Age regularities of morphological changes of urinary bladder in acute cystitis – Morphological changes of urinary bladder in acute cystitis were studied during the experiment. It was found when the simulated pathology unevenly and disproportionately grows the spatial characteristics of the membranes, and nuclei and cytoplasm of epithelial cells of the mucous membrane are impaired in nuclear–cytoplasmic changes in these structures. Structural changes were dominating in the wall of the damaged urinary bladder of animals in the older age group.