Final answer:
The suspensory muscle of the duodenum, or Ligament of Treitz, stabilizes the duodenojejunal angle, which is the junction between the duodenum and the jejunum.
Step-by-step explanation:
The ligament that stabilizes the duodenojejunal angle is known as the suspensory muscle of the duodenum, or Ligament of Treitz. This important anatomical structure is responsible for supporting the juncture where the duodenum ends, and the jejunum begins, anchoring the small intestine to the posterior abdominal wall. This allows for a smoother transition of digested material as it moves from the duodenum to the jejunum.