Circulatory system
- Pronunciation
- /SUR-kyuh-luh-tor-ee SIS-tem/
- Category
- Physiology
- Singular
- circulatory system
- Plural
- circulatory systems
Definition
The organ system that transports fluids— in , blood in vertebrates—throughout the body to distribute nutrients, respiratory gases, , and metabolic wastes, and to mediate immune responses. In arthropods, this is typically an open system in which hemolymph leaves vessels to bathe tissues directly in sinuses (hemocoel) before returning to the ; in some arachnids and certain insects, accessory augment flow to appendages.
Etymology
Latin circulare (to make round, go around) + systema (organized whole)
Example
In the , the tubular pumps anteriorly through the aorta; when the heart relaxes, hemolymph re-enters through paired ostia, completing the open circulatory circuit without a closed network of capillaries.
Synonyms
- Vascular system
- cardiovascular system
Related Terms
- Hemolymph
- hemocoel
- ostium
- open circulatory system
- closed circulatory system
- aorta
- Heart
- accessory pulsatile organ
Usage Notes
In entomology and arachnology, 'circulatory system' usually implies an open system, contrasting with the closed systems of annelids and vertebrates. The term 'cardiovascular system' is sometimes reserved for closed systems with distinct capillary beds, though usage varies. may distinguish the ' vessel' (the ) from the full circulatory apparatus including sinuses and accessory .