Urinary incontinence is a problem where the process of urination, also called micturition,
happens involuntarily, meaning that a person might urinate without intending to.
Urinary incontinence is particularly problematic because it affects a person’s personal hygiene
as well as their social life in a way that can be very limiting.
Normally, urine is held in the bladder, which receives urine from two ureters coming down
from the kidneys and then that urine leaves the bladder through the urethra.
As urine flows from the kidney, through the ureters and into the bladder, the bladder
starts to expand into the abdomen.
The bladder is able to expand and contract because it’s wrapped in a muscular layer,
called the detrusor muscle, and within that, lining the bladder itself is a layer of transitional
epithelium containing “umbrella cells”.
These umbrella cells get their name because they physically stretch out as the bladder
fills, just like an umbrella opening up in slow-motion.
In a grown adult, the bladder can expand to hold about 750ml, slightly less in women than
men because the uterus takes up space which crowds out the bladder a little bit.
Alright, so when the urine is collecting in the bladder, there are basically two “doors”
that are shut, holding that urine in.
The first door is the internal sphincter muscle, which is made of smooth muscle and is under
involuntary control, meaning that it opens and closes automatically.
Typically, that internal sphincter muscle opens up when the bladder is about half full.
The second door is the external sphincter muscle, and it’s made of skeletal muscle
and is under voluntary control, meaning that it opens and closes when a person wants it
to.
This is the reason that it’s possible to stop urine mid-stream by tightening up that
muscle, which is called doing kegel exercises.
Once urine has passed through the external sphincter muscle, it exits the body—in women
the exit is immediate and in men the urine flows through the penis before it exits.
So when specialized nerves called stretch receptors in the bladder wall sense that the
bladder is about half full, they send impulses to the spinal cord, specifically the sacral
spinal cord at levels S2 and S3, known as the micturition center, and the brain, specifically
two locations in the pons—the pontine storage center and pontine micturition center.
The spinal cord response is part of the micturition reflex.
And it causes an increase in parasympathetic stimulation and decrease in sympathetic stimulation
which makes the detrusor muscle contract and the internal sphincter relax.
It also decreases motor nerve stimulation to the external sphincter allowing it to relax
as well.
At this point, urination would occur at this point, if not for the pons.
The pons is the region of the brain that we train to voluntarily control urination.
If we want to delay urination, or hold it in, the pontine storage center overrides the
micturition reflex,
and when we want to urinate, the pontine micturition center allows for the micturition reflex to
happen.
Now, there are a few types of urinary incontinence.
The first is urge incontinence, which is when someone has a sudden urge to urinate because
of an "overactive bladder", followed immediately by involuntary urination.
This is typically due to an uninhibited detrusor muscle that contracts randomly.
This usually results in frequent urination, especially at night.
To treat urge incontinence, the focus is on decreasing the detrusor muscle activity.
Relaxation techniques to relax the bladder as well as antimuscarinic medications can
decrease detrusor muscle contractions.
Next there’s stress incontinence which is usually due to increased abdominal pressure
that overwhelms the sphincter muscles and allows urine to leak out.
Think of things that cause exertion, like sneezing, coughing, laughing—anything that
puts pressure on the bladder.
This is also relevant during pregnancy when a growing baby puts tremendous pressure on
the bladder and causes stress incontinence in some women.
The classic finding is urinary leakage with pressure applied to the abdomen.
Stress incontinence treatments typically focus on strengthening the external sphincter muscle
by doing things like Kegel exercises.
Another type is overflow incontinence which is typically caused by some sort of problem
with emptying the bladder.
This could be due to a blockage in urine flow, like a hypertrophic prostate in men which
presses on the urethra or an ineffective detrusor muscle.
Either way, thebladder doesn’t empty properly, and as a result the bladder fills up and overflows
with urine which leaks through the sphincters.
Typically this results in a weak or intermittent urinary stream or hesitancy where it takes
a while for the urine to begin to flow because of a blockage in the path.
Overflow treatments are aimed at reestablishing a clear pathway for urine flow.
For example, that might be through catheterization or medications like alpha-blockers which can
limit prostate enlargement.
Finally, there are various conditions like diabetes, bladder cancer, Parkinson’s, and
multiple sclerosis, as well as procedures such as prostatectomy or hysterectomy that
can damage the nerves involved with the micturition reflex, ultimately leading to urinary incontinence.
The symptoms and treatment for these problems depend on the exact condition.
Alright, as a quick recap, urinary incontinence occurs when urine involuntarily leaves the
bladder—through the internal and external sphincter muscles.
Urge incontinence is due to an overactive bladder, stress incontinence is due to too
much pressure for the sphincter muscles to resist, and overflow incontinence is due to
incomplete emptying of the bladder.
What's up guys, thanks for watching, hope you liked that one,
Special thanks to Vanita Gaglani for both helping to edit
the script on that one as well as
sponsor the video vanitas got our own
website called Vanitas rehab and she's a
registered physical therapist who was
actually written a book on urinary
incontinence so it's really awesome a
bore help with that video other than
that you can check out our new subreddit
called our Osmos it we're going to be
posting videos two there and having
discussions as well and then you can
also obviously subscribe to our channel
like our videos or donate to us on
patreon thanks guys bye
you