Muscle
External urethral sphincter
Striated muscle that supports urethral closure
High-yield
Somatic sacral motor pathways, prominently the pudendal nerve, control this striated muscle. Its architecture is more complex than a uniform ring attached to bone in both sexes.
Overview
The urethral rhabdosphincter contributes tonic, reflex and voluntary closure. In males it is concentrated around the membranous and apical prostatic region. The female complex includes a urethral sphincter, compressor urethrae and urethrovaginal component distributed along the urethra.
Reference facts
- Origin
- Arises within periurethral and perineal connective tissues; female compressor fibers have ramal attachments, while the urethral sphincter proper lacks one universal bony origin.
- Insertion
- Forms a periurethral sleeve with posterior connective-tissue attachments; female extensions relate to the vagina and perineal membrane.
- Innervation
- Sacral somatic motor neurons, including Onuf's nucleus, project through pudendal and described intrapelvic pathways; exact branch routes vary.
- Action
- Maintains outlet resistance and increases closure during voluntary or reflex continence responses; relaxes for coordinated voiding.
- Blood supply
- Regional internal pudendal and adjacent pelvic arterial branches, including bulbourethral supply in males.
Clinical correlation
Sphincter or supporting-tissue injury can contribute to stress incontinence after prostate surgery. Suprasacral neurological lesions may disrupt coordination with detrusor contraction, producing detrusor–sphincter dyssynergia and potentially harmful storage or voiding pressures.
Frequently asked questions
What does the external urethral sphincter do?
Maintains outlet resistance and increases closure during voluntary or reflex continence responses; relaxes for coordinated voiding.
What nerve innervates the external urethral sphincter?
Sacral somatic motor neurons, including Onuf's nucleus, project through pudendal and described intrapelvic pathways; exact branch routes vary.
Where does the external urethral sphincter attach?
Origin: Arises within periurethral and perineal connective tissues; female compressor fibers have ramal attachments, while the urethral sphincter proper lacks one universal bony origin. Insertion: Forms a periurethral sleeve with posterior connective-tissue attachments; female extensions relate to the vagina and perineal membrane.
What is the blood supply of the external urethral sphincter?
The external urethral sphincter is supplied by the regional internal pudendal and adjacent pelvic arterial branches, including bulbourethral supply in males.