duodenum /do̅o̅′ədē″nəm, do̅o̅·od″inəm/ pl. duodena, duodenums [L, duodeni, 12 fingers] , the shortest, widest, and most fixed portion of the small intestine, taking an almost circular course from the pyloric valve of the stomach so that its termination is close to its starting point. The majority of digestive enzymes secreted by the pancreas, as well as bile from the gallbladder, are ejected into the duodenum. It is about 25 cm long and is divided into superior, descending, horizontal, and ascending portions. The superior portion extends from the pylorus to the neck of the gallbladder. The descending portion extends from the neck of the gallbladder at the level of the first lumbar vertebra to the cranial border of the fourth lumbar vertebra. The horizontal portion passes from right to left, from the level of the fourth lumbar vertebra to the diaphragm. The ascending portion rises on the left side of the aorta to the level of the second lumbar vertebra, turning ventrally to become the jejunum at the duodenojejunal flexure. Compare jejunum, ileum.
