Small bowel (small intestine)
General
Normal histology

Author: Hanni Gulwani, M.D. (see Authors page)

Revised: 9 February 2018, last major update August 2012

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: Histology[TI] small bowel[TIAB]

Cite this page: Gulwani, H. Normal histology. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/smallbowelnormalhistology.html. Accessed July 18th, 2018.
Definition / general
Layers:
  • Mucosa, submucosa, muscularis propria (externa), subserosa, serosa

Mucosa:
  • Contains villi with central blood vessels, lymphatics
  • Layers are epithelium, lamina propria, muscularis mucosa

Villi:
  • Short and stubby in duodenum, very tall in jejunum, intermediate height in ileum
  • Contain microvilli
  • Villus to crypt length is 3 - 5:1
  • Lined by primarily columnar absorptive cells and goblet cells
  • Usually 1 lymphocyte per 5 enterocytes
  • Villi may be short and distorted next to lymphoid aggregates
  • 4 normal villi in a row in a biopsy suggests normal villous architecture
  • Each villus contains an arteriole with capillary network, veins and a central lymphatic with numerous nerve fibres

Absorptive cells:
  • Have microvilli on luminal surface (brush border) and underlying mat of microfilaments (terminal web)

Microvillus:
  • 1.5 - 2 m in length and 100 nm in diameter
  • PAS positive, actin myosin complexes

Goblet cells:
  • Occur in crypts and surface absorptive cells
  • Decrease towards villus tip, increase in frequency along small intestine (most numerous in lower ileum)
  • Columnar in shape, mucus droplet in supranuclear area, secretes mucus, ions and water

Crypts of Lieberkühn:
  • Lower 20% of epithelium, contain undifferentiated (immature) crypt cells, Paneth cells (have large, apical eosinophilic granules containing antimicrobial proteins), scattered goblet cells and endocrine cells
  • Are surrounded by pericrypt fibroblast sheath
  • Secrete ions, water, IgA, antimicrobial peptides into lumen
  • Crypt cells take 3 - 8 days to migrate to surface
  • Allows for rapid repair but also causes these cells to be sensitive to radiation therapy and chemotherapy

Lamina propria:
  • Contains loose connective tissue, lymphocytes, plasma cells, occasional eosinophils, macrophages, mast cells, neutrophils

Submucosa:
  • Contains connective tissue, blood vessels, lymphatics, submucosal (Meissner) plexus
  • Also Brunner glands in duodenum

Brunner glands:
  • Submucosal mucous glands in duodenum, secrete bicarbonate ions, glycoproteins, pepsinogen II
  • Resemble gastric pylorus mucous glands

Muscularis propria (externa):
  • Inner circular and outer longitudinal layer, with myenteric (Auerbach) plexus between these layers
  • Plexus also contains interstitial cells of Cajal (Am J Surg Pathol 2003;27:228), ganglion cells, fibroblasts

Serosa:
  • Contains mesothelial lining, loose connective tissue

Endocrine cells:
  • Similar to cells in pancreas, biliary tree, lung, thyroid, urethra
  • Contain fine eosinophilic granules with secretory proteins
  • Nuclei on luminal side of granules, not basal
Microscopic (histologic) images

Images hosted on other servers:

Brunner glands

Crypts of Lieberkühn

Enterocyte

Serosa

Jejunum


Villi

Duodenum