It begins with a bit of discomfort and soon becomes a pressing sensation
that's impossible to ignore. Finally, it's all you can think about, and out of sheer desperation, you go on a hunt for a bathroom
until "ahh." Humans should urinate at least
four to six times a day, but occasionally, the pressures of modern
life forces us to clench and hold it in. How bad is this habit,
and how long can our bodies withstand it? The answers lie in the workings
of the bladder, an oval pouch
that sits inside the pelvis. Surrounding this structure
are several other organs that together make up the whole
urinary system. Two kidneys, two ureters, two urethral sphincters, and a urethra. Constantly trickling down from the kidneys
is the yellowish liquid known as urine. The kidneys make urine from a mix
of water and the body's waste products, funneling the unwanted fluid
into two muscular tubes called ureters. These carry it downward into
the hollow organ known as the bladder. This organ's muscular wall is made of
tissue called detrusor muscle which relaxes as the bladder fills
allowing it to inflate like a balloon. As the bladder gets full,
the detrusor contracts. The internal urethral sphincter
automatically and involuntarily opens, and the urine is released. Whooshing downwards,
the fluid enters the urethra and stops short at the external
urethral sphincter. This works like a tap. When you want to delay urinating,
you keep the sphincter closed. When you want to release it,
you can voluntarily open the flood gates. But how do you sense
your bladder's fullness so you know when to pee? Inside the layers of detrusor muscles
are millions of stretch receptors that get triggered as the bladder fills. They send signals along your nerves
to the sacral region in your spinal cord. A reflex signal travels back to
your bladder, making the detrusor muscle
contract slightly and increasing the bladder's pressure
so you're aware that it's filling up. Simultaneously, the internal
urethral sphincter opens. This is called the micturition reflex. The brain can counter it if it's not
a good time to urinate by sending another signal to contract
the external urethral sphincter. With about 150 to 200 milliliters of urine
inside of it, the bladder's muscular wall
is stretched enough for you to sense
that there's urine within. At about 400 to 500 milliliters,
the pressure becomes uncomfortable. The bladder can go on stretching,
but only to a point. Above 1,000 milliliters, it may burst. Most people would lose bladder
control before this happens, but in very rare cases, such as when as a person can't sense
the need to urinate, the pouch can rupture painfully
requiring surgery to fix. But under normal circumstances, your decision to urinate stops the brain's
signal to the external urethral sphincter, causing it to relax
and the bladder to empty. The external urethral sphincter
is one of the muscles of the pelvic floor, and it provides support to the urethra
and bladder neck. It's lucky we have these
pelvic floor muscles because placing pressure on the system
by coughing, sneezing, laughing, or jumping could cause bladder leakage. Instead, the pelvic floor muscles
keep the region sealed until you're ready to go. But holding it in for too long, forcing out your urine too fast, or urinating without proper
physical support may over time weaken or overwork
that muscular sling. That can lead to an overactive
pelvic floor, bladder pain, urgency, or urinary incontinence. So in the interest of long-term health, it's not a great habit to hold your pee. But in the short term, at least,
your body and brain have got you covered, so you can conveniently choose
your moment of sweet release.
