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. 16.21). 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 are a prime characteristic by which the
Dental caries is an infectious microbial disease of teeth that results in the destruction of affected calcified tissues, i.e., enamel, dentin, and cementum. Carious lesions gener-ally occur under masses of bacterial colonies referred to as “dental plaque.” The onset of dental caries is primarily as-sociated with bacterial colonies of Streptococcus mutans, whereas lactobacilli are associated with active progression of the disease. These bacterial colonies metabolize carbo-hydrates, producing an acidic environment that demineral-izes the underlying tooth structure. Frequent sucrose ingestion is strongly associated with the development of these acidogenic bacterial colonies. Trace amounts of fluoride, from sources such as water supplies (0.5 to 1.0 ppm is optimal), toothpaste, and even diet, can improve resistance to the effects of cariogenic bacteria. Fluoride improves the acid resistance of the tooth structure, acts as an antimicrobial agent, and promotes remineralization of small carious lesions. Resis-tance to acid breakdown of enamel is facilitated by the substitution of fluoride ion for the hydroxyl ion in the hydroxyapatite crystal. This decreases enamel crystal solubility in acid. Treatment of cavitated lesions, or “tooth cavities” (Fig. F16.3.1), includes excavation of the infected tooth tis-sue and replacement with dental materials such as amal-gam, composite, and glass ionomer cements. Microbial invasion of tooth structure can reach the “pulp” of the tooth and elicit an inflammatory response. In this case, endodon-tic treatment, or a “root canal,” is generally recommended, with subsequent placement of a crown to add strength to the compromised coronal tooth structure.