When I set out originally to write this volume, it was my hope primarily to introduce medical and pharmacy students to the functioning of the gastrointestinal system in the context of a classical physiology curriculum. By using examples of common digestive disease states and their treatment, I sought to illuminate the normal functioning of what is, in my opinion, a supremely elegant system. It is not difficult to grasp the basic design requirements for the gut. Indeed, I have often begun my lectures with a slide of a baby's romper and arrows pointing to the two extremes of the alimentary canal labeled “in” and “out.” However, the overlapping layers of regulatory controls, the many systemic redundancies, and the existence of extensive, bidirectional signaling between the various segments of the gut and the organs that drain into it all make for a complex body of knowledge that can be challenging, sometimes, for students to master. My intent, mainly, was to generate an accessible reference that could be used to review this material, perhaps as a supplement to a more general physiology course text. I have certainly been very gratified by the positive response to the text from both students and colleagues, and surmise that it filled a need.
However, the period that has intervened since I first designed this text has seen dramatic changes in the approach to medical education in many, if not most, institutions, at least in North America. Many medical schools, including my own, have moved away from stand-alone courses in physiology as well as other preclinical subjects, and have implemented integrated curricula that examine many medically-relevant facets of body systems, including anatomy, pathophysiology, and therapeutics, in concert with physiological information. I was fortunate (I especially cannot claim any prescience) that my original template for the book actually is well-suited for an organ- or systems-based curriculum, since I had intentionally already included much of the framing material surrounding physiology in my plan for the volume. Thus, while the volume retains only the word “physiology” in its title, I believe from experience that it also represents a useful resource for the GI block of a broader course.
The second edition is not unchanged, of course. First, I am grateful to students and colleagues from both within and outside my own institution who alerted me to minor errors in the original text. While some mistakes are almost inevitable in a project of this scope, no many how many pairs of eyes pass over it, it is certainly nice to correct as many as possible. Second, I have inserted new information on emerging topics, such as the communication between the intestine and central nervous system that controls food intake, the myriad roles newly ascribed to the intestinal microbiota, contemporary approaches to therapy for a number of GI maladies, and the role of the gut in obesity. Finally, I have overhauled a substantial number of the original illustrations, both to provide a more consistent style within and between chapters, and to clarify key concepts. Illustrations that summarize new topics have also been added.
With all the changes, however, the basic premise and goal of the book remain the same as in the original edition—to convince medical students and other trainees of the beauty of the design of the GI system, so vital to life and also the source of both human pleasure and suffering. As before, I take responsibility for any errors, and encourage readers to bring them to my attention. I also thank Michael Weitz at McGraw-Hill, my editor on this and other projects, especially for his encouragement, pep talks, cajoling, and forbearance.
Kim E. Barrett, PhD
La Jolla, California