Editing Mesentery (section)

====Dorsal mesentery====
[[File:Gray1038 vector.svg|240px|thumb|left|Mesentery in red. Dorsal mesentery is the lower part of the circuit. The upper part is ventral mesentery.]]
[[File: Gray985.png |thumb|Abdominal part of digestive tube and its attachment to the primitive or common mesentery. Human embryo of six weeks.]]
[[File: Gray989.png |thumb|Schematic figure of the bursa omentalis, etc. Human embryo of eight weeks.]]
The [[primitive gut]] is suspended from the posterior abdominal wall by the '''dorsal mesentery'''. The gastrointestinal tract and associated dorsal mesentery are subdivided into [[foregut]], [[midgut]], and [[hindgut]] regions based on the respective blood supply. The foregut is supplied by the [[celiac trunk]], the midgut is supplied by the [[superior mesenteric artery]] (SMA), and the hindgut is supplied by the [[inferior mesenteric artery]] (IMA). This division is established by the fourth week of [[human embryogenesis|development]]. After this, the midgut undergoes a period of rapid elongation, forcing it to herniate through the [[navel]]. During herniation, the midgut [[intestinal rotation|rotates]] 90° anti-clockwise around the axis of the SMA and forms the midgut loop. The cranial portion of the loop moves to the right and the caudal portion of the loop moves toward the left. This [[intestinal rotation|rotation]] occurs at about the eighth week of development. The [[cranium|cranial]] portion of the loop will develop into the jejunum and most of the ileum, while the [[caudal (anatomical term)|caudal]] part of the loop eventually forms the terminal portion of the ileum, the [[ascending colon]] and the initial two-thirds of the transverse colon. As the foetus grows larger, the mid-gut loop is drawn back through the umbilicus and undergoes a further 180° rotation, completing a total of 270° rotation. At this point, about 10 weeks, the [[caecum]] lies close to the [[liver]]. From here it moves in a cranial to caudal direction to eventually lie in the lower right portion of the abdominal cavity. This process brings the ascending colon to lie vertically in the lateral right portion of the abdominal cavity apposed to the posterior abdominal wall. The descending colon occupies a similar position on the left side.<ref>{{cite journal |first1=Harold |last1=Ellis |first2=Vishy |last2=Mahadevan |date=April 2014 |title=Anatomy of the caecum, appendix and colon |journal=Surgery |volume=32 |issue=4 |pages=155–8 |doi=10.1016/j.mpsur.2014.02.001}}</ref><ref name=":7">Mitchell B, Sharma R. Embryology: An Illustrated Colour Text, 2e. Churchill Livingstone; 2 edition (June 22, 2009). {{ISBN|978-0702032257}}.{{page needed|date=July 2014}}</ref>

During these topographic changes, the dorsal mesentery undergoes corresponding changes. Most anatomical and embryological textbooks say that after adopting a final position, the ascending and descending mesocolons disappear during embryogenesis. ''Embryology—An Illustrated Colour Text'', "most of the mid-gut retains the original dorsal mesentery, though parts of the duodenum derived from the mid-gut do not. The mesentery associated with the ascending colon and descending colon is resorbed, bringing these parts of the colon into close contact with the body wall."<ref name=":7" /> In ''The Developing Human'', the author states, "the mesentery of the ascending colon fuses with the parietal peritoneum on this wall and disappears; consequently the ascending colon also becomes retroperitoneal".<ref name=":8">Moore KL, TPersaud TVN, Torchia MG. The Developing Human: Clinically Oriented Embryology with Student Consult Online Assess, 9th Edition. Saunders; {{ISBN|978-1437720020}}{{page needed|date=July 2014}}</ref> To reconcile these differences, several theories of embryologic mesenteric development—including the "regression" and "sliding" theories—have been proposed, but none has been widely accepted.<ref name=":7" /><ref name=":8" />

The portion of the '''dorsal mesentery''' that attaches to the [[greater curvature]] of the [[stomach]], is known as the '''dorsal mesogastrium'''. The part of the dorsal mesentery that suspends the [[large intestine|colon]] is termed the [[mesocolon]]. The dorsal mesogastrium develops into the [[greater omentum]].