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