duodenum

https://doi.org/10.1351/goldbook.10620

First portion of the small intestine, between the stomach and the jejunum, where bile and pancreatic digestive juices enter the intestinal tract.

Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 745 [Terms] [Paper]