pronephros
/proʊˈnɛfrɒs/
noun
- The first and most primitive of the three embryonic kidneys in vertebrates, functional only in the earliest stages of development.
- The pronephros is composed of a few nephrons and a duct that drains into the cloaca.
- The pronephros appears in the embryo before the mesonephros and metanephros.
- In lampreys, the pronephros remains functional throughout life.