During male ejaculation, the internal urethral sphincter closes tightly to ________________?

During male ejaculation, the internal urethral sphincter closes tightly to prevent the backward flow of semen into the bladder. This sphincter is located at the junction of the urethra and the bladder, and its contraction helps ensure that semen is propelled forward through the urethra and out of the body during ejaculation.

The closure of the internal urethral sphincter is a reflex action that occurs as a part of the male sexual response. It is controlled by the autonomic nervous system, specifically the sympathetic division. When sexual arousal reaches a certain level, signals from the brain trigger the release of neurotransmitters that cause the internal urethral sphincter to contract, effectively sealing off the bladder.

By closing the internal urethral sphincter, semen is directed outwards and not into the bladder. This is crucial to ensure the proper functioning of the reproductive system and prevent any potential complications. The closure of the internal urethral sphincter is a natural and involuntary response that occurs during male ejaculation, allowing for the successful delivery of sperm for potential fertilization.

In summary, the internal urethral sphincter closes tightly during male ejaculation to prevent the backward flow of semen into the bladder, ensuring the proper delivery of sperm.