Circulation. The alimentary tract provides the body with a continual supply of water, electrolytes, vitamins,
and nutrients. To achieve this requires (1) movement of food through the alimentary tract; (2) secretion
of digestive juices and digestion of the food; (3) absorption of water, various electrolytes, vitamins,
and digestive products; (4) circulation of blood through the gastrointestinal organs to carry away the
absorbed substances; and (5) control of all these functions by local, nervous, and hormonal systems.
Figure 62-1 shows the entire alimentary tract. Each part is adapted to its specific functions: some to
simple passage of food, such as the esophagus; others to temporary storage of food, such as the
stomach; and others to digestion and absorption, such as the small intestine. In this chapter, we discuss
the basic principles of function in the entire alimentary tract; in the following chapters, we discuss the
specific functions of different segments of the tract.
General Principles of Gastrointestinal Motility Physiologic Anatomy of the
