Normal exfoliation of the inner lining of the urinary bladder and urinary tract would cause to show up in the microscopic study of urine sediment.

The answer that fits the blank would be EPITHELIAL CELLS. During the exfoliation of both the urinary tract and urinary bladder, epithelial cells are normally seen in urine sediment. Normally, there are only a few of them that can be found in the urine sample.  

That would be a working theory.