1. The middle of three embryonic kidney structures in vertebrates, which functions as the main kidney in fish and amphibians but degenerates in mammals, replaced by the metanephros.
Usage: anatomy; embryology; also called Wolffian body or mesonephric kidney

Examples

• During embryonic development, the mesonephros appears after the pronephros and before the metanephros.
• In fish, the mesonephros serves as the functional kidney throughout the animal's life.
• The mesonephros degenerates in human fetuses as the metanephros develops.
• Anatomists study the mesonephros to understand kidney evolution across vertebrate species.
• The mesonephric ducts, which develop alongside the mesonephros, give rise to reproductive structures in males.