Head kidney

Head kidney –>
pronephros
1. The definitive excretory organ of primitive fishes.
Synonym: head kidney.
2. In the embryos of higher vertebrates, a vestigial structure consisting of a series of tortuous tubules emptying into the cloaca by way of the primary nephric duct; in the human embryo, the pronephros is a very rudimentary and temporary structure, followed by the mesonephros and still later by the metanephros.
Synonym: forekidney, primordial kidney.
Origin: pro– g. Nephros, kidney

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