Sphincter urethrae / external
urethral sphincter
The female or male external sphincter
muscle of urethra (sphincter urethrae):
located in the deep perineal pouch,
at the bladder's distal inferior end in females, and inferior to the prostate
(at the level of the membranous urethra) in males. It is a secondary sphincter to control the
flow of urine through the urethra. Unlike the internal sphincter muscle, the
external sphincter is made of skeletal muscle, therefore it is under voluntary control of the somatic
nervous system
Females do have a more elaborate external sphincter muscle than males as
it is made up of three parts: the sphincter urethrae, urethrovaginal muscle,
and the compressor urethrae. The urethrovaginal muscle fibers wrap around the
vagina and urethra and contraction leads to constriction of both the vagina and
the urethra. The origin of the compressor urethrae muscle is the right and left inferior pubic ramus and it
wraps anteriorly around the urethra so when it contracts it squeezes the
urethra against the vagina. The external urethrae, like in males, wraps solely
around the urethra
Function: The
external urethral sphincter provides voluntary control of urination.
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