The Purpose of the Bladder

Overview

The urinary bladder is a balloon-shaped pouch located behind the pubic bone. It is connected to the kidneys by the two ureters, which insert on the left and right sides of the bladder. The ureters enter the bladder diagonally, through the bladder wall. As the bladder fills, it squeezes the ends of the ureters shut, which prevents urine from flowing back out of the bladder. The bladder empties through a tube called the urethra. In males, the urethra is significantly longer than it is in females, due to the length of the penis. The bladder has a rich blood supply and several nerve bundles that contribute to the function of the bladder. The bladder has two major functions: the storage and voiding of urine.

Urine Storage

The kidneys produce urine continuously. Without the bladder, we would be incontinent, urinating every time the kidneys release wastes. The bladder allows us to hold urine until we are ready to urinate. The bladder can hold up to 2 cups of urine for 2 to 5 hours. When the bladder is empty, it is approximately the size of a tennis ball. The bladder has a sphincter around the opening to the urethra that prevents urine from leaking between trips to the bathroom

Voiding Urine

The bladder voids urine by contracting and relaxing the sphincter around the urethra. The bladder has a muscle, the detrusor muscle, which contracts the bladder to expel urine. The bladder also has several nerves that control the urinary sphincter and monitor when the bladder is empty or full. The nerves and muscles all work together to allow us to empty the bladder when we are ready to urinate. The abdominal muscles also play a small part in urination by applying pressure on the bladder. However, the pressure from the abdominal muscles can also compress the urinary sphincter, making it more difficult to urinate.

How the Bladder Works

The bladder has a sensitive spot, located between the opening from the ureters and the outlet to the urethra. As the bladder fills with urine, it stretches until the volume of urine stimulates that sensitive spot and sends a signal to the brain to empty the bladder. The signals continue to get stronger as the bladder fills until you voluntarily urinate. If voluntary urination does not occur, the nervous system takes over and initiates the voiding procedure and empty the bladder. Interestingly, when the bladder is full, the brain sends strong messages to urinate, even in sleep. The most common sleep signals are dreams in which the sleeper is constantly searching for and unable to find a bathroom.

When the Bladder Does Not Work

Like any organ in the body, the bladder is susceptible to disease and disorders. The most common bladder problems include cancer, bacterial infection and incontinence. Bladder cancer usually forms on the inside of the bladder and can often be cured with surgery to remove the tumor, and cancer treatments to kill any remaining cancer cells. While the bladder is not essential to life, if bladder cancer is not caught in time, it can spread to other organs, the lymph nodes and become life threatening.
Bladder infections generally occur where bacteria from outside the body makes its way into the bladder via the urethra. Bladder infections are more common in women, who have much shorter urethras. The most common source of bacteria is fecal matter from the anal canal and the best prevention is to wipe front to back after defecation.
With incontinence, the bladder does not effectively hold on to urine. In most cases, the sphincter at the urethra does not contract fully, allowing urine to leak out. In other cases, the detrusor muscle contracts involuntarily, forcibly expelling urine. Incontinence is often a function of aging but neurological diseases, like shingles and mechanical damage, as from childbirth, can also cause urinary incontinence.

Keeping the Bladder Healthy

There are several easy habits to keep the bladder healthy and functioning properly. Drink water. Water keeps the urine properly diluted and helps flush bacteria and other wastes from the bladder. Use good toilet habits. Do not force yourself to go if the bladder is not full and do not rush while urinating. While you should not void your bladder before it is full, you should also avoid holding and urinate when the bladder signals it is full. Straining to defecate weakens the pelvic floor muscles so keep the bowels regular by eating a lot of fiber. Water also plays an important part in bowel function by keeping the fecal matter moist for defecation. Strengthen the pelvic floor muscles by doing Kegel and other pelvic floor exercises. The best way to perform Kegel exercises is to stop the flow of urine mid-stream, which ensures that you are contracting the correct muscles. Finally, seek medical advice if there are any changes in bladder function and habits.