1. Anatomy and Physiology, Sixth Edition
Rod R. Seeley Idaho State University
Trent D. Stephens Idaho State University
Philip Tate Phoenix College
Chapter 24
Lecture Outline*
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Chapter 24
Digestive System

3. 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

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

5. Functions 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

6. Digestive Tract Histology

7. Digestive System Regulation
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

8. Peritoneum and Mesenteries
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

9. Oral Cavity Mouth or oral cavity Lips (labia) and cheeks
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

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

11. Teeth

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

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

14. 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

15. Phases of Deglutition (Swallowing)

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

17. 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. Phases of Gastric Secretion

21. Movements in Stomach

22. 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

23. 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

24. Duodenum and Pancreas

25. Duodenum Anatomy and Histology

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

27. Functions of the Liver Bile production Storage
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

28. Blood and Bile Flow

29. Duct System

30. 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

31. Pancreas Anatomy Secretions Endocrine Pancreatic juice (exocrine)
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

32. Bicarbonate Ion Production

33. Pancreatic Secretion Control

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

35. Large Intestine Cecum Colon Rectum Anal canal
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

36. 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

37. Histology of Large Intestine

38. 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

39. Reflexes in Colon and Rectum

40. Digestion, Absorption, Transport
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

41. Carbohydrates
Consist of starches, glycogen, sucrose, lactose, glucose, fructose
Polysaccharides broken down to monosaccharides
Monosaccharides taken up by active transport or facilitated diffusion and carried to liver
Glucose is transported to cells requiring energy
Insulin influences rate of transport

42. Lipids
Include triglycerides, phospholipids, steroids, fat-soluble vitamins
Emulsification breaks down large lipid droplets to small

43. Lipoproteins Types Chylomicrons VLDL LDL HDL Enter lymph
Transports cholesterol to cells
HDL
Transports cholesterol from cells to liver

44. Proteins Pepsin breaks proteins into smaller polypeptide chains
Proteolytic enzymes produce small peptide chains
Dipeptides, tripeptides, amino acids

45. Water and Ions Water Ions
Can move in either direction across wall of small intestine depending on osmotic gradients
Ions
Sodium, potassium, calcium, magnesium, phosphate are actively transported

46. Effects of Aging
Decrease in mucus layer, connective tissue, muscles and secretions
Increased susceptibility to infections and toxic agents
Ulcerations and cancers