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Chapter 18 Digestive System © 2009 Delmar, Cengage Learning Digestive System • Food must be converted by physical and chemical changes before it can be used by the cells; this process is called digestion • Enzymes • Alimentary canal • Accessory organs © 2009 Delmar, Cengage Learning Layers of the Digestive System • Mucosa – Innermost lining • Submucosa • Circular muscle • Longitudinal muscle © 2009 Delmar, Cengage Learning Lining of the Digestive System • Peritoneum – – – – Parietal Visceral Mesentery Greater omentum • Peritonitis © 2009 Delmar, Cengage Learning Functions of the Digestive System • • • • Break down food physically Change food chemically Absorb the nutrients Eliminate the waste products of digestion © 2009 Delmar, Cengage Learning Organs of Digestion • Mouth (oral or buccal cavity) • Tongue/accessory organ of digestion • Salivary glands © 2009 Delmar, Cengage Learning Teeth/Accessory Organ of Digestion • Gingivae or gums • Teeth – Food chewed or masticated – Deciduous and permanent teeth • Structure of the tooth © 2009 Delmar, Cengage Learning Esophagus • Muscular tube to transport swallowed food to stomach • Esophageal wall layers – – – – Mucosa Submucosa Muscular External serous © 2009 Delmar, Cengage Learning Stomach • Fundus – Upper part • Body or great curvature – Middle section • Pylorus – Lower portion © 2009 Delmar, Cengage Learning Stomach • Sphincters – Cardiac sphincter – Pyloric sphincter • Four layers of the stomach wall © 2009 Delmar, Cengage Learning Gastric Juices • Enteroendocrine glands – Secrete gastrin • Parietal cells – Produce HCL and intrinsic factor • Chief type cells – Produce pepsinogen © 2009 Delmar, Cengage Learning Gastric Juices • Mucus cells – Secrete alkaline mucus • Rennin – Found in infants and children © 2009 Delmar, Cengage Learning Small Intestine • • • • • About 20 feet long Same four layers as the stomach Duodenum Jejunum Ileum © 2009 Delmar, Cengage Learning Digestive Juices in the Small Intestine • • • • Enzymes, secretin, and cholecystokinin Pancreatic juices Bile Intestinal juices © 2009 Delmar, Cengage Learning Absorption in the Small Intestine • Villi – Makes absorption possible • Each villi contains a network of blood and lymph capillaries • Digested portion passes through the villi into the bloodstream and lacteals © 2009 Delmar, Cengage Learning Absorption in the Small Intestine • Undigested portion passes on to the large intestine © 2009 Delmar, Cengage Learning Accessory Organs of Digestion • Pancreas • Liver • Gallbladder © 2009 Delmar, Cengage Learning Large Intestine • Also called the colon • About 5 feet long • Ileum empties chyme through ileocecal valve into large intestine • Secretes mucus to lubricate passageway © 2009 Delmar, Cengage Learning Large Intestine • • • • Cecum and appendix Ascending, transverse, and descending colon Sigmoid colon Anal canal © 2009 Delmar, Cengage Learning Digestive System Structures © 2009 Delmar, Cengage Learning General Overview of Digestion • • • • • Bolus Peristalsis Digestion of protein, fats, and carbohydrates Absorption of nutrients Undigested substance - feces © 2009 Delmar, Cengage Learning General Overview of Digestion • • • • • • Action in the mouth Action in the pharynx Action in the esophagus Action in the stomach Action in the small intestine Action in the large intestine © 2009 Delmar, Cengage Learning Action in the Large Intestine • • • • • Absorption Bacterial action Gas formation Fecal formation Defecation © 2009 Delmar, Cengage Learning Metabolism • Within the cells, nutrients are changed into energy • Aerobic metabolism – Oxidation • Anaerobic metabolism – Krebs cycle © 2009 Delmar, Cengage Learning Metabolism • Anabolism and catabolism • Thyroid hormones © 2009 Delmar, Cengage Learning Animation – Digestion Click here to play Digestion animation © 2009 Delmar, Cengage Learning Effects of Aging • • • • Decrease sensory ability of taste buds Reduction of saliva Loss of teeth Slowing peristalsis © 2009 Delmar, Cengage Learning Disorders – Digestive System • • • • Stomatitis Gingivitis Periodontal disease Gastroesophageal reflux disease (GERD) © 2009 Delmar, Cengage Learning Disorders – Digestive System • • • • • Hiatal hernia Heartburn Pyloric stenosis Gastritis Gastroenteritis © 2009 Delmar, Cengage Learning Disorders – Digestive System • • • • • Enteritis Ulcer Inflammatory bowel disease (IBD) Appendicitis Hepatitis © 2009 Delmar, Cengage Learning Disorders – Digestive System • • • • • Cirrhosis Cholecystitis Gallstones Pancreatitis Diverticulosis © 2009 Delmar, Cengage Learning Disorders – Digestive System • Hemorrhoids • Diarrhea • Constipation © 2009 Delmar, Cengage Learning
