ABSTRACT
Our normal food is a mixture of complex plant and animal materials that are composed largely of carbohydrates, fats, proteins, vitamins, and minerals. The bulk of these ingested nutrients consists of large polymers that must be reduced to simpler components before they can be absorbed and thus made available to all the cells in the body. The disintegration of naturally occurring foodstuffs into assimilable forms in the gastrointestinal tract constitutes the process of digestion and involves enzymes. The gastrointestinal tract is important in terms of both maintaining the nutritional status of the gut as well as providing nutrients to maintain the nutritional status and homeostasis of the whole organism. The majority of the enzymes involved in the digestive process are hydrolases (i.e., they split bonds of esters, glycosides, or peptides by the addition of water). The powerful hydrolytic enzymes of the digestive tract catalyze the degradation of large molecules present in food (e.g., starch or protein) into small molecules that can be readily absorbed such as glucose or amino acids. The digestive tract is under neurological and hormonal control. Fear, anger, irritation, and worry all may exert unfavorable in˜uences in the digestive system, while the thought, smell, and presence of food cause secretion and motility necessary for digestion. Both types of changes are controlled via the nervous system of the body. Several areas of the digestive tract secrete hormones, which act as chemical messengers on other areas of the digestive tract to control the process of digestion.
