1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition Elaine N. Marieb Chapter 24-25 The Digestive System and Body Metabolism

2. The Digestive System and Body Metabolism Slide 14.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Digestion  Breakdown of ingested food  Absorption  Passage of nutrients into the blood  Metabolism  Production of cellular energy (ATP)

3. Organs of the Digestive System Slide 14.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Two main groups  Alimentary canal – continuous coiled hollow tube  Accessory digestive organs

4. Organs of the Digestive System Slide 14.2b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.1

5. Organs of the Alimentary Canal Slide 14.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Mouth  Pharynx  Esophagus  Stomach  Small intestine  Large intestine  Anus

6. Anatomy of the Oral Cavity: Mouth Figure 23.7a

7. Mouth (Oral Cavity) Anatomy Slide 14.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Lips (labia) – protect the anterior opening  Cheeks – form the lateral walls  Hard palate – forms the anterior roof  Soft palate – forms the posterior roof  Uvula – fleshy projection of the soft palate Figure 14.2a

8. Mouth (Oral Cavity) Anatomy Slide 14.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vestibule – space between lips externally and teeth and gums internally  Oral cavity – area contained by the teeth  Tongue – attached at hyoid and styloid processes of the skull, and by the lingual frenulum Figure 14.2a

9. Mouth (Oral Cavity) Anatomy Slide 14.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Tonsils  Palatine tonsils  Lingual tonsil Figure 14.2a

10. Processes of the Mouth Slide 14.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Mastication (chewing) of food  Mixing masticated food with saliva  Initiation of swallowing by the tongue  Allowing for the sense of taste

11. Pharynx Anatomy Slide 14.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Nasopharynx – not part of the digestive system  Oropharynx – posterior to oral cavity  Laryngopharynx – below the oropharynx and connected to the esophagus Figure 14.2a

12. Lips and Cheeks Have a core of skeletal muscles –Lips: orbicularis oris –Cheeks: buccinators Vestibule – bounded by the lips and cheeks externally, and teeth and gums internally Oral cavity proper – area that lies within the teeth and gums Labial frenulum – median fold that joins the internal aspect of each lip to the gum

13. Salivary Glands Produce and secrete saliva that: –Cleanses the mouth –Moistens and dissolves food chemicals –Aids in bolus formation –Contains enzymes that break down starch Three pairs of extrinsic glands – parotid, submandibular, and sublingual Intrinsic salivary glands (buccal glands) – scattered throughout the oral mucosa

14. Digestive Processes in the Mouth Food is ingested Mechanical digestion begins (chewing) Propulsion is initiated by swallowing Salivary amylase begins chemical breakdown of starch The pharynx and esophagus serve as conduits to pass food from the mouth to the stomach

15. Deglutition (Swallowing) Figure 23.13 (a) Upper esophageal sphincter contracted (b) Upper esophageal sphincter relaxed (c) Upper esophageal sphincter contracted (e) (d) Bolus of food Uvula Bolus Relaxed muscles Tongue Pharynx Epiglottis Glottis Trachea Bolus Epiglottis Bolus of food Longitudinal muscles contract, shortening passageway ahead of bolus Gastroesophageal sphincter closed Circular muscles contract, constricting passageway and pushing bolus down Stomach Gastroesophageal sphincter open Esophagus

16. Pharynx Function Slide 14.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Serves as a passageway for air and food  Food is propelled to the esophagus by two muscle layers  Longitudinal inner layer  Circular outer layer  Food movement is by alternating contractions of the muscle layers (peristalsis)

17. Esophagus Slide 14.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Runs from pharynx to stomach through the diaphragm  Conducts food by peristalsis (slow rhythmic squeezing)  Passageway for food only (respiratory system branches off after the pharynx)

18. Layers of Alimentary Canal Organs Slide 14.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.3

19. Mucosa Moist epithelial layer that lines the lumen of the alimentary canal Its three major functions are: –Secretion of mucus –Absorption of the end products of digestion –Protection against infectious disease Consists of three layers: a lining epithelium, lamina propria, and muscularis mucosae

20. Mucosa: Epithelial Lining Consists of simple columnar epithelium and mucus-secreting goblet cells The mucus secretions: –Protect digestive organs from digesting themselves –Ease food along the tract Stomach and small intestine mucosa contain: –Enzyme-secreting cells –Hormone-secreting cells (making them endocrine and digestive organs)

21. Lamina Propria –Loose areolar and reticular connective tissue –Nourishes the epithelium and absorbs nutrients –Contains lymph nodes (part of MALT) important in defense against bacteria Muscularis mucosae – smooth muscle cells that produce local movements of mucosa Mucosa: Lamina Propria and Muscularis Mucosae

22. Mucosa: Other Sublayers Submucosa – dense connective tissue containing elastic fibers, blood and lymphatic vessels, lymph nodes, and nerves Muscularis externa – responsible for segmentation and peristalsis Serosa – the protective visceral peritoneum

23. Enteric Nervous System Composed of two major intrinsic nerve plexuses –Submucosal nerve plexus – regulates glands and smooth muscle in the mucosa –Myenteric nerve plexus – Major nerve supply that controls GI tract mobility Segmentation and peristalsis are largely automatic involving local reflex arcs Linked to the CNS via long autonomic reflex arc

24. Stomach Anatomy Slide 14.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Located on the left side of the abdominal cavity  Food enters at the cardioesophageal sphincter

25. Stomach Anatomy Slide 14.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.4a

26. Stomach Anatomy Slide 14.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Regions of the stomach  Cardiac region – near the heart  Fundus  Body  Phylorus – funnel-shaped terminal end  Food empties into the small intestine at the pyloric sphincter

27. Stomach Anatomy Slide 14.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Rugae – internal folds of the mucosa  External regions  Lesser curvature  Greater curvature

28. Stomach Anatomy Slide 14.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Layers of peritoneum attached to the stomach  Lesser omentum – attaches the liver to the lesser curvature  Greater omentum – attaches the greater curvature to the posterior body wall  Contains fat to insulate, cushion, and protect abdominal organs

29. Stomach Functions Slide 14.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Acts as a storage tank for food  Site of food breakdown  Chemical breakdown of protein begins  Delivers chyme (processed food) to the small intestine

30. Structure of the Stomach Mucosa Slide 14.20a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Gastric pits formed by folded mucosa  Glands and specialized cells are in the gastric gland region

31. Structure of the Stomach Mucosa Slide 14.20b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.4b, c

32. Microscopic Anatomy of the Stomach Muscularis – has an additional oblique layer that: –Allows the stomach to churn, mix, and pummel food physically –Breaks down food into smaller fragments Epithelial lining is composed of: –Goblet cells that produce a coat of alkaline mucus The mucous surface layer traps a bicarbonate-rich fluid beneath it Gastric pits contain gastric glands that secrete gastric juice, mucus, and gastrin

33. Glands of the Stomach Fundus and Body Gastric glands of the fundus and body have a variety of secretory cells –Mucous neck cells – secrete acid mucus –Parietal cells – secrete HCl and intrinsic factor

34. Glands of the Stomach Fundus and Body –Chief cells – produce pepsinogen Pepsinogen is activated to pepsin by: –HCl in the stomach –Pepsin itself via a positive feedback mechanism –Enteroendocrine cells – secrete gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and somatostatin into the lamina propria

35. Stomach Lining The stomach is exposed to the harshest conditions in the digestive tract To keep from digesting itself, the stomach has a mucosal barrier with: –A thick coat of bicarbonate-rich mucus on the stomach wall –Epithelial cells that are joined by tight junctions –Gastric glands that have cells impermeable to HCl Damaged epithelial cells are quickly replaced

36. Response of the Stomach to Filling Stomach pressure remains constant until about 1L of food is ingested Relative unchanging pressure results from reflex- mediated relaxation and plasticity Reflex-mediated events include: –Receptive relaxation – as food travels in the esophagus, stomach muscles relax –Adaptive relaxation – the stomach dilates in response to gastric filling Plasticity – intrinsic ability of smooth muscle to exhibit the stress-relaxation response

37. Gastric Contractile Activity Figure 23.18

38. Regulation of Gastric Emptying Gastric emptying is regulated by: –The neural enterogastric reflex –Hormonal (enterogastrone) mechanisms These mechanisms inhibit gastric secretion and duodenal filling Carbohydrate-rich chyme quickly moves through the duodenum Fat-laden chyme is digested more slowly causing food to remain in the stomach longer

40. Small Intestine Slide 14.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The body’s major digestive organ  Site of nutrient absorption into the blood  Muscular tube extending form the pyloric sphincter to the ileocecal valve  Suspended from the posterior abdominal wall by the mesentery

41. Subdivisions of the Small Intestine “Dogs Just Itch! Slide 14.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Duodenum  Attached to the stomach  Curves around the head of the pancreas  Jejunum  Attaches anteriorly to the duodenum  Ileum  Extends from jejunum to large intestine

42. Chemical Digestion in the Small Intestine Slide 14.23a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Source of enzymes that are mixed with chyme  Intestinal cells  Pancreas  Bile enters from the gall bladder

43. Chemical Digestion in the Small Intestine Slide 14.23b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.6

44. Villi of the Small Intestine Slide 14.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Fingerlike structures formed by the mucosa  Give the small intestine more surface area Figure 14.7a

45. Microvilli of the Small Intestine Slide 14.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Small projections of the plasma membrane  Found on absorptive cells Figure 14.7c

46. Structures Involved in Absorption of Nutrients Slide 14.26 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Absorptive cells  Blood capillaries  Lacteals (specialized lymphatic capillaries) Figure 14.7b

47. Folds of the Small Intestine Slide 14.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Called circular folds or plicae circulares  Deep folds of the mucosa and submucosa  Do not disappear when filled with food  The submucosa has Peyer’s patches (collections of lymphatic tissue)

48. Digestion in the Small Intestine Slide 14.57a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Enzymes from the brush border  Break double sugars into simple sugars  Complete some protein digestion  Pancreatic enzymes play the major digestive function  Help complete digestion of starch (pancreatic amylase)  Carry out about half of all protein digestion (trypsin, etc.)

49. Digestion in the Small Intestine Slide 14.57b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Pancreatic enzymes play the major digestive function (continued)  Responsible for fat digestion (lipase)  Digest nucleic acids (nucleases)  Alkaline content neutralizes acidic chyme

50. Absorption in the Small Intestine Slide 14.59 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Water is absorbed along the length of the small intestine  End products of digestion  Most substances are absorbed by active transport through cell membranes  Lipids are absorbed by diffusion  Substances are transported to the liver by the hepatic portal vein or lymph

51. Propulsion in the Small Intestine Slide 14.60 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Peristalsis is the major means of moving food  Segmental movements  Mix chyme with digestive juices  Aid in propelling food

52. Large Intestine Slide 14.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Larger in diameter, but shorter than the small intestine  Frames the internal abdomen

53. Large Intestine Slide 14.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.8

54. Functions of the Large Intestine Slide 14.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Absorption of water  Eliminates indigestible food from the body as feces  Does not participate in digestion of food  Goblet cells produce mucus to act as a lubricant

55. Structures of the Large Intestine Slide 14.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cecum – saclike first part of the large intestine  Appendix  Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)  Hangs from the cecum

56. Structures of the Large Intestine Slide 14.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Colon  Ascending  Transverse  Descending  S-shaped sigmoidal  Rectum  Anus – external body opening

57. Food Breakdown and Absorption in the Large Intestine Slide 14.61 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  No digestive enzymes are produced  Resident bacteria digest remaining nutrients  Produce some vitamin K and B  Release gases  Water and vitamins K and B are absorbed  Remaining materials are eliminated via feces

58. Propulsion in the Large Intestine Slide 14.62 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sluggish peristalsis  Mass movements  Slow, powerful movements  Occur three to four times per day  Presence of feces in the rectum causes a defecation reflex  Internal anal sphincter is relaxed  Defecation occurs with relaxation of the voluntary (external) anal sphincter

59. Accessory Digestive Organs Slide 14.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Salivary glands  Teeth  Pancreas  Liver  Gall bladder

60. Teeth Slide 14.35a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The role is to masticate (chew) food  Humans have two sets of teeth  Deciduous (baby or milk) teeth  20 teeth are fully formed by age two

61. Teeth Slide 14.35b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Permanent teeth  Replace deciduous teeth beginning between the ages of 6 to 12  A full set is 32 teeth, but some people do not have wisdom teeth

62. Classification of Teeth Slide 14.36a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Incisors  Canines  Premolars  Molars

63. Classification of Teeth Slide 14.36b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.9

64. Regions of a Tooth Slide 14.37a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Crown – exposed part  Outer enamel  Dentin  Pulp cavity  Neck  Region in contact with the gum  Connects crown to root Figure 14.10

65. Regions of a Tooth Slide 14.37b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Root  Periodontal membrane attached to the bone  Root canal carrying blood vessels and nerves Figure 14.10

66. Pancreas Slide 14.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Produces a wide spectrum of digestive enzymes that break down all categories of food  Enzymes are secreted into the duodenum  Alkaline fluid introduced with enzymes neutralizes acidic chyme  Endocrine products of pancreas  Insulin  Glucagons

67. Liver Slide 14.39 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Largest gland in the body  Located on the right side of the body under the diaphragm  Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament  Connected to the gall bladder via the common hepatic duct

68. Bile Slide 14.40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Produced by cells in the liver  Composition  Bile salts  Bile pigment (mostly bilirubin from the breakdown of hemoglobin)  Cholesterol  Phospholipids  Electrolytes

69. Role of the Liver in Metabolism Slide 14.77 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Several roles in digestion  Detoxifies drugs and alcohol  Degrades hormones  Produce cholesterol, blood proteins (albumin and clotting proteins)  Plays a central role in metabolism

70. Gall Bladder Slide 14.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sac found in hollow fossa of liver  Stores bile from the liver by way of the cystic duct  Bile is introduced into the duodenum in the presence of fatty food  Gallstones can cause blockages

71. Processes of the Digestive System Slide 14.44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Chemical Digestion  Enzymes break down food molecules into their building blocks  Each major food group uses different enzymes  Carbohydrates are broken to simple sugars  Proteins are broken to amino acids  Fats are broken to fatty acids and alcohols

72. Processes of the Digestive System Slide 14.45 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Absorption  End products of digestion are absorbed in the blood or lymph  Food must enter mucosal cells and then into blood or lymph capillaries  Defecation  Elimination of indigestible substances as feces

73. Processes of the Digestive System Slide 14.46 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.11

74. Control of Digestive Activity Slide 14.47a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Mostly controlled by reflexes via the parasympathetic division  Chemical and mechanical receptors are located in organ walls that trigger reflexes

75. Control of Digestive Activity Slide 14.47b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Stimuli include:  Stretch of the organ  pH of the contents  Presence of breakdown products  Reflexes include:  Activation or inhibition of glandular secretions  Smooth muscle activity

76. Nutrition - Take a Class! Slide 14.63 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Nutrient – substance used by the body for growth, maintenance, and repair  Categories of nutrients  Carbohydrates: simple sugars, starches, fiber  Lipids: triglycerides, phospholipids, fatty acids  Proteins: amino acids  Vitamins  Mineral  Water

77. Body Energy Balance Slide 14.83 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Energy intake = total energy output (heat + work + energy storage)  Energy intake is liberated during food oxidation  Energy output  Heat is usually about 60%  Storage energy is in the form of fat or glycogen