Which of the following structures is found in both male and female reproductive systems?

The urethra is a structure that is present in both male and female reproductive systems. In males, the urethra serves a dual purpose, allowing for the passage of urine and semen out of the body through the penis. In females, the urethra is solely involved in the excretion of urine and opens to the outside of the body above the vaginal opening.

This anatomical feature highlights the shared pathways for urinary functions in both sexes while also emphasizing the distinct and separate reproductive roles played in each gender. Unlike the other options, which are exclusive to one sex (testes and ovaries being male and female reproductive organs, respectively, and the vagina being unique to females), the urethra's presence in both systems makes it a fundamental structure common to male and female anatomy.