File:Intestinal rotation and herniation.jpg

English: Diagram showing the normal process by which the intestine "rotates" and herniates during development

Original summary: "Graphical summary of the “en-bloc rotation” and our hierarchical model of gut morphogenesis. Panels a-c show the classic “en-bloc rotation” model of gut morphogenesis. From panel a to b (left-sided views) the midgut loop rotates 90° in a counterclockwise direction, so that its position changes from midsagittal (a) to transverse (b1). The small intestine forms loops (b2) and slides back into the abdomen (b3) during resolution of the hernia. Meanwhile, the cecum moves from the left to the right side, which represents the additional 180° counterclockwise rotation of the intestine (c, ventral view). The present study shows that the gut acquires its definitive shape by the hierarchical development of primary, secondary, and tertiary loops (panels d-f). The descent of the proximal midgut in the still helically shaped body rather than rotation accounts for the change in position of the primary loop from midsagittal (d, left-sided view) to transverse (e1 left-sided view). During the herniation phase, 4 secondary loops develop in a strict spatiotemporal fashion in the small intestine (e2 left-sided view). Tertiary loops develop within the secondary loops (e3) and these domains slide in a proximodistal fashion back into the abdomen, with the distal ileum and appendix last (e4 left-sided view). Just after return, the cecum is found medially, just dorsal to the umbilical opening. Within 4 days the cecum then assumes its right-sided, more caudal and dorsal position (f1 (colon only), f2 (colon and small intestine); ventral views)"

Legend: orange: proximal duodeno-jejunal loop; yellow: distal jejunal loop; green: proximal ileal loop; blue: distal ileal loop