AN INTRODUCTION TO GASTRO - ENTEROLOGY A CLINICAL STUDY OF THE STRUCTURE AND FUNCTIONS OF THE HUMAN ALIMENTARY TUBE BY JAMES DUNLOP LICKLEY, M.D. Hon. Consulting Physican, Sick Children's Hospital, Newcastle-upon-Tyne; Late Lecturer on Medical Applied Anatomy, Medical School, King's College, University of Durham. WITH 21 ILLUSTRATIONS BRISTOL: JOHN WRIGHT & SONS LTD. LONDON: SIMPKIN MARSHALL (1941) LTD. 1947 PRINTED IN Ο REA Τ BRITAIN BY JOHN WRIGHT AND SONS LTD. BRISTOL. ENGLAND. PREFACE THIS elementary manual is intended for those beginners who are interested in approaching from a scientific aspect the study of some of the problems arising in the diagnosis and treatment of disorders of the alimentary tube. It is hoped, therefore, that it may appeal to senior medical students and to the younger physicians. At the same time, since the subject is of such everyday importance, much of the information provided in this simplified form may be of interest and help to the general practitioner. To the medical men returning from the Forces, the résumé of anatomical and physiological data given herein may prove of some assistance in their post-war revision courses. In a manual of this size and scope no useful purpose would be served by indicating specifically the numerous sources from which information has been derived. The literature of gastro-enterology embraces several hundred articles; for lists of the more important of these the student is referred to the larger text-books. J. D. L. INTRODUCTION THE study of the alimentary tube can be approached from several angles, e.g., anatomical, physiological, pathological, bacteriological, etc. In the present manual the lines of approach selected are the anatomical, the physiological, and the clinical. The volume of literature which has grown up in connexion with each of these is enormous. Observa- tions, experiments, and deductions have accumulated until it is almost impossible for anyone commencing this study to construct for himself even a crude working plan that he might use as a basis for his investigations into the practical problems he seeks to understand. It is useful, therefore, to make an attempt to present to the beginner a simplified story of the structure and working of this important tube. Such simplification demands the selec- tion of certain details and the omission of many more. It necessitates an individual outlook, and as such is open to much criticism, but it does not ignore the fact that once a definite picture has been established, there is a huge pool of information from which verification and amplification of details can be drawn, and it is hoped that further study along these lines may be stimulated and an added interest given to the subject. The present attempt at simplification has as its ultimate object the practical application of some well-known ana- tomical and physiological facts and theories to several of the simpler medical clinical conditions ; only such details, therefore, are selected as are considered to have a direct bearing on the problems to be discussed. VÜi INTRODUCTION In order to present the subject in the clearest possible manner it is proposed to consider it under the following headings :— Part I.—The structure and divisions of the alimentary tube. Part II.—How the tube works under normal conditions. Part III.—How the working of the tube is modified by certain abnormal conditions. Part IV.—Some practical clinical applications. PART I THE STRUCTURE AND DIVISIONS OF THE ALIMENTARY TUBE "While the student may direct his attention especially to the phase of structure or the phase of function, he should understand from the outset that great progress and permanent results are to be attained only when the study of structure and the study of function go hand in hand." J. B. JOHNSTON. AN INTRODUCTION TO GASTRO-ENTEROLOGY CHAPTER I THE GENERAL STRUCTURE AND DIVISIONS OF THE ALIMENTARY TUBE THE alimentary tube is a long continuous tube with an inlet at the mouth and an outlet at the anus (Fig. i). From a functional point of view, it is possible to divide it broadly into three segments. The first segment extends from the inlet of the tube to the middle of the duodenum and may be described as preparatory; here the foodstuffs are mechanically and chemically prepared for presentation to the next segment, but are not sufficiently altered to allow of any absorption. The second segment extends from the middle of the duodenum to the middle of the transverse colon; in it all the main digestive and absorptive processes are accomplished. The third segment, which extends from the middle of the transverse colon to the outlet of the tube, may be described as expulsive; it is almost entirely devoted to the rejection of such portions of the foodstuffs and other waste materials as cannot be utilized by the body. For a more detailed study of the structure and functions of the alimentary tube, it is convenient to divide it into a series of compartments each presenting definite differences in structure that can be related to specific functions (Fig. 2). These compartments are as follows:— Compartment I.—Lips to the faucial isthmus. Compartment II.—Faucial isthmus to the cardiac orifice of the stomach. 4 GASTRO-ENTEROLOGY Fig. ι.—Scheme of the usual structural divisions of the alimentary tube. GENERAL STRUCTURE OF ALIMENTARY TUBE 5 Fig. 2.—Scheme of the proposed functional divisions (compartments) of the alimentary tube. 6 G ASTRO-EN TE ROLOGY Compartment HL—Cardiac orifice of the stomach to the middle region of the duodenum. Compartment IV.—Middle of the duodenum to the middle region of the transverse colon. Compartment V.—Middle of the transverse colon to the anal canal. Compartment VI.—The anal canal. Attention is drawn particularly tç the fact that in this description the anatomical division of the abdominal part of the alimentary tube into stomach, small intestine, and colon is replaced by one which closer study will show con- forms more intimately to embryological, anatomical, and physiological findings. The fundamental pattern of the wall of the tube may be studied readily in a transverse section taken from the lower part of the small intestine. The outermost coat is the peri- toneal covering—tunica serosa. Under this is the muscular coat—tunica muscularis—arranged in two layers, namely, an outer of longitudinal and an inner of circular fibres. The innermost coat of the tube is the mucous membrane—tunica mucosa—and in it may be recognized: (i) A surface layer of epithelial cells and simple glands resting on a basement membrane; (2) A layer of retiform tissue containing scattered lymph-cells; (3) A layer of very thin unstriped muscular tissue—the muscularis mucosae. The tunica muscularis is connected to the tunica mucosa by a loose but strong layer of areolar tissue—the submucous layer—in which run the larger blood-vessels and nerves of the wall of the tube. The fundamental pattern undergoes modifications in the separate parts of the alimentary tube, and these will be indi- cated as they are encountered in the course of the description.