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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 external urethral sphincter originates at the ...
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]
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.
That’s when the brain will send signals that relax the urethral sphincter muscle and make the bladder muscles contract to squeeze urine out, Kim said. ... Holding pee in can increase your risk ...
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 detrusor muscle remains relaxed to allow the bladder to store urine, and contracts during urination to release urine. Related are the urethral sphincter muscles which envelop the urethra to control the flow of urine when they contract.
The body is calm, the bladder muscles contract, and the internal sphincter, which is located at the opening between the bladder and urethra, opens, letting you pee.
In normal lower urinary tract function, these two separate muscle structures act in synergistic coordination. But in this neurogenic disorder, the urethral sphincter muscle, instead of relaxing completely during voiding, dyssynergically contracts causing the flow to be interrupted and the bladder pressure to rise.