Jejunum
The jejunum lies between the duodenum and the ileum and is considered to start at the suspensory muscle of the duodenum, a location called the duodenojejunal flexure. The division between the jejunum and ileum is not anatomically distinct due to the fact that in adult humans, the small intestine is usually 6-7m long, about two-fifths of which (2.5 m) is the jejunum.
Short bowel syndrome
The length of the small intestine can vary greatly, from as short as to as long as . On average it is about . Due to this variation it is recommended that following surgery the amount of bowel remaining be specified rather than the amount removed.