Question: what is the difference between internal and external urethral sphincters?
Answer: The Two Urethral Sphincters Maintain Urinary Continence The internal sphincter is involuntary. It surrounds the opening of the bladder to the urethra and relaxes to allow urine to pass. The external sphincter is voluntary. It surrounds the urethra outside the bladder and must be relaxed for urination to occur.