ABSTRACT
With the exception of intravenous infusion, nutrient entry into the body takes place by way of the gastrointestinal or alimentary tract. This tract is in essence a tube extending from the mouth to the anus, whose lumen is considered to be outside of the body (Figure 3.1). The gastrointestinal tract, or simply "the gut," along with organs such as the salivary glands, pancreas, liver, and gall bladder that empty supportive substances into the gut, make up the gastrointestinal system. The primary objectives of the gastrointestinal system are to break down complex food components into substances appropriate for absorption into the body as well as to provide a means of waste removal from digestive and metabolic opera tions. To meet these objectives the gastrointestinal system must engage in digestive, motil ity, secretory, and absorptive operations.
