internal urethral sphincter (preprostatic or supracollicular sphincter, preprostate or proximal urethral sphincter, sphincter muscle of urinary bladder)

The complete collar of the smooth muscle cells of the neck of the urinary bladder; extends distally to surround the preprostatic urethra. Function: -> prevents reflux of semen into the bladder Notes: - no comparable structure in the neck of the female bladder

References

Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999.