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Lecture DIGESTIVE SYSTEM part 2

Lecture DIGESTIVE SYSTEM part 2. INTESTINE LIVER PANCREAS. Department of histology, cytology and embryology KhNMU. Small intestine. Functions: digestion – liver, pancreas, enterocytes absorption – enterocytes STRUCTURE: 4 membranes. Intestinal lining:.

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Lecture DIGESTIVE SYSTEM part 2

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  1. LectureDIGESTIVE SYSTEM part 2 INTESTINE LIVER PANCREAS Department of histology, cytology and embryology KhNMU

  2. Small intestine • Functions: • digestion – liver, pancreas, enterocytes • absorption – enterocytes • STRUCTURE: 4 membranes

  3. Intestinal lining: 1) plicae circularis: mucosa + submucosa 2) villi -consist of: epithelium, lamina propria, mm 3) crypts: invaginations of epithelium in the lamina propria simple columnar epithelium: absorptive enterocytes, goblet, endocrine, Paneth cells and stem cells fenestrated capillaries and central lacteal

  4. Duodenum Ileum lacteal Villus serosa

  5. a Epithelium(villus) bb • high mag. 1). Enterocytes = Columnar absorptive cells (a) have microvilli =brush border (bb) for absorption of digested food. Membrane and luminal digestion 2). Mucus-secreting goblet cells (gc) produce a protective mucus. Lymphocytes and plasma cells (L) are numerous in the lamina propria of the villus. gc L

  6. Epithelium (crypt) • high mag At the bottom of intestinal glands (crypts) are 3). the granule-containing Paneth cells (p). Lysozyme. Goblet (g) and absorptive (a) cells. p g a

  7. 3. Paneth cells, 4. enteroendocrine cells (CCK, secretin, GIP), 5.undifferentiated cells=stem, at the bottom of crypt 4 5 3

  8. ivs Villus,lacteal lp l v sm The lamina propria (lp)contains blood-filledcapillariesc, and lacteal –lymphatic capillaryl, smooth muscle cells (sm),(krok – villus shortens); GALT ivs c gc GALT low

  9. v Duodenum low • Mm – 2 layers of sm.m. • Submucosa is usual. Only in the duodenum it is filled with Brunner’s mucous glands (bg), around which - 2 layers of smooth muscle of the muscularis externa (me)surrounded by the serosa(s). m lp ig v mm sm v m me sm med s bg

  10. Duodenum c villi • low & med mag. Ducts (d) from Brunner’s glands (Bg) (s) pass through the muscularis mucosa (mm) to empty their alkaline mucus in or between the crypts (c). d intestinal glands mm mm Bg low s med

  11. Duodenum m Brunner’s glands • nerve supply- submucosal (s) and myenteric (m) nerve plexuses. high s med crypts submucosa muscularis externa muscul. mucosa high

  12. Jejunum v a ig • low & med. mag. The jejunum is like the duodenum & ileum but has no submucosal glands and Peyer’s patches. Contains bigger amount of goblet cells g ig P med low

  13. Ileum cr. v muscul. mucosa • low & med. mag. The major distinguishing feature is the aggregated lymphatic nodules (ln) called Peyer’s patchesin the mucosa or submucosa v sm sm ln med low ln

  14. Duodenum Ileum lacteal Villus COMPARE !

  15. Large intestine (bowel) - general • Reabsorption of water, electrolytes, cellulous • Elimination of wastes • Inner lining - permanent internalfoldsof its mucosa & submucosa called plicae circulares and crypts. • Its mucosa lacks of villi. • The submucosa is usual • Circular & longitudinal smooth muscle form the muscularis externa. The inner circular layer is uniform but the outer longitudinal layer has 3 thicker bands, the taenia coli. • where the colon faces the abdominal cavity there is a serosa.

  16. Taenia coli

  17. cr Colon • low & med mag. Plicae circulares (pc) . Unlike the small intestine there are no mucosal villi. There are straight intestinal glands – crypts (cr) composed mainly of 1. Goblet cells – the most numerous . 2. Columnar absorptive cells 3. Enteroendocrine cells 4. Undifferentiated cells muscularis mucosa pc med submucosa low musc. ext.

  18. High.Magn.

  19. Large intestineCOMPARE ! • Appendix

  20. ss g Anal canal L • low & high mag. Anal columns Brunched tubular glands (g) Stratified squmous epithelium (ss) v ig mm v a v low gc high

  21. Liver & Gall Bladder Liver has specific location – on the way of absorbed material, that is why has very original vasculature and functions

  22. Functions: • Bile synthesis and secretion (emulsification) • Excretion of bilirubin • Protein synthesis • Gluconeogenesis • Storage • Detoxification • Protective • Hemopoietic organ • Endocrine

  23. Liver has lobulated structure

  24. Liver lobule is hexagonal in shape ① at its center - central vein ② hepatic plates（cords of cells - hepatocytes）locate radially ③ hepatic sinusoids locate between plates

  25. Liver lobule

  26. Connective tissue poor develops Central veins (cv) drainto a sublobular vein (sv). The portal triads (pt) locate at lobule coners. cv sv pt

  27. Hepatic plate(cord)is one or two cells thick • Inside the plate between cells the bile canaliculi locate Bile canaliculus hepatocyte sinusoid Kupffer cell The bile canaliculus wall is made up of hepatocytes

  28. Hepatocytes： Polyhedral 6 surfaces Vascular and bile surfaces a. RER b. SER c. Golgi complex d. Mitochondria e. Inclusions • Jaundice • ①High regeneration

  29. EM of Liver • Liver • Two hepatocytes (h) are seen. • The bile canaliculus form a network that eventually empty into bile duct at the periphery of the lobule. • Ultimately ducts will empty into the gall bladder. h h b

  30. Hepatic sinusoid Lined by endothelium Hepatic macrophages (Kupffer cell) • Space of Disse • sinusoid • Kupffer cell

  31. e d • high mag. Liver had been injected with carbon particles Kupffer cells containing carbon (red arrows) Sinusoids (s) A flattened endothelial cell (e) Space of Disse (d) between it and the hepatocytes s

  32. Adipose cells storage vit. A

  33. Blood circulation of the liver • Hepatic artery interlobular artery • Portal vein interlobular vein • hepatic sinusoid • central vein • cv • sublobular vein • hepatic vein • The way of bile draining s d cv v a

  34. At the lobule coners the portal triads are found:

  35. cv • Liver, injected with red gelatin to demonstrate the abundant vasculature. central vein (cv), the portal triad (pt) hepatic sinusoids (hs). hs pt

  36. Liver lobules – 3 types

  37. Gall bladder

  38. Pancreas. Mixed gland • Functions: • Exocrine • Trypsinogen, pepsinogen, peptidase • Amylase • Lipase • Deoxyribonuclease, ribonuclease • Endocrine

  39. Pancreas – compound acinar serous gland low lobule • Exocrine – 98-99% • Endocrine – 1-2% • Capsule • Septa • Lobules • Interlobular duct • Serous secretory units lobule id med

  40. Septa (c.t.) • Lobules • Interlobular duct • Serous secretory units

  41. Pancreas. Exocrine secretory units • Zymogen granules • Intercalated duct is intercalated into the s.unit = centroacinar cells

  42. Exocrine part Structural features of the acinus: ① Purely serous. ② the presence of centroacinar cells in the center of the acinus Intercalated duct Serous cells Centroacinar cells

  43. Pancreas. Endocrine • Islets of Langerhans, - low & med. mag. Scattered among exocrine secretory units spherical collections of light-staining cords of endocrine cells . low, H&E med, trichrome

  44. Pancreas. Endocrine • islets of Langerhans: • 1. B cell • 2. A cell • 3. D cell • 4. minor cells: PP, D1, EC,

  45. Islets of Langerhans • B - insulin blood glucose 70% • A – glucagon blood glucose 15-20% • D – somatostatin insulin 5-10% glucagon • PP – PP, • D1 – VIP, • EC – secretin, motilin

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