Saliva is used to taste and blend food. Saliva is produced by a number of glands. The parotid, submandibular, and sublingual glands are three of the major pairs of salivary glands, in addition to the numerous tiny glands that also generate saliva. The largest pair of the parotid glands is found towards the side of the face, beneath and in front of each ear. The sheaths that surround the parotid glands prevent them from expanding as much when inflamed, as in mumps. The rounded submandibular glands are located in front of the sternomastoid muscle on the inner side of the lower jaw (the prominent muscle of the jaw). The mucous membrane that covers the floor of the mouth behind the tongue is right below the sublingual glands.
Due to the cluster-like arrangement of their secreting cells in rounded sacs, termed acini, coupled to freely branching systems of ducts, the salivary glands are of the kind known as racemose, from the Latin racemosus ("full of clusters"). The acini's walls enclose an alveolus, a tiny center cavity. Pyramidal secreting cells and some flat, star-shaped contractile cells known as myoepithelial, or basket, cells can be found in the acini's walls.
Similar to the myoepithelial cells of the breast, which contract to release milk from the milk ducts, the later cells are hypothesized to contract.
The cells that secrete can be either mucous or serous in nature. The latter type secretes amylase-containing watery fluid, while the former secretes mucin, the main component of mucus. The submandibular glands produce both serous and mucous secreting cells, with serous cells outnumbering mucous cells four to one. The secreting cells of the parotid glands are of the serous type. The sublingual glands' acini are mostly made up of mucous cells.
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