head kidney -->
medical dictionary

1. The definitive excretory organ of primitive fishes.

Synonyms: 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.

Synonyms: forekidney, primordial kidney.

Origin: pro-+ G. Nephros, kidney

(05 Mar 2000)