The stomach is a saclike enlargement of the digestive tract.
By way of the esophagus, the stomach receives the food that has been processed in the oral cavity.
The stomach's capacity is great enough to allow the individual to take in enough food material at one time to last for an extended period of time.
This allows the individual to engage in activities other than eating.
Page 2 Introduction to the Stomach
In addition, certain digestive processes are initiated in the stomach.
The food is retained in the stomach for varying lengths of time, depending upon the types of food eaten, the condition of the individual, and many other factors.
Page 3 Adaptations of the Stomach for the Storage Function
The stomach is adapted as a storage area in several ways.
Its wall is quite stretchable.
The mucosal lining of the stomach is thrown up into longitudinal folds called rugae.
These rugae flatten out as the stomach capacity increases.
Page 4 Adaptations of the Stomach for the Storage Function
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 demonstrated anatomically.
(2) At the other end of the stomach is the well-developed pyloric valve.
Page 5 Adaptations of the Stomach for Additional Food Processing
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.
Page 6 Adaptations of the Stomach for Additional Food Processing
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.