Scientific Basis for Clinical Practice in Gastroenterology and Hepatology A.B.R. Thomson __________________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson Disclaimer: Neither the author(s) nor CAPStone Academic Publishers can ensure the accuracy of the information contained in these books with regards to regional variations for recommended indications, dosages, and reportable adverse events. With the rapid expansion of medical knowledge, there may be, from time to time, variations between what is published in these books and the latest information and consensus recommendations made by different organizations. It is the responsibility of the reader to confirm independently any practice decisions related to an individual patient. ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson Cover design by R. Burnett ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson iv Scientific Basis for Clinical Practice in Gastroenterology and Hepatology CAPstone (Canadian Academic Publishers Ltd) is a not- for-profit company dedicated to the use of the power of education for the betterment of all persons everywhere. “For the Democratization of Knowledge” 2012 © A.B.R. Thomson ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson v ARE YOU PREPARING FOR EXAMS IN GENERAL INTERNAL MEDICINE OR IN GASTROENTEROLOGY AND HEPATOLOGY? See the full range of examination preparation and review publications from CAPstone on Amazon.com Gastroenterology and Hepatology  First Principles of Gastroenterology and Hepatology, 6th edition (ISBN: 978-1461038467)  GI Practice Review, 2nd edition (ISBN: 978-1475219951)  Endoscopy and Diagnostic Imaging Part I (ISBN: 978-1477400579)  Endoscopy and Diagnostic Imaging Part II (ISBN: 978-1477400654) General Internal Medicine  Achieving Excellence in the OSCE. Part I. Cardiology to Nephrology (ISBN: 978-1475283037)  Achieving Excellence in the OSCE. Part II. 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Neurology to Rheumatology (ISBN: 978-1478392736) ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson vi THE WESTERN WAY ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson vii Table of Contents Page Prologue ix Dedication xi Acknowledgement xii Clinical physiological challenges xiii Overview of the GI tract 1 Luminal Anatomy of the GI Tract 2 Digestion and absorption of macronutrients 3 Control of Food Intake 7 Control Of Food Intake 8 Networks Involved in the Control of Food Intake 11 Starvation 20 Protein – Energy Malnutrition (PEM) 22 Mouth and salivary glands 25 Regulation of Salivary Secretion 31 Esophagus 33 Gross Anatomy of Esophagus 34 Lower Esophageal Sphincter 38 Gastroesophageal Reflux Disease 42 Swallowing 43 Esophageal Motility Disorders 49 Stomach 51 Gastric Anatomy 52 Gastric Hydrochloric Acid Secretion at the Macromolecular level 55 Acid Secretion 56 Gastric Hydrochloric Acid Secretion at the Micro’ (Cellular) Level 68 of the Parietal Cell Gastric Secretion of Pepsinogen 75 Gastric Filling and Emptying 77 ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson viii Determinants of Rate of Gastric Emptying 81 Tests of Gastric Neurological Function 84 Vomiting 86 Pancreas 91 Functional Anatomy of the Pancreas 92 Pancreatic Acinar Cell Secretion of Protein 93 The Macro’ Level of Pancreatic Secretion 94 The Micro’ (Cellular) Level of Pancreatic Secretion of Enzymes 101 Pancreatic Enzymes 105 Protection of the Pancreas from Auto Digestion 108 Pancreatic Stones 119 Hepatobiliary System 121 Heptatocytes, Sinusoids, and the Intrahepatic Bile System 122 Causes of Portal Hypertension 128 Portal Circulation 130 The Enterohepatic Circulation (EHC) of Bile Acids 130 Secretion of HCO3- and water by Cholangiocytes 141 Gallbladder 146 Absorption of Electrolytes and Water by Gallbladder 148 Pathophysiology of Gallstone Formation 149 Formation of Cholesterol Gallstones 150 Development of Lithogenic Bile 152 Bilirubin metabolism 161 Complications of Gallstones 164 Heterogeneity of hepatocyte metabolic function in the hepatic 166 zones Non-Alcoholic Fatty Liver Diseases (simple steatosis and non- 175 alcoholic steatohepatitis) Polycystic Liver Diseases (PLDs) 180 Hepatic Encephalopathy (HE) 180 Small Intestine 189 The Types of Epithelial Cells of the Intestinal Mucosa: 191 Enterocytes Small Intestinal Motility 194 Absorption of Water 202 ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson ix Chloride Secretion 216 Secretion 219 Potassium (K+) Absorption and Secretion 226 Absorption of Proteins,Peptides, Oligopeptides and Amino Acid 227 Carbohydrate Assimilation 236 Absorption of Triglycerides 243 Absorption of fat soluble Vitamins A, D, E, and K 252 Cholesterol 252 Bile Acids – Intestinal Components of Enterohepatic Circulation 260 (EHC) of Bile Acids Control of the Enterohepatic Circulation (EHC) of Bile Acids 264 Water Soluble Vitamins 267 Minerals 271 Colon 283 Structure 284 Movement/ Transit 284 Classification of Laxatives 290 Defecation 292 Fecal continence 296 Fecal Incontinence 297 Rectal Manometry 300 Miscellaneous Topics 301 Mucosal Immunity 302 Food Allergies 307 Oncogenesis 310 Oncogenesis – associated genes and colorectal cancer 312 Visceral Pain 313 Index 317 ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson x Prologue Like any good story, there is no real beginning or ending, just an in-between glimpse of the passing of time, a peek into a reality of people’s minds, thoughts, feelings, and beliefs. The truth as I know it has a personal perspective which drifts into the soul of creation. When does life begin, when does an idea become conceived, when do we see love or touch reality? A caring, supportive, safe, and stimulating environment creates the holding blanket, waiting for the energy and passion of those who dream, invent, create – disrupt the accepted, challenge the conventional, ask the questions with forbidden answers. Be a child of the 60’s. Just as each of us is a speck of dust in the greater humanity, the metamorphosis of the idea is but a single sparkle in the limitlessness of the Divine Intelligence. We are the ideas, and they are us. No one of us is truly the only parent of the idea, for in each of us is bestowed the intertwined circle of the external beginning and the end…. The child will grow, the images will expand, the learning of all aspects of our craft will develop and flourish amongst persons of good will. Examinations will become second nature, as each clinical encounter, each person, each patient, becomes our test, the determination of clinical competence, of caring, of compassion. May these three C’s become part of each of our live’s narrative. And from this start comes Capstone Academic Publishing, an innovation for the highest quality and value in educational material, made available at cost, speaking in tongues, in the languages of many cultures, with the dialect of the true North strong and free, so that knowledge will be available to all. Outstanding medical practice and true dedication to those from whom we receive both a privilege and pleasure of care, comes within, comes from those rare teachers who inspire us. True, we need all of these to jump over a very high bar. But to be a truly outstanding physician, you need to care for and care about people, and you must respect the dignity and rights of all others. You must strike a balance between love and justice, and you place your family and friends at the top of your wish-list of lifetime achievements. For the skeptics who ask “What do you want from me?” I simply say “You are the future; I trust that in time you too will help young people to be the best they can be.” ___________________________________________________________________ Scientific Basis for Clinical Practice in Gastroenterology and Hepatology © A.B.R Thomson