The Purpose of the Urethra

6. The Internal Urethral Sphincter

One difference between the male and female urethra is that males have a second sphincter -- the internal urethral sphincter. As the name implies, it lies closer to the internal organs of the urinary system. Specifically, it resides where the urinary bladder and the urethra meet. It, too, is under voluntary control. Unlike the external urinary sphincter that just regulates urine flow, though, this internal urethral sphincter contracts during ejaculation to keep semen from entering the bladder.

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