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The Ins and Outs of the Gut!

The Ins and Outs of the Gut!. Winter 2018 Southshore lifelong learning Peter Woodruff and David schurman. The. We need a map!. How your digestive system works - Emma Bryce. What’s Going On? Theme: In c r e a s e Surface Area. digestion

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The Ins and Outs of the Gut!

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  1. The Ins and Outs of the Gut! Winter 2018 Southshore lifelong learning Peter Woodruff and David schurman

  2. The We need a map!

  3. How your digestive system works - Emma Bryce

  4. What’s Going On?Theme: IncreaseSurface Area digestion Increase Surface area of Food SECRETION AND ABSORPTION Increase SURFACE AREA OF GUT WALL

  5. Digestion Mechanical digestion Physical breakdown of food: increases food’s surface area, decreases particle size eg: chewing, action of gut wall Chemical digestion Convert complex, large molecules into smaller bits which can be absorbed through gut wall eg: enzymatic action, pH changes (acid in stomach), “detergent” action of bile acids

  6. Secretion and absorption Daily: 8 liters of fluid secreted into GI tract + almost 2 liters ingested fluid versus 0.1 – 0.2 liters of fluid in feces Therefore gut wall must absorb ~9 liters per day of water and electrolytes.

  7. Digestive system Let’s put it all in place

  8. Digestive system Let’s put it all in place Not to scale, especially the small intestine

  9. Surface Area! SMALL INTESTINE • Without folds: 60 feet/18 meters long (NOT!) • Go for folds: each square inch has 20,000 fingerlike villi (30 per square mm) • Each villus has microvilli (the fingers have fingers!) • Each microvillus has a forest of sugary projections, the glycocalyx

  10. SURFACE AREA again

  11. Spoilsport: recent evidence Surface area of gut lining only 30-40 square meters (Half a badminton court, not the tennis court of textbooks) Mouth-anus length 5 - 7 meters (2/3 small intestine) Inner diameter small intestine: 2.5 cm, large intestine: 4.8 cm 6 m / 20 ft long Small Intestine: Folds expand ~1.6x area; villi + microvilli expand 60-120x 1.5 m / 5 ft long Large Intestine: villi expand ~6.5x area Overall gives ~32 m2(~345 ft2) of which 2 m2 is large intestine Herbert F Helander, Lars Fändriks. 2014

  12. Chewing • https://giphy.com/explore/chewing-cud

  13. swallowing <- Swallowing reflex and peristalsis https://medlineplus.gov/ency/anatomyvideos/000097.htm

  14. Stomach

  15. Stomach • Churning of stomach wall breaks up food • Releases enzymes to digest food, esp. protein by pepsin • Releases acid to denature proteins and kill bacteria • Absorptionof H2O, caffeine, medication (aspirin), alcohol (15%) • Yields Chyme

  16. Small intestine https://blausen.com/en/video/duodenum-jejunum-and-ileum/

  17. DUODENUM • Enzymatic breakdown of food • Production of mucus • Regulation of stomach emptying By Olek Remesz

  18. Liver, gallbladder and pancreas

  19. Digestive functions of liver Over 500 vital functions, too many to list • Produces Bile for emulsifying fats and removing wastes in small intestine • Clears bilirubin and related breakdown products from heme of red blood cells • Further breakdown product, stercobilin, causes brown color of feces [Another breakdown product, urobilin, causes much of straw color in urine]

  20. Pancreas and gALLBLADDER

  21. Functions of Pancreas Buffers stomach acid with bicarbonate Synthesizes and secretes digestive enzymes to digest carbohydrates, proteins, lipids, and nucleic acids synthesizes and secretes glucagon and insulin which cooperate to regulate plasma glucose levels exocrine versus endocrine

  22. Jejunum • Last-minute processing and absorption of nutrients By Olek Remesz

  23. ileum • (jejunum blends into ileum) • absorption of remaining nutrients + Vitamin B12 By Blausen.com staff (2014).

  24. Large intestine • Water absorption • Absorption of remaining nutrients • Absorption of vitamins made by colonic bacteria – vitamin B12 • Compacts and stores feces By Connormah Raster:

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