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
