ABSTRACT
Like nutrients, foodborne toxicants enter the body by way of the gastrointestinal (GI) tract or alimentary tract, particularly through the wall of the small intestine. The GI tract is a tube extending from the mouth to the anus. This hollow tube is several times longer than the height of a person, and is ca. 30 ft. The GI system includes the gut, with salivary glands, pancreas, liver, and gall bladder. The primary function of the GI tract is to break down complex food components into substances appropriate for absorption into the body. Also, it provides a means for waste removal from the digestive and metabolic operations. Lastly, the wall of the GI tract represents a barrier between the body and the outside world, i.e., the last frontier. The cell lining the GI tract not only controls the form in which nutrients enter the body but also has the ability to keep substances that are of no value or are potentially dangerous out of the body. To perform its functions, the GI tract system engages in digestive, motility, secretory, and absorptive operations (Table 8.1).
