Ultrastructure of the Salivary Glands in the Gray Short-Tailed Opossum(Monodelphis domestica)

Abstract

　The salivary glands help to keep the mouth and other parts of the digestive system moist. There have been only a few reports on the salivary glands of the marsupial gray short-tailed opossum(Monodelphis domestica). The aim of this study was to reveal the ultrastructure of the parotid and submandibular glands in the gray short-tailed opossum using transmission electron microscopy(TEM). Using TEM, the parotid glands were found to consist only of serous acinar cells. Secretory granules were highly electron dense. The submandibular glands were composed of both serous and mucous acinar cells, showing a mixture of glands. Also, the submandibular glands possessed special serous cells. Secretory granules were divided into homogeneous density type, two biphasic types and annual ring types. The properties of the granules were different in each cell type. However, some cells contained a mixture of every type of granule. It appeared that the variety of granules in the special serous cells represented stages in the cell cycle and was not a property of the cell. Striated ducts of submandibular glands consisted both of columnar epithelium with or without basal infoldings, although typical striated ducts were found in parotid glands.