Bladder: Facts, Function & Disease
Two long tubes called ureters connect the bladder, which stores urine, to the kidneys, which produce urine.
Credit: Nerthuz | Shutterstock


The bladder is a round, bag-like organ that stores urine. It is located in the pelvic area, just below the kidneys and right behind the pelvic bone.

The bladder is typically the size of a large grapefruit, according to the Weill Cornell Medical College. It can stretch much larger when needed, though, and shrinks back when it is empty. In fact, it can hold around 16 ounces (almost half a liter) of urine at one time for two to five hours comfortably, according to the U.S. National Library of Medicine (NLM).

The bladder is connected to the kidneys by two long tubes called ureters. When urine is produced by the kidneys, it travels down the ureters to the bladder, where it is stored. Though the bladder seems like a simple sack of flesh, it is actually complex and has four layers. 

The epithelium is the first layer on the inside of the bladder. It acts as a lining for the bladder. The lamina propria is the next layer. It consists of connective tissue, muscle and blood vessels. Wrapped around the lamina propria is the layer called the muscularis propria or detrusor muscle. According to John Hopkins Pathology, this layer consists of thick, smooth muscle bundles. The final, outer layer is the perivesical soft tissue, which is made up of fat, fibrous tissue and blood vessels. 

The other parts of the bladder are located at the bottom of the sack. An opening at the bottom of the bladder is connected to the urethra. A circular, muscular sphincter pinches tight to keep the opening and the urethra from leaking urine. 

To urinate, the detrusor muscles contract to squeeze the urine out of the bladder while the sphincter relaxes to open the opening of the bladder and urethra. The opening at the bottom of the bladder empties urine into the urethra, where it then empties from the body.

Many diseases and conditions can originate in the bladder. “The most common bladder problems I see in my practice in women are frequent urges to urinate and leakage of urine,” said S. Adam Ramin, urologic surgeon and founder of Urology Cancer Specialists in Los Angeles, California. Leakage and frequent urges often are caused by the decreased capacity of the bladder and over-activity of the bladder. An over active bladder, according to the Mayo Clinic, can be caused by a wide range of conditions, constipation, excess caffeine in the system and many other causes. Leakage of urine can also be caused by bladder spasms or stress. A bladder sling is sometimes used to treat stress urinary incontinence.

“The most common bladder problems in men are frequent urination at nights and incomplete bladder emptying. This is usually due to an enlarged prostate causing obstruction of bladder emptying,” Ramin told Live Science.

Bladder infections may be another cause of frequent urination. Bladder infections, also called cystitis, are among the most common bacterial infections, according to Harvard Health. Around one-third of all females get a bladder infection at least once. Some of the symptoms include burning or pain during urination, needing to urinate a lot though only a small amount of urine is passed each time, sudden needs to urinate, lower abdomen pain and cloudy or bloody urine. 

Another problem that can originate in the bladder is bladder cancer. About 577,400 people in the United States live with bladder cancer, according to the National Cancer Institute. It typically affects older people, though younger people have been known to develop bladder cancer, according to the Mayo Clinic. Some symptoms of bladder cancer include blood in the urine, frequent or painful urination and back or pelvic pain.

An anterior prolapse, also called a prolapsed bladder or cystocele, is a bladder problem specific to females. It happens when the tissue between a woman's bladder and vaginal wall weakens due to a strain. The weakening allows the tissue to stretch and the bladder bulges into the vagina, according to the Mayo Clinic

Bladder stones are caused by concentrated urine that crystalizes in the bladder. Typically, people who have problems emptying their bladder have problems with bladder stones, according to the Mayo Clinic.

Sometimes, there is no choice but to hold urine, but it may not be good for the bladder. “Holding your urine for a short period of time, usually up to one hour, is typically okay." Said Ramin. "However protracted and repeated holding of urine may cause over-expansion of bladder capacity, transmission of excess pressure into the kidneys, and the inability to completely empty the bladder. These problems in turn may lead to UTI [urinary tract infection], cystitis and deterioration of kidney function."

Editor’s Note: If you’d like more information on this topic, we recommend the following book:

 

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