MH 119 Ileum

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Ileum

The absorptive surface of the small intestine is increased by microvilli, villi and plicae circularis.

(or mucous membrane)
- - tall, slender finger-like projections.
  - (or Enterocytes) - simple columnar cells with microvilli (or brush border) and terminal web.
  - - secrete mucus for lubrication.
- - intestinal glands at the base of villi.
  - - strongly eosinophilic cells in crypts.
  - Stem Cells - all of the intestinal epithelial cells arise from stem cells in crypts.
- - loose connective tissue that supports the epithelium and forms the core of villi.
- - supports the epithelium and villi.
- connective tissue with permanent folds that circle the inner surface of the intestinal lumen to form (circular folds, folds of Kerckring).
- (or submucosal plexus) - provides secretory innervation of goblet cells and motor innervation of the muscularis mucosae. (Difficult to see in this specimen.)
- No submucosal glands (only in the duodenum).
- two orthogonal layers of smooth muscle (inner circular and outer longitudinal).
- (or myenteric plexus) - provides motor innervation of the muscularis externa.
- loose connective tissue.