Heart

Definition

A muscular pump that circulates hemolymph or blood through the body, delivering respiratory gases, nutrients, and immune factors while removing metabolic wastes. In arthropods, the heart is typically a dorsal, tubular structure with segmentally arranged ostia (valved openings) that draw hemolymph from the pericardial sinus and propel it anteriorly into the hemocoel; it lacks the four-chambered architecture of vertebrate hearts and functions as part of an open circulatory system. The term also applies to homologous contractile structures in other invertebrate phyla and to the four-chambered muscular organ of vertebrates.

Etymology

From Old English heorte, from Proto-Germanic *hertô, from Proto-Indo-European *ḱḗr (heart).

Example

In the American cockroach (Periplaneta americana), the heart consists of thirteen contractile chambers arranged along the dorsal midline, each with paired ostia that close during systole to prevent backflow of hemolymph into the pericardial sinus.

Synonyms

• dorsal vessel (in arthropods, often used interchangeably for the heart proper plus aorta)
• cardiac tube
• pulsatile organ

Related Terms

• Hemolymph
• ostium
• Pericardial sinus
• hemocoel
• aorta
• open circulatory system
• accessory pulsatile organs

Usage Notes

In arthropod literature, 'heart' often refers specifically to the contractile, ostiate portion of the dorsal vessel, while 'dorsal vessel' encompasses both the heart and the non-contractile aorta that carries hemolymph anteriorly. Some authors restrict 'heart' to the posterior, pump-like region and use 'aorta' for the anterior, conducting vessel. Accessory hearts or pulsatile organs in the appendages (e.g., in legs of spiders or wings of insects) are distinct from the main dorsal heart. The term is not typically applied to the muscular pharynx or other non-vascular contractile structures despite their pumping function.