The suspensory muscle of duodenum (also known as the ligament of Treitz) is a thin muscle connecting the junction between the duodenum and jejunum (the small intestine's first and second parts, respectively), as well as the duodenojejunal flexure to connective tissue surrounding the superior mesenteric and coeliac arteries. The suspensory muscle most often connects to both the third and fourth parts of the duodenum, as well as the duodenojejunal flexure, although the attachment is quite variable. The suspensory muscle marks the formal division between the duodenum and the jejunum. This division is used to mark the difference between the upper and lower gastrointestinal tracts, which is relevant in clinical medicine as it may determine the source of gastrointestinal bleeding. The suspensory muscle is derived from mesoderm and plays a role in the embryological rotation of the gut, by offering a point of fixation for the rotating gut. It is also thought to help digestion by widening the angle of the duodenojejunal flexure. Superior mesenteric artery syndrome is a rare abnormality caused by a congenitally short suspensory muscle. Structure The duodenum and the jejunum are the first and second parts of the small intestine, respectively. The suspensory muscle of the duodenum marks their formal division. The suspensory muscle arises from the right crus of the diaphragm as it passes around the esophagus, continues as connective tissue around the stems of the celiac trunk (celiac artery) and superior mesenteric artery, passes behind the pancreas, and enters the upper part of the mesentery, inserting into the junction between the duodenum and jejunum, the duodenojejunal flexure. Here, the muscles are continuous with the muscular layers of the duodenum. Variation Considerable anatomic variation exists, in terms of length and point of attachment. Despite the classical description, the muscle only solely attaches to the duodenojejunal flexure in about 8% of people; it is far more common, 40 to 60% of the time to attach additionally to the third and fourth parts of the duodenum; and 20 to 30% of the time it only attaches to the third and fourth parts. Moreover, separate multiple attachments are not that uncommon. According to some authors, who use the original description by Treitz, the muscle may be divided into two sections: a ligamentous portion attaching the right crus of diaphragm to the connective tissue surrounding the coeliac artery and superior mesenteric artery; and a lower muscular portion from the connective