These are made up of an acinus (a berry-shaped cluster of excretory cells) and ductal systems. Saliva is formed in the acini with the serous (watery) secretion formed by serous cells, and the mucous (viscous) secretion formed by the mucous cells. There are three major bilateral salivary glands: the parotid, the sublingual and the submandibular (Figures 2a & 2b).1,10
The parotid is the largest pair of glands, occupying the parotid facial space, an area posterior to the mandibular ramus, and anterior and inferior to the ear. It secretes saliva through the Stensen’s ducts into the oral cavity to facilitate mastication and swallowing. The submandibular are a pair of glands located beneath the lower jaws. Even though they are smaller than the parotid, they produce 70% of saliva, secreted via the Wharton’s ducts. These two glands produce “true” saliva – the combination of serous fluid and mucous. They also have acini connected to intercalated ducts (essentially, transitional tissue) which then connect to striated ducts that have the capacity to modify the mineral content of saliva. On the other hand, the third major set of glands – the sublingual glands which are located beneath the tongue – secretes mainly mucous, and does not have striated ducts, releasing its mucous directly from acini via excretory ducts.1,10
Figure 2a. Anatomy of the parotid salivary glands.
Figure 2b. Anatomy of the sublingual and the submandibular salivary glands.