<P> Secretory cells are found in a group, or acinus (plural, acini). Each acinus is located at the terminal part of the gland connected to the ductal system, with many acini within each lobule of the gland . Each acinus consists of a single layer of cuboidal epithelial cells surrounding a lumen, a central opening where the saliva is deposited after being produced by the secretory cells . The three forms of acini are classified in terms of the type of epithelial cell present and the secretory product being produced: serous, mucoserous and mucous . </P> <P> In the duct system, the lumina are formed by intercalated ducts, which in turn join to form striated ducts . These drain into ducts situated between the lobes of the gland (called interlobar ducts or secretory ducts). These are found on most major and minor glands (exception may be the sublingual gland). </P> <P> All of the human salivary glands terminate in the mouth, where the saliva proceeds to aid in digestion . The saliva that salivary glands release is quickly inactivated in the stomach by the acid that is present, however saliva also contains enzymes that are actually activated by stomach acid . </P> <P> About 20,000 protein coding genes are expressed in human cells and 60% of these genes are expressed in normal, adult salivary glands . Less than 100 genes are more specifically expressed in the salivary gland . The salivary gland specific genes are mainly genes that encode for secreted proteins and compared to other organs in the human body; the salivary gland has the highest fraction of secreted genes . The heterogeneous family of proline - rich, human salivary glycoproteins, such as PRB1 and PRH1, are salivary gland specific proteins with highest level of expression . Examples of other specifically expressed proteins include the digestive amylase enzyme AMY1A, the mucin MUC7 and statherin, all of major importance for specific characteristics of saliva . </P>

Where is the salivary gland located in humans