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