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  • 1. 1The Digestive System
  • 2. 2Digestion• Processing of food• Types– Mechanical (physical)• Chew• Tear• Grind• Mash• Mix– Chemical• Catabolic reactions• Enzymatic hydrolysis– Carbohydrate– Protein– Lipid
  • 3. 3Digestion• Phases– Ingestion– Movement– Digestion– Absorption– Further digestion
  • 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. 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. 6Anatomy of the Mouth andThroat
  • 7. 7Human Deciduous andPermanent Teeth
  • 8. 8Dorsal Surface of the Tongue
  • 9. 9The Major Salivary Glands
  • 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. 11Deglutition (swallowing)• Control– Nerves• Glossopharyngeal• Vagus• Accessory– Brain stem• Deglutition center– Medulla oblongata– Pons– Disorders• Dysphagia• Aphagia
  • 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. 13Peristalsis and Segmentation
  • 14. 14Esophagus• Sphincters– Upper– Lower• Abnormalities– Achalasia– Atresia– Hernia– Barret’s esophagus– Esophageal varices
  • 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. 16Anatomy of the Stomach
  • 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. 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. 19Small Intestine• Extends from pyloricsphincter  ileocecalvalve• Regions– Duodenum– Jejenum– Ileum• Movements– Segmentation– Peristalsis
  • 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. 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. 22Structure of the Villi in theSmall Intestine
  • 23. 23Small Intestine• Secretes digestiveenzymes– Peptidases• Amino-• Di-• Tri-– Sucrases– Maltase– Lactase– Saccharidases• Di-• Tri-– Lipase– Nucleases
  • 24. 24Small Intestine• Control• Requires pancreaticenzymes & bile tocomplete digestion
  • 25. 25Large Intestine• Extends from ileocecal valve to anus• Regions– Cecum – Appendix– Colon• Ascending• Transverse• Descending– Rectum– Anal canal
  • 26. 26Anatomy of the Large Intestine
  • 27. 27Large Intestine• Histology– No villi– No permanent circular folds– Smooth muscle• Taeniae coli• Haustra– Epiploic appendages– Otherwise like rest of Gl tract
  • 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. 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. 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. 31Liver• Functions– Makes bile• Detergent – emulsifiesfats• Release promoted by:– Vagus n.– CCK– Secretin• Contains– Water– Bile salts– Bile pigments– Electrolytes– Cholesterol– Lecithin
  • 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. 33Liver• Dual blood supply– Hepatic portal vein• Direct input from smallintestine– Hepatic artery/vein• Direct links to heart
  • 34. 34The Duodenum and RelatedOrgans
  • 35. 35The Organs and Positions in theAbdominal Cavity
  • 36. 36Structures of the AlimentaryCanal