This video is available for licensing on our website. Click HERE!
Urinary incontinence (UI) is twice more common in women than in men. About one out of three women over the age of 60 is estimated to be incontinent. Pregnancy, childbirth, hormonal changes during menopause, and anatomy of the urinary tract account for this difference.
Urinary incontinence is involuntary leakage of urine. Urine is produced in the kidneys and stored in urinary bladder. Urination is the process of emptying the bladder through the urethra that connects the urinary bladder to the external urethral orifice. There are two sphincters (valves) that keep the urethra closed to prevent leak: internal urethral sphincter located at the neck of the bladder, and external urethral sphincter located right above the external urethral orifice and is supported by the pelvic floor muscles (See Fig. 1). The urethra is much shorter in women than in men.
Fig.1: Anatomy of female urinary organs. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
When the bladder is full, stretch receptors in the wall of the bladder send a signal to the spinal cord and the brain. At times when it’s not appropriate to urinate, the brain sends back an inhibitory signal to keep the sphincters closed and prevent voiding. When you wish to urinate, this inhibition is removed, the spinal cord instructs the muscle of the bladder (detrusor muscle) to contract and the sphincters to open to let the urine out (Fig. 2).
Below is a narrated animation of neural control of micturition. Click here to license this video and/or other urinary system related videos on Alila Medical Media website.
Fig.2: Neural control of urine voiding. Sensory nerve sends the signal from the full bladder to the nervous system; motor nerve brings instruction from the nervous system to the muscles. See text for more details. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Causes of urinary incontinence
– Problems with the nervous system: stroke, multiple sclerosis, Pakinson’ s disease and spinal cord injuries may affect the neural control loop illustrated in Fig.2 and cause incontinence.
– Weakness of sphincters, or lack of support from underneath muscles (muscles of the pelvic floor) making the sphincters weak so they can not close properly.
– Blocked or narrowed urethra, weakness of bladder muscles: bladder can not empty, urine builds up and leaks.
Fig.3: Female urinary and reproductive organs, median section, side view. Note the pelvic floor muscles that support the urinary bladder and the uterus. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Types of urinary incontinence in women and typical cause of each type.
1. Stress incontinence: small amount of urine leakage while sneezing, coughing, laughing or any activity that creates abdominal pressure on the bladder. This usually occurs because the muscles underneath the bladder (pelvic floor muscles) are weakened and can no longer support it (Fig. 3 and 4). In women, this typically happens as a result of pregnancy, childbirth during which these muscles are overstretched. Stress incontinence symptoms usually worsen during certain times in the menstrual cycle when your estrogen level is low. Incidents are also increased following menopause. This is by far the most common type of incontinence in women.
Fig.4: Stress urinary incontinence in women. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Below is a narrated animation of stress urinary incontinence. Click here to license this video (and other related videos) on Alila Medical Media website.
2. Urge incontinence: need to void that can not be deferred, inability to hold resulting in sudden loss of a large amount of urine. This is commonly caused by overactive bladder, a condition in which muscles in the wall of the bladder contract in an uncontrollable manner. The reason why this happens is unclear but it’s likely to involve problems in the nervous system.
3. Overflow incontinence: constant dribbling of urine. This happens when the bladder does not empty properly while voiding making it almost always full and urine overflows. This is due to weak detrusor muscle in the bladder wall or a blocked/narrowed urethra. This type of incontinence is rare in women.
> NEXT PAGE : Treatment for UI in women
