e. Tongue. The tongue is a muscular organ. The tongue is capable of internal
movement to shape its body. It is moved as a whole by muscles outside the tongue.
Interaction between the tongue and cheeks keeps the food between the molar teeth
during the chewing process. When the food is properly processed, the tongue also
initiates the swallowing process.
f. Salivary Glands. Digestion is a chemical process that takes place at the wet
surfaces of food materials. The chewing process has greatly increased the surface
area available. The surfaces are wetted by saliva produced by glands in the oral cavity.
Of these glands, three pairs are known as the salivary glands proper.
g. Taste Buds. Associated with the tongue and the back of the mouth are
special clumps of cells known as taste buds. These taste buds literally taste the food.
That is, they check its quality and acceptability.
The pharynx (pronounced "FAIR-inks") is a continuation of the rear of the mouth
region, just anterior to the vertebral column (spine). It is a common passageway for
both the respiratory and digestive systems.
The esophagus is a muscular, tubular structure extending from the pharynx,
down through the neck and the thorax (chest), and to the stomach. During swallowing,
the esophagus serves as a passageway for the food from the pharynx to the stomach.
Section III. THE STOMACH
The stomach is a sac-like enlargement of the digestive tract specialized for the
storage of food. Since food is stored, a person does not have to eat continuously all
day. One is freed to do other things. The presence of valves at each end prevents the
stored food from leaving the stomach before it is ready. The pyloric valve prevents the
food from going further. The inner lining of the stomach is in folds to allow expansion.
a. While the food is in the stomach, the digestive processes are initiated by
juices from the wall of the stomach. The musculature of the walls thoroughly mixes the
food and juices while the food is being held in the stomach. In fact, the stomach has an
extra layer of muscle fibers for this purpose.
b. When the pyloric valve of the stomach opens, a portion of the stomach
contents moves into the small intestine.