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Encyclopedia > Urethral sphincter

In mammals the flow of urine from the urinary bladder is controlled by a group of muscles collectively called the urethral sphincter, named for their proximity to the urethra. Both sexes have at least two areas of muscle: the internal sphincter, or bladder neck; and the external, or distal, sphincter.

In males the internal and external urethral sphincters are more powerful, able to retain urine for twice as long as females, and are furthermore backed up by the tertiary rings of urethral sphincters along the length of the penis.

Both sexes can use the levator ani, the voluntary muscle of the pelvic floor, to control urination. In females this muscle is more important because of the weakness of the urethral sphincters. Kegel exercises are a form of exercise intended to strengthen the pelvic floor muscles.

Urinary incontinence is the inability to control urination, and is more common in women than men.

There are anecdotal reports that many men, although able to control the onset of urination, are unable to stop urinating once they have started. It is uncertain whether this is a common phenomenon in real life.

Urinary system

Kidneys - Ureters - Urinary bladder - Urethral sphincters - Urethra

  Results from FactBites:
Urethral sphincter definition - Medical Dictionary definitions of popular medical terms (143 words)
Urethral sphincter: The muscular mechanism that controls the retention and release of urine from the bladder.
Internal sphincter: Part of the muscular bladder wall acts as the internal urethral sphincter and prevents urine from leaving the bladder to enter the urethra.
External sphincter: A layer of muscle, called the urogenital diaphragm, supplies support for the contents of the pelvis and acts as the external urethral sphincter.
Ultrasonic Assessment of the Internal Urethral Sphincter in Stress Urinary Incontinence (1947 words)
Sometimes weakness of the internal urethral sphincter was in the lower part, and rupture and widening of the urethral lumen was seen in the lower part, giving a “flask shape” appearance.
II- The internal sphincter is composed mainly of collagenous and elastic tissues extending concentrically outwards from an inner mucosa which lies on the “lamina propria” followed by the collagenous bundles extending beyond the muscle layer.
In conclusion, three dimension vaginal ultrasonic assessment of the internal urethral sphincter is an additional informative, non-invasive tool in the evaluation of cases of SUI as it is both sensitive and specific in the diagnosis of SUI.
  More results at FactBites »



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