The peritoneum responsible for connecting the jejunum and ileum (parts of the small intestine) to the back wall of the abdomen. Between the two sheets of peritoneum are blood vessels, lymph vessels, and nerves. This allows these parts of the small intestine to move relatively freely within the abdominopelvic cavity. The brain, however, cannot map sensation accurately, so sensation is usually referred to the midline, an example of referred pain[WP]. [ Wikipedia:Mesentery#Mesentery_.28proper.29 ]