The stomach is a J-shaped, pouchlike organ, about 25-30 centimeters long, which hangs inferior to the diaphragm in the upper left portion of the abdominal cavity. It has a capacity of about one liter or more, and its inner lining is marked by thick folds (rugae) of the mu-cosal and submucosal layers that disappear when its wall is distended. The stomach receives food from the esophagus, mixes it with gastric juice, initiates the digestion of proteins, carries on a limited amount of absorption, and moves food into the small intestine.
In addition to the two layers of smooth muscle—an inner circular layer and an outer longitudinal layer— found in other regions of the alimentary canal, some parts of the stomach have another inner layer of oblique fibers. This third innermost muscular layer is most highly developed near the opening of the esophagus and in the body of the stomach (fig. 17.17).
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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.