Digestive System Chapter 18 PDF

Digestive System Chapter 18  Learning Objectives Lesson 18.1: The Digestive Tract: Part I 1. List the main and accessory organs of the digestive system and discuss primary mechanisms of the digestive system. 2. List and describe the four layers of the diges...

Digestive System Chapter 18  Learning Objectives Lesson 18.1: The Digestive Tract: Part I 1. List the main and accessory organs of the digestive system and discuss primary mechanisms of the digestive system. 2. List and describe the four layers of the digestive tract wall, and discuss the value of each layer to the digestive system. 3. Discuss the structures of the mouth: the oral cavity, teeth, and salivary glands, as well as the disorders of the mouth. 4. Discuss the structure and function of the pharynx, esophagus, and stomach, as well as the disorders of the stomach.  Structures of the Digestive System  Alimentary canal, digestive tract, or gastrointestinal (GI) tract  Extends from mouth to anus: 9 meters (29 feet) in length  Involved in digestion, absorption, and metabolism of nutrients  Main organs 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 Location of Digestive Organs  Wall of the Digestive Tract (1 of 2)  Four layers  Mucosa or mucous membrane  Submucosa  Muscularis  Serosa Wall of the Digestive Tract (2 of 2)  Mouth (1 of 2)  Also known as oral cavity: Hollow chamber with a roof, floor, and walls  Roof: Formed by hard palate (parts of maxillary and palatine bones) and soft palate (an arch-shaped muscle separating mouth from pharynx) Mouth (2 of 2)  Uvula  A downward projection of the soft palate  Uvula and soft palate prevent food and liquid from entering nasal cavities  Assists in speech and swallowing (deglutition)  Floor of Mouth  Floor: Formed by tongue and its muscles  Lingual frenulum: fold of mucous membrane that helps anchor the tongue to the floor of the mouth  Papillae: Small elevations on mucosa of tongue  Taste buds: Found in many papillae  Teeth  Types of teeth: Incisors, cuspids, bicuspids, and tricuspids  Deciduous teeth (also known as baby teeth or primary teeth): Full set equals 20 teeth First tooth erupts at about 6 months Complete set in place at about 2 years of age  Permanent Teeth  Full set equals 32 in most; 28 teeth is a normal variation in others  First permanent tooth erupts at about 6 years of age  Set complete between ages 17 and 24 years  Structures of a typical tooth: Crown, neck, and root Deciduous (Primary) and Adult Teeth Longitudinal Section of a Tooth  Structure of a Tooth  Crown is exposed part that is visible in the mouth  Dentin is bony material that makes up crown and is covered by hard enamel  Neck is narrow portion surrounded by pink gingival (gum) tissue and is covered in cementum  Root fits into the socket of the jaw and is supported by a fibrous periodontal membrane  Salivary Glands (1 of 2)  Three pairs of salivary glands  Secrete about 1 L of saliva per day  Located outside of GI tract  Convey secretions via ducts into tract lumen  Parotid glands: Largest of salivary glands  Located in front of ear at angle of jaw  Ducts open into mouth opposite second molars  Inflamed in mumps  Salivary Glands (2 of 2)  Submandibular glands: Ducts open on either side of lingual frenulum  Sublingual glands: Ducts open into floor of mouth  Saliva contains salivary amylase: Begins digestion of carbohydrates Location of the Salivary Glands  Conditions of the Mouth and Teeth (1 of 2)  Infections, cancer, congenital defects, and other conditions can cause serious complications including malnutrition  Infections and cancer of the mouth may spread to other parts of the body  Leukoplakia: Precancerous condition of mouth tissue  Snuff dipper’s pouch: Caused by use of chewing tobacco  Squamous cell carcinoma: Most common form of mouth cancer  Conditions of the Mouth and Teeth (2 of 2) From Regezi JA, Sciubba JJ, Pogrel MA: Atlas of oral and From Callen JP, Paller AS, Greer KE et al: Color atlas of From Grundy JR, Jones JG: A color atlas of clinical operative maxillofacial pathology, Philadelphia, 2000, Saunders. dermatology, ed 2, Philadelphia, 2000, WB Saunders. dentistry: crowns and bridges, ed 2, London, 1993, Mosby-Wolfe.  Dental Caries and Gingivitis  Dental caries  Tooth disease resulting in permanent defect called a “cavity”  Infection may spread to other adjacent tissues or to blood  Lost or diseased teeth may be replaced by dentures or implants  Gingivitis: Gum inflammation or infection  Most cases result from poor oral hygiene  Can be a complication of diabetes, vitamin deficiency, or pregnancy  Dental Implant From Christensen GJ: A consumer's guide to dentistry, ed 2, St Louis, 2002, Mosby.  Thrush and Periodontitis  Thrush, or oral candidiasis: Caused by yeastlike fungal organism  Patches of “cheesy”-looking exudate form over an inflamed tongue and oral mucosa, which itches and bleeds easily  Common in immunosuppressed individuals (with AIDS) or after antibiotic therapy  Periodontitis: Inflammation of periodontal membrane  Often a complication of advanced or untreated gingivitis  Leading cause of tooth loss among adults Oral Thrush (Candida albicans) From Emond RTD, Welsby PD, Rowland HAK: Colour atlas of infectious diseases, ed 4, Edinburgh, 2003, Mosby.  Cleft Lip and Cleft Palate  Most common congenital defects of the mouth  May occur alone or together  Caused by failure of mouth structures to fuse during embryonic development  Congenital Defects of the Mouth From Wilson SF, Giddens JF: Health assessment for nursing practice, ed 2, From Greig JD, Garden OJ: Color atlas of surgical diagnosis, London, 1996, Times Mirror St Louis, 2001, Mosby. International Publishers.  Pharynx (1 of 2)  Muscular tube (throat) lined with mucous membrane  Functions as part of both respiratory and digestive systems  Subdivided into three anatomical segments Pharynx (2 of 2)  Esophagus  Muscular, mucus-lined tube about 25 cm (10 inches) long  Connects pharynx to stomach  Muscular walls help push food toward stomach  Sphincters at each end of esophagus help keep ingested material moving in one direction down the tube  Upper esophageal sphincter (UES)  Lower esophageal sphincter (LES) Gastroesophageal Reflux Disease (GERD)  Backflow of acidic stomach contents into esophagus causes symptoms of heartburn and indigestion  Mild symptoms treated by nonsurgical measures include dietary changes, weight loss, acid-blocking or buffering medications, and drugs that strengthen LES  Severe GERD  Severe and frequent episodes of GERD can trigger asthma attacks or cause severe chest pain, bleeding, or narrowing and chronic irritation of esophagus  Untreated GERD may result in a precancerous condition called Barrett esophagus  Common symptom of hiatal hernia Reflux Hiatal Hernia  Stomach (1 of 2)  Pouch for food that lies in upper part of abdominal cavity just under diaphragm  About the size of a large sausage when empty  Expands considerably after a large meal  Contraction of muscular walls of stomach mixes food with gastric juice and breaks it down into chyme Stomach (2 of 2)  Anatomy of Stomach  Mucous membrane lines the stomach  Membrane lies in folds (rugae) when stomach is empty  Many microscopic glands secrete gastric juice and hydrochloric acid into stomach  Divisions of stomach: Fundus, body, and pylorus  Pyloric sphincter muscle closes opening of pylorus (lower part of stomach) to retain food to facilitate partial digestion  Gastroenterology  Study of stomach and intestines and their diseases  Stomach is potential site of numerous diseases and conditions  Gastric diseases often exhibit these signs or symptoms: Gastritis (inflammation), anorexia (appetite loss), nausea (upset stomach), and emesis (vomiting)  Conditions of the Stomach (1 of 2)  Pylorospasm: Abnormal spasms of the pyloric sphincter  Common in infants  Pyloric stenosis is similar abnormality: Obstructive narrowing of the pyloric opening  Ulcer: Open wound caused by acid in gastric juice  Often occurs in duodenum or stomach  Associated with infection by the bacterium Helicobacter pylori and use of NSAIDs  Current treatment involves triple therapy Conditions of the Stomach (2 of 2)  Stomach Cancer  Associated with excessive consumption of alcohol or preserved food, use of chewing tobacco, and infection by H. pylori  No practical way to screen for early stages  Learning Objectives Lesson 18.2: The Digestive Tract Part II and Digestion (1 of 2) 5. Discuss the structure, function, and disorders of the small intestine. 6. Discuss the structure, function, and disorders of the liver, gallbladder, and pancreas. 7. Discuss the structure, function, and disorders of the large intestine, appendix, and peritoneum. 8. Define and contrast mechanical and chemical digestion.  Learning Objectives Lesson 18.2: The Digestive Tract Part II and Digestion (2 of 2) 9. Discuss the basics of carbohydrate, protein, and lipid digestion and give the end-products of each process. 10. Describe the process of absorption and how structural adaptations of the digestive tube affect the rate and efficiency of nutrient absorption.  Small Intestine (1 of 2)  Lining: Mucous membrane; many microscopic glands (intestinal glands) secrete intestinal juice; circular folds (plicae) are covered in villi (microscopic finger-shaped projections from surface of mucosa into intestinal cavity) that contain blood and lymph capillaries  Three sections: Duodenum, jejunum, and ileum Small Intestine (2 of 2) Disorders of the Small Intestine  Enteritis: Intestinal inflammation  Gastroenteritis: Inflammation of stomach and intestines  Malabsorption syndrome: Group of symptoms resulting from failure to absorb nutrients properly (e.g., anorexia, weight loss, abdominal bloating, cramps, anemia, and fatigue)  Maldigestion: Deficit of digestive enzymes or bile salts; reduces amount of nutrients for absorption  Liver  Size and location  Liver is largest gland  Fills upper right section of abdominal cavity and extends over into left side  Classified as exocrine gland  Secretes bile  Has a variety of metabolic functions  Liver and Gallbladder  Liver  Ducts Hepatic: Drains bile from liver Cystic: Duct by which bile enters and leaves gallbladder Common bile: Formed by union of hepatic and cystic ducts and drains bile from hepatic or cystic ducts into duodenum  Gallbladder  Location: Undersurface of the liver  Function: Concentrates and stores bile produced in the liver Gallbladder and Bile Ducts  Gallstones (1 of 2)  Calculi (stones) made of crystallized bile pigments and calcium salts  Cholelithiasis: Condition of having gallstones  Cholecystitis: Inflammation of the gallbladder; may accompany cholelithiasis  Stones can obstruct bile canals, causing jaundice  Gallstones (2 of 2) Courtesy Thompson JM, Wilson SF: Health assessment for nursing practice, St Louis 1996, Mosby.  Hepatitis  Liver inflammation  Characterized by liver enlargement, jaundice, anorexia, discomfort, gray-white feces, and dark urine  Caused by a variety of factors: Toxins, bacteria, viruses, hepatitis A, B, and C, and parasites  Cirrhosis and Portal Hypertension  Degeneration of liver tissue involving replacement of normal (but damaged) tissue with fibrous and fatty tissue  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  Liver Damage From Kumar V, Abbas AK, Fausto N: Robbins and Cotran pathologic basis of disease, ed 6, Philadelphia, 1999, Elsevier.  Pancreas  Location: Behind stomach  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 glucagon and insulin into the blood  Pancreatic Conditions  Pancreatitis: Inflammation of pancreas  Acute pancreatitis results from blocked ducts that force pancreatic juice to backflow  Pancreatic enzymes digest the gland  Cystic fibrosis: Thick secretions block flow of pancreatic juice  Pancreatic cancer: Very serious; fatal in the majority of cases  Large Intestine  Size and location: 1.5 meters long; forms lower, or terminal, portion of digestive tract  Divisions  Cecum  Colon: Ascending, transverse, descending, and sigmoid  Rectum  Anal canal  Opening to exterior: Anus Divisions of the Large Intestine C from Heuman DM, Mills AS, McGuire HH: Gastroenterology, Philadelphia, 1997, Saunders. D from Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis, ed 3, Philadelphia, 1997, Mosby. Conditions of the Large Intestine  Conditions of the large intestine often relate to conditions of motility (rate of movement of contents)  Diarrhea: Results from atypically increased intestinal motility; may result in dehydration or convulsions  Constipation: Results from decreased intestinal motility  Diverticulitis (inflammation of atypical outpouchings called diverticula): May cause constipation  Colitis and Colorectal Cancer  Colitis: General name for any inflammatory condition of the large intestine  Colorectal cancer: Common malignancy of the colon and rectum associated with colonic polyps; advanced age; low-fiber, high-fat diets; and genetic predisposition  Appendix and Appendicitis  Vermiform appendix is blind tube attached directly to cecum; no important digestive function in humans  Appendicitis: Inflammation or infection of appendix  If appendix ruptures, infectious material may spread to other organs  Most common acute abdominal condition requiring surgery  Affects 7% to 12% of population younger than 30 years  Peritoneum  Description: Large sheet of serous membrane  Parietal layer of peritoneum lines abdominal cavity  Visceral layer of peritoneum covers abdominal organs  Peritoneal space lies between parietal and visceral layers  Extensions of Peritoneum  Largest are the mesentery and greater omentum  Mesentery: 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 The Peritoneum  Peritonitis and Ascites  Peritonitis: Inflammation of peritoneum resulting from infection or other irritant; often a complication of ruptured appendix  Ascites: Abnormal accumulation of fluid in peritoneal space, often causes bloating of abdomen Ascites From Swartz MH: Textbook of physical diagnosis, ed 6, Philadelphia, 2010, Saunders.  Digestion  Definition: Process that transforms food into a form that can be absorbed and used by cells  Mechanical digestion: Chewing, swallowing, and peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract  Chemical digestion: Breaks up large food molecules into compounds having smaller molecules; brought about by digestive enzymes  Enzymes and Chemical Digestion  Enzymes: Protein molecules that act as catalysts, speeding up chemical reactions  Chemical digestion: Specific enzymes speed up breakdown of specific molecules and no others  Hydrolysis: Enzymes speed up reactions that add water to break large molecules into smaller molecules  Carbohydrate Digestion  Occurs mainly in small intestine  Pancreatic amylase: Changes starches to maltose  Intestinal juice enzymes Maltase: Changes maltose to glucose Sucrase: Changes sucrose to glucose Lactase: Changes lactose to glucose  Protein Digestion  Starts in stomach; completed in small intestine  Gastric juice enzyme pepsin partially digests proteins  Pancreatic enzyme trypsin completes digestion of proteins to amino acids  Intestinal enzymes, peptidases, complete digestion of partially digested proteins to amino acids  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  Absorption  Definition: Digested food moves from intestine into blood or lymph  Absorption site: Nutrients and most water are absorbed from small intestine; some water also absorbed from large intestine  Fractal geometry: Scientists study surfaces with a seemingly infinite area, like the lining of the small intestine that have bumps that have bumps, and so on, creating almost limitless absorptive surface area Questions?