal torsion, intestinal strangulation, intestinal obstruction colic.
- c. obstruction — see colonic impaction (above), intestinal obstruction.
- right dorsal c. displacement — displacement of the right dorsal colon in the horse to the area between the right body wall and the cecum, in an anterior direction so that the pelvic flexure comes to lie against the diaphragm.
- c. rupture — occurs, apparently spontaneously, in mares at foaling, death occurring soon afterwards.
- c. torsion — in horses, see under equine colic. In cattle, torsion of the coiled colon is an acute obstruction with coils of gas-distended colon visible in the right flank and palpable per rectum.
- c. wash — fecal samples can be collected from reptiles by flushing the colon with saline through a catheter inserted through the cloaca and into the colon.
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n
The body of the large intestine between the cecum and rectum.
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categories related to 'colon'
- Digestive and Excretory System - colon: main absorptive part of large intestine, running from cecum to rectum
- World Currencies - colon: currency of Costa Rica, El Salvador
- Punctuation and Diacritics - colon: : used to direct attention to matter that follows, esp. list, quotation, or explanation, and indicating a nearly full stop
Wikipedia on Answers.com:
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Colon (anatomy)
For other uses, see Colon.
| Colon (anatomy) | |
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| Front of abdomen, showing surface markings for liver, stomach, and large intestine. | |
| Gray's | subject #249 1177 |
| Dorlands/Elsevier | Colon |
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided (largely bacterial) fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a major role in absorption of foods and nutrients. However, the colon does absorb water, sodium and some fat soluble vitamins.[1]
In mammals, the colon consists of four sections: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon (the proximal colon usually refers to the ascending colon and transverse colon). The colon, cecum, and rectum make up the large intestine.[2]
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Contents
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Anatomy
The location of the parts of the colon is either in the abdominal cavity (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. [3]
Of the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the caecum, appendix, transverse colon and sigmoid colon are intraperitoneal. [4] This is important as it affects which organs can be easily accessed during surgery, such as a laparotomy.
The haustra of the colon are the small pouches caused by sacculation, which give the colon its segmented appearance. The taenia coli runs the length of the large intestine. Because the taenia coli is shorter than the intestine, the colon becomes sacculated between the taenia, forming the haustra.
Blood supply and lymphatics
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 a "marginal artery" that runs parallel to the colon for its entire length. Historically, it has been believed that the arc of Riolan, or the meandering mesenteric artery (of Moskowitz), is a variable vessel connecting the proximal SMA to the proximal IMA that can be extremely important if either vessel is occluded. However, recent studies conducted with improved imaging technology have questioned the actual existence of this vessel, with some experts calling for the abolition of the terms from future medical literature.
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.
Lymphatic drainage from the entire colon and proximal two-thirds of the rectum is to the paraaortic lymph nodes that then drain into the cisterna chyli. The lymph from the remaining rectum and anus can either follow the same route, or drain to the internal iliac and superficial inguinal nodes. The pectinate line only roughly marks this transition.
By segment
Ascending colon
The ascending colon is one part of four sections of the large intestine. This first section of the large intestine is connected to the small intestine by a section of bowel called the cecum. The ascending colon runs through the abdominal cavity, upwards toward the transverse colon for approximately eight inches (20 cm).
One of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it back into the body. As the waste material exits the small intestine it will move into the cecum and then the ascending colon where this process of extracting starts. The waste material is moved upwards toward the transverse section of the colon by a process called peristalsis.
Transverse colon
The transverse colon is the part of the colon from the hepatic flexure to the splenic flexure (the turn of the colon by the spleen). The transverse colon hangs off the stomach, attached to it by a wide band of tissue 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). Cancers form more frequently further along the large intestine as the contents become more solid (water is removed) in order to form feces.
The proximal two-thirds of the transverse colon is perfused by the middle colic artery, a branch of SMA, while the latter third is supplied by branches of the 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
The descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon. The function of the descending colon in the digestive system is to store food 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. The arterial supply comes via the left colic artery.
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 sigmoid). The walls of the sigmoid colon are muscular, and contract to increase the pressure inside the colon, causing the 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.
Redundant colon
One variation on the normal anatomy of the colon occurs when extra loops form, resulting in a longer than normal organ. 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.[5] 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.[6]
Standing gradient osmosis
Water absorption at the colon typically proceeds against a transmucosal osmotic pressure gradient. The standing gradient osmosis is a term used to describe the reabsorption of water against the osmotic gradient in the intestines. This hypertonic fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via tight junctions and adjacent cells, which then in turn moves across the basement membrane and into the capillaries.
Function
There are differences in the large intestine between different organisms. The large intestine is mainly responsible for storing waste, reclaiming water, maintaining the water balance, absorbing some vitamins, such as vitamin K, and providing a location for flora-aided fermentation.
By the time the chyme has reached this tube, most nutrients and 90% of the water have been absorbed by the body. At this point some electrolytes like sodium, magnesium, and chloride are left as well as indigestible parts of ingested food (e.g., a large part of ingested amylose, protein 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. The stools get to become semi solid as they move along into the descending colon[7] 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. No protein is made available. In humans, perhaps 10% of the undigested carbohydrate thus becomes available; 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. This is an example of a symbiotic relationship and provides about one hundred calories a day to the body. The large intestine produces no digestive enzymes -— 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 acidic to neutral).[8]
Pathology
Following are the most common diseases or disorders of the colon:
- Angiodysplasia of the colon
- Appendicitis
- Chronic functional abdominal painNF
- Colitis
- Colorectal cancer
- Constipation
- Crohn's disease
- Diarrhea
- DiverticulitisNF
- Diverticulosis
- Hirschsprung's disease (aganglionosis)
- Ileus
- Intussusception
- Irritable bowel syndrome
- Polyp (medicine) (see also Colorectal polyp)
- Pseudomembranous colitis
- Ulcerative colitis and toxic megacolon
Gallery
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Intestines
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Scheme
See also
References
- ^ Colon Function And Health Information Retrieved on 2010-01-21
- ^ http://definr.com/large+intestine
- ^ http://www.mananatomy.com/digestive-system/peritoneum
- ^ http://www.ucd.ie/vetanat/ga-subject/abdomen/ab13.html
- ^ Mayo Clinic Staff (2006-10-13). "Redundant colon: A health concern?". Ask a Digestive System Specialist. MayoClinic.com. Archived from the original on 2007-09-29. http://web.archive.org/web/20070929110621/http://www.mayoclinic.com/health/redundant-colon/AN00239/rss=1. Retrieved 2007-06-11.
- ^ Lichtenstein, Gary R.; Peter D. Park, William B. Long, Gregory G. Ginsberg, Michael L. Kochman (18 August 1998). "Use of a Push Enteroscope Improves Ability to Perform Total Colonoscopy in Previously Unsuccessful Attempts at Colonoscopy in Adult Patients". The American Journal of Gastroenterology 94 (1): 187–90. doi:10.1111/j.1572-0241.1999.00794.x. PMID 9934753. Note:Single use PDF copy provided free by Blackwell Publishing for purposes of Wikipedia content enrichment.
- ^ The Function Of The Colon Retrieved on 2010-01-21
- ^ Function Of The Large Intestine Retrieved on 2010-01-21
External links
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Wikimedia Commons has media related to: Colon (anatomy) |
- Overview and diagrams at seer.cancer.gov
- 09-118h. at Merck Manual of Diagnosis and Therapy Home Edition
- MeSH Large+Intestine
- Virtual Slidebox at Univ. Iowa Slide 393
- SUNY Labs 37:13-0100 - "Abdominal Cavity: The Colon and its Divisions"
- Video: What is Colorectal Cancer? NONE
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations:
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Colon
Dansk (Danish)
1.
n. - tyktarm, colon
2.
n. - kolon
3.
n. - nybygger
Nederlands (Dutch)
karteldarm, dubbele punt
Français (French)
1.
n. - (Anat) côlon
2.
n. - (Ling) deux points
3.
n. - colon (d'une ferme ou d'une plantation)
Deutsch (German)
1.
n. - Doppelpunkt
2.
n. - Grimmdarm
3.
n. - Colon (Währungseinheit in Costa Rica u. El Salvador)
Ελληνική (Greek)
n. - (ανατ.) κόλον, (τυπογρ.) άνω και κάτω τελεία (:)
Italiano (Italian)
colon, due punti
Português (Portuguese)
n. - dois (m pl) pontos (Gram.), cólon (m) (Anat.)
Русский (Russian)
ободочная кишка, двоеточие
Español (Spanish)
1.
n. - colon
2.
n. - dos puntos
3.
n. - parte principal de un período
Svenska (Swedish)
n. - grovtarm, kolon
中文（简体）(Chinese (Simplified))
1. 结肠
2. 冒号
3. 科朗
中文（繁體）(Chinese (Traditional))
1.
n. - 冒號
2.
n. - 結腸
3.
n. - 科朗
한국어 (Korean)
1.
n. - 구두점의 하나인 콜론
2.
n. - 결장, 대장 전체
3.
n. - 코스타리카 화폐단위 콜론
العربيه (Arabic)
(الاسم) قولون, الأمعاء الغليظه, نقطتان):( في الكتابه أو الطباعه
עברית (Hebrew)
n. - המעי הגס
n. - נקודתיים
n. - מטבע הנהוגה באמריקה המרכזית, בעל משק או מטעים בייחוד באלג'יריה
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