Which of the following is NOT true about ligament of Treitz?

(Refer: Richard S. Snell’s Clinical Anatomy by Regions, 9th edition, pg no: 186)   Ligament of Treitz Is a double fold of peritoneum. Suspends duodenojejunal flexure from the retroperitoneum. It prevents DJ flexure from being dragged down by weight of small intestinal loops. May contain a small slip of muscle, called the suspensory muscle of the duodenum. Contains skeletal muscle fibres in the upper part that run from the left crus of diaphragm to connective tissue a rough the coeliac axis. Smooth muscle fibres in the lower part that run from the coeliac axis to duodenojejunal flexure. Important radiological landmark in the diagnosis of incomplete rotation and malrotation of the small intestine.