Chapter 16 Digestive System - Human Physiology PDF

Chapter 16 The Digestive System Sherwood Modified, Edited and Presented by Marios Z Panos Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning  DIGESTIVE SYSTEM OUTLINE Overview of Anatomy and Function...

Chapter 16 The Digestive System Sherwood Modified, Edited and Presented by Marios Z Panos Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning  DIGESTIVE SYSTEM OUTLINE Overview of Anatomy and Function Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning  DIGESTIVE SYSTEM OUTLINE 1. Overview of Anatomy 2. Overview of Function - Motility - Secretion - Digestion - Absorption Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning The Digestive System OESOPHAGUS STOMACH DUODENUM SMALL INTESTINE Mean length 3-5 m (2.8-10.5m)  LARGE BOWEL– COLON ILEOCAECAL VALVE CAECUM (6-8cm) and APPENDIX ASCENDING COLON TRANSVERSE COLON DESCENDING COLON SIGMOID COLON Mean length 1.5-1.7m RECTUM (15-20cm) LIVER Weight 1.2 - 1,5 kg BILIARY TREE AND PANCREAS  DIGESTIVE SYSTEM OUTLINE 1. Overview of Anatomy 2. Overview of Function - Motility - Secretion - Digestion - Absorption Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning  Digestive System Primary function – Transfer nutrients, water, and electrolytes from ingested food into body’s internal environment Four functions – Motility – Secretion – Digestion – Absorption  Digestive System Motility – Muscular contractions that mix and move forward the contents of the digestive tract – Two types of digestive motility Propulsive movements – Push contents forward through the digestive tract Mixing movements – Serve two functions » Mixing food with digestive juices promotes digestion of foods » Facilitate absorption by exposing all parts of intestinal contents to absorbing surfaces of digestive tract  Digestive System Digestive secretions – Consist of water, electrolytes and specific organic constituents e.g. enzymes, antibodies – Secretions are released into digestive tract lumen on appropriate neural or hormonal stimulation – Normally reabsorbed in one form or another back into blood* after their participation in digestion * How ?  Digestive System Digestion – Biochemical breakdown of structurally complex foodstuffs into smaller, absorbable units – Accomplished by enzymatic hydrolysis – Complex foodstuffs and their absorbable units Carbohydrates → monosaccharides Proteins → amino acids Fats → glycerol and fatty acids Q: Name 3 monosaccharides  Digestive System Absorption – Small units resulting from digestion, along with water, vitamins, and electrolytes are transferred from digestive tract lumen into blood or lymph Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning  Digestive System Digestive tract Accessory digestive organs – Continuous from mouth to – Salivary glands anus – Exocrine pancreas – Consists of – Biliary system Mouth Liver Pharynx Gallbladder Esophagus Stomach Small intestine – Duodenum – Jejunum – Ileum Large intestine – Cecum – Appendix – Colon – Rectum Anus  Digestive Tract Wall has same general structure throughout length from oesophagus to anus Four major tissue layers – Mucosa Innermost layer – Submucosa – Muscularis externa – Serosa Outer layer Layers of Digestive Tract Wall  Mucosa Lines luminal surface of digestive tract Highly folded surface greatly increases absorptive area Three layers – Mucous membrane Serves as protective surface Modified for secretion and absorption Contains – Exocrine gland cells – secrete digestive juices – Endocrine gland cells – secrete blood-borne gastrointestinal hormones – Epithelial cells – specialized for absorbing digestive nutrients – Lamina propria Houses gut-associated lymphoid tissue (GALT) – Important in defense against disease-causing intestinal bacteria – Muscularis mucosa Sparse layer of smooth muscle  Submucosa Thick layer of connective tissue Provides digestive tract with distensibility and elasticity Contains larger blood and lymph vessels Contains nerve network known as submucosal plexus  Muscularis Externa Major smooth muscle coat of digestive tube In most areas consists of two layers – Circular layer Inner layer Contraction decreases diameter of lumen – Longitudinal layer Outer layer Contraction shortens the tube Contractile activity produces propulsive and mixing movements Myenteric plexus – Lies between the two muscle layers  Serosa Secretes serous fluid – Lubricates and prevents friction between digestive organs and surrounding viscera Continuous with mesentery throughout much of the tract – Attachment provides relative fixation – Supports digestive organs in proper place while allowing them freedom for mixing and propulsive movements Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Layers of Digestive Tract Wall  MESENTERY Provides relative fixation of G.I. strustures  Digestive System Function Digestive motility and secretion are regulated by – Autonomous smooth muscle function – Intrinsic nerve plexuses – Extrinsic nerves – Gastrointestinal hormones Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning Summary of Pathways Controlling Digestive System Activities  DIGESTIVE SYSTEM In this lecture we covered 1. Overview of Anatomy 2. Overview of Function - Motility - Secretion - Digestion - Absorption Chapter 16 The Digestive System Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning  Chapter 16 The Digestive System Overview of Anatomy and Function Sherwood Modified, Edited and Presented by Marios Z Panos Thank you for your attention ! Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning