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How does the bladder work?

The bladder is like a balloon—it’s small when empty, but as it fills with urine, it gets bigger and bigger. A strong muscle at the base of the bladder, called a sphincter, acts like a gate, keeping urine in. When the bladder is full, the sphincter relaxes to allow urine out so the bladder empties completely. Normally, the urine moves from the bladder through a tube called the urethra, to leave the body.

The bladder's first job is to store urine that has been filtered by the kidneys and delivered through the ureter. The bladder should be able to hold 3-5 hours worth of urine. Once the bladder is nearly full, the nerves send a signal to the brain. To urinate, you relax the urethral sphincter muscle and the brain signals the bladder muscle (detrusor) to contract to push the urine out.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.