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The transverse colon is the longest and most mobile segment of the large intestine, connecting the ascending colon to the descending colon.[7] It is responsible for the continued processing and transport of digestive material. Suspended by the transverse mesocolon, it is intraperitoneal and has a distinct horizontal orientation. Where is Transverse colon Located? The transverse colon is located in the upper abdomen. It extends from the hepatic flexure (right colic flexure) near the liver to the splenic flexure (left colic flexure) near the spleen. It crosses the abdomen anteriorly to the pancreas and stomach, running horizontally across the abdominal cavity. Anatomy The transverse colon is a key section of the large intestine and the most mobile segment of the colon.[5] It plays a central role in connecting the ascending and descending colons while occupying a prominent position in the abdominal cavity. Below is a detailed description of its anatomy: Location and Orientation Dimensions The transverse colon is the longest segment of the colon, measuring approximately 45-50 cm in length, though this can vary. Structure The wall of the transverse colon is composed of the four typical layers found throughout the gastrointestinal tract: Mucosa: Submucosa: Muscularis Externa: Consists of two layers of smooth muscle: Inner circular layer: Facilitates segmentation. Outer longitudinal layer: Arranged into three distinct bands called teniae coli, which run along the length of the colon. The teniae coli cause the colon to have sacculations, or haustra, giving it a segmented appearance. Serosa/Adventitia: The transverse colon is covered by serosa, as it is an intraperitoneal organ, suspended by the transverse mesocolon. Peritoneal Relationships Vascular Supply Arterial Supply: Venous Drainage: Blood drains into the superior mesenteric vein (SMV), which contributes to the portal venous system. Lymphatic Drainage Lymphatic vessels from the transverse colon drain into: Nervous Supply Sympathetic Innervation: Provided by the superior mesenteric plexus.[8] Relationships to Adjacent Structures Function The transverse colon plays a vital role in the digestion process, serving as an intermediary segment of the large intestine. Its functions revolve around the continued processing of digested material, reabsorption, and preparation of waste for elimination. Below is a detailed breakdown of its functions: Transport of Digestive Material The transverse colon moves partially digested material (chyme) from the ascending colon to the descending colon: Water and Electrolyte Absorption The transverse colon absorbs:Water:The colon reabsorbs significant amounts of water from the chyme, converting it into more solid feces. Electrolytes:Important electrolytes like sodium and chloride are absorbed, maintaining the body’s fluid and electrolyte balance.[6] Fermentation of Undigested MaterialThe transverse colon hosts a diverse population of gut microbiota that ferment undigested carbohydrates: This process produces short-chain fatty acids (SCFAs), such as butyrate, which: Serve as an energy source for colonocytes. Support the health of the colonic mucosa. Fermentation also produces gases, such as carbon dioxide, hydrogen, and methane, which are eventually expelled as flatus. Formation and Storage of FecesThe transverse colon consolidates and compacts digested material into semi-solid feces by removing water. Temporary storage of fecal material occurs in the transverse colon before it is moved to the descending colon. Coordination with the Immune System The transverse colon contains gut-associated lymphoid tissue (GALT), which:Monitors and responds to pathogens in the digestive material. Plays a key role in maintaining a balance between beneficial and harmful microorganisms. Regulation of Bowel Movements The transverse colon contributes to the regulation of defecation:As fecal material accumulates, stretch receptors signal the need for mass movements. These movements push material toward the rectum for elimination. Role in Gas Management The transverse colon facilitates the segregation of gas (flatus) from fecal material: Gas, produced by microbial fermentation, is moved toward the rectum, where it can be expelled without the passage of solid waste.[2] Clinical Significance The transverse colon is clinically significant as it is a common site for various gastrointestinal disorders due to its anatomical position and functions:Colorectal Cancer: The transverse colon can develop malignant tumors, often presenting with symptoms like altered bowel habits, abdominal pain, and rectal bleeding. Early detection is crucial for management.[4] Volvulus: Although less common than sigmoid volvulus, the transverse colon’s mobility can lead to twisting, causing intestinal obstruction and severe abdominal pain. Diverticulosis: Pouches (diverticula) can form along the transverse colon, especially with chronic constipation, which may lead to inflammation (diverticulitis). Ischemia: The transverse colon is prone to ischemic colitis due to its watershed location between the superior and inferior mesenteric artery blood supplies. Inflammatory Bowel Disease (IBD): Conditions like Crohn’s disease and ulcerative colitis often involve the transverse colon, causing inflammation, pain, and diarrhea. (责任编辑：) |