Pericardial sinus

Definition

In arthropods with an open circulatory system, the pericardial sinus is the dorsal hemocoelic compartment that encloses the heart (dorsal vessel) and contains the pericardial cells (nephrocytes). It is bounded ventrally by the dorsal diaphragm, a fibromuscular septum perforated by ostia that allow hemolymph to enter the heart during diastole. The sinus serves as a collecting chamber for hemolymph returning from the body cavity before propulsion into the arterial system.

Etymology

Greek peri- (around) + kardia (heart) + Latin sinus (cavity or hollow)

Example

In a locust, the pericardial sinus extends along the abdominal tergites; hemolymph filtered through the pericardial cells in this sinus helps regulate ionic composition before cardiac contraction pumps it anteriorly through the aorta.

Synonyms

• pericardial chamber

Related Terms

• hemocoel
• dorsal vessel
• ostium
• pericardial cell
• dorsal diaphragm
• open circulatory system
• nephrocyte

Usage Notes

Distinguished from the pericardial cavity of vertebrates, which is the fluid-filled space between the heart and the pericardial sac. In insects and other arthropods, the pericardial sinus is part of the hemocoel, not a separate serous cavity. The term is sometimes used loosely for the space around the heart in any animal, but specialists reserve it for the hemocoelic compartment in arthropods and some other invertebrates with open circulation.