The medull oblongata contains the main brain centers regulating digestive functions, taste fibers primary centers, cell bodies of vagus nerve, and cell bodies of the salivary nerves. There are two other phases of neural regulation, gastric and intestinal. Interaction of digestive, neural and nervous systems Food enters the digestive tract through the mouth. The mechanical activity of chewing, grinding and mixing the food with saliva starts the digestive process. Saliva is mucus containing juice that is secreted from the salivary glands in the mouth.
Saliva starts the process of dissolving food.
The chewed food forms a bolus and when it gets to the back of the tongue it triggers the deglutition reflexes. From the back of the tongue the bolus is pushed into the pharynx where other reflexes move it to the esophagus which moves it into the stomach by peristalsis. There are three pairs of salivary glands. The cheeks contain the parotid gland that secrete a serous juice. The salivary glands are acinar exocrine glands.