Anatomy d igestivechapter_017


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Digestion lecture

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  • How long is the gastrointestinal tract? 9 m (29 ft) long Foods are digested in and absorbed from the gastrointestinal tract. Metabolism: products of digestion are metabolized in the cells of the body.
  • Location of digestive organs.
  • What is the function of the uvula? It prevents food from entering the nasal cavities. What is the lingual frenulum? A thin membrane that attaches the tongue to the floor of the mouth What happens when the frenulum is too short? Free movements of the tongue is severely restricted; individuals with this condition cannot enunciate words normally and are said to be “tongue-tied.” See Figure 17-2. Discuss therapies for this condition. Surgery, speech therapy
  • Mouth cavity and tongue. A, Mouth cavity showing hard and soft palates, tongue surface, and uvula. B, Undersurface of tongue showing frenulum, sublingual gland, and opening of sublingual duct. C, Photograph shows an abnormally short lingual frenulum, which may result in faulty speech. D, Papillae with taste buds located on the lateral surfaces. (C, From Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis , ed 5, Philadelphia, 2007, Mosby., D, Dennis Strete.)
  • What is the major function of the bicuspids and tricuspids? They begin the mechanical breakdown of food by chewing. How are they structurally suited to performing this function? They have large surfaces with several grinding or crushing sharp points on the surface. Crown: visible part of tooth. What covers the outside of the tooth? Enamel What is the neck of the tooth? The portion in direct contact with the gums Root: holds the tooth in the socket, which is lined with a fibrous periodontal membrane and is connected to the pulp, which is the central-most part of the tooth. What important structures are found in the pulp? Nerves, blood and lymphatic vessels Why does a dentist anesthetize the patient when drilling a tooth? In the process of drilling out the decayed part of a tooth, the drill tip may enter the pulp cavity of the tooth, which contains sensory nerves. Discuss the importance of the baby teeth in maintaining the health of the permanent teeth. Healthy teeth are important for good nutrition. When are baby teeth formed, as opposed to when they erupt? Tooth buds are formed prenatally. What is gum disease, and why is it significant? Gum disease, or gingivitis, is inflammation or infection of the guns. Most cases result from poor oral hygiene – inadequate brushing and/or flossing. Gingivitis is the leading cause of adult tooth loss. Why do heart patients and diabetics take prophylactic antibiotics before a dental visit? Gingivitis may be a complication of diabetes mellitus, vitamin deficiency, or pregnancy. Patients with cardiac disease or diabetes mellitus should try to avoid infections. Any dental procedure may dislodge bacteria around the gum tissue and thereby facilitate its transport to other parts of the body.
  • The deciduous (primary) teeth and adult teeth. In the deciduous (primary) set, also called “baby” teeth, there are no premolars and only two pairs of molars in each jaw. Generally the lower teeth erupt before the corresponding upper teeth. (Barbara Cousins.)
  • Longitudinal section of a tooth. A molar is sectioned here to show its bony socket and details of its three main parts: crown, neck, and root. Enamel (over the crown) and cementum (over the neck and root) surround the dentin layer. The pulp contains nerves and blood vessels.
  • What is snuff dipper’s pouch? An area between the cheek and the gum where leukoplakia often develops
  • Disorders of the mouth and teeth. A, Snuff dipper’s pouch. This individual has developed leukoplakia in the area between cheek and gum used for placement of chewing tobacco. B, Squamous cell carcinoma of lip. Excessive long-term exposure to ultraviolet light (UV) such as in sunlight increases the risk of skin cancer. C, Dental caries. These permanent defects, or cavities, are filled with decayed dental tissues. (A, From Regezi JA, Sciubba JJ, Pogrel MA: Atlas of oral and maxillofacial pathology , Philadelphia, 2000, Saunders., B, From Swartz MH: Textbook of physical diagnosis , ed 4, Philadelphia, 2002, Saunders., C, From Grundy JR, Jones JG: A color atlas of clinical operative dentistry: crowns and bridges , ed 2, London, 1993, Mosby-Wolfe.)
  • Dental implant. A permanent dental prosthesis will be affixed to the anchor after bone grows and healing has occurred. (From Christensen GJ: A consumer’s guide to dentistry , ed 2, St Louis, 2002, Mosby.)
  • Oral thrush (Candida albicans). Inflamed mucous membrane is covered with patches of creamy-white exudates. (From Emond R, Welsby P, Rowland H: Colour atlas of infectious diseases , ed 4, Edinburgh, 2003, Mosby.)
  • What is cleft lip? An abnormality that results in f ailure of the upper lip to close properly What is a cleft palate? An abnormality that results in failure of the palate to close or fuse properly How and when are cleft lip and palate treated? Both deformities are treated surgically. Cleft lip is repaired soon after birth, and cleft palate is repaired within the first year of life.
  • Congenital defects of the mouth. A, Bilateral cleft lip in an infant. B, Cleft palate. (A, From Wilson SF, Giddens JF: Health assessment for nursing practice , ed 2, St Louis, 2001, Mosby., B, From Greig JD, Garden OJ: Color atlas of surgical diagnosis , London, 1996, Times Mirror International Publishers.)
  • Location of the salivary glands. A, The salivary glands and their associated ducts. B, Photo shows the inflamed opening of the parotid duct into the mouth of a patient with mumps. C, Mumps (paramyxovirus) inflammation and swelling of the parotid gland in a child. (A, Rolin Graphics., B, From Emond R, Welsby P, Rowland H: Colour atlas of infectious diseases , ed 4, Edinburgh, 2003, Mosby., C, From Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis , ed 5, Philadelphia, 2007, Mosby. Courtesy GDW McKendrick, MD.)
  • What do the salivary glands secrete? Saliva What important digestive enzyme is in saliva? Salivary amylase, which begins the chemical digestion of carbohydrates Where does the process of digestion begin? In the mouth
  • The pharynx is a tubelike structure made of muscle and lined with mucous membrane. What two systems are served by the pharynx? It serves both the respiratory system and the digestive system. Air must pass through the pharynx on its way to the lungs. Food must pass through the pharynx on its way to the stomach.
  • Pharynx. This midsagittal section shows the three divisions of the pharynx (nasopharynx, oropharynx, and laryngopharynx) and nearby structures.
  • Layers of the small intestine. The four layers include the mucosa, submucosa, muscularis, and serosa.
  • Peristalsis conducts food to the stomach. Mucous membrane secretion facilitates passage of food.
  • Gastroesophageal reflux disease (GERD). Reflux of gastric acid up into the esophagus, causing irritation of the lining of the esophagus.
  • Hiatal hernia. Note herniated portion of stomach pushed through diaphragm. LES, Lower esophageal sphincter.
  • Discuss the location of the stomach relative to other structures of the gastrointestinal tract and other structures of the body. Discuss gastric juice composition and function. Explain how the three muscle layers running lengthwise, crosswise, and obliquely contribute to the process of digestion.
  • What are rugae? The lining of the stomach lies in folds called rugae when the stomach is empty.
  • Stomach. A portion of the anterior wall has been cut away to reveal the three muscle layers of the stomach wall. Notice that the mucosa lining the stomach forms folds called rugae.
  • Gastroenterology is the study of the stomach and intestines and their diseases. Disorders and diseases of the stomach usually present one or more of the following symptoms: gastritis, anorexia, nausea, or emesis. What is triple therapy? Three medications are taken concurrently for 2 to 4 weeks to treat ulcers and Crohn disease. The medications are Pepto-Bismol and two antibiotics.
  • Discuss the function of the villi and microvilli and how they are a prime example of the intimate relationship between structure and function. Villi project into the lumen of the intestine. Each villus contains a rich network of blood capillaries to absorb the products of carbohydrate and protein digestion and lymph capillaries (lacteals) to absorb fats. Microvilli are tiny villi on the villi that phenomenally increase the surface area for absorption.
  • The small intestine. A, Note the four tissue coats or layers and the presence of villi and microvilli, whichincrease the area available for absorption. B, X-ray study. C, Laparoscopic view. (B, From Weir J, Abrahams PH: Imaging atlas of human anatomy , ed 3, St Louis, 2004, Mosby., C, From Abrahams PH, Marks S, Hutchings R: McMinn’s color atlas of human anatomy , ed 5, Philadelphia, 2003, Mosby.)
  • What are some of the common symptoms of malabsorption syndrome? Anorexia, abdominal bloating, cramps, anemia, and fatigue These same symptoms often occur in many other diseases of the digestive tract. How then is a definitive diagnosis often made? With information gained from endoscopy and x-ray studies
  • What are the two main components of bile? Cholesterol and bile pigments that emulsify fat What effect might dieting have on the production of bile? Severely obese individuals produce higher levels of cholesterol and have an increased risk of developing gallstones. Significant and rapid weight loss greatly increases the risk of symptomatic gallstone formation. What is jaundice? A yellowish skin color that develops from bile pigments being absorbed into the blood. Explain under what circumstances it might occur. Blockage of the common bile duct prevents bile from draining into the duodenum.
  • The gallbladder and bile ducts . Obstruction of the hepatic or common bile duct by stone or spasm blocks the exit of bile from the liver, where it is formed, and prevents bile from being ejected into the duodenum. The drawing shows gallstone locations: in the gallbladder (a), blocking the cystic duct (b), in the common bile duct (c), and blocking both the pancreatic duct and the common bile duct (d). Inset shows an x-ray of the gallbladder and the ducts that carry bile taken during a specialized procedure called an endoscopic cholangiography . See text for explanation. Inset: 1, Common bile duct; 2, common hepatic duct; 3, cystic duct; 4, gallbladder; 5, left hepatic duct; 6, liver shadow with tributaries of hepatic ducts; 7, right hepatic duct. (From Abrahams PH, Marks S, Hutchings R: McMinn’s color atlas of human anatomy , ed 5, Philadelphia, 2003, Mosby., X-Ray: From Abrahams PH, Marks S, Hutchings R: McMinn’s color atlas of human anatomy , ed 5, Philadelphia, 2003, Mosby.)
  • What would happen if the common bile duct were obstructed by a gallstone? The condition of cholelithiasis occurs. What signs and symptoms would appear? Gray-white feces would be passed because of the absence of bile pigments; jaundice would occur because of bile pigments being absorbed into the blood; pain, called biliary colic, would be felt. What would happen if the cystic duct was blocked? No jaundice would occur. What extreme diets are more commonly associated with the formation of gallstones? Rapid weight loss diets What is the relationship between significant weight loss and gallstones? Significant and rapid weight loss greatly increases the risk of gallstone formation.
  • Gallstones. A, Inflamed gallbladder filled with yellow cholesterol gallstones. B, Laparoscopic view of the gallbladder before removal. (Courtesy Thompson JM, Wilson SF: Health assessment for nursing practice , St Louis, 1996, Mosby.)
  • Discuss the differences among hepatitis A, B, and C. Hepatitis is a general term referring to inflammation of the liver characterized by jaundice, liver enlargement, anorexia, abdominal discomfort, gray-white feces, and dark urine. A number of different conditions can cause hepatitis. The letters associated with the disease distinguish the cause: Hepatitis A is caused by a virus and contracted through contaminated food; Hepatitis B is also caused by a virus and is contracted through contact with contaminated blood or improperly sterilized equipment; Hepatitis C is caused by a virus and associated with transfusion of contaminated blood or intravenous drug use.
  • Portal hypertension is high blood pressure in the hepatic portal veins caused by obstruction of blood flow in a diseased liver. What is the danger of this condition? Varicosities of surrounding veins occur. These can rupture and cause death.
  • Liver damage. A, Alcoholic cirrhosis where liver surface is hard and covered with nodules that look like pebbles. B, Varicose veins (varicies) of the esophagus caused by reduction of blood flow through liver with cirrhosis. (A, Copyright Kevin Patton, Lion Den Inc, Weldon Spring, MO.)
  • The pancreatic duct joins the common bile duct and empties into the duodenum. Why is pancreatic juice the most important digestive juice? It contains enzymes that digest all three major kinds of food (carbohydrates, fats, proteins).
  • How long does it normally take for food to pass through the entire alimentary canal? 3 to 5 days Of what consistency is the chyme by the time it reaches the large intestine? The consistency of chyme changes to a more solid fecal matter as water and salts are reabsorbed from it back into the body. Is it still referred to as chyme at this point? No, it is then called feces. From what food materials can the large intestine extract some nutrient value? From cellulose and other fibrous materials What is in the large intestine that enables this digestion? Bacteria What other functions do the intestinal bacteria perform? Synthesis of vitamin K and some B-complex vitamins
  • Divisions of the large intestine. A, Artist’s drawing of the large intestine. B, X-ray of large intestine and terminal ileum filled with barium contrast material (barium enema). C, X-ray of a barium enema showing diverticulosis (arrowheads). D, Acute appendicitis. Appendix is gangrenous and showing signs of ischemia and putrefaction. (B, Courtesy Thompson JM, Wilson SF: Health assessment for nursing practice , St Louis, 1996, Mosby., C, From Chabner DE: The language of medicine , ed 8, St Louis, 2008, Mosby., D, From Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis , ed 3, Philadelphia, 1997, Mosby.)
  • Colorectal cancer is the second leading cause of death from cancer in the United States. What are some of the early warning signs? Change in bowel habits, decreased stool diameter, bleeding in stool, abdominal pain, anemia, weight loss, and fatigue Colon cancer is often treated by surgically creating a colostomy. What is this procedure? It involves diversion of a part of the colon to an opening on the abdomen.
  • The parietal layer lines the abdominal cavity. The visceral layer forms the outer covering of each abdominal organ. The peritoneal space is the space between the two layers. What is contained in the peritoneal space and what function does it serve? It contains peritoneal fluid, which serves to keep both layers of the peritoneum moist and able to slide freely against each other to reduce friction during breathing and peristalsis.
  • The peritoneum. A, The parietal layer of the peritoneum lines the abdominopelvic cavity and then extends as a series of mesenteries to form the visceral layer that covers abdominal organs. B, The transversecolon and greater omentum are raised and the small intestine is pulled to the side to show the mesentery.
  • Ascites. Ascites results from an accumulation of fluid in the peritoneal space. The arrows indicate water filtering out of the peritoneal blood vessels, resulting from hypertension, or diff using out of the vessels because of an osmotic imbalance in the blood. ( Photo: From Swartz MH: Textbook of physical diagnosis , ed 4, Philadelphia, 2002, Saunders.)
  • How do mechanical and chemical digestion differ? Mechanical digestion breaks food into tiny particles, mixes them with digestive juices, and moves them along the alimentary canal until the digestive wastes are eliminated through the anus. Chewing (mastication), swallowing (deglutition), peristalsis, and defecation are the main processes of mechanical digestion. Chemical digestion breaks down large, nonabsorbable food molecules into smaller, absorbable molecules that can pass through the intestinal mucosa into blood and lymph.
  • What is the difference between simple sugars and complex sugars? Complex sugars are broken down into simple sugars for use as energy. Why do complex sugars have to be broken down to be absorbed? They are too large to be absorbed. Why is active transport used to move monosaccharides into the cell, but diffusion is used to get them into the blood capillaries? Monosaccharides can diffuse through the villi into the capillaries because the process of diffusion can transport substances from a greater concentration to a lesser concentration; active transport is necessary to move monosaccharides into the cell. What are the major end products of carbohydrate digestion? Simple sugars, especially glucose Discuss the cause and treatment of lactose intolerance. The cause is absence of lactase, which is needed to digest lactose; enzymes can be given orally when lactose is ingested to assist in digestion.
  • Why is active transport used to move amino acids into the cell, but diffusion is used to get them into the blood capillaries?
  • Is bile a component of chemical digestion or mechanical digestion? Mechanical digestion because of emulsification. Why? Why aren’t fatty acids secreted into the blood capillaries instead of the lacteals? They won’t mix with water. Why is diffusion used to move amino acids into the cell, but secretion is used to get them into the lymph capillaries (lacteals)?
  • What is the difference between digestion and absorption of foods? Digestion simply breaks food down; absorption transports the nutrients of food into the blood stream so they be used by body cells. What is the significance of salt being actively transported through the intestinal mucosa? It responds to the sodium needs of the body. What is the principle on which fluid replacement drinks such as Gatorade and other sport drinks are based? An electrolyte solution is absorbed to avoid water intoxication.
  • Anatomy d igestivechapter_017

    1. 1. Chapter 17 The Digestive System
    2. 2. Objectives <ul><li>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 </li></ul><ul><li>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. </li></ul>
    3. 3. Objectives <ul><li>List and describe the major disorders of the digestive organs </li></ul><ul><li>Discuss the basics of protein, fat, and carbohydrate digestion and give the end-products of each process </li></ul><ul><li>Define and contrast mechanical and chemical digestion </li></ul><ul><li>Define peristalsis, bolus, chyme, jaundice, ulcer, and diarrhea </li></ul>
    4. 4. The Digestive System <ul><li>Alimentary canal or GI tract </li></ul><ul><ul><li>Extends from mouth to anus—9 m (29 feet) </li></ul></ul><ul><ul><li>Involved in digestion, absorption and metabolism of nutrients </li></ul></ul><ul><li>System includes main and accessory organs </li></ul><ul><ul><li>Main organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anal canal </li></ul></ul><ul><ul><li>Accessory organs: teeth and tongue, salivary glands, liver, gallbladder, pancreas, and vermiform appendix </li></ul></ul>
    5. 5.
    6. 6. Mouth <ul><li>Also known as oral cavity —hollow chamber with a roof, floor, and walls </li></ul><ul><li>Roof—formed by hard palate (parts of maxillary and palatine bones) and soft palate (an arch-shaped muscle separating mouth from pharynx) </li></ul>
    7. 7. Mouth <ul><li>Uvula—a downward projection of the soft palate </li></ul><ul><ul><li>Uvula and soft palate prevent food and liquid from entering nasal cavities </li></ul></ul><ul><ul><li>Assists in speech and swallowing (deglutition) </li></ul></ul>
    8. 8. Mouth <ul><li>Floor—formed by tongue and its muscles </li></ul><ul><ul><li>Lingual frenulum—fold of mucous membrane that helps anchor the tongue to the floor of the mouth </li></ul></ul><ul><ul><li>Papillae—small elevations on mucosa of tongue </li></ul></ul><ul><ul><li>Taste buds—found in many papillae </li></ul></ul>
    9. 9.
    10. 10. Teeth <ul><li>Types of teeth—incisors, cuspids, bicuspids, and tricuspids </li></ul><ul><ul><li>Deciduous (also known as baby or primary) teeth—full set equals 20 teeth </li></ul></ul><ul><ul><ul><li>First tooth erupts at about 6 months </li></ul></ul></ul><ul><ul><ul><li>Complete set in place at about 2 years of age </li></ul></ul></ul>
    11. 11. Teeth <ul><li>Permanent teeth—full set equals 32 in most; 28 teeth is a normal variation in others </li></ul><ul><ul><li>First permanent tooth erupts at about 6 years of age </li></ul></ul><ul><ul><li>Set complete between ages 17 and 24 years </li></ul></ul><ul><li>Structures of a typical tooth—crown, neck, and root </li></ul>
    12. 12.
    13. 13.
    14. 14. Disorders of the Mouth and Teeth <ul><li>Infections, cancer, congenital defects, and other disorders can cause serious complications including malnutrition </li></ul><ul><ul><li>Infections and cancer of the mouth may spread to other parts of the body </li></ul></ul><ul><ul><ul><li>Leukoplakia—precancerous mouth tissue </li></ul></ul></ul><ul><ul><ul><ul><li>Snuff dipper’s pouch—from use of chewing tobacco </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Squamous cell carcinoma—most common form of mouth cancer </li></ul></ul></ul></ul>
    15. 15.
    16. 16. Disorders of the Mouth and Teeth <ul><ul><ul><li>Dental caries </li></ul></ul></ul><ul><ul><ul><ul><li>Tooth disease resulting in permanent defect called “cavity” </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Infection may spread to other adjacent tissues or to blood </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Lost or diseased teeth may be replaced by dentures or implants </li></ul></ul></ul></ul><ul><ul><ul><li>Gingivitis—gum inflammation or infection </li></ul></ul></ul><ul><ul><ul><ul><li>Most cases result from poor oral hygiene </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Can be a complication of diabetes, vitamin deficiency, or pregnancy </li></ul></ul></ul></ul>
    17. 17.
    18. 18. Disorders of the Mouth and Teeth <ul><ul><ul><li>Thrush, or oral candidiasis—caused by yeastlike fungal organism </li></ul></ul></ul><ul><ul><ul><ul><li>Patches of “cheesy”-looking exudate form over an inflamed tongue and oral mucosa, which itches and bleeds easily </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Common in immunosuppressed individuals (AIDS) or after antibiotic therapy </li></ul></ul></ul></ul><ul><ul><ul><li>Periodontitis—inflammation of periodontal membrane </li></ul></ul></ul><ul><ul><ul><ul><li>Often a complication of advanced or untreated gingivitis </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Leading cause of tooth loss among adults </li></ul></ul></ul></ul>
    19. 19.
    20. 20. Disorders of the Mouth and Teeth <ul><ul><ul><li>Cleft lip and cleft palate are most common types </li></ul></ul></ul><ul><ul><ul><ul><li>May occur alone or together </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Caused by failure of mouth structures to fuse during embryonic development </li></ul></ul></ul></ul>
    21. 21.
    22. 22. Salivary Glands <ul><li>Three pairs of salivary glands </li></ul><ul><ul><li>Secrete about 1 L of saliva/day </li></ul></ul><ul><ul><li>Located outside of GI tract </li></ul></ul><ul><ul><li>Convey secretions via ducts into tract lumen </li></ul></ul><ul><li>Parotid glands—largest of salivary glands </li></ul><ul><ul><li>Located in front of ear at angle of jaw </li></ul></ul><ul><ul><li>Ducts open into mouth opposite second molars </li></ul></ul><ul><ul><li>Inflamed in mumps </li></ul></ul>
    23. 23.
    24. 24. Salivary Glands <ul><li>Submandibular glands—ducts open on either side of lingual frenulum </li></ul><ul><li>Sublingual glands—ducts open into floor of mouth </li></ul><ul><li>Saliva contains salivary amylase—begins digestion of carbohydrates </li></ul>
    25. 25. Pharynx <ul><li>Muscular tube (throat) lined with mucous membrane </li></ul><ul><li>Functions as part of both respiratory and digestive systems </li></ul><ul><li>Subdivided into three anatomical segments </li></ul>
    26. 26.
    27. 27. Wall of the Digestive Tract <ul><li>Lumen—hollow space within the “tube” of the digestive tract </li></ul><ul><li>Tissue layers of the wall of the digestive tube from inside to outside </li></ul><ul><ul><li>Mucosa—mucous epithelium </li></ul></ul><ul><ul><li>Muscularis—two layers of smooth muscle that move food through the tube by rhythmic muscular waves known as peristalsis </li></ul></ul>
    28. 28. Wall of the Digestive Tract <ul><li>Tissue layers (cont’d) </li></ul><ul><ul><li>Serosa—serous membrane that covers the outside of abdominal organs </li></ul></ul><ul><ul><ul><li>Composed of visceral peritoneum in abdominal cavity </li></ul></ul></ul><ul><ul><ul><li>It attaches the digestive tract to the wall of the abdominopelvic cavity by forming folds called mesenteries </li></ul></ul></ul>
    29. 29.
    30. 30. Esophagus <ul><li>Muscular, mucus-lined tube about 25 cm (10 inches) long </li></ul><ul><li>Connects pharynx with stomach </li></ul><ul><li>Muscular walls help push food toward stomach </li></ul><ul><li>Sphincters at each end of esophagus help keep ingested material moving in one direction down the tube </li></ul><ul><ul><li>Upper esophageal sphincter (UES) </li></ul></ul><ul><ul><li>Lower esophageal sphincter (LES) </li></ul></ul>
    31. 31. Esophagus <ul><li>GERD—gastroesophageal reflux disease </li></ul><ul><ul><li>Backflow of acidic stomach contents into esophagus causes symptoms of heartburn and indigestion </li></ul></ul><ul><ul><li>Mild symptoms treated by nonsurgical measures include dietary changes, weight loss, acid-blocking or buffering medications, and drugs that strengthen LES </li></ul></ul>
    32. 32. Esophagus <ul><li>GERD </li></ul><ul><ul><li>Severe and frequent episodes of GERD can trigger asthma attacks, cause severe chest pain, bleeding, or narrowing and chronic irritation of esophagus (Figure 17-12) </li></ul></ul><ul><ul><li>Untreated GERD may result in a precancerous condition called Barrett esophagus </li></ul></ul><ul><ul><li>Common symptom of hiatal hernia </li></ul></ul>
    33. 33.
    34. 34.
    35. 35. Stomach <ul><li>Pouch for food that lies in upper part of abdominal cavity just under diaphragm </li></ul><ul><ul><li>The size of a large sausage when empty </li></ul></ul><ul><ul><li>Expands considerably after a large meal </li></ul></ul><ul><li>Contraction of muscular walls of stomach mixes food with gastric juice and breaks it down into chyme </li></ul>
    36. 36. Stomach <ul><li>Mucous membrane lines the stomach </li></ul><ul><ul><li>Membrane lies in folds (rugae) when stomach is empty </li></ul></ul><ul><ul><li>Many microscopic glands secrete gastric juice and hydrochloric acid into stomach </li></ul></ul><ul><li>Divisions of stomach—fundus, body, and pylorus </li></ul><ul><li>Pyloric sphincter muscle closes opening of pylorus (lower part of stomach) to retain food to facilitate partial digestion </li></ul>
    37. 37.
    38. 38. Disorders of the Stomach <ul><li>Gastroenterology—study of stomach and intestines and their diseases </li></ul><ul><ul><li>Stomach is site of numerous diseases and conditions </li></ul></ul><ul><ul><li>Gastric diseases often exhibit the following signs or symptoms: gastritis (inflammation), anorexia (appetite loss), nausea (upset stomach), and emesis (vomiting) </li></ul></ul>
    39. 39. Disorders of the Stomach <ul><li>Pylorospasm—abnormal spasms of the pyloric sphincter </li></ul><ul><ul><li>Common in infants </li></ul></ul><ul><ul><li>Pyloric stenosis is similar abnormality—obstructive narrowing of the pyloric opening </li></ul></ul><ul><li>Ulcers—open wounds caused by acid in gastric juice </li></ul><ul><ul><li>Often occurs in duodenum or stomach </li></ul></ul><ul><ul><li>Associated with infection by the bacterium Helicobacter pylori and use of NSAIDs </li></ul></ul><ul><ul><li>Current treatment involves triple therapy </li></ul></ul>
    40. 40. Disorders of the Stomach <ul><li>Stomach cancer </li></ul><ul><ul><li>Associated with consumption of alcohol or preserved food and use of chewing tobacco </li></ul></ul><ul><ul><li>No practical way to screen for early stages </li></ul></ul>
    41. 41. Small Intestine <ul><li>About 7 m (20 feet) long but only 2 cm or so in diameter </li></ul><ul><li>Divisions </li></ul><ul><ul><li>Duodenum </li></ul></ul><ul><ul><li>Jejunum </li></ul></ul><ul><ul><li>Ileum </li></ul></ul><ul><li>Wall—contains smooth muscle fibers that contract to produce peristalsis </li></ul>
    42. 42. Small Intestine <ul><li>Lining—mucous 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 </li></ul>
    43. 43.
    44. 44. Disorders of the Small Intestine <ul><li>Enteritis—intestinal inflammation </li></ul><ul><li>Gastroenteritis—inflammation of stomach and intestines </li></ul><ul><li>Malabsorption syndrome—group of symptoms resulting from failure to absorb nutrients properly (anorexia, abdominal bloating, cramps, anemia, and fatigue) </li></ul>
    45. 45. Liver and Gallbladder <ul><li>Liver </li></ul><ul><ul><li>Size and location </li></ul></ul><ul><ul><ul><li>Liver is largest gland </li></ul></ul></ul><ul><ul><ul><li>Fills upper right section of abdominal cavity and extends over into left side </li></ul></ul></ul><ul><ul><li>Classified as exocrine gland </li></ul></ul><ul><ul><ul><li>Secretes bile </li></ul></ul></ul><ul><ul><ul><li>Has a variety of metabolic functions </li></ul></ul></ul>
    46. 46. Liver and Gallbladder <ul><li>Liver </li></ul><ul><ul><li>Ducts </li></ul></ul><ul><ul><ul><li>Hepatic—drains bile from liver </li></ul></ul></ul><ul><ul><ul><li>Cystic—duct by which bile enters and leaves gallbladder </li></ul></ul></ul><ul><ul><ul><li>Common bile—formed by union of hepatic and cystic ducts and drains bile from hepatic or cystic ducts into duodenum </li></ul></ul></ul><ul><li>Gallbladder </li></ul><ul><ul><li>Location—undersurface of the liver </li></ul></ul><ul><ul><li>Function—concentrates and stores bile produced in the liver </li></ul></ul>
    47. 47.
    48. 48. Disorders of the Liver and Gallbladder <ul><li>Gallstones—calculi (stones) made of crystallized bile pigments and calcium salts </li></ul><ul><ul><li>Cholelithiasis—condition of having gallstones </li></ul></ul><ul><ul><li>Cholecystitis—inflammation of the gallbladder; may accompany cholelithiasis </li></ul></ul><ul><ul><li>Stones can obstruct bile canals, causing jaundice </li></ul></ul>
    49. 49.
    50. 50. Disorders of the Liver and Gallbladder <ul><li>Hepatitis—liver inflammation </li></ul><ul><ul><li>Characterized by liver enlargement, jaundice, anorexia, discomfort, gray-white feces, and dark urine </li></ul></ul><ul><ul><li>Caused by a variety of factors—toxins, bacteria, viruses, and parasites </li></ul></ul>
    51. 51. Disorders of the Liver and Gallbladder <ul><li>Cirrhosis—degeneration of liver tissue involving replacement of normal (but damaged) tissue with fibrous and fatty tissue </li></ul><ul><li>Portal hypertension—high blood pressure in the hepatic portal veins caused by obstruction of blood flow in a diseased liver; may cause varicosities of surrounding systemic veins </li></ul>
    52. 52.
    53. 53. Pancreas <ul><li>Location—behind stomach </li></ul><ul><li>Functions </li></ul><ul><ul><li>Pancreatic cells secrete pancreatic juice into pancreatic ducts; main duct empties into duodenum </li></ul></ul><ul><ul><li>Pancreatic islets (of Langerhans)—cells not connected with pancreatic ducts; secrete hormones glucagons and insulin into the blood </li></ul></ul>
    54. 54. Pancreas <ul><li>Pancreatic disorders </li></ul><ul><ul><li>Pancreatitis—inflammation of pancreas </li></ul></ul><ul><ul><ul><li>Acute pancreatitis results from blocked ducts that force pancreatic juice to backflow </li></ul></ul></ul><ul><ul><ul><li>Pancreatic enzymes digest the gland </li></ul></ul></ul><ul><ul><li>Cystic fibrosis—thick secretions block flow of pancreatic juice </li></ul></ul><ul><ul><li>Pancreatic cancer is very serious—fatal in the majority of cases </li></ul></ul>
    55. 55. Large Intestine <ul><li>Size and location—1.5 m long; forms lower, or terminal, portion of digestive tract </li></ul><ul><li>Divisions </li></ul><ul><ul><li>Cecum </li></ul></ul><ul><ul><li>Colon—ascending, transverse, descending, and sigmoid </li></ul></ul><ul><ul><li>Rectum </li></ul></ul><ul><ul><li>Anal canal </li></ul></ul><ul><li>Opening to exterior—anus </li></ul>
    56. 56.
    57. 57. Disorders of the Large Intestine <ul><li>Disorders of the large intestine often relate to abnormal motility (rate of movement of contents) </li></ul><ul><ul><li>Diarrhea—results from abnormally increased intestinal motility; may result in dehydration or convulsions </li></ul></ul><ul><ul><li>Constipation—results from decreased intestinal motility </li></ul></ul><ul><ul><li>Diverticulitis (inflammation of abnormal outpouchings called diverticula )—may cause constipation </li></ul></ul>
    58. 58. Disorders of the Large Intestine <ul><ul><li>Colitis—general name for any inflammatory condition of the large intestine </li></ul></ul><ul><ul><li>Colorectal cancer—a common malignancy of the colon and rectum associated with colonic polyps; advanced age; low-fiber, high-fat diets; and genetic predisposition </li></ul></ul>
    59. 59. Appendix and Appendicitis <ul><li>Vermiform appendix is blind tube attached directly to cecum; no important digestive function in humans </li></ul><ul><li>Appendicitis—inflammation or infection of appendix </li></ul><ul><ul><li>If appendix ruptures, infectious material may spread to other organs </li></ul></ul><ul><ul><li>Most common acute abdominal condition requiring surgery </li></ul></ul><ul><ul><li>Affects 7% to 12% of population younger than 30 years </li></ul></ul>
    60. 60. Peritoneum <ul><li>Description—large sheet of serous membrane </li></ul><ul><ul><li>Parietal layer of peritoneum lines abdominal cavity </li></ul></ul><ul><ul><li>Visceral layer of peritoneum covers abdominal organs </li></ul></ul><ul><ul><li>Peritoneal space lies between parietal and visceral layers </li></ul></ul>
    61. 61. Peritoneum <ul><li>Extensions of peritoneum—largest are the mesentery and greater omentum </li></ul><ul><ul><li>Mesentery—extension of parietal peritoneum, which attaches most of small intestine to posterior abdominal wall </li></ul></ul><ul><ul><li>Greater omentum, or “lace apron”—hangs down from lower edge of stomach and transverse colon over intestines </li></ul></ul>
    62. 62.
    63. 63. Peritoneum <ul><li>Peritonitis—inflammation of peritoneum resulting from infection or other irritant; often a complication of ruptured appendix </li></ul><ul><li>Ascites—abnormal accumulation of fluid in peritoneal space, often causes bloating of abdomen </li></ul>
    64. 64.
    65. 65. Digestion <ul><li>Definition—process that transforms food into a form that can be absorbed and used by cells </li></ul><ul><ul><li>Mechanical digestion—chewing, swallowing, and peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract </li></ul></ul><ul><ul><li>Chemical digestion—breaks up large food molecules into compounds having smaller molecules; brought about by digestive enzymes </li></ul></ul>
    66. 66. Digestion <ul><li>Enzymes and chemical digestion </li></ul><ul><ul><li>Enzymes—protein molecules that act as catalysts, speeding up chemical reactions </li></ul></ul><ul><ul><li>Chemical digestion—specific enzymes speed up breakdown of specific molecules and no others </li></ul></ul><ul><ul><li>Hydrolysis—enzymes speed up reactions that add water to break large molecules into smaller molecules </li></ul></ul>
    67. 67. Digestion <ul><li>Carbohydrate digestion—mainly in small intestine </li></ul><ul><ul><li>Pancreatic amylase—changes starches to maltose </li></ul></ul><ul><ul><li>Intestinal juice enzymes </li></ul></ul><ul><ul><ul><li>Maltase—changes maltose to glucose </li></ul></ul></ul><ul><ul><ul><li>Sucrase—changes sucrose to glucose </li></ul></ul></ul><ul><ul><ul><li>Lactase—changes lactose to glucose </li></ul></ul></ul>
    68. 68. Digestion <ul><li>Protein digestion—starts in stomach; completed in small intestine </li></ul><ul><ul><li>Gastric juice enzymes, rennin and pepsin, partially digest proteins </li></ul></ul><ul><ul><li>Pancreatic enzyme, trypsin, completes digestion of proteins to amino acids </li></ul></ul><ul><ul><li>Intestinal enzymes, peptidases, complete digestion of partially digested proteins to amino acids </li></ul></ul>
    69. 69. Digestion <ul><li>Fat digestion </li></ul><ul><ul><li>Bile contains no enzymes but emulsifies fats (breaks fat droplets into very small droplets) </li></ul></ul><ul><ul><li>Pancreatic lipase changes emulsified fats to fatty acids and glycerol in small intestine </li></ul></ul>
    70. 70. Absorption <ul><li>Definition—digested food moves from intestine into blood or lymph </li></ul><ul><li>Absorption site—foods and most water are absorbed from small intestine; some water also absorbed from large intestine </li></ul>