All of these glands are tubuloacinar glands , i.e. they have secretory acini but the first part of the duct system originating from the acini also participates in the secretory process. The salivary glands are divided by connective tissue septae into lobes, which are further subdivided into lobules. This functional differentiation is reflected in the appearance of these acini in histological sections. The cells forming the serous acini contain a round or slightly ovoid nucleus which is placed basally in the cell. The granules represent the vesicles which contain the secretory products of the cell.
Secretory vesicles fill much of the apical cytoplasm.
The secretory product has either been dissolved during the staining process or remains unstained. Occasionally, and in particular in glands located relatively close to the oral cavity, serous cells and mucous cells may form compound or mixed acini. Following their appearance they are called serous demilunes . Both serous and mucous acini and parts of the secretory duct system are surrounded by myoepithelial cells which by their contraction participate in the secretory process. They are usually difficult to distinguish in histological sections.