The mesonephric duct, also known as the Wolffian duct, is a structure that forms during early embryonic development in both males and females. It plays a crucial role in the formation of the urinary and reproductive systems. In males, the mesonephric duct develops into parts of the male reproductive tract, including the epididymis, vas deferens, and seminal vesicles. In females, the mesonephric duct typically regresses and does not contribute significantly to the reproductive system. Instead, the Müllerian duct becomes the primary structure for female reproductive organs, such as the uterus and fallopian tubes. The mesonephric duct's development and regression are essential for sexual differentiation.