micturition


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urination

 [u″rĭ-na´shun]
the discharge of urine from the bladder; urine from the kidneys is passed in spurts every few seconds along the ureters to the bladder, where it collects and later is passed to the outside via the urethra. Called also micturition and voiding.

The Urinary Process. Urination is a complex process controlled by muscles of the bladder and sphincter mechanism and by modulatory centers in the central and peripheral nervous systems. The detrusor muscle is a complex meshwork of interlaced smooth muscle bundles that contract in a way that squeezes urine from the bladder vesicle. The sphincter mechanism consists of smooth muscle in the bladder neck and proximal urethra, a striated muscle sphincter consisting of slow twitch muscle fibers in the urethral wall, and periurethral muscles that are a component of the pelvic floor muscles. The detrusor relaxes during bladder filling to accommodate increasing volumes at a low pressure, and the sphincter remains tightly closed. During urination, the detrusor contracts and the sphincter mechanism relaxes, allowing smooth outflow of urine.



As the bladder fills, modulatory centers in the brain prevent the occurrence of contractions. Meanwhile, the sphincter mechanism remains closed under autonomic and somatic nervous system control. During urination, the inhibition of contractions is removed and a reflex originates in the pontine micturition center. That causes the detrusor muscle to contract and the sphincter mechanism to relax. The location of the final output of central nervous system impulses to and from the bladder and sphincter is the sacral micturition center, located in spinal segments 2, 3, and 4, which must be intact for contraction to occur. Injury to the pontine micturition center will compromise the smooth coordination between sphincter mechanism and detrusor muscle, and injury to the brain will affect the volitional control of urine (bladder stability). See also urinary incontinence.

mic·tu·ri·tion

(mik'chū-rish'ŭn), Avoid the misspelling/mispronunciation micturation.
1. Synonym(s): urination
2. The desire to urinate.
3. Frequency of urination.
[L. micturio, to desire to make water]

micturition

Urination; the act of voiding urine.

micturition

 Urination; the process of voiding urine

mic·tu·ri·tion

(mik-chŭr-ish'ŭn)
1. Synonym(s): urination.
2. The desire to urinate.
3. Frequency of urination.
[L. micturio, to desire to make water]

micturition

the release of urine from the body. see BLADDER.
References in periodicals archive ?
In this study, mirabegron 50 mg was found to be significantly more efficacious than placebo for all efficacy measures, including micturition frequency, UUI, dry rate, and 50% reduction in incontinence.
Neurologically, instrumental delivery might damage the pudendal nerves that affect the reflexes and voluntary mechanism in normal micturition. Similarly, perineal trauma might result in mechanical obstruction due to vaginal haematoma or oedema [4].
Micturition-postponing-behavior did not affect significantly the maximum capacity to hold urine but played significant role on voluntary control of micturition under unfavorable circumstances.
Functionally, the accumulation of norepinephrine inhibits micturition by relaxing the detrusor muscle and constricting the urethral smooth muscle.
Dark pigmentation of ear cartilage, urolithiasis and multiple joint complaints are hints for ochronosis disease and darkening the urine one hour after micturition supports the diagnosis.
In 1992, Harada proved that dexmedetomidine inhibits the micturition reflex activated by high bladder volume in rats (16).
Most common adverse events reported include hematuria, dysuria, micturition urgency, pelvic pain, and urge incontinence.
"These two stimulation maneuvers were repeated until micturition began or for a maximum of 300 seconds."
Other than pruritus, burning micturition, dysuria, local irritation were also reported whereas 21% of the females were asymptomatic, their only complaint being profuse discharge.
A 25-years old unmarried male complaining of dysuria and increased frequency of micturition for a week was referred to the Urology Clinic.