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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. [4]
For example, a patient complaining of urinary urgency (or rushing to the toilet), with increased frequency of urination can have overactive bladder syndrome. The cause of this might be detrusor overactivity, in which the bladder muscle (the detrusor) contracts unexpectedly during bladder filling. Urodynamics can be used to confirm the presence ...
The detrusor muscle, also detrusor urinae muscle, muscularis propria of the urinary bladder and (less precise) muscularis propria, is smooth muscle found in the wall of the bladder. The detrusor muscle remains relaxed to allow the bladder to store urine , and contracts during urination to release urine.
In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. [1] [2] In humans, the bladder is a distensible organ that sits on the pelvic floor. The typical adult human bladder will hold between 300 and 500 ml (10 and 17 fl oz) before the urge to empty occurs, but can hold considerably more. [3] [4]
Urination is the release of urine from the bladder to the outside of the body. Urine is released through the urethra and exits the penis or vulva through the urinary meatus in placental mammals, [1] [2]: 38, 364 but is released through the cloaca in other vertebrates.
In males, the internal urethral sphincter has the additional function of preventing the flow of semen into the male bladder during ejaculation. [ 3 ] Females do have a more elaborate external sphincter muscle than males as it is made up of three parts: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae.
The curve formed by the bottom of the plot reflects the level of pressure necessary to void. In normal patients, the first couple hundred milliliters of urine flow with minimal applied pressure. Increasing pressure is necessary to void 200 to 300 milliliters of urine. Beyond that, the pressure necessary to void additional urine rises sharply. [7]
A post-void residual urine greater than 50 ml is a significant amount of urine and increases the potential for recurring urinary tract infections. [citation needed] In adults older than 60 years, 50-100 ml of residual urine may remain after each voiding because of the decreased contractility of the detrusor muscle. [7]