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  1. 1. 1The Digestive System
  2. 2. 2Digestion• Processing of food• Types– Mechanical (physical)• Chew• Tear• Grind• Mash• Mix– Chemical• Catabolic reactions• Enzymatic hydrolysis– Carbohydrate– Protein– Lipid
  3. 3. 3Digestion• Phases– Ingestion– Movement– Digestion– Absorption– Further digestion
  4. 4. 4Digestive System Organization• Gastrointestinal (Gl) tract (Alimentary canal)– Tube within a tube– Direct link/path between organs– Structures• Mouth• Oral Cavity• Pharynx• Esophagus• Stomach• Duedenum• Jejenum• kIleum• Cecum• Ascending colon• Transverse colon
  5. 5. 5Digestive System Organization• Descending colon• Sigmoid colon• Rectum• Anus• Accessory structures– Not in tube path– Organs• Teeth• Tongue• Salivary glands• Liver• Gall bladder• Pancreas
  6. 6. 6Anatomy of the Mouth andThroat
  7. 7. 7Human Deciduous andPermanent Teeth
  8. 8. 8Dorsal Surface of the Tongue
  9. 9. 9The Major Salivary Glands
  10. 10. 10Deglutition (swallowing)• Sequence– Voluntary stage• Push food to back ofmouth– Pharyngeal stage• Raise– Soft palate– Larynx + hyoid– Tongue to soft palate– Esophageal stage• Contract pharyngealmuscles• Open esophagus• Start peristalsis
  11. 11. 11Deglutition (swallowing)• Control– Nerves• Glossopharyngeal• Vagus• Accessory– Brain stem• Deglutition center– Medulla oblongata– Pons– Disorders• Dysphagia• Aphagia
  12. 12. 12Esophagus• Usually collapsed (closed)• 3 constrictions– Aortic arch– Left primary bronchus– Diaphragm• Surrounded by– SNS plexus– Blood vessels• Functions– Secrete mucous– Transport food
  13. 13. 13Peristalsis and Segmentation
  14. 14. 14Esophagus• Sphincters– Upper– Lower• Abnormalities– Achalasia– Atresia– Hernia– Barret’s esophagus– Esophageal varices
  15. 15. 15Stomach• Usually “J” shaped• Left side, anterior to the spleen• Mucous membrane– G cells – make gastrin– Goblet cells – make mucous– Gastric pit – Oxyntic gland – Parietal cells – MakeHCl– Chief cells – Zymogenic cells• Pepsin• Gastric lipase
  16. 16. 16Anatomy of the Stomach
  17. 17. 17Stomach• 3 muscle layers– Oblique– Circular– Longitudinal• Regions– Cardiac sphincter– Fundus– Antrum (pylorus)– Pyloric sphincter• Vascular• Inner surface thrown intofolds – Rugae• Contains enzymes that workbest at pH 1-2
  18. 18. 18Stomach• Functions– Mix food– Reservoir– Start digestion of• Protein• Nucleic acids• Fats– Activates some enzymes– Destroy some bacteria– Makes intrinsic factor – B12 absorption– Destroys some bacteria– Absorbs• Alcohol• Water• Lipophilic acid• B 12
  19. 19. 19Small Intestine• Extends from pyloricsphincter  ileocecalvalve• Regions– Duodenum– Jejenum– Ileum• Movements– Segmentation– Peristalsis
  20. 20. 20Small Intestine• Histology– Intestinal glands – Intestinal enzymes– Duodenal glands – Alkaline mucous– Paneth cells – Lysozyme– Microvilli– Lacteals– Plica circularis– Smooth muscle– Lymphatic tissue – GALT– Vascular
  21. 21. 21Small Intestine• Absorbs– 80% ingested water– Electrolytes– Vitamins– Minerals– Carbonates• Active/facilitatedtransport• Monosaccharides– Proteins• Di-/tripeptides• Amino acids– Lipids• Monoglycerides• Fatty acids• Micelles• Chylomicrons
  22. 22. 22Structure of the Villi in theSmall Intestine
  23. 23. 23Small Intestine• Secretes digestiveenzymes– Peptidases• Amino-• Di-• Tri-– Sucrases– Maltase– Lactase– Saccharidases• Di-• Tri-– Lipase– Nucleases
  24. 24. 24Small Intestine• Control• Requires pancreaticenzymes & bile tocomplete digestion
  25. 25. 25Large Intestine• Extends from ileocecal valve to anus• Regions– Cecum – Appendix– Colon• Ascending• Transverse• Descending– Rectum– Anal canal
  26. 26. 26Anatomy of the Large Intestine
  27. 27. 27Large Intestine• Histology– No villi– No permanent circular folds– Smooth muscle• Taeniae coli• Haustra– Epiploic appendages– Otherwise like rest of Gl tract
  28. 28. 28Large Intestine• Functions– Mechanical digestion• Haustral churning• Peristalsis• Reflexes– Gastroileal– Gastrocolic– Chemical digestion –Bacterial digestion• Ferment carbohydrates• Protein/amino acidbreakdown– Absorbs•More water•Vitamins– B– K– Concentrate/eliminatewastes
  29. 29. 29Feces Formation and Defecation• Chyme dehydrated toform feces• Feces composition– Water– Inorganic salts– Epithelial cells– Bacteria– Byproducts of digestion• Defecation– Peristalsis pushes fecesinto rectum– Rectal walls stretch• Control– Parasympathetic– Voluntary
  30. 30. 30Liver• Location– R. Hypochondrium– Epigastric region• 4 Lobes– Left– Quadrate– Caudate– Right• Each lobe has lobules – Contains hepatocytes –Surround sinusoids – Feed into central vein
  31. 31. 31Liver• Functions– Makes bile• Detergent – emulsifiesfats• Release promoted by:– Vagus n.– CCK– Secretin• Contains– Water– Bile salts– Bile pigments– Electrolytes– Cholesterol– Lecithin
  32. 32. 32Liver– Detoxifies/removes• Drugs• Alcohol– Stores• Gycolgen• Vitamins (A, D, E, K)• Fe and other minerals• Cholesterol– Activates vitamin D– Fetal RBC production– Phagocytosis– Metabolizes absorbed foodmolecules• Carbohydrates• Proteins• Lipids
  33. 33. 33Liver• Dual blood supply– Hepatic portal vein• Direct input from smallintestine– Hepatic artery/vein• Direct links to heart
  34. 34. 34The Duodenum and RelatedOrgans
  35. 35. 35The Organs and Positions in theAbdominal Cavity
  36. 36. 36Structures of the AlimentaryCanal
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