Leydig's organ

A hemopoietic organ found in elasmobranchs. Along with the spleen and special tissue around the gonads, this structure produces red blood cells and it is nestled along the top and bottom of the esophagus.

Type Organ
Body System Lymphatic/Immune
Parent Structure hemopoietic organ

Frequently Asked Questions

What is Leydig's organ and which animals have it?
Leydig's organ is a hemopoietic (blood-forming) organ found exclusively in elasmobranchs — the group of cartilaginous fish that includes sharks, rays, and skates. It is embedded along the upper and lower walls of the esophagus and produces red blood cells, functioning similarly to bone marrow in other vertebrates.
How does Leydig's organ compare to other hemopoietic tissues in sharks?
Elasmobranchs have multiple hemopoietic sites including Leydig's organ, the spleen, and specialized tissue around the gonads. Leydig's organ is notable for its location along the esophagus and its substantial contribution to red blood cell production. The relative importance of each site varies among elasmobranch species.
Is Leydig's organ related to Leydig cells in the testes?
No — these are completely unrelated structures that share a name because both were described by the 19th-century German anatomist Franz von Leydig. Leydig cells in the testes produce testosterone in mammals, whereas Leydig's organ in elasmobranchs is an esophageal hemopoietic organ with no reproductive function.

Related Structures

arthropod hepatopancreas crustacean digestive gland bone marrow medulla of bone dorsal patch of Leydig's organ epigonal organ subgonal organ haemal node hemal node hematopoietic tissue bone marrow tissue hilum of spleen hilum immune organ immune system organ

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Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.