b. Major Organs. The major organs involved in the human digestive system
are listed below. They are each discussed later in this lesson.
Mouth or oral complex.
Small intestines and associated glands.
Anal canal and anus.
c. Digestive Enzymes. A catalyst is a substance that accelerates (speeds up)
a chemical reaction without being permanently changed or consumed itself. A digestive
enzyme serves as a catalyst, aiding in digestion. Digestion is a chemical process by
which food is converted into simpler substances that can be absorbed or assimilated by
the body. Enzymes are manufactured in the salivary glands of the mouth, in the lining
of the stomach, in the pancreas, and in the walls of the small intestine.
FOODS AND FOODSTUFFS
Examples of food items are a piece of bread, a pork chop, and a tomato. Food
items contain varying proportions of foodstuffs. Foodstuffs are the classes of chemical
compounds that make up food items. The three major types of foodstuffs are
carbohydrates, lipids (fats and oils), and proteins. Food items also contain water,
minerals, and vitamins.