They then pass down along the sides of the pelvis, and finally curve forwards and enter the bladder from its left and right sides at the back of the bladder.[1]:324–326 This is classically depicted as running "posteroinferiorly on the lateral walls of the pelvis and then curve anteromedially to enter the bladder". The orifices of the ureters are placed at the postero-lateral angles of the trigone of the bladder, and are usually slit-like in form. In the contracted bladder they are about 25 mm (1 in) apart and about the same distance from the internal urethral orifice; in the distended bladder these measurements may be increased to about 50 mm (2 in).