Objective   To investigate the aging changes of histological components of the urinary sphincter in female rats and explore the morphology to discuss the mechanism of age-related urinary continence dysfunction.     Methods   Twenty-eight adult female nonporous Fisher rats at different ages were divided equally into 4 groups

group Ⅰ (6 months)

group Ⅱ (12 months)

group Ⅲ (24 months) and group Ⅳ (32 months). The dorsal urethra wall thickness

urethral lumen area

cross section area of crista urethralis

mucosa thickness and area

number of submucosal vessels

the mount of collagen and striated and smooth muscle fibers of the mid-urethra cross-sections of adult female rats at different ages were evaluated by computerized morphometric analysis system after staining with Masson’s Trichrome procedure.    Results   The amount of striated muscle fibers was decreased remarkably from 12 months old female rats. The mucosal area

the number of submucosal vessels and the cross section area of crista urethralis were decreased from 24 months (each P0.05). While the amount of collagen (P=0.047) and the radio of the longest and shortest urethral diameters (P=0.049) were increased. The urethral lumen area (P=0.026) and the dorsal urethra wall thickness (P=0.034) were changed in 32 months rats. It was verified that the whole urethra area and the amount of smooth muscle fibers did not change significantly with aging (each P0.05).    Conclusion   There are a series of changes in the microarchitecture and morphology of the urinary sphincter with aging. These changes provide insight into the understanding of the aging changes of urethral sphincter function.