The jejunum is located on the left side and ileum in lower abdomen, to be continued by colon in the ileo-cecal region. This must be shown in any series of the small intestine.
There is no definite border between jejunum and ileum, but the most of the small bowel consists of ileum.
The mucosa of the small bowel is characterized by the connivent valves (also called Kerkrin or circular valves). These start from the second part of the duodenum, which has the largest number of them, decreasing in number as the small bowel approaches the ileocecal valve.