Scanning electron microscopy (SEM) offers the biomedical investigator an advantage over transmission electron microscopy in that he can work with considerably larger specimens, ranging up to 3 cm in diameter, applying to them a variety of different procedures. SEM is used for the evaluation of surface features of tissues, giving a three-dimensional quality to the observations. The distinctive surface membrane of the lower urinary tract lends itself particularly well to the use of SEM techniques. Surface changes which occur during hyperplasia and carcinogenesis are readily assessed, and in small animals the entire bladder surface can be evaluated. Special techniques for evaluation of subepithelial structures, e.g., the basement membrane and the blood vessels, have also been developed. The ready availability of exfoliated cells in urine samples and bladder washing specimens offers the potential of clinical application of SEM techniques. These various features will be discussed in this chapter. For other details provided by transmission electron microscopy, one should consult Chapter 2, Volume II.
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