Editing Functional: Neural Control of Storage and Voiding (section)

=== External urinary (striated) sphincter (EUS) ===
* '''Striated muscles are characterized as slow vs. fast-twitch'''
** '''Slow-twitch fibers: suitable for maintaining sphincter tone for prolonged periods'''
** '''Fast-twitch fibers: may be needed to add to sphincter tone rapidly (i.e. to maintain continence when intra-abdominal pressure is abruptly increased)'''
* '''Composed of 2 parts:'''
*# '''Periurethral striated muscle of the pelvic floor'''
*#* Closely surrounds the urethra at the level of the membranous portion in males and primarily the middle segment in females
*#* '''Contains both fast-twitch and slow-twitch fibers'''
*#** '''Hypothesized that pelvic floor exercises or electrostimulation improve continence in SUI by causing by the conversion of fast-twitch to slow-twitch striated muscle fibers'''
*# '''Striated muscle that is a part of the outer wall of the proximal urethra in males and females (also known as rhabdosphincter)'''
*#* '''Contains predominantly slow-twitch fibers'''
* '''In males,'''
** '''Covers the ventral surface of the prostate as a crescent shape proximal to the verumontanum'''
** '''Then assumes a horseshoe shape distal to the verumontanum'''
** '''Then as a crescent shape at the bulbar urethra'''
* '''In females,'''
** '''Covers the ventral surface of the urethra in a horseshoe shape'''
* '''<span style="color:#ff0000">Under voluntary control</span>'''
* '''<span style="color:#ff0000">Innervation: pudendal nerve (S2-S4)</span>'''
* '''In addition to striated muscle, the EUS contains smooth muscle which receives sympathetic (noradrenergic) innervation'''[https://www.auanet.org/guidelines/urethral-stricture-guideline §]