Duodena, also known as the duodenum, is a part of the small intestine. It is responsible for the initial breakdown of food after it leaves the stomach and before it enters the rest of the small intestine. There are a few synonyms for duodena, which can be useful in medical terminology and text. Some of the synonyms include the first part of the small intestine, the first portion of the jejunum, and the upper intestinal tract. Other often-used phrases include the upper digestive tract and upper gastrointestinal tract. While all of these refer to slightly different areas, they are often used interchangeably in medical literature.