1. Three Main Functions. Chapter 19: 2. Two Groups of digestive organs. 2. Two Groups of digestive organs 6/1/2015. The Wall of the Digestive Tract

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1 1. Three Main Functions Chapter 19: General Structure and Function of the Digestive System Digestion-breakdown of food into small particles for transport to blood Absorption- into bloodstream to take to cells Elimination- removal of waste from body 2. Two Groups of digestive organs a. Digestive tract- alimentary canal; tube from mouth to anus (trace the pathway on your diagram sheet) 2. Two Groups of digestive organs b. Accessory organs -organs that assist in digestion; but not part of alimentary canal, ie FOOD DOES NOT GO THROUGH THEM! The Wall of the Digestive Tract i.mucous membrane (mucosa) Digestive juice-secreting cells Mucus-secreting cells (goblet cells) ii.submucosa Contains blood vessels and nerves that help regulate digestion iii.smooth muscle- moves food along Peristalsis- wavelike action to move food iv.serous membrane encloses the tube Peritoneum - Membrane that lines the abdominopelvic cavity Mesentery thin tissue that holds the small intestine together Greater omentum fatty covering over intestines under peritoneum 1

2 4. Organs of the Digestive Tract A. The Mouth - A. also called oral cavity, processes food by:, Ingestion Mastication (chewing) Mixing with saliva Deglutition (swallowing) i. Incisors for cutting ii. Cuspids (fangs) for tearing, iii. Molars for grinding; iv. 20 deciduous, 32 permanent (adult) 1. The Teeth b. The Pharynx - Also called the throat, connects to esophagus Soft palate-skin at back/top of mouth Uvula- hangs from soft palate & covers sinus when swallowing Bolus lump of food in mouth that is swallowed swallowing animation Muscular tube that leads to stomach, lies behind the trachea Esophageal hiatus- where esophagus ends/meets stomach Hiatal hernia weak diaphragm allows stomach to protrude upward through esophagus animation c. The Esophagus d. The Stomach - J-shaped pouch that receives food from esophagus 2 sphincters- control entrance of food in & out of stomach i. Lower esophageal sphincter (LES)-top of stomach ii. Pyloric sphinctercontrols release of chyme into duodenum ii. FUNCTIONS of the stomach 1. Storage of food and liquid during digestion 2. Secrete gastric juice for digestion 3. Secrete mucus while churning 4. Rugae muscular folds allow for expansion 5. Gastric juices hydrochloric acid and pepsin to break down protein 6. Chyme semiliquid mixture that leaves stomach and goes to small intestine 2

3 f. The Small Intestine - 10 foot long structure, about 1 inch diameter, begins with duodenum Functions: 1. Mucus is secreted to protect from acid 2. Segmentation muscle activity that moves the food. 3. Absorption of nutrients into bloodstream absorption animation ii. Villi-tiny fingerlike projections provide surface area for absorption 1. blood vessels for absorption of nutrients; 2. Lacteals specialized capillaries that absorb fats f. Large Intestine 5 feet long, 2.5in diameter i. Teniae coli coiled bands that give the puckered appearance. ii. iii. Cecum, ascending colon(rt), transverse colon, descending colon (lf) i. Appendix-lymphoid tissue attached to cecum Functions: i. Mucus secretion ii. Water absorption iii. Storage of undigested waste iv. Defecation of waste 4. Accessory Organs for Digestion food doesn t go through them 1. Salivary Glands 3 pairs release saliva in mouth to start digestion Moistens food Facilitates mastication and deglutition Helps keep teeth and mouth clean 2. Liver the body s largest glandular organ Manufactures bile Store glycogen, convert to glucose Modify fats Destroy old red blood cells Synthesize urea Detoxify harmful substances Bile is the liver s main digestive enzyme Function of the Liver 3

4 3. Gallbladder A sac that stores bile for digestion of fats 4. Pancreas - produces enzymes that digest fats, proteins, carbs and amino acids 5. Enzymes and the Digestive Process 1. Enzymes A. Enable food molecules to break apart B all enzymes are released into common bile duct and then into duodenum. 2. Water key factor in process of digestion About 7 liters secreted into digestive tract each day Hydrolysis splitting of molecules using water Structure Digestion Step by Step Enzymes Released What s broken down Mouth Amylase starch Stomach Hydrochloric acid, pepsin Protein Small intestine intestinal enzymes fats, proteins, Pancreatic enzymes carbohydrates, Bile from liver amino acids IV. Absorption the means by which nutrients reach the blood 1. Fats absorbed by lacteals into lymphatic vessels, then digested and returned to blood 2. Vitamins and minerals - absorbed directly into blood from small intestine Large intestine no enzymes no digestion V. Control of Digestion must be regulated for proper nourishment Nervous by nerves located in intestinal muscle walls Hormonal secretions by digestive organs into blood aid digestion 8. Hunger and appetite Hunger the need for food, regulated by the hypothalamus Appetite desire for food, but not necessarily need; affected by emotions, culture, habits, memory, etc. 4

5 9. Eating disorders Eating disorders Anorexia chronic loss of appetite due to variety of issues (drugs, emotions, social) Anorexia nervosa psychological disorder, obsessive desire to be thin 10. Effects of Aging 1. taste and smell receptors deteriorate leading to loss of appetite 2. Decrease in saliva makes swallowing difficult 3. Digestion slows resulting in chronic constipation 5