There is a thin layer of tissue that protects and repairs damage to the intestines. What is it called?

This layer of either muscle or tissue lies atop the large and small intestine underneath the skin. If any damage occurs to the colon, this material latches onto the injured area and repairs it. If the stomach sustains a blow, this membrane can also detatch from its normal position and get caught around part of the small intestine. I cannot remember what it's called.