Sphincter vesicae
·
The internal sphincter muscle of
urethra: located at the bladder's inferior end and the urethra's proximal end
at the junction of the urethra with the urinary bladder. The internal sphincter
is a continuation of the detrusor muscle and is made of smooth
muscle, therefore it is under involuntary or autonomic control. This is the
primary muscle for prohibiting the release of urine.
In males and females, both internal and external urethral
sphincters function to inhibit the release of urine. In males, the internal
sphincter muscle of urethra functions to prevent reflux of seminal fluids
into the male bladder during ejaculation.
Histology of sphincter urethrae:
All part of musculature of urinary bladder is composed of
outer and inner longitudinal and middle circularly arranged smooth muscle cell
. in the bladder neck the outer longitudinal layer merge with circular layer
and it become thick and formed sphincter urethrae
Function
The internal urethral
sphincter provides involuntary control of urination.
The
muscular coat of the urinary
bladder is composed of inner
longitudinal, middle circular,and
outer longitudinal layers of
smooth muscle that are frequently interlaced and are indistinguishable as
distinct layers. The internal sphincter muscle of the urethra is formed by the
thick, middle circular layer
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