A comparative morphometric analysis of the component tissues of the urethra in young and old female C57BL/ICRFAt mice.

: Histologic preparations of the urethras of 3 and 30-month-old virgin female C57 mice were stereologically analyzed with a light microscope with an eyepiece grid. Serial sections of entire urethras were stained and divided into ten representative regions; the component tissues of each region were analyzed. There was no significant change with age in the total muscle component in each region. The muscle, however, was divided into two types: muscle with and muscle without the infiltration of collagen fibers. The amount of muscle with collagen infiltration was significantly increased in some regions of the urethra in the 30-month-old group. There was no age-associated significant difference in the vascular or connective tissue components of the urethra. A difference in the glandular component was recorded in one region only, because of change in the ducts of the clitoral glands. We noted differences in the lumen and its epithelium that were attributable to the more open urethral lumen in the young group in certain regions.