Figure 418

Photomicrograph of smooth muscle cells stained by the PAS method. This photomicrograph is stained by the PAS method and counterstained with hematoxylin (pale nuclei). The muscle cells have been cut in cross section and appear as polygonal profiles because of the presence of PAS-positive basement membrane material surrounding each cell. As the plane of section passes through each smooth muscle cell, it may or may not pass through the portion of the cell that includes the nucleus. Therefore, in some of the polygonal profiles, nuclei can be seen; in other profiles, no nuclei are seen. The cytoplasm is not stained. x850.

The basal lamina is the structural attachment site for overlying cells and underlying connective tissue

Examination of the site of epithelial basement membranes with the EM reveals a discrete layer of electron-dense matrix material 40- to 60-nm thick between the ep-

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