Digestive System Anatomy

1. Digestive System Anatomy • Digestive tract • Alimentary tract or canal • GI tract • Accessory organs • Primarily glands • Regions • Mouth or oral cavity • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Anus

2. Functions • Ingestion: Introduction of food into stomach • Mastication: Chewing • Propulsion • Deglutition: Swallowing • Peristalsis: Moves material through digestive tract

3. Digestive Tract Histology

4. Nervous regulation Involves enteric nervous system Types of neurons: sensory, motor, interneurons Coordinates peristalsis and regulates local reflexes Chemical regulation Production of hormones Gastrin, secretin Production of paracrine chemicals Histamine Help local reflexes in ENS control digestive environments as pH levels Digestive System Regulation

5. Peritoneum and Mesenteries • Peritoneum • Visceral: Covers organs • Parietal: Covers interior surface of body wall • Retroperitoneal: Behind peritoneum as kidneys, pancreas, duodenum • Mesenteries • Routes which vessels and nerves pass from body wall to organs • Greater omentum • Lesser omentum

6. Oral Cavity • Mouth or oral cavity • Vestibule: Space between lips or cheeks and alveolar processes • Oral cavity proper • Lips (labia) and cheeks • Palate: Oral cavity roof • Hard and soft • Palatine tonsils • Tongue: Involved in speech, taste, mastication, swallowing

7. Teeth • Two sets • Primary, deciduous, milk: Childhood • Permanent or secondary: Adult (32) • Types • Incisors, canine, premolar and molars

8. Tooth structure:

9. Salivary Glands • Produce saliva • Prevents bacterial infection • Lubrication • Contains salivary amylase • Breaks down starch • Three pairs • Parotid: Largest • Submandibular • Sublingual: Smallest

11. Pharynx Nasopharynx Oropharynx: Transmits food normally Laryngopharynx: Transmits food normally Esophagus Transports food from pharynx to stomach Passes through esophageal hiatus (opening) of diaphragm and ends at stomach Hiatal hernia Sphincters Upper Lower Pharynx and Esophagus

12. Deglutition (Swallowing) • Three phases • Voluntary • Bolus of food moved by tongue from oral cavity to pharynx • Pharyngeal Reflex: Upper esophageal sphincter relaxes, elevated pharynx opens the esophagus, food pushed into esophagus • Esophageal • Reflex: Epiglottis is tipped posteriorly, larynx elevated to prevent food from passing into larynx

13. Phases of Deglutition (Swallowing)

14. Stomach Anatomy: • Openings • Gastroesophageal: To esophagus • Pyloric: To duodenum • Regions • Cardiac • Fundus • Body • Pyloric

15. Stomach Histology: • Layers • Serosa or visceral peritoneum: Outermost • Muscularis: Three layers • Outer longitudinal • Middle circular • Inner oblique • Submucosa • Mucosa

18. Stomach Histology • Rugae: Folds in stomach when empty • Gastric pits: Openings for gastric glands • Contain cells • Surface mucous: Mucus • Mucous neck: Mucus • Parietal: Hydrochloric acid and intrinsic factor • Chief: Pepsinogen • Endocrine: Regulatory hormones

19. Hydrochloric Acid Production

20. Movements in Stomach

21. Phases of Gastric Secretion

25. Small Intestine • Site of greatest amount of digestion and absorption • Divisions • Duodenum • Jejunum • Ileum: Peyer’s patches or lymph nodules • Modifications • Circular folds or plicae circulares, villi, lacteal, microvilli • Cells of mucosa • Absorptive, goblet, granular, endocrine

26. Small Intestine Secretions • Mucus • Protects against digestive enzymes and stomach acids • Digestive enzymes • Disaccharidases: Break down disaccharides to monosaccharides • Peptidases: Hydrolyze peptide bonds • Nucleases: Break down nucleic acids • Duodenal glands • Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa

27. Duodenum and Pancreas

29. Duodenum Anatomy and Histology

30. Liver • Lobes • Major: Left and right • Minor: Caudate and quadrate • Ducts • Common hepatic • Cystic • From gallbladder • Common bile • Joins pancreatic duct at hepatopancreatic ampulla

33. Functions of the Liver • Bile production • Salts emulsify fats, contain pigments as bilirubin • Storage • Glycogen, fat, vitamins, copper and iron • Nutrient interconversion • Detoxification • Hepatocytes remove ammonia and convert to urea • Phagocytosis • Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria • Synthesis • Albumins, fibrinogen, globulins, heparin, clotting factors

34. Blood and Bile Flow

35. Duct System

36. Gallbladder • Bile is stored and concentrated • Stimulated by cholecystokinin and vegal stimulation • Dumps into small intestine • Production of gallstones possible • Drastic dieting with rapid weight loss

37. Anatomy Endocrine Pancreatic islets produce insulin and glucagon Exocrine Acini produce digestive enzymes Regions: Head, body, tail Secretions Pancreatic juice (exocrine) Trypsin Chymotrypsin Carboxypeptidase Pancreatic amylase Pancreatic lipases Enzymes that reduce DNA and ribonucleic acid Pancreas

38. Bicarbonate Ion Production

39. Gastric hormones:

40. Movement in small intestine: • Mixing: Segmental contraction that occurs in small intestine • Secretion: Lubricate, liquefy, digest • Digestion: Mechanical and chemical • Absorption: Movement from tract into circulation or lymph • Elimination: Waste products removed from body

41. Large Intestine: • Extends from ileocecal junction to anus • Consists of cecum, colon, rectum, anal canal • Movements sluggish (18-24 hours)

42. Large Intestine • Cecum • Blind sac, vermiform appendix attached • Colon • Ascending, transverse, descending, sigmoid • Rectum • Straight muscular tube • Anal canal • Internal anal sphincter (smooth muscle) • External anal sphincter (skeletal muscle) • Hemorrhoids: Vein enlargement or inflammation

43. Secretions of Large Intestine • Mucus provides protection • Parasympathetic stimulation increases rate of goblet cell secretion • Pumps • Exchange of bicarbonate ions for chloride ions • Exchange of sodium ions for hydrogen ions • Bacterial actions produce gases called flatus

44. Histology of Large Intestine

45. Movement in Large Intestine • Mass movements • Common after meals • Local reflexes in enteric plexus • Gastrocolic: Initiated by stomach • Duodenocolic: Initiated by duodenum • Defecation reflex • Distension of the rectal wall by feces • Defecation • Usually accompanied by voluntary movements to expel feces through abdominal cavity pressure caused by inspiration

46. Reflexes in Colon and Rectum:

47. Digestion, Absorption, Transport • Digestion • Breakdown of food molecules for absorption into circulation • Mechanical: Breaks large food particles to small • Chemical: Breaking of covalent bonds by digestive enzymes • Absorption and transport • Molecules are moved out of digestive tract and into circulation for distribution throughout body