There is no line of demarcation between the jejunum and the ileum. However, there are subtle histological differences: The jejunum has less fat inside its mesentery than the ileum. The jejunum is typically of larger diameter than the ileum. The villi of the jejunum look like long, finger-like projections, and are a histologically identifiable structure. While the length of the entire intestinal tract contains lymphoid tissue, only the ileum has abundant Peyer's patches, which are unencapsulated lymphoid nodules that contain large numbers of lymphocytes and immune cells, like microfold cells.
There is no line of demarcation between the jejunum and the ileum However there are subtle histological differences The jejunum has less fat inside its mesentery than the ileum The jejunum is typically of larger diameter than the ileum The villi of the jejunum look like long finger-like projections and are a histologically identifiable structure While the length of the entire intestinal tract contains lymphoid tissue only the ileum has abundant Peyer's patches which are unencapsulated lymphoid nodules that contain large numbers of lymphocytes and immune cells like microfold cells