Mollusca circulatory system is described as which of the following?

Mollusca circulatory system is described as which of the following?

• A. Closed circulatory system
• B. Open circulatory system; hemocoel
• C. Lymphatic system
• D. No circulatory system

Answer: (B)

Mollusks mostly use an open circulatory system, where the circulating fluid (hemolymph) is not confined to a complete network of blood vessels. Instead, the heart pumps this hemolymph into body cavities called sinuses, and the fluid bathes tissues directly in a spacious space called the hemocoel. From there, the hemolymph returns to the heart to be pumped again. This arrangement makes sense for many mollusks with relatively slower metabolisms, providing enough circulation without the need for a fully closed loop. The term hemocoel is key here because it describes the primary body cavity where the hemolymph resides and around which tissues are perfused. It’s also worth noting that cephalopods are an exception within Mollusca; they have a closed circulatory system with blood confined to vessels, unlike the open system typical of many other mollusks.

Mollusks mostly use an open circulatory system, where the circulating fluid (hemolymph) is not confined to a complete network of blood vessels. Instead, the heart pumps this hemolymph into body cavities called sinuses, and the fluid bathes tissues directly in a spacious space called the hemocoel. From there, the hemolymph returns to the heart to be pumped again. This arrangement makes sense for many mollusks with relatively slower metabolisms, providing enough circulation without the need for a fully closed loop.

The term hemocoel is key here because it describes the primary body cavity where the hemolymph resides and around which tissues are perfused. It’s also worth noting that cephalopods are an exception within Mollusca; they have a closed circulatory system with blood confined to vessels, unlike the open system typical of many other mollusks.