Roles of the lamina propria and the detrusor in tension transfer during bladder filling

In this study, structural changes within the lamina propria and detrusor la yers were analysed during development as a function of bladder filling. Sec ond-, third- and full-term foetal bovine bladders were filed to 0%, 25%, 50 %, 75% and 100% of their total capacity and snap frozen. The bladders were analysed histochemically and the relative thicknesses of the lamina propria and detrusor were measured. In all gestational stages examined, the total thickness of the bladder wall decreased during bladder filling. The lamina propria of the full-term bladder thinned at a consistently faster rate than did the detrusor. The lamina propria of second and third trimester bladder s followed the same thinning pattern, except when the bladders were filled from 25% to 50% of their capacities. At these gestational stages, the detru sor thinned at a faster rate than the lamina propria. Our results demonstra te that the detrusor layer carries tension only during a specific portion o f the Ailing cycle and only during the second and third trimesters. We conc lude that the lamina propria acts as the capacitance layer, while the detru sor functions as the "limiting" or "girding" layer to prevent over-distensi on of the bladder wall.