The cytology of submandibular glands of the opossum

Abstract

Abstract Submandibular glands of the opossum have been studied by light and electron microscopy and compared with other mammalian salivary glands. The glands have four parenchymal segments which connect in the order named below to convey saliva toward the oral cavity. Secretory units are elongated branching tubules exhibiting mucous and special serous cell types. Mucous cells predominate and resemble those in other salivary glands. Special serous cells differ from “typical” serous cells. They contain a preponderance of tubular or vesicular endoplasmic reticulum and secretory granules which vary from electron lucent to electron opaque. Intercalated ducts are short segments lined by nonsecretory, cuboidal cells. Striated ducts are numerous and lie in the center of the lobule. The duct epithelium has four cell types, designated light cells, dark cells, Type I basal cells , and Type II basal cells . Light cells possess basal infoldings associated with mitochondria, but the other cell types lack this characteristic. Excretory ducts are also lined by four cell types which bear the same names as those of striated ducts. Three of the four cell types are virtually identical to those of striated ducts, but light cells differ. They do not always contain basal infoldings and the supranuclear cytoplasm lacks distinct inner and outer zones. The glands resemble salivary glands of higher mammals in many respects while possessing certain unique cytological features which may reflect the secretory needs of the organism.