(voluntary urination) or escape the normal suppressive channels (resulting
in leakage). It can thicken due to pushing against a resistance (like the biceps
muscle) or it can be thin and paper-like, with no change in symptoms. It
can be overdistended and lose its ability to function for weeks or months
on end, only to become decompressed and return to normal activity within
days. In short, it is quite a resilient muscle that is at the root of many urination
problems among men and women.
In women, the detrusor muscle tends to be thin and floppy. Because
women don’t have prostates to block the flow of urine, they never develop
the thick-walled muscle from which men with enlarged prostates suffer.
Women suffer from the opposite problem; as a woman ages, her urinary
sphincter becomes less efficient, creating less resistance to outflow, often
resulting in incontinence. In older women, nothing exists between the
bladder and the outside except a very inefficient valve. This is one reason
why women suffer from incontinence more than men.
The second reason that men don’t develop incontinence is also related
to differences in their anatomy. Men have a prostate that supports the
bladder (the prostate provides the juice in which the sperm swim around
in the ejaculate). Because of that support, and the fact that no empty cavity
sits under the bladder (in women, that would be the vagina), a man cannot
suffer from a “fallen bladder” (more about that later). So, anatomically,men
and women are very different in this area, resulting in different problems
requiring different treatments.
The final path of the urine as it leaves the urinary bladder is through
the urethra. In women, the urethra is only 3 cm long (about 11/2 inches);
whereas in men, it is about 15 cm long (about 8 inches). This tiny tube sits
above the vagina inside the labia.Many women do not realize that the urine
comes out of a separate opening.Women have three openings: the urethra,
through which urine passes; the vagina, through which a baby passes; and
the anus, through which stool passes. Men only have two openings: one at
the tip of the penis, the urethra, for both urine and semen; and one behind,
the anus, for stool.
The urinary sphincter comprises about one-half the length of the
urethra in women. As a muscle, the function of the urinary sphincter is to
hold urine in the bladder while the bladder is filling without letting a drop
come out. During voluntary urination, the urinary sphincter opens and lets
the urine pass out into the toilet. It clamps shut when the bladder is empty
in order to allow for bladder filling to resume. It is always contracted and
closed, except for the few seconds each day that it relaxes in order for the
bladder to empty.
T H E N U T S A N D B O L T S O F T H E F E M A L E P E L V I S
