Urinary system - Landmarks (English)

Urine enters the cavity of the urinary bladder through two ureteric orifices located on its posterolateral walls, allowing urine to enter and be stored in the urinary bladder due to the reflex contraction of the internal urethral sphincter. When micturition is initiated, the muscular wall of the urinary bladder, known as the detrusor vesicae muscle, contracts while the internal urethral sphincter muscle relaxes, allowing urine to flow through the internal urethral orifice into the upper part of the urethra. Relaxation of the external urethral sphincter allows urine to continue into the distal part of the urethra where it is eliminated into the outside environment through the external orifice of urethra.