Jejunum

This cross section through the jejunum shows very prominent plicae circulares lined by numerous villi. Plicae circulares are more extensive in the jejunum compared to the duodenum and ileum. Plicae circulares are out foldings of both the mucosa and submucosa. Projecting from these folds are numerous villi that are outfoldings of the mucosa. Note that while the submucosa and mucosa extend into the plicae circulares, the muscularis externa does not.