Neck of bladder

The internal urethral orifice is placed at the apex of the trigonum vesicæ, in the most dependent part of the bladder, and is usually somewhat crescentic in form; the mucous membrane immediately behind it presents a slight elevation, the uvula vesicæ, caused by the middle lobe of the prostate. The external aspect of the the apex and internal urethral oifice is called the neck of the bladder.