During fetal development, the mesentery of the duodenum, ascending colon, and descending colon becomes fixed to the posterior peritoneum.These segments of the bowel become retroperitoneal.

• 在胎儿发育阶段，十二指肠、升结肠和降结肠的肠系膜固定于腹腔的后壁，这些肠管位于腹膜后。