The 'internal urethral orifice' is the opening of the
urethra into the
urinary bladder. It is placed at the apex of the
trigonum vesicae, in the most dependent part of the bladder, and is usually somewhat crescent-shaped; the
mucous membrane immediately behind it presents a slight elevation in males, the
uvula vesicae, caused by the middle lobe of the
prostate.
External links
★
★ - "The Male Pelvis: The Urethra"