1. Digestion, Absorption, Metabolism, and Excretion Chapter 9 J Pistack MS/Ed

2. Digestion Food is broken down mechanically and chemically in the gastrointestinal tract Takes place in the alimentary canal Aided by “accessory” organs

3. Absorption Occurs when ingested food is broken down during digestion into chemicals the body can use Metabolism – the some of all physical and chemical changes that take place in the body

4. Excretion The elimination of anything the body cannot use

5. Alimentary Canal Oral cavity Pharynx Esophagus Large intestine Small intestine Stomach

6. Accessory Organs Located outside the alimentary canal and are considered part of the digestive system Liver—produces bile Gall bladder—stores bile Pancreas—secretes enzymes

7. Liver Second largest organ Liver—produces bile Bile exits the liver through the hepatic bile duct

8. Gall bladder Gall bladder – concentrates and stores bile until it is needed in the small intestine Delivered to the small intestine through the common bile duct 2~3 cups are secreted daily

9. Pancreas Pancreas—secretes enzymes involved with digestion of all energy nutrients Secretions are known as pancreatic juice Arrives in the small intestine through the pancreatic and common bile duct

10. Digestive Action Mechanical—physical “breaking down” of food: mastication, peristalsis Chemical—chemical “breaking down” of food: enzymes, hydrolysis Digestive enzymes are present in Saliva Gastric juice Pancreatic juice Intestinal juice

11. End Products 4 to 6 hours after a meal: body has broken down the food into some trillion molecules Carbohydrates = monosaccharides Fats = glycerol, fatty acids, monoglycerides Protein = amino acids and small peptides

12. Alimentary canal No digestion takes place in the pharynx or esophagus Food enters the stomach from the esophagus through the cardiac sphincter

13. Alimentary canal Stomach Constructed with rugae for expansion Contains HCl, mucus, and the enzymes pepsin, rennin, and gastric lipase Churning action of the stomach mixes food with gastric juices to produce chyme Peristaltic motion pushes the chyme out of the stomach through the pyloric sphincter

14. Alimentary canal Small intestine About 20 feet long Made up of the duodenum, jejunum, and ileum 90% of the digestive action and nearly all end product absorption occur in the small intestine Emulsification – a process of breaking down non soluble fats - takes place in the small intestine

15. Elimination/Excretion Solid waste products are eliminated as feces via the alimentary canal Liquid wastes are excreted in urine via the kidneys and bladder Some liquid wastes are excreted via perspiration through the skin Carbon dioxide is exhaled via the lungs

16. Illnesses Steatorrhea—malabsorption of fat Food allergies—sensitivity; some life threatening Celiac disease—gluten sensitivity; leads to malabsorption Lactose intolerance—deficient in lactase enzyme; leads to digestive difficulties

17. Reintroducing Food After Illness Decreased or no food intake occurs for a variety of reasons: flu, stomach virus, etc. Always encourage liquids to prevent dehydration Can be done with clear liquids in small sips Patients may experience abdominal cramping and diarrhea on reintroducing food

18. Surgery of the Alimentary Canal A variety of illnesses may warrant part of alimentary canal resection This causes problems for the patient with malabsorption of necessary nutrients This is also being done in some cases as a weight loss procedure—bariatric-stomach pouching, resection

19. Learning Objectives List the anatomic structures of gastrointestinal (GI) tract Describe dietary treatments: lactose intolerance, food allergies, and gluten sensitivity List the ways the body eliminates waste