anat28.txt

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stephjg
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183278
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anat28.txt
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2012-12-13 19:43:09
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ANAT390 GI System
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ANAT390 Lecture 28 GI System 3
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  1. How do digestive glands develop?
    • They develop from evagination of endodermal tube near the start of the small intestine- around 6th week of embryogenesis.
    • Connections are maintained as ducts that drain all three glands to the small intestines.
  2. What are the three digestive glands?
    • Pancreas
    • Liver
    • Gallbladder
  3. What is the sphincter of Oddi?
    • Sphincter that controls what comes out of the pancreas, liver, and gall bladder into the small intestine
    • Embedded in pancreatic tissue
    • Smooth muscle of muscularis is dominant
  4. Where is the pancreas located?
    Located on the posterior abdominal wall behind stomach and duodenum.
  5. What is the function of the pancreas?
    • Dual exocrine/endocrine gland
    • Endocrine- ductless 'islets' secrete insulin and glucagon
    • Exocrine - Acini secrete digestive enzymes and bicarbonate ions into ducts
  6. What are the two major cell types in the endocrine islets of the pancreas?
    • alpha cells- secrete glucagon which increases the blood glucose level
    • beta cells- secrete insulin which decreases the blood glucose level
  7. Name one important difference between type I and type II diabetes?
    Type I diabetes occurs I is a result of a decrease in functional ß cells which results in a decrease in insulin production; In contrast, in Type II diabetes there is often a decrease in responsiveness of target cells to insulin
  8. How do the endocrine islets appear under LM and EM?
    • LM: appear as pale/chromophobic cells under H&E
    • EM: small secretory vesicles
  9. What are the two main types of cells in the exocrine islets?
    • Acinar cells (zymogenic)- secrete digestive enzymes in their inactive forms (zymogens)
    • Centroacinar cells- secrete bicarbonate ions to prevent the activation of zymogens until they reach the duodenum
  10. How do zymogenic cells appear under LM and EM?
    • Dark/chromophilic with H&E staining (L.M.)
    • Large vesicles (E.M.)
  11. How do centroacinar cells appear under LM and EM?
    • Pale/chromophobic with H&E staining (L.M.)
    • No large secetory vesicles, many tight junctions between cells (E.M.)
  12. What stimulates the activity of exocrine cells in the pancreas?
    • endocrine hormone- Cholecystokinin (CCK)
    • Produced by DNES cells in the small intestines
  13. Which chemical relaxes the sphincter of Oddi?
    CCK
  14. Name four functions of the liver.
    • Bile production (exocrine gland)
    • Plasma protein production (endocrine gland)
    • Detoxification ie. Alcohol dehydrogenase
    • Storage ie. glycogen
    • All these functions are performed by hepatocytes (multiple functions in the same cell)
  15. Which two blood vessels supply the liver?
    • Hepatic Portal Vein: high in nutrients and bilirubin- drains GI tract, spleen, and enters liver
    • Hepatic Artery: high in O2 from abdominal aorta and enters liver
    • These two mix in venous sinusoids
  16. What are the components of the hepatic portal triad?
    • Hepatic portal vein
    • hepatic artery
    • hepatic bile duct- drains liver of exocrine product (bile)
  17. How does blood leave the liver?
    • Blood from branches of the hep. artery and hep. portal vein flow inward via hepatic sinusoids (expanded capillaries), mix, and enter central veins of the hepatic lobule
    • The central veins drain into the inferior vena cava
  18. Describe the important cellular features of a hepatocyte.
    • Prominent euchromatin
    • RER produces plasma proteins
    • SER involved in detox (drugs/bile)
    • Mitochrondria
    • Glycogen granules
  19. What are the secretory domains of a hepatocyte?
    • 1) Biliary domain (apical): empties into Bile Canaliculi, closed by hepatocyte tight juctions, drain to bile ducts
    • Exocrine products include conjugated/water soluble bilirubin, bile salts, and cholesterol
    • 2) Sinusoidal Domain (Basal): empties into sub-sinusoidal 'Space of Disse'
    • Endocrine products include plasma proteins and lipoproteins
    • Hepatocytes can have more than one apical or basal doman because of their particular orientation
  20. What are Kupffer cells?
    macrophages which patrol sinusoids and Space of Disse
  21. What is cirrhosis?
    • Chronic inflammation of the liver
    • Fibrosis= increased CT/collagen and decreased hepatocytes, form nodules on the surface of the liver
    • Fibrosis decreases blood flow through the sinusoids leading to portal vein hypertension- blood backs up in veins that drain the GI tract, can lead to terminal venous swelling ie. esophageal veins and hemorrhoidal veins can burst/hemorrhage
  22. Describe the structure of the gall bladder.
    • Simple columnar epl- highly absorptive to concentrate bile
    • Lamina propria- highly vascular, loose CT
    • Mucosa- highly folded without clearly organized villi or crypts/glands
    • No seperate muscularis mucosa or muscularis externa
    • Prominent muscularis of overlapping smooth muscle fibers- contractions initiate peristaltic waves in response to CCK and autonomic stimulation
    • Adventitia- dense CT
  23. What are gall stones?
    Precipitation of bile (esp. salts and cholesterol) that becomes trapped in the draining cystic duct

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