A salivary gland is subdivided into lobules by connective tissue septae containing interlobular excretory ducts. These ducts are continuous with branching intralobular ducts that connect to acini.

The purely serous acinus characterizes the parotid gland. It is composed of serous pyramidal cells pouring their secretions into a narrow central lumen either directly at their apex or indirectly via intercellular canaliculi. These acini connect with narrow ducts called intercalated ducts lined with flattened epithelial cells. These ducts open into larger ducts lined with cuboidal cells. The epithelial cells show their elongated mitochondria arranged linearly and vertically within their cytoplasm, giving a striated appearance to the epithelium of the ducts called intralobular striated ducts. These ducts lose their striations as they become the non-striated intralobular ducts and the larger non-striated interlobular ducts present in the connective tissue septae.

In the sublingual and submandibular salivary glands, the acini may be purely mucous or mixed as illustrated in this drawing. Both types of acini have mucous cells in contact with short intercalated ducts that open into striated ducts. The mixed acini have not only mucous cells but also crescent-shaped or serous demilune cells at their tips. These serous demilune cells pour their secretions into narrow intercellular canaliculi that open into the central lumen of the acinus.