Secretory Gland Acini

Secretory acini are organized into lobules

The major salivary glands are surrounded by a capsule of moderately dense connective tissue from which septa divide the secretory portions of the gland into lobes and lobules. The septa contain the larger blood vessels and excretory ducts. The connective tissue associated with the groups of secretory acini blends imperceptibly into the surrounding loose connective tissue. The minor salivary glands do not have a capsule.

Numerous lymphocytes and plasma cells populate the connective tissue surrounding the acini in both the major and minor salivary glands. Their significance in the secretion of salivary antibodies is described below.

Acini are of three types: serous, mucous, or mixed

The basic secretory unit of salivary glands, the salivon, consists of the acinus, intercalated duct, and excretory duct (Fig. 15.22). The acinus is a blind sac composed of secretory cells. The term acinus [L„ berry or grape] refers to the secretory unit of the salivary glands. The acini of salivary glands contain either serous cells (protein secreting), mucous cells (mucin secreting), or both. The relative frequencies of the three types of acini is a prime characteristic by which the major salivary glands are distinguished. Thus, three types of acini are described:

• Serous acini, which contain only serous cells and are generally spherical

• Mucous acini, which contain only mucous cells and are usually more tubular

• Mixed acini, which contain both serous and mucous cells. In routine H&E preparations, mucous acini have a cap of serous cells that are thought to secrete into the highly convoluted intercellular space between the mucous cells. Because of their appearance in histologic sections, such caps are called serous demilunes ¡Fr., half-moon].

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salivon parotid submandibular sublingual

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