Two types of glands secrete saliva into the mouth. The first type of glands are called intrinsic salivary glands. These are small glands dispersed throughout the mouth. They have openings in different parts of the mouth, such as under the base of the tongue, on the inside of the lips, and on the inside of the cheeks. They secrete saliva regardless of whether we are eating. The saliva that they secrete contains lipase, an enzyme that breaks down fats when it comes into contact with the hydrochloric acid in the stomach, and lysozyme, an enzyme that destroys bacteria.
Extrinsic salivary glands are the second type of salivary gland. These glands, which include the parotid glands, the submandibular gland, and the sublingual gland, are much larger and are located outside of the mouth itself. The parotid glands are located just below the skin in front of the earlobe. These glands secrete saliva through ducts that have openings on the roof of the mouth next to the second molar. The sublingular glands are found just below the tongue. These ducts have multiple openings along the floor of the mouth past the lower two front teeth. The submandibular glands are located halfway along the lower jaw below the sublingular glands. These glands have ducts that empty behind our two lower front teeth. The saliva that these glands secrete contains a mixture of mucus, amylase, and electrolytes.
When we place food into our mouth, tactile receptors, pressure receptors, and taste receptors send a signal to the medulla. These signals, combined with other signals from other organs such as the eyes and the nose, cause the glands to secrete saliva. Secretion of saliva can also be caused by irritation of the stomach or esophagus. This saliva mixes with the food particles to help them stick together and be more slippery so that they can go down the esophagus more easily. Thus, saliva also helps to form food particles into a bolus so that they can travel down the esophagus. Amylase in the saliva also helps to break the starch in the food down. By mixing with saliva, starches in food are broken down into simple sugars so that they can be more easily absorbed by the body later.Last Updated: Saturday, July 16, 2011