Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 0

1 Chapter 17 The Digestive System

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 2 Objectives List in sequence each of the component parts or segments of the alimentary canal from the mouth to the anus and identify the accessory organs of digestion. List and describe the four layers of the wall of the alimentary canal. Compare the lining layer in the esophagus, stomach, small intestine, and large intestine.

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 3 Objectives (Contd.) List and describe the major disorders of the digestive organs. Discuss the basics of protein, fat, and carbohydrate digestion and give the end- products of each process. Define and contrast mechanical and chemical digestion. Define peristalsis, bolus, chyme, jaundice, ulcer, and diarrhea.

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 4 Chapter 17 Lesson 17.1

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 5 The Digestive System Alimentary canal or GI tract –Extends from mouth to anus9 m (29 feet) –Involved in digestion, absorption and metabolism of nutrients –System includes main and accessory organs Main organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anal canal Accessory organs: teeth and tongue, salivary glands, liver, gallbladder, pancreas, and vermiform appendix

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 6 Mouth Roofformed by hard palate (parts of maxillary and palatine bones) and soft palate (an arch-shaped muscle separating mouth from pharynx); uvula, a downward projection of soft palate

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 7 Mouth Floorformed by tongue and its muscles; papillae, small elevations on mucosa of tongue; taste buds, found in many papillae; lingual frenulum, fold of mucous membrane that helps anchor the tongue to the floor of the mouth

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 8 Teeth Names of teethincisors, cuspids, bicuspids, and tricuspids Twenty teeth in temporary set; average age for cutting first tooth about 6 months; set complete at about 2 years of age

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 9 Teeth Thirty-two teeth in permanent set; 6 years is average age for starting to cut first permanent tooth; set complete usually between ages of 17 and 24 years Structures of a typical toothcrown, neck, and root

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 10 Disorders of the Mouth and Teeth Problems include infections, cancer and congenital defects –Infections and cancer may spread –Leukoplakiaprecancerous condition of mouth tissue Snuff dippers pouchcaused by use of chewing tobacco Squamous cell carcinomamost common form of mouth cancer

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 11 Disorders of the Mouth and Teeth –Dental caries Tooth disease resulting in permanent defect called cavity Infection may spread to other adjacent tissues or to blood Lost or diseased teeth may be replaced by dentures or implants –Gingivitisgum inflammation or infection May result from poor oral hygiene, diabetes, vitamin deficiency, or pregnancy

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 12 Disorders of the Mouth and Teeth –Periodontitisinflammation of periodontal membrane Often a complication of advanced or untreated gingivitis Leading cause of tooth loss among adults –Thrush or oral candidiasiscaused by yeast- like fungal organism Patches of cheesy looking exudate form over an inflamed tongue and oral mucosa which itches and bleeds easily Common in immunosuppressed individuals (AIDS) or after antibiotic therapy

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 13 Disorders of the Mouth and Teeth –Congenital defects of mouth Cleft lip and cleft palate are most common types –May occur alone or together –Caused by failure of mouth structures to fuse during embryonic development

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 14 Salivary Glands Three pairs of glands produce about 1 liter of saliva each daylocated outside of GI tractconvey secretions via ducts into tract lumen Parotid glands –Largest of salivary glandslocated in front of ear at angle of jaw –Ducts open into mouth opposite second molars –Inflamed in mumps

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 15 Salivary Glands Submandibular glandsducts open on either side of lingual frenulum Sublingual glandsducts open into floor of mouth Saliva contains salivary amylasebegins digestion of carbohydrates

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 16 Pharynx Muscular tube lined with mucous membrane Functions as part of both respiratory and digestive systems Subdivided into three anatomical segments

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 17 Wall of the Digestive Tract The wall of the digestive tube is formed by four layers of tissue –Mucosamucous epithelium –Submucosaconnective tissue –Muscularistwo layers of smooth muscle –Serosaserous membrane that covers the outside of abdominal organs; it attaches the digestive tract to the wall of the abdominopelvic cavity by forming folds called mesenteries

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 18 Esophagus Muscular, mucus-lined tube about 25 cm (10 inches) long Connects pharynx with stomach Muscular walls help push food toward stomach Sphincters in GI tract help keep ingested material moving in one direction down the tube Each end of esophagus guarded by a sphincterupper esophageal sphincter (UES) and lower esophageal sphincter (LES)

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 19 Esophagus GERDgastroesophageal reflux disease (severe/ongoing heartburn); backflow of acidic stomach contents into esophagus –Causes include problem foods and hiatal hernia –Nonsurgical treatments include dietary changes, weight loss, acid blocking medications, and drugs which strengthen LES

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 20 Esophagus –Surgical treatments include fundoplication, Stretta, and Bard endoscopic suturing procedures

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 21 Stomach Sizeexpands after large meal; about size of large sausage when empty Pyloruslower part of stomach; pyloric sphincter muscle closes opening of pylorus into duodenum Wallmany smooth muscle fibers; contractions produce churning movements (peristalsis)

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 22 Stomach Liningmucous membrane; many microscopic glands that secrete gastric juice and hydrochloric acid into stomach; mucous membrane lies in folds (rugae) when stomach is empty

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 23 Disorders of the Stomach Gastroenterologystudy of stomach and intestines and their diseases; gastric diseases often exhibit these signs or symptoms: gastritis (inflammation), anorexia (appetite loss), nausea (upset stomach), and emesis (vomiting) Pylorospasmabnormal spasms of the pyloric sphincter; pyloric stenosis is similar, also narrowing the pyloric opening

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 24 Disorders of the Stomach Ulcersopen wounds caused by acid in gastric juice –Often occur in duodenum or stomach –Associated with infection by the bacterium Helicobacter pylori and use of NSAIDs Stomach cancer is associated with consumption of alcohol or preserved food and use of chewing tobacco

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 25 Small Intestine Sizeabout 7 meters (20 feet) long but only 2 cm or so in diameter Divisions –Duodenum –Jejunum –Ileum Wallcontains smooth muscle fibers that contract to produce peristalsis

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 26 Small Intestine Liningmucous membrane; many microscopic glands (intestinal glands) secrete intestinal juice; villi (microscopic finger-shaped projections from surface of mucosa into intestinal cavity) contain blood and lymph capillaries

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 27 Disorders of the Small Intestine Enteritisintestinal inflammation; gastroenteritisinflammation of stomach and intestines Malabsorption syndromegroup of symptoms resulting from failure to absorb nutrients properly (e.g., anorexia, abdominal bloating, cramps, anemia, and fatigue)

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 28 Liver and Gallbladder Size and locationliver is largest gland; fills upper right section of abdominal cavity and extends over into left side Liver secretes bile Ducts –Hepaticdrains bile from liver

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 29 Liver and Gallbladder –Cysticduct by which bile enters and leaves gallbladder –Common bileformed by union of hepatic and cystic ducts; drains bile from hepatic or cystic ducts into duodenum

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 30 Liver and Gallbladder Gallbladder –Locationundersurface of the liver –Functionconcentrates and stores bile produced in the liver Disorders of the liver and gallbladder –Gallstonescalculi (stones) made of crystallized bile pigments and calcium salts

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 31 Liver and Gallbladder Cholelithiasiscondition of having gallstones (Figure 17-13) Cholecystitisinflammation of the gallbladder; may accompany cholelithiasis Can obstruct bile canals, causing jaundice

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 32 Liver and Gallbladder –Hepatitisliver inflammation Characterized by liver enlargement, jaundice, anorexia, discomfort, gray–white feces, and dark urine Caused by a variety of factorstoxins, bacteria, viruses, and parasites

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 33 Liver and Gallbladder –Cirrhosisdegeneration of liver tissue involving replacement of normal (but damaged) tissue with fibrous and fatty tissue –Portal hypertensionhigh blood pressure in the hepatic portal veins caused by obstruction of blood flow in a diseased liver; may cause varicosities of surrounding systemic veins

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 34 Pancreas Locationbehind stomach B Functions –Pancreatic cells secrete pancreatic juice into pancreatic ducts; main duct empties into duodenum –Pancreatic islets (of Langerhans)cells not connected with pancreatic ducts; secrete hormones glucagons and insulin into the blood

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 35 Pancreas Pancreatic disorders –Pancreatitisinflammation of pancreas; acute pancreatitis results from blocked ducts that force pancreatic juice to backflow, digesting the gland –Cystic fibrosisthick secretions block flow of pancreatic juice –Pancreatic cancer is very seriousfatal in the majority of cases

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 36 Large Intestine Divisions –Cecum –Colonascending, transverse, descending, and sigmoid –Rectum Opening to exterioranus

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 37 Large Intestine Wallcontains smooth muscle fibers that contract to produce churning, peristalsis, and defecation Liningmucous membrane

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 38 Large Intestine Disorders of the large intestine often relate to abnormal motility (rate of movement of contents) –Diarrhea results from abnormally increased intestinal motility; may result in dehydration or convulsions –Constipation results from decreased intestinal motility

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 39 Large Intestine –Diverticulitis (inflammation of abnormal outpouchings called diverticula) may cause constipation –Colitis is the general name for any inflammatory condition of the large intestine –Colorectal cancer is a common malignancy of the colon and rectum associated with colonic polyps; advanced age; low-fiber, high-fat diets; and genetic predisposition

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 40 Appendix and Appendicitis Blind tube off cecum; no important digestive function in humans Appendicitisinflammation or infection of appendix; if appendix ruptures, infectious material may spread to other organs

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 41 Peritoneum Definitionsperitoneum, serous membrane lining abdominal cavity and covering abdominal organs; parietal layer of peritoneum lines abdominal cavity; visceral layer of peritoneum covers abdominal organs; peritoneal space lies between parietal and visceral layers

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 42 Peritoneum Extensionslargest ones are the mesentery and greater omentum; mesentery is extension of parietal peritoneum, which attaches most of small intestine to posterior abdominal wall; greater omentum, or lace apron, hangs down from lower edge of stomach and transverse colon over intestines

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 43 Peritoneum Peritonitisinflammation of peritoneum resulting from infection or other irritant; often a complication of ruptured appendix Ascitesabnormal accumulation of fluid in peritoneal space, often causing bloating of abdomen

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 44 Chapter 17 Lesson 17.1

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 45 Digestion Meaningchanging foods so that they can be absorbed and used by cells Mechanical digestionchewing, swallowing, and peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 46 Digestion Chemical digestionbreaks up large food molecules into compounds having smaller molecules; brought about by digestive enzymes

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 47 Digestion Carbohydrate digestionmainly in small intestine –Pancreatic amylasechanges starches to maltose –Intestinal juice enzymes Maltasechanges maltose to glucose Sucrasechanges sucrose to glucose Lactasechanges lactose to glucose

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 48 Digestion Protein digestionstarts in stomach; completed in small intestine –Gastric juice enzymes, rennin and pepsin, partially digest proteins –Pancreatic enzyme, trypsin, completes digestion of proteins to amino acids –Intestinal enzymes, peptidases, complete digestion of partially digested proteins to amino acids

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 49 Digestion Fat digestion –Bile contains no enzymes but emulsifies fats (breaks fat droplets into very small droplets) –Pancreatic lipase changes emulsified fats to fatty acids and glycerol in small intestine

Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 50 Absorption Meaningdigested food moves from intestine into blood or lymph Where absorption occursfoods and most water from small intestine; some water also absorbed from large intestine