ABSTRACT
The gastrointestinal system of an animal serves four functions. The first of these functions is feeding — that is, the delivery of food to the start of the gastrointestinal tract. The second function is digestion. The process of digestion permits the third aspect of gastrointestinal function to occur, which is absorption. The final role of the gastrointestinal system is elimination or excretion. This chapter looks at these aspects of the gastrointestinal system. The reception region of the gastrointestinal system is the mouth. In some respects, the process of digestion may be considered to begin here. Ingestion of small particles, sometimes called suspension feeding is generally restricted to aquatic animals, the majority of which live in the marine environment. The simplest way to obtain large particulate food matter, is to eat inactive food masses. Perhaps the simplest and most convenient way of obtaining food is by the absorption of nutrients across the general body surface area.
