The Salivary Glands
The process of digestion begins in your mouth. The salivary glands start to function as soon as you take the first bite of food. There are three large salivary glands and numerous smaller ones located in your mouth and throat. The larger salivary glands occur in pairs and are located on either side of your mouth. The parotid glands are in the upper part of your cheek near your ear and their ducts open near your molars. The submandibular glands are under jaw, opening behind your lower front teeth, and the sublingual glands are beneath your tongue, opening on the floor of your mouth. There are hundreds of smaller salivary glands interspersed throughout your mouth, lips, inner cheeks, sinuses and throat; all salivary glands produce and release saliva.
The salivary glands are responsible for the production of saliva and mucus, as well as a mixture of both, depending on the specific gland. Saliva is a clear, serous fluid composed of water and proteins, including the digestive enzyme amylase. Mucus is a thicker liquid which is somewhat slimy. Saliva is needed to keep the mucous membranes in your mouth from drying out; it is also needed to moisten food for chewing and swallowing. Saliva produced by the salivary glands begins the process of digestion and protects your teeth from tooth decay. According to Encyclopaedia Britannica, the parotid glands produce saliva, the submandibular glands produce a mixed fluid that is mostly saliva and the sublingual glands produce a mixed fluid which is largely mucus. The salivary glands become stimulated at the thought of eating food as well as through smell and during the eating process.
Secretion of Saliva
The salivary glands produce saliva and mucus which is secreted from ducts into the mouth. Colorado State University states each salivary gland contains a cluster of cells called acini cells, whose function is to secrete the mix of saliva and/or mucus particular to each type of gland. Once produced, the saliva fluids pass out of the acinus through collecting ducts that empty into the mouth. Saliva passes from the parotid gland via Stenson's duct and the mostly saliva mixed fluid is secreted from the submandibular glands through Wharton's duct. The sublingual gland forms a network of ducts, Rivinus's ducts, which unite to form one main duct called Bartholin's duct where the largely mucus fluid is secreted. Secretions from the salivary glands are controlled by your autonomic nervous system, which also determines what type of fluid is secreted from the salivary glands and how much.
Digestion Of Food
The mucus from the submandibular and sublingual glands lubricates and binds food as you chew it. Mucus holds the chewed food together in a slippery mass, coating it so it can pass down the esophagus into the stomach without causing damage. According to Colorado State University, saliva contains alpha-amylase, an enzyme that begins breaking down starches into a sugar called maltose while still in your mouth. In addition, saliva coats the lining of your mouth and esophagus to aid passage of food and makes dry food more soluble so its flavor can be detected by your taste buds.