The functional regions of the stomach do not correspond to the anatomic regions. The anatomic regions are the fundus, corpus (body), antrum, and pylorus (Fig. 26.24). Functionally, the stomach is divided into a proximal reservoir and distal antral pump on the basis of distinct differences in motility between the two regions. The reservoir consists of the fundus and approximately one third of the corpus,- the antral pump includes the caudal two thirds of the corpus, the antrum, and the pylorus.
Differences in motility between the reservoir and antral pump reflect adaptations for different functions. The muscles of the proximal stomach are adapted for maintaining continuous contractile tone (tonic contraction) and do not contract phasically. By contrast, the muscles of the antral pump contract phasically. The spread of phasic contractions in the region of the antral pump propels the gastric contents toward the gastroduodenal junction. Strong propulsive waves of this nature do not occur in the proximal stomach.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.