The mesentery is a fold of membranous tissue that arises from the posterior wall of the peritoneal cavity and attaches to the intestinal tract. Within it are the arteries and veins that supply the intestine. The term can be used narrowly to denote just the material that supplies the jejunum and ileum of the small intestine, or broadly to include the right, left and transverse mesocolon, mesoappendix, mesosigmoid and mesorectum.