What keeps the urine in bladder from entering urethra during intercourse?

During intercourse, the muscles surrounding the bladder, also known as the urethral sphincters, contract to prevent the backward flow of urine into the urethra. These sphincters act as valves, tightly closing the opening of the bladder to maintain continence. The internal urethral sphincter is an involuntary muscle that works subconsciously, while the external urethral sphincter can be consciously controlled. Together, these muscles ensure that urine is expelled only during urination.

Additionally, the pressure exerted on the bladder and urethra during intercourse may aid in keeping the urine from entering the urethra. Intercourse can compress the urethra, further preventing urine leakage. It's worth noting that certain factors, such as a weakened pelvic floor or specific medical conditions, can disrupt this mechanism and lead to urinary incontinence during intercourse, which is referred to as coital incontinence.