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Digestive glands

Digestive glands. General outline. small digestive glands. distributed in the wall of digestive tract esophageal glands, gastric glands and intestine glands. large digestive glands. outside the wall of digestive tract salivary glands, liver and pancreas. Large salivary glands.

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Digestive glands

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  1. Digestive glands

  2. General outline • small digestive glands • distributed in the wall of digestive tract • esophageal glands, gastric glands and • intestine glands • large digestive glands • outside the wall of digestive tract • salivary glands, liver and pancreas

  3. Large salivary glands • Include parotid, submandibular and sublingual glands • are compound tubuloacinar glands • are composed of acini and ducts

  4. Acinus : • acinar epithelium: simple cuboidal or pyramidal cells • myoepithelial cell • basal membrane Structure: Serous acini Mucous acini Mixedacini Be divided into

  5. Serous acini • cytoplasma are deep stained • nucleus are spherical in shape and near the base • secretion is thin, contains salivary amylase and a little mucus

  6. Serous acini and striated duct

  7. Mucous acini • cytoplasma are light-blue stained • nucleus are flattened ovoid shaped and close to the base • secretion is thick; contains mucoprotein

  8. Mucous acini

  9. Mixedacini • consist of above two kinds of cells • demilunes: several serous cells are attached eccentrically to the mucous acini

  10. Mixed acini

  11. Ducts: • Intercalated ducts diameter: thinnest wall: simple low cuboidal epithelium

  12. Striated duct (secretory duct) • wall: simple columnar epithelium; the nucleus is near the cell apex; cytoplasm is acidpphilic; has basal striations • EM: the basal striations created by membrane infolding and mitochondia • reabsorbing sodium and excreting potassium; transport water and ions

  13. Intercalated ducts and striated ducts

  14. Interlobular duct Wall: pseudostratified epithelium • Main duct Near its orifice become stratified squamous epithelium

  15. Parotid gland • pure serous gland • longer intercalated duct • secrete 25% of saliva, more salivary amylase, less mucus

  16. Parotid gland

  17. Submandibular gland • mixed gland. Serous acini are more than mixed or mucous acini • short intercalated duct, longer striated duct • secrete 70% of saliva, less salivary amylase, more mucus

  18. Submandibular gland

  19. Sublingual gland • mixed gland, mucous and mixed acini predominant, more demilune • without intercalated duct, obscure striated duct • secrete 5% of saliva, most mucus

  20. Sublingual gland

  21. Pancreas Exocrine portion: • the features of the acini • a single layer of pyramidal serous cells surrounded by basal lamina, without myoepithelial cells • centro-acinar cells: the epithelial cells of intercalated duct penetrating into the lumen of the acinus

  22. the feature of ducts • the intercalated duct is long and has branches • no striated duct • main duct: lined by simple columnar epithelium in which a few goblet cells and endocrine cells can be seen

  23. The functions of exocrine portion Secret abundant trypsinogen, chymotrypsinogen, amylase, lipase, sodium bicarbonate and trypsin inhibitor

  24. Pancreas

  25. Pancreas ( show centro-acinar cells and intercalated ducts)

  26. Endocrine portion (pancreatic islet): • rounded clusters of cells embedded within exocrine pancreatic tissue • are divided into three kinds of cells: A, B, and D cells • fenestrated capillaries are among the cells

  27. Pancreas (show pancreatic islet)

  28. Endocrine portion PP cells: pancreatic polypeptide G cells: gastrin Other cells

  29. A cells B cells D cells

  30. Liver Hepatic plates Sinusoid Central vein Liver lobule Interlobular arteries Interlobular veins Interlobular bile ducts Portal area

  31. Functions of liver: • bile secretion • synthesize: protein, glycogen, cholesterin • detoxification and inactivation • defence • hemopoiesis

  32. Human liver Pork liver

  33. Liver lobule: • hepatic plates: are composed of a single layer of hepatocytes arranged in radial • sinusoid: situated between the hepatic plates, forming a complex network • central vein: occupies the centre of the liver lobule

  34. Liver lobule

  35. Hepatic plates

  36. Hepatic cords and liver sinusoids

  37. Hepatocytes • polyhedral in shape, eosinophilic cytoplasm, one or two large rounded nuclei with one or 2 typical nucleoli • EM: Mi, RER, SER, Golgi apparatus, lysosomes, microbodies, inclusions

  38. Mitochondria provide the energy for the hepatocytes • Rough endoplasmic reticulum synthesize some plasma proteins • Golgi apparatus participate in the formation of bile and lipoprotein

  39. Smooth endoplasmic reticulum • synthesize bile, triglyceride and LDL • metabolism of the lipid, hormones and cholerythrin • inactivate steroid hormone • biotransformation of some materials • detoxification of noxious substances

  40. Lysosomes • actively participate the metabolism of hepatocyte and renewal of organelles • play a role in metabolism and transport of cholerythrin • storage of iron

  41. Microbodies detoxification: catalase and peroxidase; reduce the hydrogen peroxide into H2O • Inclusions include glycogen, lipid droplets, pigment etc; These contents vary according to physiologic state of human body

  42. Bile canaliculi • between two adjacent hepatocytes • the membrane of hepatocyte projects to the lumen, forming many microvilli • the cell membranes near the bile canaliculi are firmly bound by junctional complexes

  43. Bile canaliculi

  44. Liver sinusoid • spaces between the hepatic plates • irregular in shape • composed of only one discontinuous layer of fenestrated endothelial cells, no diaphragm, no basement membrane • Kupffer cells are located within the sinusoid cavities

  45. Kuffer cells in liver sinusoid

  46. Liver sinusoid and space of Disse

  47. Space of Disse • separates the endothelium from the hepatocytes • contains some reticular fibers and fat-storing cells

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