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Digestion, Absorption, and Transport

Digestion, Absorption, and Transport. Chapter 3. Digestion. Breaking down foods into nutrients Prepare for absorption Challenges of digestion Tasks of the mouth Diaphragm Steady movement Lubrication of food Digestive enzyme functions. Anatomy of the Digestive Tract.

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Digestion, Absorption, and Transport

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  1. Digestion, Absorption, and Transport Chapter 3

  2. Digestion • Breaking down foods into nutrients • Prepare for absorption • Challenges of digestion • Tasks of the mouth • Diaphragm • Steady movement • Lubrication of food • Digestive enzyme functions

  3. Anatomy of the Digestive Tract

  4. Anatomy of the Digestive Tract • Gastrointestinal (GI) tract • Flexible and muscular • Path • Mouth → esophagus → stomach → small intestine → large intestine → rectum → anus • Lumen • Continuous

  5. Anatomy of the Digestive Tract • Mouth • Process of digestion begins • Mastication • Four basic taste sensations • Savory • Aroma, texture, and temperature • Pharynx • Bolus

  6. Anatomy of the Digestive Tract • Esophagus • Two sphincters • Upper esophageal sphincter • Lower esophageal sphincter • Stomach • Movement of bolus • Chyme • Pyloric sphincter

  7. Anatomy of the Digestive Tract • Small intestine • Common bile duct • Pancreas and gall bladder • Three segments • Large intestine (colon) • Ileocecal valve • Withdrawal of water • Rectum and anus

  8. Anatomy of the Digestive Tract

  9. Transverse colon Ascending colon End of small intestine Opening from small intestine to large intestine Descending colon Appendix Rectum Sigmoid colon Anus Stepped Art Fig. 3-2, p. 72

  10. Muscular Action of Digestion • Peristalsis • Circular and longitudinal muscles working together • Rate and intensity of contractions vary • Factors that may interfere with peristalsis • Stomach action • Circular, longitudinal, and diagonal muscles • Timing the release of chyme

  11. Muscular Action of Digestion

  12. Muscular Action of Digestion • Segmentation • Contraction of circular muscles in small intestine • Mix chyme • Promote contact with absorption cells • Sphincter contractions • Periodically open and close • Control pace of GI tract contents

  13. Muscular Action of Digestion

  14. Muscular Action of Digestion

  15. Secretions of Digestion • Five organs • Salivary glands, stomach, pancreas, liver, small intestine • Secretions • Water • Enzymes • Protein facilitator of chemical reactions • Hydrolysis

  16. Secretions of Digestion • Saliva • Moisten food for easy passage • Protective role • Carbohydrate digestion • Gastric juice • Protein digestion • Mucus • pH units

  17. Secretions of Digestion • Pancreatic juice • Released via ducts into duodenum • Enzymes act on all three energy nutrients • Sodium bicarbonate • Bile • Liver • Gallbladder

  18. Secretions of Digestion

  19. The Final Stage • Vitamin and mineral absorption • Undigested residues • Exercise intestinal muscles • Retention of water • Colon • Intestinal bacteria • Recyclable materials • Water and dissolved salts

  20. Absorption • Small intestine • Majority of absorption • Ten feet long • Surface area • Absorption techniques • Simple diffusion • Facilitated diffusion • Active transport

  21. Absorption

  22. Energy SIMPLE DIFFUSION ACTIVE TRANSPORT FACILITATED DIFFUSION Some nutrients (such as water and small lipids) are absorbed by simple diffusion. They cross into intestinal cells freely. Some nutrients (such as the water-soluble vitamins) are absorbed by facilitated diffusion. They need a specific carrier to transport them from one side of the cell membrane to the other. (Alternatively, facilitated diffusion may occur when the carrier changes the cell membrane in such a way that the nutrients can pass through.) Some nutrients (such as glucose and amino acids) must be absorbed actively. These nutrients move against a concentration gradient, which requires energy. Carrier loads nutrient on outside of cell . . . Carrier loads nutrient on outside of cell . . . Outside cell Cell membrane . . . and then releases it on inside of cell. . . . and then releases it on inside of cell. Inside cell Stepped Art Fig. 3-9, p. 78

  23. Anatomy of the Absorptive System • Villi • Select and regulate nutrients absorbed • Microvilli • Enzymes and “pumps” • Crypts • Secretion of intestinal juices • Goblet cells • Mucus secretion

  24. Preparing Nutrients for Transport • Transport pathways • Bloodstream • Water-soluble nutrients and smaller products of fat digestion • Liver • Lymphatic system • Larger fats and fat-soluble vitamins • Chylomicrons • Bypass liver at first

  25. The Vascular System • Closed system of vessels • Heart pump • Blood • Delivers oxygen and nutrients • Removes carbon dioxide and wastes • Blood flow • Special routing for digestive system • Liver

  26. The Vascular System

  27. The Vascular System

  28. The Lymphatic System • One-way route • No pump • Circulation between cells • Entry into bloodstream • Subclavian vein • Nutrients in lymphatic vessels • Bypass liver at first

  29. Health and Regulation of GI Tract • Gastrointestinal bacteria – flora • Most are not harmful • Benefits of gastrointestinal bacteria • Factors influencing bacteria presence • Diet – probiotics • Others • Digestion of fibers and complex proteins • Vitamin production

  30. Health and Regulation of GI Tract • Endocrine and nervous systems • Homeostatic regulation • Hormones and nerve pathways • Stimulation and inhibition of digestive secretions • Feedback mechanisms • Examples • GI hormones

  31. Health and Regulation of GI Tract

  32. Health and Regulation of GI Tract

  33. The Digestive System at Its Best • Sensitive and responsive to environment • Immunity against intestinal diseases • Defense against foreign invaders • Health of digestive system • Healthy supply of blood • Lifestyle factors • Types of foods eaten • Balance, moderation, adequacy, and variety

  34. Highlight 3 Common Digestive Problems

  35. Choking • Food slips into trachea • Cuts off breathing • International sign for choking • Heimlich maneuver • Foods commonly associated with choking • Prevention of choking

  36. Choking

  37. Choking

  38. Vomiting and Diarrhea • Vomiting • Adaptive mechanism of the body • Medical treatment • Dehydration and projectile vomiting • Diarrhea • Symptom of medical conditions & treatments • Irritable bowel syndrome (IBS) • Colitis • Treatment

  39. Constipation • Not a disease • Symptoms of constipation • Causes • Lifestyle • Side effect of medications • Prevention • Fiber and water • Physical activity

  40. Belching and Gas • Belching • Swallowed air • Prevention • Intestinal gas • Consumption of certain foods • Individually determined • Hiccups

  41. Heartburn and “Acid Indigestion” • Gastroesophageal reflux (heartburn) • Causes • Prevention • Indigestion • Causes • Antacids and acid controllers • Damage to esophagus • Barrett’s esophagus

  42. Ulcers • Peptic ulcers • Gastric ulcers • Duodenal ulcers • Causes • Bacterial infection • Anti-inflammatory drugs • Excessive gastric acid secretion • Ulcer treatment regimen

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