Question

Which of the following statements best defines the open circulatory system?

a) Blood is enclosed within vessels and distinct from interstitial fluid.

b) Blood is pumped through vessels, but it directly bathes tissues.

c) Oxygen is transported by hemocyanin instead of hemoglobin.

d) The heart has multiple chambers for efficient oxygenation.

Answer 1

The best definition of an open circulatory system is that blood is pumped through vessels but directly bathes tissues, as seen in invertebrates like bees and mollusks.

Step-by-step explanation:

The statement that best defines an open circulatory system is: (b) Blood is pumped through vessels, but it directly bathes tissues.

In an open circulatory system, a fluid called hemolymph is pumped by the heart through vessels that empty into the body cavity. The hemolymph directly bathes the organs and tissues, providing them with nutrients and oxygen, and then returns to the heart through openings called ostia. This system is found in many invertebrates, such as arthropods like bees and most mollusks. Contrary to closed circulatory systems, where blood is separated from interstitial fluid and contained within blood vessels, the open circulatory system allows for direct contact between hemolymph and tissue cells.