Ileum

This cross section through the ileum shows less dramatic plicae circularis compared to the jejunum. The villi remain quite prominent, but are shorter than those in the previous portions of the tract. The submucosal layer contains Peyer's patches, diffuse lymphoid tissue that play an important immunological role in sampling the contents of the tract. Peyer's patches are unique to the ileum. The muscularis externa is visible most externally.