b. At each end of the stomach, there is a structure to keep the contents from
leaving the stomach.
(1) At the point where the esophagus enters the stomach, there is a
"gastroesophageal valve." This valve appears to be functional, although it has not been
(2) At the other end of the stomach is the well-developed pyloric valve.
6-14. ADAPTATIONS OF THE STOMACH FOR ADDITIONAL FOOD PROCESSING
a. Gastric Glands. The mucosal lining of the stomach contains a number of
gastric glands. These gastric glands produce gastric digestive juices for initiating
digestion, particularly of proteins. Some of the gastric glands also produce hydrochloric
acid. Thus, chyme, the mixture produced by the stomach, is quite acid.
b. Additional Musculature. A third inner, oblique layer of muscle has been
added to the stomach wall. With the three layers of muscles, the contents of the
stomach are thoroughly mixed.
Section V. DIGESTION AND ABSORPTION
The small intestines are the primary area of the body for digestion of foodstuffs.
Digestion occurs through the action of enzymes. The results of the digestion are the
end-products. These end-products (molecules or particles) are of such size that they
can be absorbed through the walls of the small intestines. The end-products are then
distributed throughout the body by the body's circulatory systems.
6-16. DIGESTION AS A CHEMICAL PROCESS
a. Digestion is the chemical process that breaks foodstuffs down into their basic
constituents. In general, chemical processes are expected to occur at a rate
proportional to the temperature. However, in the human body, the temperature is not
high enough for the chemical process of digestion to produce a sufficient quantity of the
b. Therefore, digestive enzymes are present to maintain the appropriate rates of
reaction. Digestive enzymes are catalysts. A catalyst is a substance that improves the
rate of a reaction without being consumed itself. Because of digestive enzymes,
digestion proceeds at a pace fast enough to provide the materials needed by the body.