Vascular system
- Pronunciation
- /VAS-kyoo-lur SIS-tum/
- Category
- Anatomy
- Singular
- vascular system
- Plural
- vascular systems
Definition
A network of fluid-conducting vessels that transport nutrients, respiratory gases, metabolic wastes, and signaling molecules throughout an organism. In , the vascular system is typically open: a tubular pumps into arteries that discharge into the hemocoel (body cavity), where tissues are bathed directly; hemolymph returns to the heart through valved ostia. This contrasts with the closed vascular systems of vertebrates, where blood remains confined within continuous vessels. The term is often used interchangeably with 'cardiovascular system' in vertebrate contexts, but in it properly denotes the vessel network alone, distinct from the heart and associated pumps.
Etymology
Latin vasculum, diminutive of vas (vessel) + Greek systema (organized whole)
Example
In insects, the vessel—the primary vascular system—runs longitudinally from the through the , with segmental pairs of alary muscles that dilate the chambers to draw in through lateral ostia; anteriorly, the aorta delivers hemolymph to the , while posteriorly the heart propels it backward, creating directional flow without the closed capillary networks found in vertebrates.
Synonyms
- circulatory system (vertebrate context, often interchangeable)
- cardiovascular system (vertebrate context)
- blood-vascular system
Related Terms
Usage Notes
In entomology and arachnology, 'vascular system' usually refers specifically to the vessel network ( vessel, aorta, arteries), while '' encompasses the , vessels, and together. Some authors restrict 'vascular system' to vertebrates with closed circulation; when applied to , the term implies functional rather than structural . The adjective 'vascular' describes any tissue or organ rich in vessels (e.g., vascularized wings in some ). Contrast with 'lacunar system' in some annelids and 'water vascular system' in echinoderms.