As the primary i testinal loop herniates into the umbilicus, it also rotates 90 degree counterclockwise (as viewed from in.front) around an axis formed by the superior mesenteric artery. As a result of this rotation, the cranial limb of the midgut loop moves caudally and to the embryo's right and the caudal limbs cranially and to the embryo's left. This rotation is complete by the early eighth week. By this time the jejunum and ileum are thrown into a series of folds called jejunal-ileal loops and from the expanding cecum sprouts a worm-like vermiform appendix.
The midgut loop undergoes an additional 180 degree counterclockwise rotation during re-entry of the intestines into the abdomen (described below).
Thus, the total rotation of the intestinal loop is 270 degrees (90+180 = 270).