Chapter 18 Digestive System 2009 Delmar Cengage Learning

Chapter 18 Digestive System © 2009 Delmar, Cengage Learning

Objective • Describe the general function of the digestive system • List the structures and the functions of the digestive system • Describe the action of the enzymes on carbohydrates, fats and protein • Trace food from the beginning of the digestive process to the end • Describe common disorders of the digestive system • Define the key words that relate to this chapter © 2009 Delmar, Cengage Learning

The Digestive System • http: //www. youtube. com/watch? v=n. M 5 k. MSj. Brmw © 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 – Chemical substances that promote chemical reactions in living things • 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 • Two-layered membrane – Parietal (lines the abdominal cavity) – Visceral (covers the outside of each organ in the abdominal cavity • Specialized layers – Mesentery (attaches to the posterior wall of the abdominal cavity and the small intestines) – Greater omentum (contains large amounts of fat and hangs over the abdominal organs like a protective apron) © 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) – Functions • Receive food by ingestion • Break food into small particles by mastication • Mix food with saliva • Tongue/accessory organ of digestion – The tongue and its muscles are attached to the floor of the mouth, helping in both chewing and swallowing • Salivary glands – Functions of saliva • • Cleansing action on the teeth Moistens and lubricates food during mastication and swallowing Dissolves certain molecules so that foods can be tasted Begins the chemical digestion of starches © 2009 Delmar, Cengage Learning

Teeth/Accessory Organ of Digestion • Gingivae or gums – Support and protect the teeth • Teeth – Food chewed or masticated – Deciduous and permanent teeth • Structure of the tooth – – Crown Neck Root Pulp cavity © 2009 Delmar, Cengage Learning

Esophagus • Muscular tube to transport swallowed food to stomach • Muscles in the upper third are voluntary and lower portion is smooth muscle, or involuntary © 2009 Delmar, Cengage Learning

Stomach • Divided into 3 portions – Fundus (upper part) – Body or great curvature (middle section) – Pylorus (lower portion) • Sphincters – Cardiac sphincter – Pyloric sphincter • Four layers of the stomach wall © 2009 Delmar, Cengage Learning

© 2009 Delmar, Cengage Learning

The Stomach © 2009 Delmar, Cengage Learning

Gastric Juices • Enteroendocrine glands – Secrete gastrin • Parietal cells – Produce HCL and intrinsic factor • Chief type cells – Produce pepsinogen • Mucus cells – Secrete alkaline mucus © 2009 Delmar, Cengage Learning

Small Intestine • About 20 feet long • Same four layers as the stomach • Divided into 3 sections – Duodenum – Jejunum – Ileum • Functions – Finishes the process of digestion – Absorbs the nutrients – Passes the residue on to the large intestine © 2009 Delmar, Cengage Learning

Small Intestine © 2009 Delmar, Cengage Learning

Digestive Juices in the Small Intestine • Enzymes, secretin, and cholecystokinin • Pancreatic juices – Protease or trypsin – Amylase or amylopsin – Lipase or steapsin • Bile • Intestinal juices – Maltase, lactase, sucrase – Peptidase – Steapsin © 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 • Undigested portion passes on to the large intestine © 2009 Delmar, Cengage Learning

Accessory Organs of Digestion • Pancreas – Functions both as an exocrine and as an endocrine • Liver – Functions • • Manufactures bile Produce and store glucose in the form of glycogen Detoxify harmful substances Manufacture blood proteins necessary for blood clotting Store vitamins A, D and B complex Converts ammonia into urea Break down hormones no longer useful Remove worn-out red blood cells from circulation and recycle the iron content • Gallbladder – Function is to store and concentrate bile when it is not needed by the body © 2009 Delmar, Cengage Learning

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 • Regions of the large intestine – – Cecum and appendix Ascending, transverse, and descending colon Sigmoid colon Anal canal • Functions – Absorption of fluid and electrolytes and the elimination of waste products © 2009 Delmar, Cengage Learning

General Overview of Digestion • Mouth • Small intestine – Bolus • Pharynx – Swallowing, or deglutition – Process of digestion is completed and absorption occurs • Digestion of protein, fats and carbohydrates • Absorption of nutrients • Esophagus – Peristalsis • Stomach – The action of gastric juices is helped by the chuming of the stomach walls – Semiliquid food is called chyme © 2009 Delmar, Cengage Learning • Large intestine – – water absorption bacterial action fecal formation gas formation and defecation

Action in the Large Intestine • • • Absorption Bacterial action Gas formation Fecal formation Defecation © 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

Metabolism • Within the cells, nutrients are changed into energy • Aerobic metabolism • Anaerobic metabolism • Thyroid hormones © 2009 Delmar, Cengage Learning

Disorders – Digestive System • • Stomatitis Gingivitis Periodontal disease Gastroesophageal reflux disease (GERD) Hiatal hernia Heartburn Pyloric stenosis Gastritis © 2009 Delmar, Cengage Learning • • Gastroenteritis Enteritis Ulcer Inflammatory bowel disease (IBD) • Appendicitis • Hepatitis

Disorders – Digestive System • • • Cirrhosis Cholecystitis Gallstones Pancreatitis Diverticulosis © 2009 Delmar, Cengage Learning • Hemorrhoids • Diarrhea • Constipation