1. BY DR. UCHE AMAEFUNA Human Digestive System Biology Chapter 7

2. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Overview of the Digestive System  Organs are divided into two groups  Alimentary canal  Mouth, pharynx, and esophagus  Stomach, small intestine, and large intestine  Accessory digestive organs  Teeth and tongue  Gallbladder, salivary glands, liver, and pancreas

3. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.1 The Alimentary Canal and Accessory Digestive Organs

4. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes  Ingestion – occurs in the mouth  Propulsion – movement of food  Peristalsis – major means of propulsion  Mechanical digestion – prepares food for chemical digestion  Chewing, churning of food in stomach, segmentation  Segmentation is rhythmic local constrictions of intestine

5. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes  Chemical digestion – complex molecules broken down to chemical components  Mouth  Stomach  Small intestine  Absorption – transport of digested nutrients  Defecation – elimination of indigestible substances as feces

6. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes Figure 22.2

7. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Peristalsis  Major means of propulsion  Adjacent segments of the alimentary canal relax and contract Figure 22.3a

8. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Segmentation  Rhythmic local contractions of the intestine  Mixes food with digestive juices Figure 22.3b

9. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Abdominal Regions  Four lines divide abdominal wall into 9 regions  Midclavicular lines – vertical lines of grid  Subcostal plane – superior horizontal line  Connects inferior points of costal margin  Transtubercular plane – inferior horizontal line  Connects tubercles of iliac crests

10. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nine Regions of Anterior Abdominal Surface Figure 22.4a

11. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nine Regions of Anterior Abdominal Surface  How regions relate to abdominal viscera Figure 22.4b

12. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Abdominal Quadrants  A simpler scheme defining four quadrants Figure 22.4c

13. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Wall  Same four layers from esophagus to anus  The mucosa – innermost layer  Consists of  Epithelium  Lamina propria  Muscularis mucosae  The submucosa – external to the mucosa  Contains blood and lymphatic vessels, nerve fibers

14. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Wall  The muscularis externa – external to the submucosa  Two layers  Circular muscularis – inner layer  Longitudinal muscularis – outer layer  The serosa – the outermost layer  Is the visceral peritoneum

15. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Figure 22.5

16. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle  Primarily found in walls of viscera  Fibers elongated  Have one centrally-located nucleus  Grouped into sheets  Longitudinal layer – parallel to long axis of organ  Circular layer – deeper layer, fibers run around circumference of organ

17. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Figure 22.6a, b

18. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Contraction  Myofilaments operate by interaction with cytoskeleton  Dense bodies – correspond to Z- discs of skeletal muscle Figure 22.7a–c

19. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle  Innervated by ANS  Few fibers per sheet innervated  Sheet of smooth muscle contracts as a unit  Exceptions  Iris of eye  Arrector pili muscles in skin

20. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle Figure 22.8

21. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Plexuses  Myenteric nerve plexus  Lies between circular and longitudinal muscularis  Controls peristalsis and segmentation  Submucosal nerve plexus  Lies in submucosa  Signals glands to secrete  Innervation  Sympathetic and parasympathetic motor fibers  Visceral sensory fibers

22. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Peritoneal Cavity and Peritoneum  Peritoneum – a serous membrane  Visceral peritoneum – surrounds digestive organs  Parietal peritoneum – lines the body wall  Peritoneal cavity – a slit-like potential space

23. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Peritoneal Cavity and Peritoneum  Mesentery – a double layer of peritoneum  Holds organs in place  Sites of fat storage  Provides a route for circulatory vessels and nerves Figure 22.9a

24. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.9b The Peritoneal Cavity and Peritoneum  Retroperitoneal organs  Behind the peritoneum  Peritoneal organs  Digestive organs that keep their mesentery

25. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Superficial view of abdominal organs Figure 22.10a

26. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Lesser omentum attaches to lesser curvature of stomach Figure 22.10b

27. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Greater omentum – a “fatty apron” of peritoneum  Greater omentum and transverse colon reflected Figure 22.10c

28. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Sagittal section through the abdominopelvic cavity  Mesenteries attach to posterior abdominal wall Figure 22.10d

29. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Secondarily Retroperitoneal Organs  Initially formed within peritoneum  Become retroperitoneal  Fuse to posterior abdominal wall Figure 22.11

30. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Summary of Intraperitoneal and Secondarily Retroperitoneal Organs Table 22.1

31. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Mouth and Associated Organs  The mouth – oral cavity  Mucosal layer  Stratified squamous epithelium  Lamina propria  The lips and cheeks  Formed from orbicularis oris and buccinator muscles, respectively

32. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Mouth Figure 22.12a

33. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.12b Anatomy of the Mouth  The labial frenulum  Connects lips to gum  The palate  Forms the roof of the mouth

34. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Tongue  Interlacing fascicles of skeletal muscle  Grips food and repositions it  Helps form some consonants  Intrinsic muscles – within the tongue  Extrinsic muscles – external to the tongue  Lingual frenulum  Secures tongue to floor of mouth

35. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Superior Surface of the Tongue  Tongue papillae  Filiform papillae – no taste buds  Fungiform papillae  Circumvallate papillae  Sulcus terminalis  Marks border between mouth and pharynx  Posterior 1/3 of tongue lies in oropharynx  Lined with lingual tonsil

36. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Superior Surface of the Tongue Figure 22.13

37. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Teeth  Deciduous teeth – 20 teeth  First appear at 6 months of age  Permanent teeth – 32 teeth  Most erupt by the end of adolescence  Dental formula – shorthand  Way to indicate number and position of teeth  2I, 1C, 2P, 3M

38. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Teeth Figure 22.14

39. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Tooth Structure  Longitudinal section of tooth in alveolus Figure 22.15

40. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Salivary Glands  Produce saliva  Compound tubuloalveolar glands  Parotid glands  Parotid duct – parallel to zygomatic arch  Contains only serous cells  Submandibular glands  Lies along medial surface of mandible  Sublingual glands  Lies in floor of oral cavity  Contains primarily mucous cells

41. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Salivary Glands Figure 22.16

42. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Pharynx  Oropharynx and laryngopharynx  Passages for air and food  Lined with stratified squamous epithelium  External muscle layer  Consists of superior, middle, and inferior pharyngeal constrictors

43. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Esophagus  Gross anatomy – muscular tube  Begins as a continuation of the pharynx  Joins the stomach inferior to the diaphragm  Cardiac sphincter – closes lumen to prevent stomach acid from entering esophagus

44. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Esophagus  Microscopic anatomy  Epithelium is stratified squamous epithelium  When empty – mucosa and submucosa in longitudinal folds  Mucous glands – primarily compound tubuloalveolar glands  Muscularis externa  Skeletal muscle first third of length  Adventitia – most external layer

45. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Structure of the Esophagus Figure 22.17a, b

46. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Stomach  Site where food is churned into chyme  Secretion of pepsin begins protein digestion  Functions under acidic conditions  Food remains in stomach approximately 4 hours

47. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Stomach Figure 22.18a

48. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Stomach Figure 22.18b

49. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Stomach  Muscularis has three layers  Circular and longitudinal layers and oblique layer  Epithelium is simple columnar epithelium  Mucosa dotted with gastric pits  Gastric glands – deep to gastric pits

50. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Stomach  Gastric glands of fundus and body  Mucous neck cells  Secrete a special mucus  Parietal (oxyntic) cells  Secrete hydrochloric acid and gastric intrinsic factor  Chief (zymogenic) cells  Secrete pepsinogen

51. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Stomach – Microscopic Anatomy Figure 22.19a–d

52. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Small Intestine – Gross Anatomy  Longest portion of the alimentary canal  Site of most enzymatic digestion and absorption  Three subdivisions  Duodenum  Jejunum  Ileum

53. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Duodenum  Receives digestive enzymes and bile  Main pancreatic duct and common bile duct enter duodenum  Sphincters control entry of bile and pancreatic juices

54. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Duodenum and Related Organs Figure 22.20

55. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Small Intestine – Microscopic Anatomy  Modifications for absorption  Circular folds (plicae circulares)  Transverse ridges of mucosa and submucosa  Villi  Finger-like projections of the mucosa  Covered with simple columnar epithelium  Microvilli  Further increase surface area for absorption

56. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Intestinal Wall  Absorptive cells  Uptake digested nutrients  Goblet cells  Secrete mucus that lubricates chyme  Enteroendocrine cells  Secrete hormones  Intestinal crypts  Epithelial cells secrete intestinal juice

57. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Small Intestine – Structural Features Figure 22.21a–d

58. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Large Intestine  Digested residue contains few nutrients  Small amount of digestion by bacteria  Main functions  Absorb water and electrolytes  Mass peristaltic movements force feces toward the rectum

59. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine  Subdivided into  Cecum, vermiform appendix, colon, rectum, anal canal  Special features of large intestine  Teniae coli  Thickening of longitudinal muscularis  Haustra  Puckering created by teniae coli  Epiploic appendages  Fat-filled pouches of visceral peritoneum

60. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine  Cecum  Blind pouch  Beginning of large intestine  Vermiform appendix  Contains lymphoid tissue  Neutralizes pathogens  Colon  Divided into distinct segments  Ascending, transverse, descending, and sigmoid colon

61. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine  Rectum  Descends along the inferior half of the sacrum  Anal Canal  The last subdivision of the large intestine  Lined with stratified squamous epithelium

62. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine Figure 22.22a

63. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine Figure 22.22b

64. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Vessels and Nerves of the Large Intestine  First half of large intestine  Arterial supply - superior mesenteric artery  Innervation  Sympathetic innervation – superior mesenteric and celiac ganglia  Parasympathetic innervation – vagus nerve

65. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Vessels and Nerves of the Large Intestine  Distal half of large intestine  Arterial supply - inferior mesenteric artery  Innervation  Sympathetic innervation – inferior mesenteric and hypogastric plexuses  Parasympathetic innervation – pelvic splanchnic nerves

66. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Defecation Reflex Figure 22.23

67. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Large Intestine  Villi are absent  Contains numerous goblet cells  Intestinal crypts – simple tubular glands  Lined with simple columnar epithelial tissue  Epithelium changes at anal canal  Becomes stratified squamous epithelium

68. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mucosa of the Large Intestine Figure 22.24

69. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Liver  Largest gland in the body  Performs over 500 functions  Digestive function  Bile production  Performs many metabolic functions

70. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Visceral Surface of the Liver Figure 22.26

71. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Liver  Hepatocyte – functional cells of the liver  Portal triad composed of  Bile duct tributary  Branch of hepatic portal vein  Branch of hepatic artery  Kupffer cells – destroy bacteria

72. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Liver  Some functions of hepatocytes  Rough ER manufactures blood proteins  Smooth ER produces bile salts, detoxifies poisons  Peroxisomes detoxify poisons (alcohol)  Golgi apparatus packages secretory products  Mitochondria provide energy for liver processes  Glycosomes store sugar  Great capacity for regeneration

73. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Liver Figure 22.27a, c, d

74. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Gallbladder  Stores and concentrates bile  Expels bile into duodenum  Bile emulsifies fats  Cholecystokinin – released from enteroendocrine cells in response to fatty chyme

75. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Gallbladder Figure 22.20

76. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Pancreas  Exocrine function  Acinar cells make, store, and secrete pancreatic enzymes  Enzymes are activated in the duodenum  Endocrine function  Produces insulin and glucagon  Regulates blood sugar

77. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Exocrine Pancreas: Histology Figure 22.29a, b

78. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Digestive System  Intestinal obstruction  Mechanical obstructions  Adhesions, tumors, or foreign objects  Nonmechanical obstruction  Halt in peristalsis  Trauma  Intestines touched during surgery

79. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Digestive System  Inflammatory bowel disease  Inflammation of intestinal wall  Crohn’s disease  Ulcerative colitis  Viral hepatitis  Jaundice and flu-like symptoms  Major types – A, B, C, and G

80. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Digestive System  Cystic Fibrosis and the Pancreas  Pancreatic ducts become blocked with mucus  Clogged ducts prevent pancreatic juices from entering small intestine  Leads to malabsorption of fats and other nutrients

81. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Embryonic Development of the Digestive System  Alimentary canal formed in week three  Encloses tubular portion of yolk sac  Vitelline duct  Landmark dividing into three regions  Forgut  Midgut  Hindgut

82. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Embryonic Development of the Digestive System Figure 22.30a, b

83. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Digestive System in Later Life  Middle age – gallstones and ulcers  Old age – activity of digestive organs decline  Fewer digestive juices and enzymes produced  Absorption is less efficient  Dehydration of fecal mass leads to constipation  Diverticulosis and cancer of digestive organs