Internal urethral sphincter

Urethral sphincter muscle which constricts the internal urethral orifice

The internal urethral sphincter is a urethral sphincter muscle which constricts the internal urethral orifice. It is located at the junction of the urethra with the urinary bladder and is continuous with the detrusor muscle, but anatomically and functionally fully independent from it. It is composed of smooth muscle, so it is under the control of the autonomic nervous system, specifically the sympathetic nervous system.

This keyword could refer to multiple things. Here are some suggestions: