Final answer:
The mesenteries are the double sheets of peritoneal membrane that suspend the visceral organs and provide them with necessary nerves and blood vessels.
Step-by-step explanation:
The mesenteries are double sheets of peritoneal membrane that suspend the visceral organs and carry nerves, lymphatics, and blood vessels. The visceral peritoneum includes these folds that envelope various abdominal organs, securing them to the body wall and ensuring that they are well-supplied with the necessary nerves and vessels for proper function. The serosa, also associated with the gastrointestinal tract, is a different structure that represents the outermost layer of the GI organs and is made up of connective tissue that separates these organs from surrounding cavities.