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  • 1. 2013 Pearson Education, Inc. PowerPoint Lecture Slides prepared by Meg Flemming Austin Community College C H A P T E R 16 The Digestive System
  • 2. 2013 Pearson Education, Inc. Chapter 16 Learning Outcomes 16-1 Identify the organs of the digestive system, list their major functions, and describe the four layers of the wall of the digestive tract. 16-2 Discuss the anatomy of the oral cavity, and list the functions of its major structures. 16-3 Describe the structures and functions of the pharynx and esophagus, and the key events of the swallowing process. 16-4 Describe the anatomy of the stomach, including its histological features, and discuss its roles in digestion and absorption.
  • 3. 2013 Pearson Education, Inc. Chapter 16 Learning Outcomes 16-5 Describe the anatomy of the small intestine, including its histological features, and explain the functions and regulation of intestinal secretions. 16-6 Describe the structure and functions of the pancreas, liver, and gallbladder, and explain how their activities are regulated. 16-7 Describe the structure of the large intestine, including its regional specializations, and list its absorptive functions. 16-8 List the nutrients required by the body, describe the chemical digestion of organic nutrients, and discuss the absorption of organic and inorganic nutrients.
  • 4. 2013 Pearson Education, Inc. Chapter 16 Learning Outcomes 16-9 Describe the effects of aging on the digestive system. 16-10 Give examples of interactions between the digestive system and each of the other organ systems.
  • 5. 2013 Pearson Education, Inc. Digestive System Basics (16-1) Digestive tract, or gastrointestinal (GI) tract Mouth, pharynx, esophagus, stomach, small and large intestines, rectum, anus Accessory organs contribute to digestion Teeth, tongue, salivary glands, gallbladder, liver, and pancreas
  • 6. 2013 Pearson Education, Inc. Six Functions of the Digestive System (16-1) 1. Ingestion Food enters mouth 2. Mechanical processing Physical manipulation that enhances movement Increases surface area for enzymes to work 3. Digestion Chemical breakdown of food to absorbable size
  • 7. 2013 Pearson Education, Inc. Six Functions of Digestive System (16-1) 4. Secretion Release of water, acids, enzymes, and buffers into lumen 4. Absorption Movement of nutrient molecules across digestive epithelium and into interstitial fluid of body 6. Excretion Elimination of waste products
  • 8. 2013 Pearson Education, Inc. Figure 16-1 The Components of the Digestive System. Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones Major Subdivisions of the Digestive Tract Oral Cavity, Teeth, Tongue Mechanical processing, moistening, mixing with salivary secretions Pharynx Muscular propulsion of materials into the esophagus Esophagus Transport of materials to the stomach Stomach Chemical breakdown of materials by acid and enzymes; mechanical processing through muscular contractions Small Intestine Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions Large Intestine Dehydration and compaction of indigestible materials in preparation for elimination Anus Accessory Organs of the Digestive System Salivary glands Secretion of lubricat- ing uid containing enzymes that break down carbohydrates Liver Secretion of bile (important for lipid digestion), storage of nutrients, many other vital functions Gallbladder Storage and concentration of bile Pancreas Mouth
  • 9. 2013 Pearson Education, Inc. Four Histological Layers of the GI Tract (16-1) 1. Mucosa 2. Submucosa 3. Muscularis externa 4. Serosa
  • 10. 2013 Pearson Education, Inc. Mucosa (16-1) Inner lining of lumen of GI tract Layered epithelium, lamina propria Stratified squamous in high physical stress organs Rest is simple columnar with surface modifications Ducts of secretory glands open to surface of epithelium Villi and microvilli increase surface area Muscularis mucosae moves mucosal folds and villi
  • 11. 2013 Pearson Education, Inc. Submucosa (16-1) Dense irregular connective tissue Binds mucosa to muscularis externa Contains blood vessels and lymphatics Submucosal plexus on outer border A neural network that can function without CNS Regulates secretions and motility Also has parasympathetic neurons and sensory neurons
  • 12. 2013 Pearson Education, Inc. Muscularis Externa (16-1) Inner circular and outer longitudinal layer of smooth muscle Function to mix and propel materials Myenteric plexus between layers of muscle Contains parasympathetic ganglia, sensory neurons, interneurons, and sympathetic postganglionic fibers Parasympathetic is excitatory, increases activity Sympathetic is inhibitory, decreases activity
  • 13. 2013 Pearson Education, Inc. Serosa (16-1) Serous membrane is the peritoneum Mesenteries Specialized peritoneum helps to organize and stabilize GI tract, lymphatics, blood vessels, and nerves Adventitia Name of outer layer of oral cavity, pharynx, esophagus, and rectum
  • 14. 2013 Pearson Education, Inc. Figure 16-2 The Structure of the Digestive Tract. Mesenteric artery and vein Mesentery Circular fold Circular fold Mucosa Submucosa Muscularis externa Serosa (visceral peritoneum) Mucosal epithelium Lamina propria Mucosa Villi Mucosal glands Submucosal gland Muscularis mucosae Lymphatic vessel Artery and vein Submucosal plexus Circular muscle layer Myenteric plexus Longitudinal muscle layer
  • 15. 2013 Pearson Education, Inc. Movement of Digestive Materials (16-1) Pacesetter cells in smooth muscle trigger contraction Peristalsis Waves of contraction initiated by circular layer, followed by longitudinal layer Propels material down tract Segmentation A mixing action with no propulsion
  • 16. 2013 Pearson Education, Inc. Figure 16-3 Peristalsis. Circular muscle Longitudinal muscle Initial State To anus Contraction of circular muscles behind bolus Contraction Contraction of longitudinal muscles ahead of bolus Contraction Contraction in circular muscle layer forces bolus forward Contraction From mouth
  • 17. 2013 Pearson Education, Inc. Checkpoint (16-1) 1. Identify the organs of the digestive system. 2. List and define the six primary functions of the digestive system. 3. Describe the functions of the mesenteries. 4. Name the layers of the digestive tract from superficial to deep. 5. Which is more efficient in propelling intestinal contents from one place to anotherperistalsis or segmentation?
  • 18. 2013 Pearson Education, Inc. The Oral Cavity (16-2) Also called the buccal cavity Receiver of food lined with oral mucosa Senses material before swallowing Mechanically processes material Lubricates material with saliva and mucus Begins enzymatic digestion of carbohydrates and lipids Gingivae The gums that surround base of teeth
  • 19. 2013 Pearson Education, Inc. The Oral Cavity (16-2) Boundaries Cheeks form lateral walls Labia or lips are continuous with cheeks Hard and soft palates form roof of cavity Tongue forms the floor Free edge of tongue is attached to floor with lingual frenulum Oropharynx starts at base of tongue and uvula
  • 20. 2013 Pearson Education, Inc. Hard palate Soft palate Palatal arches Palatine tonsil Lingual frenulum Gingiva Vestibule An anterior view of the oral cavity, as seen through the open mouth Upper labium (lip) CheekUvula Lower labium (lip) Hyoid bone Nasal cavity Pharyngeal tonsil Entrance to auditory tube Nasopharynx Uvula Palatine tonsil Palatal arch Oropharynx Lingual tonsil Epiglottis Laryngopharynx Sagittal section of the oral cavity Hard palate Soft palate Gingiva Vestibule Tongue Tongue Figure 16-4 The Oral Cavity.
  • 21. 2013 Pearson Education, Inc. The Tongue (16-2) Manipulates food within oral cavity Mechanically compresses, abrades, distorts material Assists in chewing and forming a bolus to swallow Sensory analysis of taste, touch, temperature Lingual tonsils Paired lymphoid nodules at base of tongue
  • 22. 2013 Pearson Education, Inc. The Salivary Glands (16-2) Parotid On each side