Dog Circulatory System Closed. In (b) open circulatory systems, a fluid called hemolymph is pumped through a blood vessel that empties into the body cavity. This is a closed circulatory system.

They don’t tend to need quick energy or immune defenses. The circulatory system is one of the transport systems that transports nutrients, gases, and other substances throughout an animal’s body. Here, the blood flows freely through cavities since there are no vessels to conduct the blood.