Cranial part

The cranial part of duodenum (Pars cranialis duodeni) is relatively short. From the pylorus, it goes to the right, more or less caudally and dorsally depending on the species, and ends at the cranial duodenal flexure (Flexura duodeni cranialis). In many species, just after the pylorus, it presents a more or less distinct dilation: the duodenal ampulla (Ampulla duodeni) or duodenal bulb. Well defined in the Horse, voluminous in Camels, this ampulla is less pronounced or absent in other domestic mammals.

In most herbivores, the cranial part of the duodenum is longer in proportion than in carnivores and shows a sigmoid ansa (sigmoid inflection; Ansa sigmoidea) near the right liver lobe, particularly prominent in ruminants, barely visible in equids and pigs. This is the part where the bile duct (from the liver) and the pancreatic duct(s) open. However, embryological development differences mean that in some species, the pancreas has only one duct, which opens instead into the descending part (Cattle, Pig), or even at the beginning of the ascending part (Rabbit) of the duodenum.