1. 1 The Digestive System

2. 2 Digestion Digestion allows processing of food to release energy present in the nutrients we eat There are TWO overall types of digestion: –Mechanical Chew Tear Grind Mash Mix

3. Digestion –Chemical Enzymatic reactions –Carbohydrate –Protein –Lipid 3

4. 4 Digestion Phases –Ingestion –Movement –Digestion –Absorption –Further digestion

5. 5 Digestive System Organization Gastrointestinal (GI) tract –Direct path between organs –Structures Mouth Pharynx Esophagus

6. Digestive Organs Stomach Small Intestine: Duodenum Jejenum Ileum Large Intestine/Colon: ascending, transverse, descending colon Rectum/Anus 6

7. 7 Digestive System Organization Accessory structures Teeth Tongue Salivary glands Liver Gall bladder Pancreas

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10. Mouth and Pharynx Mouth: Lined by epithelium (oral mucosa) Lips Cheeks Palate (hard and soft) Teeth Tongue Pharynx: Lined by epithelium (mucosa) Common opening for both digestive and respiratory systems 10

11. 11 Anatomy of the Mouth &Throat

12. 12 Dorsal Surface of the Tongue

13. 13 The Major Salivary Glands

14. Digestion Starts in the Mouth 14 Digestion of carbohydrates starts in the mouth: Salivary amylase digests starch  simple sugar Demo: chew a saltine cracker until it is mush. What does your cracker taste like before you chew and after you chew?

15. 15 Esophagus Usually collapsed (closed) Functions –Secrete mucous –Transport food –No digestion occurs in the esophagus –It is a passageway from the oral cavity to the stomach

16. 16 Peristalsis and Segmentation

17. 17 Stomach Usually “C” or “J” shaped Left side, anterior to the spleen Lined by epithelial tissue (mucosa) –Goblet cells – make mucous –Parietal cells – Make HCl (hydrochloric acid)

18. Stomach –Chief cells – make digestive enzymes Pepsin Gastric lipase Pyloric Sphincter = valve between the stomach and small intestine -Stomach is bout 10 inches (25 cm) long -When full, holds about 4 liters of food 18

19. 19 Anatomy of the Stomach

20. 20 Stomach 3 muscle layers Inner surface thrown into folds – Rugae (mucosa) Contains enzymes that work best at pH 1-2

21. 21 Stomach Functions –“churns” food –Start digestion of Protein Digestion of carbohydrates continues –Activates some enzymes –Makes intrinsic factor protein – B 12 absorption –Destroys some bacteria

22. Stomach Gastric juice -chemically breaks down foods Stomach cells include: Chief cells – make enzymes e.g. pepsin Parietal cells – make acid (HCl) Endocrine cells – make gastrin hormone 22

23. Stomach Cells 23

24. 24 Small Intestine Extends from pyloric sphincter  ileocecal valve Regions –Duodenum –Jejenum –Ileum

25. 25 Small Intestine –Up to 18 feet long –1 st part: duodenum –2 nd part: jejunum –3 rd part: ileum –Digestion of fats and nucleic acids occurs here –Pancreas secretes enzymes into the small intestine through pancreatic ducts –Bile enters from the liver (gallbladder) via the bile duct

26. Duodenum and Related organs 26

27. 27 Small Intestine Absorbs –80% ingested water –Vitamins –Minerals –Proteins –Carbohydrates –Lipids –Nucleic Acids

28. Absorption & the Small Intestine Villi – fingerlike projections of the mucosal lining (epithelial tissue) that give the intestine a velvety appearance Microvilli: tiny projections of the mucosa cells Lacteals – lymphatic vessels that carry digested foods into the bloodstream 28

29. Absorption in Small Intestine 29

30. 30 Structure of the Villi in the Small Intestine

31. Homeostatic Balance in Small Intestine 31 The release of chyme (digested food mass) into the duodenum stimulates the small intestinal cells to make other hormones: -secretin -cholecystokinin (CCK) Which further influence the release of bile and pancreatic juice

32. 32 Large Intestine Extends from ileocecal valve to anus/rectum Regions –Cecum – Appendix –Colon Ascending Transverse Descending –Rectum/Anal canal

33. 33 Anatomy of the Large Intestine

34. 34 Large Intestine Much larger in diameter Is about 5 feet long –No villi –Smooth muscle wall –Absorbs all water from indigestible food residue –No digestion occurs here

35. 35 Feces Formation and Defecation Feces composition –Water –salts –Epithelial cells –Bacteria –Byproducts of digestion Defecation –Peristalsis pushes feces into rectum –Rectal walls stretch Control –Parasympathetic –Voluntary

36. 36 Liver –Right upper quadrant of the abdomen, under the diaphragm –Largest gland in the body –Can regenerate itself!! –Makes bile to aid digestion –Bile is yellow-green; it does not have enzymes in it –Bile emulsifies fats by breaking them down into smaller particles

37. 37 Liver & Biliary System

38. 38 Liver –Detoxifies/removes Drugs Alcohol –Stores Gycogen Vitamins (A, D, E, K) Iron/minerals Cholesterol –Activates vitamin D

39. 39 The Duodenum and Related Organs

40. 40 The Organs and Positions in the Abdominal Cavity

41. Functions of Digestive System 41 1.Ingestion 2.Propulsion 3.Mechanical Digestion 4.Chemical Digestion 5.Absorption 6.Defecation

42. Diseases of the Digestive Tract 42 Peptic Ulcer Disease Stomach Perforation Emesis Diarrhea Constipation

43. Other Diseases of Digestive System 43 Inflammatory Bowel Disease: Ulcerative Colitis Crohn’s Disease Irritable Bowel Disease