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The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut.
The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system.The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle.
The external urethral sphincter is a striated muscle that allows voluntary control over urination. [5] The internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the sympathetic division of the autonomic nervous system. [6] The internal sphincter is present both in males ...
The internal urethral sphincter is a urethral sphincter muscle which constricts the internal urethral orifice.It is located at the junction of the urethra with the urinary bladder and is continuous with the detrusor muscle, [1] [2] but anatomically and functionally fully independent from it. [3]
Part of the urethra is surrounded by the male or female external urethral sphincter, which is innervated by the somatic pudendal nerve originating in the cord, in an area termed Onuf's nucleus. [ 7 ] Smooth muscle bundles pass on either side of the urethra, and these fibers are sometimes called the internal urethral sphincter , although they do ...
The internal urethral orifice is the opening of the urinary bladder into the urethra. [1] ... Internal sphincter muscle of urethra; ... "The Male Pelvis: The Urethra"
First things first, know that poop is rarely an issue. Dr. Goldstein, says feces is stored in the upper bowels, which is separated by your internal sphincter. For the sphincter to relax and ...
During urination, the detrusor muscle contracts, the external urinary sphincter and muscles of the perineum relax, and urine flows through the urethra [13] and exits the penis or vulva through the urinary meatus. [11] The urge to pass urine stems from stretch receptors that activate when between 300 - 400 mL urine is held within the bladder. [13]