Open circulatory systems

Definition

Open circulatory systems are a type of circulatory system where the blood is not confined to vessels but flows freely through cavities. This system allows the organs to be directly bathed in blood.

5 Must Know Facts For Your Next Test

1. Open circulatory systems are primarily found in arthropods and most mollusks.
2. Hemolymph is the fluid that serves as both blood and interstitial fluid in open circulatory systems.
3. In this system, hemolymph bathes organs directly in a cavity called the hemocoel.
4. The heart pumps hemolymph into the hemocoel, where it diffuses back to the cells before returning to the heart.
5. Open circulatory systems are less efficient at transporting oxygen compared to closed circulatory systems.

Review Questions

• What kind of animals typically have open circulatory systems?
• What is hemolymph and what role does it play in open circulatory systems?
• How does an open circulatory system differ from a closed circulatory system in terms of efficiency?

Related terms

Closed Circulatory System: A type of circulatory system where blood is confined within vessels, allowing for more efficient transport of oxygen and nutrients.

Hemocoel: The primary body cavity of most invertebrates containing hemolymph.

Heart: An organ that pumps blood or hemolymph throughout the body, varying in complexity between open and closed systems.