Scanning electron microscopy of acinar cells of rat submandibular salivary glands.

1. The submandibular salivary gland of rats was observed by high-resolution scanning electron microscopy employing the aldehyde-osmium-DMSO-osmium method. 2. The intracellular membranous components and sponge-like structures of basement membrane containing the fine collagen fibrils of acinar cells were clearly identified in three-dimensional images. The granular endoplasmic reticulum and Golgi apparatus showed the luminal surface. The mitochondria were small, ranging in diameter from 0.3 to 0.5 microns, and revealed their cristae. The secretory granules ranged in diameter from 0.3 to 1.4 microns. Ribosome granules were attached to the surfaces of cisterns, and measured 20 to 25 nm in diameter. 3. The contact areas between the acinar cells revealed numerous cytoplasmic protrusions. In the striated duct cells, the mitochondria were arranged vertically and surrounded by basal infoldings of the plasma membranes. At high magnification, the mitochondrial cristae were visualized in their three-dimensional characteristics.