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Chapter 14 Digestive System

Chapter 14 Digestive System. Anatomy and Physiology II Ms. Harborth. PART I: Digestive System. Takes in food (ingests) Breaks it down physically (digests) Absorbs nutrients Rids body of indigestible remains (defecates). Anatomy of the Digestive System. Alimentary canal (GI tract)

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Chapter 14 Digestive System

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  1. Chapter 14Digestive System Anatomy and Physiology II Ms. Harborth

  2. PART I:Digestive System • Takes in food (ingests) • Breaks it down physically (digests) • Absorbs nutrients • Rids body of indigestible remains (defecates)

  3. Anatomy of the Digestive System • Alimentary canal (GI tract) • Ingests, digests, absorbs, defecates • Accessory digestive organs • Teeth, tongue, large digestive glands

  4. Alimentary Canal • Continuous, hollow muscular tube • Submucosaland myenteric nerve plexuses • 30 feet long in cadaver • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Anus

  5. Mouth • Labia • Cheeks • Hard and soft palate • Uvula • Vestibule • Oral cavity proper • Tongue • Lingual frenulum

  6. Pharynx • Oropharynx • Laryngopharynx • 2 skeletal muscle layers • Inner layer longitudinal • Outer layer circular • Peristalsis

  7. Esophagus • 10 inches long • 4 tissue layers • Mucosa – innermost • Submucosa • Muscularisexterna • Serosa • Visceral peritoneum • Parietal peritoneum • Mesentery

  8. Stomach • 10 inches long, can hold 1 gallon • Diameter changes • Cardiac region • Cardioesphageal sphincter • Fundus • Body • Pylorus • Pyloric sphincter

  9. Stomach • Rugae • Greater curvature • Lesser curvature • Lesser omentum • Greater omentum

  10. Stomach • Gastric pits • Gastric glands • Gastric juice • Ex: Intrinsic factor • Chief cells • pepsinogens • Parietal cells • Mucous neck cells • Chyme

  11. Small Intestine • 6-13 ft long • Ileocecal valve • Duodenum • Jejunum • Ileum • Pancreatic ducts • Bile duct • Peyer’s patches

  12. Food Absorption • Microvilli • Villi • Lacteal lymphatic capillary • Circular folds

  13. Large Intestine • 5 ft • Cecum • Appendix • Colon • Ascending colon • Transverse colon • Descending colon • Sigmoid colon • Rectum • Anal canal

  14. Accessory Digestive Organs • Salivary glands • Parotid glands • Submandibular glands • Sublingual glands • Saliva • Bolus • Salivary amylase • Lysozyme and IgA antibodies

  15. Accessory Digestive Organs • Teeth • Masticate • Deciduous teeth • Permanent teeth • Incisors • Canines • Premolars (bicuspids) • Molars

  16. Teeth Continued • Crown and Root • Gingiva • Enamel • Neck • Cementum • Periodontal membrane (ligament) • Dentin • Pulp cavity • Pulp • Root canal

  17. Accessory Digestive Organs • Pancreas • Retroperitoneal • Digestive enzymesin alkaline fluid • Endocrine organ

  18. Accessory Digestive Organs • Liver and Gallbladder • Liver • 4 lobes • Bile • Common hepatic duct • Gallbladder • Cystic duct • Stores and concentrates bile

  19. Functions of Digestive System • 1. Ingestion • 2. Propulsion • 3. Food breakdown: mechanical digestion • 4. Food breakdown: chemical digestion • 5. Absorption • 6. Defecation digestion animation

  20. Digestion Reflexes • Mechano/Chemoreceptors triggered by: • Stretch of organ by food • pH of contents • Presence of certain breakdown products • Activate or Inhibit: • Glands that secrete digestive juices or hormones • Smooth muscles that mix and propel food

  21. Activities of Mouth, Pharynx, and Esophagus • Mouth – mechanical and chemical digestion • Deglutition (tongue, soft palate, pharynx, and esophagus) • Buccal phase • Pharyngeal-esophageal phase FYI: Swallowing can occur while standing on your head!

  22. Activities of Stomach • Sight, smell, and taste of food stimulates parasympathetic reflexes • Gastric juices secreted • Hormone gastrin released • Makes stomach glands produce pepsinogens, mucus, and HCl FYI: You make 2-3 Liters of gastric juice a day!

  23. Chemistry in the Stomach • HCl makes pepsinogen pepsin • Rennin: works on milk protein (only in infants) • Hardly any chemical digestion occurs • Aspirin and alcohol are absorbed through stomach wall

  24. Food Propulsion from Stomach • Chyme is end product • Pylorus only allows liquid and small particles to pass through sphincter • Each contraction squirts 3 ml of chyme • Rest is squeezed back into stomach • Causing enterogastric reflex FYI: It usually takes 4 hours for your stomach to empty, or 6 hours if meal was high in fat

  25. Activities of Small Intestine • Carb and protein digestion had begun in stomach, but no fat digestion • Microvilli make few enzymes • Brush border enzymes • Hormones: • Secretin • Cholecystokinin (CCK) • Pancreatic juices are enzyme and bicarbonate rich • Complete digestion of starch • Carry out ½ of protein digestion • Responsible for fat digestoin • Digest nucleic acids

  26. Absorption in Small Intestine • Water and end products absorbed through intestinal cell plasma membranes via active transport • Except lipids – absorbed through diffusion • Then to the hepatic portal vein • By the end of ileum, only water and indigestible food materials and LOTS of bacteria FYI: Takes about 3-6 hours for food to go through small intestine

  27. Activities of Large Intestine • Bacteria metabolize and release gases (methane and hydrogen sulfide) and some vitamins • These gases make feces smell • Peristalsis and mass movements • Defecation reflex

  28. PART II:Nutrition and Metabolism • Major nutrients • Carbohydrates • Lipids • Proteins • Vitamins and minerals • Water

  29. Metabolism • Catabolism and anabolism • Carbohydrate metabolism • Fat metabolism • Protein metabolism

  30. Carbohydrate Metabolism • Glucose ATP • Cellular respiration • Glycolysis, Krebs cycle, electron transport chain

  31. Fat Metabolism • Liver • Fat is broken down to acetic acid • Acetic acid is broken down in mitochondria to make ATP, CO2, and water

  32. Protein Metabolism • Proteins are broken down into amino acids • Cellular uptake • 20 amino acids are needed, 8 can’t be made by our cells (“essential amino acids”) • IF no other energy source is available, amine groups are removed as ammonia, and rest is used by mitochondria for ATP

  33. Liver’s Role in Metabolism • Used in digestion, detoxifying drugs & alcohol, degrades hormones, makes cholesterol, albumin, clotting proteins and lipoproteins, and METABOLISM • Blood circulates through, liver grabs nutrients and macrophages kill pathogens

  34. Liver • Glycogenesis • Glycogenolysis • Gluconeogenesis

  35. Cholesterol • HDL and LDL

  36. Body Energy Balance • Energy intake = heat + work + energy source • Rising or falling blood levels of nutrients, hormones, or body temperature affect eating behavior • Psychological factors influence as well

  37. Metabolic Rate • Basal metabolic rate • Amount of heat produced when at rest • Influenced by: • Surface area • Sex • Age • Emotions • Amount of thyroxine • Total metabolic rate • Amount of kilocalories body needs to fuel all activities • Stays elevated well after exercise

  38. Body Temperature Regulation • Hypothalamus • Heat-promoting mechanisms • Vasoconstriction • Shivering • Heat loss mechanisms • Radiation through skin

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