The Digestive System

1. The Digestive System

2. fuel O2 ATP What do we need to live? • Energy using: • fuel • oxygen • Building Blocks using: • food for raw materials • amino acids, sugars, fats, nucleotides • ATP energy for synthesis mitochondria

5. What is the function of the digestive system? • Provide the body w/nutrients, water and electrolytes. • The organs of this system are responsible for: • Food ingestion • Digestion • Absorption • Elimination • The digestive system consists of a hollow tube extending from the mouth to the anus (GI tract or alimentary canal). • Various accessory organs empty secretions into them.

6. Digestive Process • Ingestion • Propulsion • Mechanical Digestion • Mastication • Churning food in stomach • Chemical digestion • Absorption • Defecation

7. GI Tract- 4 basic tunics: • Mucosa • Submucosa • Muscularis externa • Serosa (adventia)

8. GI Tract (alimentary canal) 1. Mucosa- wet epithelial membrane Major function: • secretion • absorption • protection • reduce friction • protect cells from being digested 2. Submucosa- moderately dense connective tissue Contains: • blood • lymphatic vessels • scattered lymph nodules and nerve fibers Major function: • nutrition • protection

9. 3. Muscularis externa- bilayer of smooth muscle and superficial longitudinal muscle • Major function: • regulate GI motility (churning) • 4.Serosa- serous membrane • Major function: • reduce friction • anchor and protect the surrounding GI tract organ

11. Enteric Nervous System Parasympathetic Nerve- Innervation of the GI Tract

12. incisors Teeth cuspid premolars molars

13. enamel crown dentin neck pulp cavity root canal bone root nerve blood vessels

16. Salivary Glands parotid submandibular sublingual

17. Saliva • Water (99.5%) • mucin • Amylase • Electrolytes • Glycoproteins • antibacterial compounds

18. The Tongue

19. Taste Buds

20. Deglutition (swallowing)

22. Peristalsis

23. The Stomach Fundus Body Oblique Muscle Rugae Greater Curve

24. Gastric Pit: Gastric pits Surface epithelium (mucous cells) Gastric pit Mucous neck cells Parietal cell Gastric gland Chief cell Enteroendocrine cell (b) Enlarged view of gastric pits and gastric glands

25. Stomach Secretions • Gastric Pit: • mucus • hydrochloric acid • pepsinogen • Hormones that regulate GI motility

26. Mucous neck cells- found in upper region of gastric glands • produce • mucous • Parietal cells- in gastric gland of mucosa • produce • HCl – kills most bacteria • Intrinsic factor (required for absorption of vit. B12 in sm intestine, which is needed for producing mature erythrocytes) • Zymogenic (chief) cells- • produce • pepsinogen • (inactive form of pepsin, which becomes active in presence of HCl) • rennin • (milk digestion in children)  protein digestion

27. Enteroendocrine cellsproduces: • Gastrin- regulates stomach secretions and mobility • Histamine- activates parietal cells to release HCl • Endorphins- natural opiates • Serotonin- causes contraction of stomach muscle • Cholecystokinin (CCK)- (in duodenal mucosa) many functions and affects many organs • Somatostatin- (stomach and duodenal mucosa) - inhibits gastrin, pancreatic secretions, inhibits GI blood flow in sm intestine…

28. Gastric ulcers • erosion of stomach wall; pain occurs 1-3 hrs after eating • 90% of recurrent ulcers due to bacterial infection, which destroys mucous protective barrier; • Treatment- use antibiotic therapy to kill bacteria Helicobacter pylori Barry Marshal

30. Intestinal Structure muscle layers lumen folds villi

31. Intestinal Villus epithelial cells capillaries lacteal

32. Intestinal Epithelial Cell

33. Liver • Detoxify poisonous substances • Make bile (500-1000 ml/day) • Store glycogen (100 g) • Stores vitamin A, D, B12 and iron • Stores fat • Regulates plasma cholesterol • Forms urea

34. liver gallbladder common bile duct pancreas pancreatic duct duodenum

35. Bile • bile salts (potassium & sodium) • bile pigments (bilirubin) • cholesterol

36. Normal Liver Liver with Cirrhosis Hepatitis B or C, chronic alcoholism, fat buildup (scar tissue forms)

37. Gallstones

38. Pancreas • Produces digestive enzymes • digest proteins • trypsin, chymotrypsin • digest starch • amylase • digest lipids • lipase • Buffers • neutralizes acid from stomach

39. Pancreas

40. Intestinal Enzymes

41. Intestinal Membrane Enzymes • disaccharidases • aminopeptidase • dipeptidases • nucleotidases • nucleosidases

42. Large Intestine • Reabsorbs water, bile salts and electrolytes • Eliminate waste • Absorb vitamins Escherichia coli: E. coli • digest cellulose digests fruits & vegetables • produce vitamins vitamin K & B vitamins • BUT generate gases

43. transverse colon descending colon ascending colon sigmoidal colon appendix cecum rectum internal anal sphincter external anal sphincter anal canal

44. INQUIRY • Which layer of the alimentary canal contains loose connective tissue, glands, blood, lymphatic vessels, and nerves? • What type of nervous stimulation increase digestive activities? • What type of tooth is likely to be involved in grinding food? • What portion of the tooth is below the gum line? • Which gastric cells secrete HCl? • Which enzyme secreted from the pancreas breaks down fats? • The surface area of the stomach is enhanced by the presence of folds called ____. • Name the valve between the stomach and duodenum.