Chapter 6 - Gastroduodenal anatomy and physiology

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Before understanding motility and neurogastroenterology disorders of the fore- and midgut, it is critical to be knowledgeable of the anatomy and physiology of this portion of the gastrointestinal tract. Coordinated appropriate gastroduodenal function represents the initiation of digestion. Organic diseases affecting the anatomy and vasculature of the foregut and proximal midgut are plentiful and represent a variety of disease processes beyond the scope of this chapter; a basic review of the macroscopic and microscopic anatomy, though, follows. In terms of the focus of the chapter, namely, providing a basis for discussion of neurogastroenterology and motility disorders of the proximal GI tract, a key element is that such disorders generally are derived broadly from a perturbed “brain-gut” axis and likely represents dysfunction of the central nervous system, enteric nervous system, and/or of the vagus nerve (or of some combination of these components of the axis). The result of such pathology is not only impaired motility but also disturbed sensation. Here, we review not only the mechanical and neurohumoral aspects of digestion in the stomach and duodenum, but also the often-ignored sensory components that are increasingly being recognized as critical to the understanding and management of “functional” disorders. This makes the discussion relevant not only for gastroenterologists with neurogastroenterology/motility focus, but for the entire medical community given the prevalence of such disorders in the general population.