Ultrastructure of the submandibular gland in the rabbit

Abstract

The secretory endpieces of the rabbit submandibular gland are unusual in that they consist of seromucous acini (not demilunes) that empty into serous tubules that in turn drain into intercalated ducts. Seromucous granules consist of a moderately dense spherule in a fibrillogranular matrix. Serous granules contain a feltwork of filaments, which are liberated as a tangled skein during exocytosis. Peculiar granulated cells that have secretory granules of complex morphology are present at each end of the serous tubules. Intercalated ducts are, cytologically speaking, relatively simple, but the duct cells may contain a few oblong secretory granules. Striated ducts are typical in structure, although postfixation with ferrocyanide-reduced osmium reveals significant amounts of glycogen in the basal processes. Modified mitochondria are present in striated duct cells, but their frequency varies from rabbit to rabbit. Such mitochondria contain either an array of parallel, rigid cristae linked by intermembranous bridges, or a bundle of helical filaments within an expanded crista. Interspersed with the striated duct cells, especially near the duct origin, are some highly vacuolated cells with sparse mitochondria. Excretory ducts consisting of stratified columnar (sometimes pseudostratified) epithelium often show bleb formation of the luminal surface of the tall cells.

Fine Structure of the Mandibular Gland in Crest-tailed Marsupial-rat (<I>Dasyuroides byrnei</I>)

“…The granular tubules of mice [10] and rats [9] are known to exhibit sexual dimorphism. In the present study on D. byrnei, the striated duct cells contained numerous vesicles, without electron-dense granules, did not show any morphological evidence suggestive of secretory granules, revealed no morphological differences between the sexes, and were similar to those of opossum [30], rabbits [6,17,29] and volcano rabbits [23].…”

“…Fine structures of the mandibular glands are reported in many mammalian species and show great variety in the form and configuration of the acini and striated ducts. The mandibular glands of many rodents [4,7,17,21,22,25], rabbits [2,29] and volcano rabbits [23] have acini consisting of only one cell type and are homocrine, possessing only seromucous cells. On the other hand, the mandibular glands of dogs [26], cats [5,18], pigs [18], horses [27], kobe mole [8] and several ruminant species [19,24,26] are composed of acini of two different cell types and are heterocrine, possessing mucous and seromucous cells with a PAS-, AB-positive nature.…”

Fine Structure of the Mandibular Gland in Volcano Rabbit

“…Similar cells in the acinus-intercalated duct junctional region were described in the mandibular gland of rabbits [4,16,22,23], rats [9,16], and Djungarian hamsters [18], and were given different nomenclatures, such as, terminal tubule cell, granular intercalated duct cell, granular cell and serous cell. The characteristic features of these cells are the numerous granules with high densities and the RER with dilated cisternae.…”

“…As to the mandibular glands of the rabbit, there are several reports describing that the acini are composed of seromucous cells [1,11,12,14,22,23]. Recently, Toyoshima and Tandler [231 described the three cell types consisting of seromucous cell, peculiar granulated cell and serous cell in the rabbit mandibular acini.…”

Observations Concerning the Structure of the Major Salivary Glands in Chinchilla (Chinchilla lanigera)

“…In rabbit, parotid gland contains serous acini (Al-Saffar and Simawy, 2014; Yasear et al, 2012) and mandibulary gland presents a particularity in comparison with other species, even if it has mixed secretion: it has seromucous acini without serous demilune (Toyoshima and Tandler, 1986). Other authors affirm that normally, rabbit's mandibular gland has mixed secretion, with serous tubes in the proximal portion and seromucous acinar cells in the distal portion (Ahlmer, 1993).…”