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

Introduction

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

More general terms

• urethral sphincter