Ultrastructure of the ferret submandibular gland.

Submandibular glands of two male and two female adult ferrets were examined using electron microscopy. The secretory endpiece consisted of mucous acini and seromucous demilunes. The acinar cells were filled with mucous granules of moderate electron density. Each granule had a fine fibrillar substructure. Two types of demilune cells could be identified, based on the differing electron density of their secretion granules. In some cells the granules were more electron-dense than in others. These granules may contain the two types of mucosubstances identified in an earlier study. The demilunes probably drained into the intercellular canaliculi present in between them and eventually into the acinar lumen through a demilune projecting into it. The intercalated ducts were shorter compared to those of the parotid glands. Many of the striated duct cells contained electron-dense secretion granules. The basal plasmalemma of these cells was invaginated to form linear folds. Few agranular cells were interspersed among the granulated cells of the striated ducts.