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Chapter 14 Digestive System

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Presentation on theme: "Chapter 14 Digestive System"— Presentation transcript:

1 Chapter 14 Digestive 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
Submucosal and 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 Peristalsis
Inner layer longitudinal Outer layer circular Peristalsis

7 Esophagus 10 inches long 4 tissue layers Mucosa – innermost Submucosa
Muscularis externa 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 Ex: Intrinsic factor Chief cells Parietal cells
Gastric glands Gastric juice Ex: Intrinsic factor Chief cells pepsinogens Parietal cells Mucous neck cells Chyme


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

13 Food Absorption Microvilli Villi Circular folds
Lacteal lymphatic capillary Circular folds

14 Large Intestine 5 ft Cecum Appendix Colon Rectum Anal canal
Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anal canal

15 Accessory Digestive Organs
Salivary glands Parotid glands Submandibular glands Sublingual glands Saliva Bolus Salivary amylase Lysozyme and IgA antibodies

16 Accessory Digestive Organs
Teeth Masticate Deciduous teeth Permanent teeth Incisors Canines Premolars (bicuspids) Molars

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

18 Accessory Digestive Organs
Pancreas Retroperitoneal Digestive enzymes in alkaline fluid Endocrine organ

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

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

21 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

22 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!

23 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!

24 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

25 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

26 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

27 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

28 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

29 PART II: Nutrition and Metabolism
Major nutrients Carbohydrates Lipids Proteins Vitamins and minerals Water

30 Metabolism Catabolism and anabolism Carbohydrate metabolism
Fat metabolism Protein metabolism

31 Carbohydrate Metabolism
Glucose ATP Cellular respiration Glycolysis, Krebs cycle, electron transport chain

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

33 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

34 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

35 Liver Glycogenesis Glycogenolysis Gluconeogenesis

36 Cholesterol HDL and LDL

37 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

38 Metabolic Rate Basal metabolic rate Total 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

39 Body Temperature Regulation
Hypothalamus Heat-promoting mechanisms Vasoconstriction Shivering Heat loss mechanisms Radiation through skin

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