Editing Jejunum (section)

===Histology===

The jejunum contains very few [[Brunner's glands]] (found in the duodenum) or [[Peyer's patches]] (found in the ileum). However, there are a few jejunal [[lymph node]]s suspended in its mesentery. The jejunum has many large [[circular folds]] in its [[submucosa]] called [[plicae circulares]] that increase the surface area for nutrient absorption. The plicae circulares are best developed in the jejunum.

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 nodule]]s that contain large numbers of [[lymphocyte]]s and immune cells, like [[microfold cell]]s.

<gallery mode="packed">
 Image:Microvilli.jpg|[[Transmission electron microscopy|Transmission electron microscope]] (TEM) image of human jejunum
 Image:Nudemousejejunum EM.jpg|TEM image of mouse jejunum (14,000-fold magnification)
 Image:Dogjejunum100x.jpg|Dog jejunum (magnified 100-fold)
</gallery>