Head Kidney

**Definition:** A primitive form of vertebrate kidney that is found in adults of some primitive FISHES and in the embryos of more advanced fishes. In some species of fishes it contains phagocytic cells and is also a major site of HEMATOPOIESIS, analogous to the mammalian BONE MARROW.

**Tree numbers:** - A13.449 - A16.835.400

**Synonyms:** - Anterior Kidney