The trigone is a triangular region in the urinary bladder, demarcated by the two ureteral orifices and the internal urethral orifice, and is clinically significant due to its role in urinary tract infections and its lack of rugae, which makes it relatively smooth. It is important in maintaining the proper flow of urine and can be a site of pathological concern, such as in cases of bladder cancer or vesicoureteral reflux.