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Memmler’s The Human Body in Health and Disease 11th edition Chapter 19 The Digestive System Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Function and Design of the Digestive System • Chief functions – Digestion – Absorption – Elimination • Organs – Digestive tract – Accessory organs Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-1: Why does food have to be digested before cells can use it? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Wall of the Digestive Tract • Mucous membrane (mucosa) • Smooth muscle – Digestive juice-secreting cells – Inner layer – Mucus-secreting cells (goblet cells) – Peristalsis – Outer layer • Serous membrane • Submucosa – Connective tissue – Epithelium – Contains blood vessels and nerves that help regulate digestion – Loose connective tissue Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Wall of the digestive tract. The mucous membrane of the small intestine shown here has numerous projections called villi. Zooming In: What type of tissue is between the submucosa and the serous membrane in the digestive tract wall? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-2: The digestive tract has a wall that is basically similar throughout its length and is composed of four layers. What are the typical four layers of this wall? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Peritoneum Membrane that lines the abdominopelvic cavity • Parietal peritoneum • Visceral peritoneum • Mesentery • Mesocolon • Greater omentum • Lesser omentum Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Peritoneum (cont’d) Peritoneal cavity: space between two layers of the membrane • Greater peritoneal cavity: main portion, located in abdominal cavity, extends into pelvic cavity • Lesser peritoneal cavity: extends to the liver and the back attachment of the diaphragm Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The abdominopelvic cavity. Subdivisions of the peritoneum fold over, supporting and separating individual organs. Zooming In: What part of the peritoneum is around the small intestine? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-3: What is the name of the large serous membrane that lines the abdominopelvic cavity and covers the organs it contains? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: What type of tissue makes up the outermost layer of the wall of the digestive tract? a. smooth muscle b. mucous membrane c. serous membrane Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: c. serous membrane Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Organs of the Digestive Tract • Alimentary tract or gastrointestinal (GI) tract • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The digestive system. Zooming In: What accessory organs of digestion secrete into the mouth? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Mouth Also called oral cavity, processes food by • Ingestion • Mastication • Mixing with saliva • Deglutition Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Teeth • Deciduous teeth (baby teeth) – 20 teeth – Dentin – Blood vessels • Adult permanent teeth – Nerves – Gingiva – 32 teeth – Crown – Incisors – Enamel – Cuspids (canines or eyeteeth) – Molars • Structure – Roots – Cementum Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-4: How many baby teeth are there and what is the scientific name for the baby teeth? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Pharynx Also called the throat • Oropharynx • Palatine tonsils • Nasopharynx • Laryngeal pharynx • Soft palate • Uvula • Epiglottis Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Esophagus • Muscular tube – No digestion occurs here – Joins with stomach • Esophageal hiatus Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: What structure guards the entrance to the trachea during swallowing? a. uvula b. epiglottis c. esophageal sphincter Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: b. epiglottis Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Stomach – Structure • Additional angled muscle layer • Greater and lesser curvature • Fundus • Lower esophageal sphincter (LES) (cardiac sphincter) • Pylorus • Pyloric sphincter • Rugae Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Stomach – Functions • Store food and liquid • Secrete gastric juice (hydrochloric acid and pepsin) • Secrete mucus • Chyme: highly acidic mixture of gastric juice and food that leaves the stomach for the small intestine Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Longitudinal section of the stomach. The stomach’s interior is visible, along with a portion of the esophagus and the duodenum. Zooming In: What additional muscle layer is in the wall of the stomach that is not found in the rest of the digestive tract? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-5: What type of food is digested in the stomach? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Small Intestine – Structure • Duodenum • Jejunum • Ileum Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Small Intestine – Function • Secrete mucus • Secrete enzymes • Absorb digested food – Villi – Microvilli – Blood vessels – Specialized lymphatic capillaries (lacteals) Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The small and large intestines. Zooming In: What part of the small intestine joins the cecum? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-6: What are the three divisions of the small intestine? Checkpoint 19-7: How does the small intestine function in the digestive process? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Large Intestine — Structure • Cecum • Ileocecal valve • Vermiform appendix • Colon – Ascending – Transverse – Descending – Sigmoid • Rectum • Anal canal • Anus Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Large Intestine – Function • Secrete mucus • Reabsorb some water • Form feces (stool) • Defecation Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-8: What are the divisions of the large intestine? Checkpoint 19-9: What are the functions of the large intestine? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: True or False?: The descending colon is a part of the small intestine. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: False: The descending colon is part of the large intestine. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Accessory Organs Release secretions through ducts into digestive tract • Salivary glands to mouth • All other organs to duodenum Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Accessory organs of digestion. Zooming In: Into what part of the intestine do these accessory organs secrete? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Salivary Glands • Functions of saliva – Moistens food – Facilitates mastication and deglutition – Helps keep teeth and mouth clean • Production of saliva – Parotid glands – Submandibular (submaxillary) glands – Sublingual glands Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-10: What are the names of the salivary glands? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Liver – Structure • Right, left lobes • Portal vein • Hepatic artery Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Liver – Function • Manufacture bile • Store glycogen, convert to glucose • Modify fats • Store vitamins, iron • Form blood plasma proteins • Destroy old red blood cells • Synthesize urea • Detoxify harmful substances Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Gallbladder Bile • Flows from liver through cystic duct • Is stored in gallbladder • Flows through cystic duct and common bile duct to duodenum when needed Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Pancreas • Releases enzymes that digest fats, proteins, carbohydrates, and nucleic acids • Produces alkaline (basic) fluid to neutralize acidic chyme in small intestine • Produces insulin and glucagon to regulate sugar metabolism Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-11: What is the role of the gallbladder? Checkpoint 19-12: What is the role of the bile in digestion? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: What two organs are involved in the production of bile? a. the gallbladder and the stomach b. the liver and the gallbladder c. the liver and the spleen Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: b. the liver and the gallbladder Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Enzymes and the Digestive Process Enzymes • Speed up rate of chemical reactions • Are not changed or used up in reactions • Are proteins • Are highly specific in their actions Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Role of Water Process of digestion technically hydrolysis (split by water) Water is used to • Produce digestive juices • Dilute food • Aid chemical process of digestion • Added to nutrient molecules as they are split by enzymes Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Digestion, Step-by-Step • Mouth – Chews food, mixes with saliva – Some starches changed to sugars • Stomach – Secretes hydrochloric acid, enzymes – Secretes mucus – Forms chyme – Begins digestion of proteins (with pepsin) • Small intestine – Mixes chyme with bile – Receives pancreatic juice enzymes – Produces enzymes – Emulsifies fats Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-13: What organ produces the most complete digestive secretions? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Absorption • Villi in mucosa of small intestine – Arteriole and venule bridged with capillaries • Capillaries absorb – Simple sugars – Small proteins – Amino acids – Simple fatty acids – Water • Portal system transports nutrients to liver Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Absorption of Fats • Lacteals absorb fat • Fat/lymph mixture (chyle) drains from small intestine • Chyle merges with lymphatic circulation, enters blood in veins near heart • Liver further processes absorbed fats Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Absorption of Vitamins and Minerals When vitamins and minerals are • Dissolved in water – Absorbed directly into blood • Incorporated in fats – Absorbed with fats • Produced by bacterial action – Absorbed in large intestine Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-14: What is absorption? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Control of Digestion • Nervous – Parasympathetic stimulation increases activity – Sympathetic stimulation decreases activity • Hormonal – Digestive organs produce hormones • Gastrin • Gastric-inhibitory peptide (GIP) • Secretin • Cholecystokinin Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-15: What are the two types of control over the digestive process? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Hunger and Appetite • Hunger – Hypothalamic centers regulate – Blood nutrient levels stimulate – Satisfied by adequate meal • Appetite – No relationship to need for food – May not be satisfied by adequate meal – Leptin; hormone produced in adipose tissue; involved in weight regulation Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Eating Disorders • Anorexia – Chronic loss of appetite – Possible emotional, social factors • Anorexia nervosa – Psychological disorder – Bulimia (binge-purge syndrome) Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-16: What is the difference between hunger and appetite? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Disorders of the Digestive System Sources of digestive problems • Mechanical • Nervous • Chemical • Hormonal Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Peritonitis Infection of the peritoneum following infection of an organ covered by peritoneum • Localized • Generalized Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Diseases of the Mouth and Teeth • Dental caries • Gingivitis • Periodontitis • Vincent disease • Leukoplakia Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-17: What are some common diseases of the mouth and teeth? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Disorders of the Esophagus and Stomach • Acid reflux • Varicose veins of the esophagus • Hiatal hernia • Heartburn • Chronic reflux or gastroesophageal reflux disease (GERD) • Nausea • Vomiting (emesis) • Gastritis • Flatulence • Stomach cancer • Peptic ulcer • Pyloric stenosis Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Intestinal Disorders • Appendicitis • Constipation • Inflammatory bowel disease (IBD) • Intestinal obstruction – Crohn disease – Ulcerative colitis • Irritable bowel syndrome (IBS) • Gastroenteritis • Diverticulitis – Intussusception – Volvulus – Ileus – Hemorrhoids • Colon and rectum cancer • Diarrhea Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: The condition in which a portion of the stomach protrudes upward into the esophagus is named: a. intussusception b. volvulus c. hiatal hernia Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: c. hiatal hernia Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 19-18: What two diseases fall into the category of inflammatory bowel disease? Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Infection of the Salivary Glands Mumps • Contagious viral infection of parotid salivary glands • Possible complications – Inflammation of testicles – Sterility in males • Prevented by childhood vaccine (MMR) Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Cirrhosis and Other Liver Diseases • Cirrhosis – Active liver cells replaced by scar tissue – Alcoholic (portal) type is most common • Jaundice • Hepatitis – Liver inflammation – Viral causes – Known viruses that cause h. are named A through E (e.g., hepatitis A) • Cancer Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Gallstones Cholelithiasis • Most common gallbladder disease • May remain in gallbladder or lodge in bile ducts Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Pancreatitis • Pancreatic enzymes back up into pancreas • Can be fatal (acute pancreatitis) Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: The medical term for gallstones is: a. cholelithiasis b. GERD c. fecaliths Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: a. cholelithiasis Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Aging and the Digestive System • Loss of appetite • Difficulty swallowing • Decreased digestive organ activity • Digestive disorders • Tumors and cancer Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins End of Presentation Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins