<prompt> FALSE regarding trigone of bladderLined by transitional epitheliumMucosa smooth and firmly adherentInternal urethral orifice lies at lateral angle of baseDeveloped from mesonephric duct  <response>: Internal urethral orifice lies at the apex not the lateral angle of base of urinary bladder. Note: Its the ureters that open at lateral angles. Embryologically, the trigone of the bladder is derived from the caudal end of mesonephric ducts, which is of mesodermal origin the rest of the bladder is derived from the endodermal urogenital sinus. Urinary bladder is lined by transitional epithelium including trigone. 