The embryologic midgut gives rise to the proximal colon, including the cecum, the ascending colon, and the first two thirds of the transverse colon. The rest of the colon and rectum derive from the embryologic hindgut. The colon comes to lie in its final position in the abdominal cavity through a complex series of rotations (Fig. 13.2). Early in development, midgut lengthening results in the formation of a dorsal mesentery that suspends the developing intestine from the posterior abdominal wall. Rapid elongation of the midgut results in formation of the primary intestinal loop, which communicates with the yolk sac via the vitellointestinal duct. Concurrent rapid hepatic growth decreases the space in the abdominal cavity, causing the midgut to herniate into the umbilical coelom during the sixth embryonic week. The cecum becomes recognizable as a small diverticulum of the caudal limb of the midgut at approximately 6 weeks’ gestation. The midgut returns to the abdominal cavity during the third fetal month. The small intestine enters the abdomen first, followed by the cecum. During re-entry, the gut rotates an additional 180 degrees, so that the cecum comes to lie in the right upper quadrant. Later, elongation of this portion of the gut results in cecal descent to the right lower quadrant and formation of the ascending colon. The postsplenic colon is pushed to the left side and lies anterior to the small intestine.