The ureteric orifices and the internal urethral orifice are at the angles of the trigone of the bladder. The ureteric orifices are encircled by loops of detrusor musculature that tighten when the bladder contracts to assist in preventing reflux of urine into the ureter. The uvula of the bladder is a slight elevation of the trigone; it is usually more prominent in older men owing to enlargement of the posterior lobe of the prostate.