Both major and minor salivary glands are composed of both epithelium and connective tissue (Figure 11-1). Epithelial cells both line the ducts and produce the saliva. Connective tissue surrounds the epithelium, protecting and supporting the gland. The connective tissue of the gland is divided into the capsule, which surrounds the outer part of the entire gland, and the septa. Each septum (plural, septa) helps divide the inner part of the gland into the larger lobes and smaller lobules. Both the capsule and septa carry nerves and blood vessels that serve the gland.

Epithelial cells that produce the saliva are the secretory cells (Figure 11-2). The two types of secretory cells are classified as either mucous or serous cells, depending on the type of secretion produced. Mucous cells have a cloudier-looking cytoplasm and produce mucous secretory product. In contrast, serous cells have a clear cytoplasm and produce serous secretory product. A combination of secretory cells present in the gland can produce a mixed secretory product. In some glands, one type of cell predominates so that the product is either more mucous or more serous than if it had a range of both cell types.

Secretory cells are found in a group, or acinus (plural, acini), which resembles a cluster of grapes. 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. The major and minor salivary glands have different types of acini (Table 11-1). However, the different types of acini are often difficult to classify on histological sections of the glands.

Serous acini are composed of serous cells producing serous secretory product and have a narrow lumen (Figure 11-3). In contrast, mucous acini are composed of mucous cells producing mucous secretory product, and their lumen is wider. Mucoserous acini have both a group of mucous cells surrounding the lumen and a serous demilune, or “bonnet” of serous cells superficial to the group of mucous secretory cells (Figures 11-4 and 11-5). Because the mucoserous acini contain both types of secretory cells, they produce a mixed secretory product. However, the major distinctions between serous and mucous cells have become less important with additional studies of their cellular functioning.

To facilitate the flow of saliva out of each lumen into the connecting ducts, myoepithelial cells are located on the surface of some of the acini, as well as on parts of the ductal system, the intercalated ducts (Figure 11-6). Each myoepithelial cell consists of a cell body with four to eight cytoplasmic processes radiating outward. They are specialized cells of epithelium that resemble an octopus on a rock; they are situated on the surface of the acini and have a contractile nature.

When these cells contract, they squeeze the acinus, forcing the saliva out of the lumen and into the connecting duct. When />