What happens to the internal urethral sphincter during micturition?

During micturition, the internal urethral sphincter relaxes to allow urine to flow from the bladder through the urethra and out of the body. The function of the internal urethral sphincter is critical in the process of urination; its relaxation is essential for voiding to occur. When the bladder fills and signals the brain that it is time to urinate, the autonomic nervous system triggers the relaxation of this sphincter. This allows the detrusor muscle of the bladder to contract, further pushing urine toward the external urethral sphincter and out of the body.

In contrast, during the storage phase, the internal sphincter remains contracted to maintain continence, which is why understanding its role during micturition, when it actively relaxes, is essential for comprehending normal urinary function.