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DIGESTION

DIGESTION. ABSORPTION. GI TRACT. ANATOMY OF GI TRACT. MOUTH. Chewing  surface area of food Mixes fluid (saliva) in with food Taste Ease of swallowing CHO digestion (amylase) NO digestion of fibers and sugars Epiglottis  prevents choking cartilage in throat to close off

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DIGESTION

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  1. DIGESTION ABSORPTION

  2. GI TRACT

  3. ANATOMY OF GI TRACT

  4. MOUTH • Chewing  surface area of food • Mixes fluid (saliva) in with food • Taste • Ease of swallowing • CHO digestion (amylase) NO digestion of fibers and sugars • Epiglottis prevents choking cartilage in throat to close off windpipe

  5. NORMAL SWALLOW STAGES • ORAL PHASE- food bolus moves to back of mouth (voluntary) • PHARYNGEAL PHASE – triggering of the swallow (reflexive stage) • ESOPHAGEAL PHASE – actual swallow (reflexive)

  6. DYSPHAGIA - SYMPTOMS • ORAL PHASE drooling pocketing facial droop inadequately chewed foods food falling out of the mouth excessive tongue movement

  7. DYSPHAGIA CONT’D • PHARYNGEAL PHASE “Gurgling” voice food getting stuck nasal regurgitation delayed swallowing reflex coughing while eating or drinking

  8. TEST OF SALIVARY SECRETIONS

  9. GI TRACT • BOLUS – mouthful of swallowed food • PERISTALSIS – powerful rhythmic waves propels food along circular and longitudinal muscles speed varies

  10. PERISTALISIS

  11. ESOPHAGUS TO STOMACH • Esophagus  diaphragm • Cardiac sphincter – 1 way valve between esophagus and stomach • Stomach • CHO digestion stops in the stomach • Saliva – is a protein and is digested • Problems: Hiatal hernia GERD Heartburn – acidic stomach contents into esophagus

  12. HERNIA

  13. GERD

  14. STOMACH • Muscular, elastic, saclike, thickest walls, strongest muscles in GI tract • Parietal cells on wall release Gastrin • Gastrin stimulates release of HCl (1.5-1.7 pH) • HCl denatures protein • HCl activates pepsinogen (enzyme)  pepsin • Pepsin  large proteins smaller amino acids • Digestion of protein – little else

  15. STOMACH • Churning circular longitudinal diagonal • Food mixed with water ~ 2 liters per day • Chyme (“kime”) – very acidic semiliquid mass of partly digested food and fluid • Stomach protected by mucus membrane-from goblet cells

  16. STOMACH

  17. pH VALUES

  18. STOMACH SURGERY

  19. PYLORIC SPHINCTER • Circular muscle-1 way valve • Opens 3 times/minute • Waits to re-open until chyme neutralized • Chyme released in small squirts • Neutralized by bicarbonate from pancreas

  20. SMALL INTESTINE • Three segments Duodenum Jejunum Ileum • Digestion completed for CHO, PRO, Fat • Pancreatic enzymes-specific to need proteases, lipases, carbohydrases • Intestinal enzymes • Bile (emulsifier)-livergallbladder

  21. SMALL INTESTINE - ABSORPTION • Microvilli- fingerlike projections • Crypts – secrete digestive enzymes • Specific areas for absorption of specific nutrients- absorption of most nutrients • Absorbed into lymph or blood • BLOOD – liver via portal vein • LYMPH – bloodstream via thoracic duct and subclavian vein

  22. SMALL INTESTINAL VILLI

  23. ABSORPTION OF NUTRIENTS • Diffusion – freely crosses cell membrane • Facilitated diffusion – specific carriers required but no energy • Active transport – requires carriers and energy

  24. ILEOCECAL VALVE • One way valve between small and large intestine

  25. ABSORPTION SITES

  26. LARGE INTESTINE • Colon – three segments • Ascending colon • Transverse colon • Descending colon • Normal bacterial action Fiber  kcals Vitamin K + others? • Absorption water and some minerals

  27. LARGE INTESTINE FUNCTION • Food in large intestine 20-36 hours • Water reabsorbed – if not diarrhea • Home for bacteria • Feces formed here • Few minerals absorbed

  28. STOMAS

  29. CROSS-SECTION

  30. THE END • Rectum – semisolid waste (feces) • Defecation – elimination of waste from body – “moving of bowels” • Anus – terminal sphincter, opens to outside of body – YOU control this valve

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