Abnormalities of micturition
There are three major types of bladder dysfunction due to neural lesions: (1) the type due to interruption of the afferent nerves from the bladder; (2) the type due to interruption of both afferent and efferent nerves; and (3) the type due to interruption of facilitatory and inhibitory pathways descending from the brain. In all three types the bladder contracts, but the contractions are generally not sufficient to empty the viscus completely, and residual urine is left in the bladder. Paruresis, also known as shy bladder syndrome, is an example of a bladder interruption from the brain that often causes total interruption until the person has left a public area.
Effects of deafferentation
When the sacral dorsal roots are cut in experimental animals or interrupted by diseases of the dorsal roots such as tabes dorsalis in humans, all reflex contractions of the bladder are abolished. The bladder becomes distended, thin-walled, and hypotonic, but there are some contractions because of the intrinsic response of the smooth muscle to stretch.
Effects of denervation
When the afferent and efferent nerves are both destroyed, as they may be by tumors of the cauda equina or filum terminale, the bladder is flaccid and distended for a while. Gradually, however, the muscle of the "decentralized bladder" becomes active, with many contraction waves that expel dribbles of urine out of the urethra. The bladder becomes shrunken and the bladder wall hypertrophied. The reason for the difference between the small, hypertrophic bladder seen in this condition and the distended, hypotonic bladder seen when only the afferent nerves are interrupted is not known. The hyperactive state in the former condition suggests the development of denervation hypersensitization even though the neurons interrupted are preganglionic rather than postganglionic.
Effects of spinal cord transection
During spinal shock, the bladder is flaccid and unresponsive. It becomes overfilled, and urine dribbles through the sphincters (overflow incontinence). After spinal shock has passed, the voiding reflex returns, although there is, of course, no voluntary control and no inhibition or facilitation from higher centers when the spinal cord is transected. Some paraplegic patients train themselves to initiate voiding by pinching or stroking their thighs, provoking a mild mass reflex. In some instances, the voiding reflex becomes hyperactive. Bladder capacity is reduced, and the wall becomes hypertrophied. This type of bladder is sometimes called the spastic neurogenic bladder. The reflex hyperactivity is made worse by, and may be caused by, infection in the bladder wall.
Causes of incontinence
The initiation of urination is caused by the stretch in the wall of the bladder. But also irritation such as bacterial infections of the urinary bladder or the urethra or other conditions can initiate the desire to urinate, even when the urinary bladder is nearly empty. Consumption of alcoholic beverages or those containing caffeine may irritate the lining of the bladder, initiating a need to urinate.
During urination, muscles in the wall of the bladder contract, forcing urine out of the bladder and into the urethra. At the same time, sphincter muscles surrounding the urethra relax, letting urine pass out of the body. Urinary incontinence will occur if the bladder muscles suddenly contract or muscles surrounding the urethra suddenly relax.
Stress Incontinence occurs when a person laughs, sneezes, or puts stress on the pelvic muscles and cannot maintain a normal volume of urine, for women during pregnancy and sometimes following childbirth. This type of incontinence is sometimes helped by Kegel exercises to strengthen the pelvic floor. Secondary incontinence refers to incontinence caused by disease or condition. Any damage to the nervous system, such as may occur with a spinal cord injury or a demyelinating disease like multiple sclerosis, may result in loss of urinary control.
Urge Incontinence is when urine leaks before an individual can reach a toilet (when you have 'urgency'). This may not be pathological and maybe actually be related to a mobility issue i.e. the individual is physically unable to get to a toilet before they begin to micturate.
Due to the differences in where the urethra ends, men and women use different techniques for urination.
Due to the flexible and protruding nature of the penis, it is easy to control the direction of the urine stream. This makes it easy to urinate standing up, and most men urinate this way. The foreskin, if left in place during urination, may block the direct path of the outgoing stream by causing turbulence, resulting in a slower, but thicker stream of urine that may also dribble. Men who choose to retract their foreskin, or who have been circumcised, may have a more focused stream of urine that travels at the same speed it exits the urethra.
It is also possible for men to urinate sitting down. This is normally done when defecation has to take place as well. Some men also prefer to urinate this way.
When a man is done urinating, he will usually shake his penis to expel the excess urine trapped in the opening of the foreskin or on the glans.
In women, the urethra opens straight into the vulva. Because of this, the urine does not exit at a distance from her body and is, therefore, hard to control. Because of surface tension in the urine, the easiest method is to just rely on gravity to take over once the urine has exited her body. This can easily be achieved if the woman is sitting down, although some women choose to squat or hover. Those alternative choices are sometimes made due to the perceived or actual unsanitary conditions at the location where the woman is urinating. When sitting, it helps if the woman leans forward and keeps her legs together, as this helps direct her stream downwards. When not urinating into a toilet, squatting is the easiest way for a woman to direct her urine stream. Some women use one or both hands to focus the direction of the urine stream, which is more easily achieved while in the squatting position.
It is also possible for many women to urinate standing up by spreading their legs and pushing hard to avoid urine running down their legs. This technique for urinating while standing can be common when women often wear a sarong, skirt, or other such open bottomed garments, and either wear no underwear, or remove it. It is considered normal for women to urinate like this in many parts of Africa, whereas in contrast, it is not completely accepted in countries such as India. In Africa, even signs which forbid public urination often show a picture of a woman urinating while standing.
Though uncommon, it is possible for women to urinate standing up in a way similar to that of men. This may be done by manipulating the genitalia in a certain way, orienting the pelvis at an angle and rapidly forcing the urine stream out. An alternative method is to use a tool to assist
Length of urination
The time it takes to urinate differs from person to person and from urination session to urination session. For example, it may take some people up to several minutes to fully void, while it may take others 5-10 seconds. The average time is much closer to the lower end of the scale. Normally, this depends on how long it has been and how much and what type of liquid the person has consumed since the last urination. Other factors include a size of the Prostate in men and the strength of the Urethral sphincter
July 16, 2007
Urination - Continuation
Abnormalities of micturition