2. CHAPTER © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29 The Digestive System

3. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-2 Learning Outcomes 29.1List the functions of the digestive system. 29.2Trace the pathway of food through the alimentary canal. 29.3Describe the structure and functions of the mouth, teeth, tongue, and salivary glands. 29.4Describe the structure and function of the pharynx.

4. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-3 Learning Outcomes (cont.) 29.5Describe the swallowing process. 29.6Describe the structure of the esophagus and tell how it propels food into the stomach. 29.7Describe the structure and functions of the stomach. 29.8List the substances secreted by the stomach and give their functions.

5. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-4 Learning Outcomes (cont.) 29.9Describe the structure and functions of the small intestine. 29.10List the substances secreted by the small intestine and describe the importance of each. 29.11Describe the structure and functions of the large intestine, including the anal canal and rectum. 29.12Explain the structures and functions of the liver, gallbladder, and pancreas.

6. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-5 Learning Outcomes (cont.) 29.13List the substances released by the liver, gallbladder, and pancreas into the small intestine and give the function of each secretion. 29.14Tell what types of nutrients are absorbed by the digestive system and where they are absorbed. 29.15Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the digestive system.

7. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-6 Introduction Digestion –Mechanical and chemical breakdown of foods into forms that body cells can absorb –The organs of the digestive system carry out digestion Two categories –Alimentary canal organs – Accessory organs

8. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-7 Alimentary Canal Wall of alimentary canal –Mucosa Innermost layer; epithelial tissue Secretes enzymes and mucus into lumen Absorbs nutrients –Submucosa Inferior to mucosa; loose connective tissue, blood vessels, glands, and nerves Blood vessels carry away absorbed nutrients –Muscular layer Just outside submucosa; layers of smooth muscle Contracts to move materials through the canal

9. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-8 Alimentary Canal (cont.) –Serosa Double-walled outermost layer: peritoneum –Visceral peritoneum » Innermost wall of serosa » Secretes serous fluid to keep outside of canal moist –Parietal peritoneum » Abdominal lining Movements –Churning – mixes substances in the canal –Peristalsis – propels substances through the tract

10. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-9 Apply Your Knowledge What are the layers of the wall of the alimentary canal and what do they do? ANSWER: The layers are: Mucosa: innermost layer; secretes enzymes and mucus into the canal and absorbs nutrients Submucosa: inferior to the mucosa; carries away absorbed nutrients Muscular layer: just outside the submucosa; contracts to move materials through the canal Serosa: double-walled outer layer; secretes serous fluid to keep outside of canal moist Bravo!

11. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-10 The Mouth Buccal cavity Mechanical digestion –Takes in food and reduces its size by chewing Starts chemical digestion –Saliva contains the enzyme amylase, which breaks down carbohydrates

12. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-11 The Mouth (cont.) Cheeks hold food in mouth Lips – sensory nerve fibers that judge temperature of food Tongue –Skeletal muscles covered by mucous membrane –Lingual frenulum – holds tongue to floor of mouth –Mixes food, holds food between teeth, contains taste buds –Lingual tonsils – lymphatic tissue destroys bacteria and viruses on back of tongue

13. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-12 The Mouth (cont.) Palate –Roof of mouth –Separates oral cavity from nasal cavity –Uvula – portion of soft palate that hangs down in throat Lymph tissue –Palatine tonsils (oropharynx) –Pharyngeal tonsils – adenoids (nasopharynx)

14. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-13 The Mouth (cont.) Teeth – decrease size of food particles –Incisors – bite off food pieces –Cuspids – tear tough food –Bicuspids and molars – grind food Salivary glands –Cells Serous Mucous –Glands Parotid Submandibular Sublingual

15. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-14 Apply Your Knowledge Matching: ___ Buccal cavityA.Saliva ___ Roof of mouth B.Mouth ___ Grind foodC.Bolus ___ AdenoidsD.Palate ___ Water, enzymes, and mucusE.Bicuspids ___ Mass of food mixed with saliva and mucusF.Pharyngeal gland D E F A B B ANSWER:

16. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-15 Pharynx Throat Functions –Connects nasal cavity with oral cavity for breathing –Pushes food into esophagus Divisions –Nasopharynx Behind nasal cavity –Oropharynx Behind oral cavity –Laryngopharynx Behind larynx Continues as esophagus

17. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-16 Pharynx (cont.) Swallowing – automatic process 1. Soft palate rises, uvula covers opening between nasal and oral cavity 2. Epiglottis covers larynx, keeping food out of it 3. Tongue presses against roof of mouth, forcing food into oropharynx

18. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-17 Pharynx (cont.) Muscles in pharynx contract, moving food toward esophagus Esophagus opens Food is pushed into esophagus by muscles of pharynx

19. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-18 The Esophagus Muscular tube connecting pharynx to stomach –Esophageal hiatus – hole in diaphragm through which esophagus passes Cardiac sphincter –Circular band of muscle at the opening of the stomach –controls movement of food into stomach

20. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-19 Apply Your Knowledge Matching: ___ Connects nasal cavity with oral cavityA.Cardiac sphincter ___ Covers the opening of larynxB.Esophageal hiatus ___ Hole in diaphragmC.Sphincter ___ Controls movement of food into stomachD.Epiglottis ___ Circular bands of muscle E.Pharynx C A B D E ANSWER:

21. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-20 The Stomach Below the diaphragm in the upper left quadrant of the abdominal cavity Functions –Receive food from esophagus –Mix bolus with gastric juice –Start protein digestion –Move food into small intestine Sections –Cardiac region –Fundus –Body –Pylorus Pyloric sphincter –Controls movement of substances into small intestine Stomach

22. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-21 The Stomach (cont.) Lining of stomach –Rugae – folds of the inner lining –Gastric glands Mucous cells – secrete mucus to protect the lining Chief cells – secrete pepsinogen  pepsin, which digests protein Parietal cells –Hydrochloric acid needed to convert pepsinogen to pepsin –Intrinsic factor needed for vitamin B 12 absorption Stomach

23. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-22 Back

24. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-23 The Stomach (cont.) Gastric glands stimulated by –Parasympathetic nervous system –Gastrin (hormone) Cholesystokinin (hormone) secreted by the small intestine inhibits gastric glands Stomach absorbs alcohol, water, and some fat- soluble drugs Chyme – mixture of food and gastric juices

25. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-24 Apply Your Knowledge What are the functions of the stomach? ANSWER: The stomach’s functions are to receive the bolus of food, mix it with gastric juice, start protein digestion, and move food into the small intestine. It also absorbs alcohol, water, and some drugs. Right Answer!

26. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-25 The Small Intestine Tubular organ extending from the stomach to the large intestine Functions –Digestion –Absorption of nutrients Duodenum –C-shaped –Short Jejunum –Coiled –Majority of small intestine Small Intestine

27. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-26 The Small Intestine (cont.) Ileum – attached to large intestine Mesentery –Fan-like tissue that holds jejunum and ileum in the abdominal cavity –Attaches to the posterior wall of the abdomen Ileocecal sphincter –Controls movement of chyme from the ileum to the cecum of the large intestine Small Intestine

28. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-27 The Small Intestine (cont.) Lining of small intestine –Microvilli – increase surface area –Intestinal glands Mucus and water Enzymes –Peptidases – digest proteins –Sucrase, maltase, and lactase – digest sugars –Intestinal lipase – digests fats Primary controls –Parasympathetic nervous system –Stretching of intestinal wall

29. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-28 Back

30. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-29 Apply Your Knowledge ANSWER: She cannot produce lactase and cannot digest lactose, which is the sugar in dairy products. Your patient states that she is lactose intolerant. What does that mean?

31. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-30 The Large Intestine Extends from the ileum to the anus Cecum –Beginning of large intestine –Veriform appendix Ascending colon –Portion that goes up the right side of the abdominal cavity Large Intestine

32. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-31 The Large Intestine (cont.) Transverse colon – crosses abdominal cavity from right to left Descending colon – down left side of abdominal cavity Sigmoid colon – S-shaped portion in pelvic cavity Absorbs water and electrolytes Large Intestine

33. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-32 The Rectum and Anal Canal Rectum – off sigmoid colon Anal canal –Last few centimeters of rectum –Opening to outside of body is the anus Large Intestine

34. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-33 The Rectum and Anal Canal (cont.) Feces –Leftover chyme –Consists of undigested solid materials, little water, ions, mucus, cells of intestinal lining, and bacteria Defecation reflex –Triggered by periodic contractions of large intestine –Allows anal sphincters to relax

35. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-34 Back

36. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-35 Apply Your Knowledge Matching: ___ Vermiform appendixA.Feces ___ Crosses the abdomenB.Ascending colon ___ Up right side of abdomen C.Anal canal ___ S-shaped tubeD.Defecation reflex ___ Down left side of abdomenE.Sigmoid ___ Leftover chymeF.Transverse colon ___ Last section of rectumG.Cecum ___ Allows anal sphincters to relaxH.Descending colon H G F E D C B A ANSWER: Super!

37. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-36 The Liver Lobular organ in right upper quadrant –Large right lobe and smaller left lobe Hepatic lobules – contain macrophages Hepatocytes – process nutrients in blood and make bile Part of liver’s function –Store vitamins and iron

38. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-37 The Liver (cont.) Hepatic portal vein – carries blood from digestive organs to hepatic lobules Hepatic duct – bile from liver Hepatic duct merges with cystic duct from gallbladder and forms common bile duct Common bile duct – delivers bile to duodenum

39. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-38 The Gallbladder Small sac-like structure located beneath the liver Only function is to store bile Cholecystokinin causes the gallbladder to release bile Gallbladder

40. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-39 Apply Your Knowledge What is the route of bile through the liver and gallbladder? ANSWER: Bile is made in the hepatocytes and leaves the liver through the hepatic duct. The hepatic duct merges with the cystic duct from the gallbladder to form the common bile duct, which delivers bile to the duodenum.

41. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-40 The Pancreas Pancreatic amylase – digests carbohydrates Pancreatic lipase – digests lipids Nucleases – digest nucleic acids Trypsin, chymotrypsin, and carboxypeptidase – digest proteins  Located behind the stomach  Acinar cells produce pancreatic juice, which contains these enzymes:

42. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-41 The Pancreas (cont.)  Also secretes bicarbonate ions into duodenum Neutralize acidic chyme  Enzyme release stimulated by Parasympathetic nervous system Hormones secretin and cholecystokinin (from small intestine)

43. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-42 Apply Your Knowledge What are the pancreatic enzymes and what do they do? ANSWER: They are:  Pancreatic amylase – digests carbohydrates  Pancreatic lipase – digests lipids  Nucleases – digest nucleic acids  Trypsin, chymotrypsin, and carboxypeptidase – digest proteins Good Job!

44. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-43 The Absorption of Nutrients Nutrients are necessary food substances –Carbohydrates –Proteins –Lipids –Vitamins –Minerals –Water

45. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-44 The Absorption of Nutrients (cont.) Carbohydrates – provide energy –Polysaccharides – starches –Monosaccharides and disaccharides – simple sugars –Cellulose – provides fiber or bulk Lipids – used for energy when glucose levels are low –Triglycerides –Cholesterol – essential for cell growth and function

46. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-45 The Absorption of Nutrients (cont.) Protein – used for growth and repair of tissue –Essential amino acids body cannot make Vitamins –Fat-soluble –Water-soluble Minerals – used to make enzymes, cell membranes, and proteins

47. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-46 Apply Your Knowledge True or False: ___ Carbohydrates are starches, simple sugars, and cellulose. ___ Excess glucose is stored in the gallbladder as glycogen. ___ Triglycerides are the least abundant lipids ___ Linoleic acid is an essential fatty acid. ___ A, D, E and K are water-soluble vitamins. ___ Minerals are used by cells to make enzymes. F F F T T ANSWER: T liver most fat-soluble

48. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-47 Aging and the Digestive System Decreased motility – GERD Decreased absorption More likely to develop ulcers and cancers Decreased ability to detoxify blood Sense of taste altered Dietary changes due to –Isolation –Depression

49. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-48 Common Diseases and Disorders Disease/DisorderDescription AppendicitisInflammation of the appendix; can be life- threatening if not treated promptly CirrhosisChronic liver disease; normal tissue is replaced with nonfunctional scar tissue ColitisInflammation of the large intestine; can be acute or chronic Colorectal cancerArises from lining of rectum or colon; curable if treated early

50. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-49 Common Diseases and Disorders (cont.) Disease/DisorderDescription ConstipationDifficult defecation Crohn’s diseaseInflammatory bowel disease; typically effects small intestine DiarrheaWatery and frequent feces; usually self-limiting DiverticulosisAbnormal pouches in the intestinal wall; no inflammation present

51. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-50 Common Diseases and Disorders (cont.) Disease/DisorderDescription DiverticulitisInflammation of diverticuli (abnormal pouches in intestinal wall) of the intestine GastritisInflammation of the stomach lining; “upset stomach” HeartburnGastroesophageal reflux disease (GERD); stomach acids push into esophagus HemorrhoidsVaricose veins of rectum or anus HepatitisInflammation of the liver; various types

52. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-51 Common Diseases and Disorders (cont.) Disease/DisorderDescription Hiatal herniaPortion of stomach protrudes into the chest through an opening (usually the esophageal hiatus) in the diaphragm Inguinal herniaPortion of large intestine protrudes in the inguinal canal (where thigh and trunk meet) or, in males, into the scrotum Oral cancerUsually involves the lips or tongue but can occur anywhere in the mouth; tends to spread rapidly

53. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-52 Common Diseases and Disorders (cont.) Disease/DisorderDescription Pancreatic cancerFourth leading cause of cancer deaths in the U.S. Stomach cancerCommonly in cardiac portion of the stomach; occurs more frequently in Japan, Chili, and Iceland Stomach ulcersBreakdown in lining of the stomach; can be caused by bacteria (H. pylori) or smoking, alcohol, excessive aspirin use, and hypersecretion of stomach acid

54. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-53 Apply Your Knowledge Matching: ___ Inflammation of the large intestineA.Heartburn ___ Inflammatory bowel diseaseB.Hemorrhoids ___ Watery and frequent fecesC.Constipation ___ Difficult defecationD.Crohn’s disease ___ Inflammation of the stomach liningE.Colitis ___ Inflammation of pouches in the intestinal wallF.Diarrhea ___ GERDG.Gastritis ___ Varicose veins of rectumH.Diverticulitis H G F D C B A E ANSWER:

55. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-54 In Summary 29.1The digestive system uses mechanical and chemical mechanisms to break down food into forms that the body’s cells can use. 29.2The pathway of food through the alimentary canal starts with the mouth through the pharynx, esophagus, stomach, small intestines, large intestines, and anal canal. 29.3The mouth takes in food and the teeth assist in reducing its size through chewing. The tongue mixes food and holds it between the teeth. The salivary glands produce saliva to assist in moistening and breaking down food.

56. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-55 In Summary (cont.) 29.4The pharynx is a long muscular tube extending from behind the nose to the esophagus, connecting the oral and nasal cavities. It also acts to push food into the esophagus. 29.5The soft palate rises, closing the opening between the nasal and oral cavities. The epiglottis covers the laryngeal opening. Food is forced into the oropharynx by the tongue, and the pharynx contracts, pushing food to the esophagus. 29.6The esophagus is a muscular tube that pushes food toward the stomach through muscular contractions. At the end of the esophagus is the cardiac sphincter, the entrance to the stomach.

57. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-56 In Summary (cont.) 29.7The stomach is in the LUQ. It receives food, mixes it with gastric juices, starting protein digestion, and moves food into the small intestine. The stomach has four regions: cardiac region, fundus, body, and pylorus. 29.8The stomach’s gastric glands include mucous cells that secret mucus, chief cells that secret pepsinogen, and parietal cells that secrete hydrochloric acid and intrinsic factor. 29.9The small intestine carries out most of the nutrient absorption. The sections of the small intestine are, in order, duodenum, jejunum, and ileum.

58. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-57 In Summary (cont.) 29.10The small intestine secretes peptidases to digest protein; sucrase, maltase and lactase, which digest sugars; and intestinal lipase, which digests fats. 29.11The components of the large intestine are the cecum with its vermiform appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal ending in the anus. The large intestine’s primary job is to rid the body of solid waste by defecation.

59. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-58 In Summary (cont.) 29.12The liver is in the RUQ. It stores vitamins and iron and produces macrophages to fight infection. The gallbladder stores the bile produced by the liver. The pancreas produces pancreatic juices that assist in carbohydrate, lipid, and protein digestion. 29.13The liver secretes bile for fat digestion. Bile is released by the gallbladder for fat digestion. Pancreatic juices contain pancreatic amylase for carbohydrate digestion; lipase for lipid digestion; nucleases to digest nucleic acids; and trypsin, chymotrypsin, and carboxypeptidase to digest proteins.

60. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-59 In Summary (cont.) 29.14Nutrients absorbed by the body include carbohydrates, proteins, lipids, vitamins, minerals, and water. Most of the absorption takes place in the small intestine. 29.15Common diseases and disorders of the digestive system include inflammatory disorders such as appendicitis and colitis; cancers including colorectal, oral, and pancreatic cancers; as well as common symptoms such as diarrhea, constipation, and GERD. For more detailed information regarding these and other common disorders, please see the Pathophysiology section at the end of this chapter.

61. © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 29-60 Take all that is given whether wealth, love or language; nothing comes by mistake and with good digestion all can be turned to health. ~ George Herbert End of Chapter 29