Section II. INGESTION AND INITIAL PROCESSING OF FOODS
a. Hunger. When an individual needs foods, he experiences a sensation known
as hunger. The hypothalamus area of the brain controls the degree of hunger or
satiation (feeling of being well fed). To do this, the hypothalamus receives various types
of information from throughout the body.
b. Food Selection. When food is presented, an individual goes through a
process of food selection. He or she has a greater appetite for some foods than others.
This process is related both to previous learning and to current, internal chemical
c. Biting. Together, the upper and lower incisors (anterior teeth) create two
cutting surfaces like a pair of scissors. As food items are placed in the opening of the
oral cavity, bite-size chunks of food are cut off. These chunks are usually just the right
size for the mouth to handle.
6-5. TWO KEY FACTS ABOUT DIGESTION
In general terms, there are two key facts to understand about digestion:
a. First, digestion is a chemical process. Through a process called hydrolysis,
food is broken down into its constituent parts.
b. Second, this chemical process takes place only at wet surfaces of the food.
During the process known as mastication (chewing), the food particles are
gradually broken down into smaller and smaller pieces. At the same time, the total
surface area of the food increases greatly.
a. This grinding and crushing of the food particles are accomplished by the
posterior teeth, the premolar and molar teeth. For this purpose, these teeth have broad,
b. Together, the tongue and cheeks act to keep the food particles between the
surfaces of the grinding teeth. This is accomplished as the lower jaw moves up and