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Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
Gut 2
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Gut 2

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  • 1. Histology of Intestine Assoc. Prof. Dr. Karim Al-Jashamy IMS/MSU 2010
  • 2. Small Intestine • The small intestine is the site of terminal food digestion, nutrient absorption, and endocrine secretion. • The processes of digestion are completed in the small intestine, where the nutrients (products of digestion) are absorbed by cells of the epithelial lining. • The small intestine is relatively long— approximately 5 m—and consists of three segments: the duodenum, jejunum, and ileum. These segments have many characteristics
  • 3. SMALL INTESTINE • Plicae circularis • Villus • Enterocyte • Brush border (microvilli) • Crypts of Lieberkuhn • Brunner glands (Duodenum) • Peyer’s patches
  • 4. DUODENUM
  • 5. Subdivisions of the Small Intestine  Duodenum  Attached to the stomach  Curves around the head of the pancreas  Jejunum  Attaches anteriorly to the duodenum  Ileum  Extends from jejunum to large intestine Chemical Digestion in the Small Intestine  Source of enzymes that are mixed with chyme  Intestinal cells  Pancreas  Bile enters from the gall bladder Slide 14.22
  • 6. The Small Intestine • Plays key role in digestion and absorption of nutrients • 90% of nutrient absorption occurs in the small intestine The Duodenum  The segment of small intestine closest to stomach  25 cm (10 in.) long  ―Mixing bowl‖ that receives: • chyme from stomach (Mixture of secretions and food in the stomach) • digestive secretions from pancreas and liver • To neutralize acids before they can damage the absorptive surfaces of the small intestine
  • 7. Chemical Digestion in the Small Intestine Slide 14.23b
  • 8. Duodenum Histology
  • 9. Intestinal Villi • A series of fingerlike projections: – in mucosa of small intestine • Covered by simple columnar epithelium: – covered with microvilli • Intestinal Glands • Goblet cells between columnar epithelial cells • Eject mucins onto intestinal surfaces
  • 10. Duodenum - H&E • In the epithelium lining, the villi and crypts of the duodenum, and note the absence of plicae circulares. • The tall columnar epithelium composed of enterocytes, goblet cells and endocrine cells throughout the remainder of the GIT. • The identify of the lamina propria, muscularis mucosae and the "packages" of glandular tissue (Brunner's glands) in the connective tissue between the muscularis mucosae and muscularis externa
  • 11. • Occasionally can see ducts of Brunner's gland which penetrate the muscularis mucosae and ascend through the lamina propria. • Note that goblet cells are absent from these ducts. • Not be able to identify endocrine cells in the H&E stained sections.
  • 12. The Jejunum • Is the middle segment of small intestine • 2.5 meters (8.2 ft) long • Is the location of most: – chemical digestion – nutrient absorption
  • 13. Segments of the Intestine
  • 14. Jejunum - H&E • identify plicae circulares, muscularis externa and villi. • Next identify surface epithelium (simple columnar with goblet cells), crypts, muscularis mucosae, submucosa and muscularis externa. • Crypts will probably be small, short and narrow. • The connection of the crypt with the lumen of the intestine will not always be visible in the plane of the section. Plicae circulares • Transverse folds in intestinal lining, permanent features
  • 15. •Accumulations of lymphocytes are common in the mucosa of the GIT, and they occur frequently in the small intestine. •These specialized parts of the small intestine are called Peyer's patches
  • 16. The Ileum  The final segment of small intestine  3.5 meters (11.48 ft) long
  • 17. Crypt
  • 18. ENTEROCYTES
  • 19. Small Int Ileum The ileum has proportionally more goblet cells . Its proportion of goblet cells generally increases as one progresses down the GI tract, The ileum also displays an increase in the amount of mucosal lymphoid tissue, which forms conspicuous clusters of lymph nodules, called Peyer's patches. The lymphoid tissue of Peyer's patches may bulge out toward the lumen, displacing villi, and inward across the muscularis mucosae into the submucosa. The epithelium overlying this lymphoid tissue is cuboidal (rather than columnar as on villi). These structures, together with other more diffuse lymphoid tissue, constitute the Gut-Associated Lymphoid Tissues, or GALT. For more on GALT (or, more generally, MALT for Mucosa-Associated Lymphoid Tissues)
  • 20. SI Crypts x20
  • 21. SI Ileum Peyer’s Patch x4
  • 22. The Colon • Mucosa with crypts (glands) • Glands consist of absorptive cells and mucus secreting cells • Muscularis propria is very pronounced • Longitudinal muscle occurs in 3 bands (taeniae coli) rather than completely surrounding tract.
  • 23. Large Intestine: Microscopic Anatomy • Colon mucosa is simple columnar epithelium except in the anal canal • Has numerous deep crypts lined with goblet cells • Anal canal mucosa is stratified squamous epithelium • Anal sinuses exude mucus and compress feces • Superficial venous plexuses are associated with the anal canal • Inflammation of these veins results in itchy varicosities called hemorrhoids
  • 24. Histology of Large Intestine
  • 25. • Colon • Bundles of longitudinal muscle should be clearly visible on the outside of the colon. • Plicae circulares are absent from the luminal side of the colon. • Villi are absent and the crypts appear deeper than the ones you observed in the small intestine. • Goblet cells are numerous. • The lamina propria and muscularis mucosae may be difficult to distinguish. • Note also that a thin layer of longitudinal muscle is found between the taenia coli on the outside of the inner circular muscle layer.
  • 26. • The vermiform appendix • is a small blind-ending diverticulum from the cecum. • The most important features of the appendix is the thickening of its wall, which is mainly due to large accumulations of lymphoid tissue in the lamina propria and submucosa. • Intestinal villi are usually absent, and crypts do not occur as frequently as in the colon. • There is often fatty tissue in the submucosa. • The muscularis externa is thinner than in the remainder of the large intestine and, the outer, longitudinal smooth muscle layer of the muscularis externa does not aggregate into taenia coli.
  • 27. • Ano-rectal junction, human - van Gieson Identify in this or another section which contains a junction of two parts of the alimentary canal • glands are typically not visible in "regular" stomach sections. • Note that the tubules of the glands branch and that they are lined by an almost homogenous population of mucus-producing cells.

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