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 hangs off the stomach, attached to it by a large fold of peritoneum called the greater omentum. The transverse colon is the part of the colon from the hepatic flexure, also known as the right colic, (the turn of the colon by the liver) to the splenic flexure also known as the left colic, (the turn of the colon by the spleen). Taking into account all ages and sexes, colon cancer occurs here most often (41%). In ruminants, the ascending colon is known as the spiral colon. The ascending colon is sometimes attached to the appendix via Gerlach's valve. The waste material is pumped upwards toward the transverse colon by peristalsis. 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. One of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it. The ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20 cm). It is connected to the small intestine by a section of bowel called the cecum. The ascending colon is the first of four main sections of the large intestine. The appendix has also been shown to have a high concentration of lymphatic cells. 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 cecum is the first section of the large intestine and is involved in digestion, while the appendix which develops embryologically from it, is not involved in digestion and is considered to be part of the gut-associated lymphoid tissue. Diameters larger than certain thresholds for each colonic section can be diagnostic for megacolon.ģD File generated from computed tomography of large intestine Cecum and appendix The descending and sigmoid colon are slightly smaller, with the sigmoid colon averaging 4–5 cm (1.6–2.0 in) in diameter. In terms of diameter, the cecum is the widest, averaging slightly less than 9 cm in healthy individuals, and the transverse colon averages less than 6 cm in diameter. This is important as it affects which organs can be easily accessed during surgery, such as a laparotomy. Of the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the cecum, appendix, transverse colon and sigmoid colon are intraperitoneal. Intraperitoneal organs are completely surrounded by peritoneum and are therefore mobile. Retroperitoneal organs, in general, do not have a complete covering of peritoneum, so they are fixed in location.
The parts of the colon are either intraperitoneal or behind it in the retroperitoneum. These sections turn at the colic flexures. The four sections of the colon are: the ascending colon, transverse colon, descending colon, and sigmoid colon. In mammals, the large intestine consists of the cecum (including the appendix), colon (the longest part), rectum, and anal canal.
Overall, in humans, the large intestine is about 1.5 metres (5 ft) long, which is about one-fifth of the whole length of the human gastrointestinal tract. It then continues as the colon ascending the abdomen, across the width of the abdominal cavity as the transverse colon, and then descending to the rectum and its endpoint at the anal canal. 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. Some other sources exclude the anal canal. The colon is the longest portion of the large intestine, and the terms are often used interchangeably but most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being removed by defecation. The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods.
0 kommentar(er)
