accessory circulatory organ

An accessory circulatory organ is any circulatory organ that is not responsible for primary circulation in an organism. These structures assist in moving blood or fluid through the body but are subordinate to the principal heart or main circulatory pump.

Accessory circulatory organs are found at various locations depending on the organism. In some invertebrates and lower vertebrates, accessory hearts or booster pumps are found at specific points in the circulatory system — such as at the base of the gills or limbs — to augment flow in specific regions.

Accessory circulatory organs boost blood or fluid pressure in specific vascular territories where the main heart's pressure is insufficient. They are particularly important in animals with long bodies or extensive peripheral circulation, such as cephalopods (which have branchial hearts) and certain fish.

Impaired function of accessory circulatory organs can lead to regional circulatory insufficiency in the areas they supply. Information on specific pathologies of these structures in clinical medicine is limited, as they are primarily studied in comparative physiology.

The primary heart drives systemic circulation throughout the body, while accessory circulatory organs supplement flow in specific regions — they are typically smaller, have less power, and serve a supporting rather than a central role in the circulatory system.