Localization of acid phosphatase, nonspecific esterases and ?-D-galactosidase in parotid and submaxillary glands of domestic and laboratory animals

Interlobular excretory ducts of mammalian salivary glands: structural and histochemical review

In the major salivary glands of mammals, excretory ducts (EDs) succeed striated ducts. They are for the most part interlobular in position, although their proximal portions sometimes are on the periphery of a lobule, where they occasionally retain some of the structural features of striated ducts. Based on a survey of a broad range of mammalian species and glands, the predominant tissue type that composes EDs is pseudostratified epithelium. In some species, there is a progression of epithelial types: the proximal EDs are composed of simple cuboidal or columnar epithelium that, in the excurrent direction, usually gives way to the pseudostratified variety. Secretory granules are visible in the apical cytoplasm of the principal cells of the EDs of only a few species, but histochemistry has shown the presence of a variety of glycoproteins in these cells in a spectrum of species. Moreover, the latter methodology has revealed the presence of a variety of oxidative, acid hydrolytic, and transport enzymes in the EDs, showing that, rather than simply acting as a conduit for saliva, these ducts play a metabolically active role in gland function. It is difficult to describe a "typical" mammalian ED because it can vary along its length and interspecific variation does not follow a phylogenetic pattern. Moreover, in contrast to intercalated and striated ducts, ED cellular features do not exhibit a relationship to diet.

The granular convoluted tubule (GCT) cell of rodent submandibular glands

The granular convoluted tubule (GCT) is a segment of the duct system of all rodents, situated between the striated and intercalated ducts. It has the peculiar property of synthesizing a large variety of biologically active polypeptides whose role in saliva remains unknown. The literature on the fine structure of GCT cells is critically reviewed. Some recent developments on endocrine regulation of the structure and contents of rodent GCT cells are summarized, with emphasis on EGF, NGF, renin, and kallikrein proteases. A survey of the distribution of GCT cells in several vertebrate families is presented.

Branchings and course of the larger ducts and accompanying structures within the rat submandibular salivary gland

In the rat submandibular gland, the larger ducts, vessels, and autonomic elements are surrounded by appreciable collagen to form an extensive, ramifying core for the bulk of the parenchyma. This entity is analogous to the armature within a clay sculpture because it provides a framework supporting softer surroundings. Its largest portion, the trunk, begins dorsorostrally at the hilus. Along its caudal course, the trunk emits limbs that, in turn, branch. Rostrally, the trunk and major limbs have their greatest diameters and contain lymphatic vessels and autonomic ganglia that are fewer or absent in the smaller divisions. Four to six orders of branching commonly occur. This architectural device constitutes a physical gradient which peaks at the hilus and is minimal where its components undergo the transition to the lobular parenchyma. The presence of an appreciable amount of connective tissue, nerves, and larger vessels would make this entity firmer than the highly hydrated parenchyma. The major divisions of this grouping are contacted by septa that extend from the organ capsule and demarcate lobules into which smaller divisions penetrate. The parenchyma is consequently ensconced between several strong structures containing abundant connective tissue. The dense collagen encompassing individual components of the biological armature would stabilize duct epithelium and its intercellular channels as well as brace vessels' walls. As a result of this architectural arrangement, the patency of all acinar, duct, and vascular structures is likely to persist despite neck and jaw movements that would otherwise distort them and thus hinder the formation and flow of saliva during feeding. This mechanism may be widespread among organs.