The membrane that holds the coils of the small intestine together is called the mesentery.
The mesentery is a fold of tissue that attaches the intestines to the abdominal wall and supports the small intestine by anchoring it in place. This structure not only provides support but also contains blood vessels, nerves, and lymphatics that supply the intestines. The mesentery is crucial for the overall organization and function of the digestive system, ensuring that the small intestine maintains its position while allowing for the movements necessary for digestion and nutrient absorption.