What type of circulatory system do annelids possess?

What type of circulatory system do annelids possess?

• A. Closed circulatory system
• B. Open circulatory system
• C. No circulatory system
• D. Pseudocirculatory system

Answer: (A)

Annelids have a closed circulatory system, where blood remains inside a network of vessels—the arteries, veins, and capillaries—throughout its whole route. Muscular vessels act as pumps, with several hearts or aortic arches driving blood through a dorsal vessel along the body and smaller vessels branching out to tissues before returning through the venous network. This setup creates pressurized, efficient circulation that supports their segmented, relatively active bodies, delivering oxygen and nutrients where they’re needed. In contrast, an open circulatory system lets blood (hemolymph) flow freely into body cavities and mix with interstitial fluid, which isn’t how annelids operate. Having no circulatory system wouldn’t meet their metabolic needs, and a pseudocirculatory system isn’t a recognized type of circulation.

Annelids have a closed circulatory system, where blood remains inside a network of vessels—the arteries, veins, and capillaries—throughout its whole route. Muscular vessels act as pumps, with several hearts or aortic arches driving blood through a dorsal vessel along the body and smaller vessels branching out to tissues before returning through the venous network. This setup creates pressurized, efficient circulation that supports their segmented, relatively active bodies, delivering oxygen and nutrients where they’re needed.

In contrast, an open circulatory system lets blood (hemolymph) flow freely into body cavities and mix with interstitial fluid, which isn’t how annelids operate. Having no circulatory system wouldn’t meet their metabolic needs, and a pseudocirculatory system isn’t a recognized type of circulation.