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