Arteries in the flippers are surrounded by veins. Thus, some heat from the blood traveling through the arteries is transferred to the venous blood rather than the environment. This countercurrent heat exchange aids dolphins in conserving body heat. Each lobe of the tail is called a fluke. Flukes are flattened pads of tough, dense, fibrous connective tissue, completely without bone or muscle.
Dolphins propel themselves forward by moving their flukes up and down.
Like the arteries of the flippers, the arteries of the flukes are surrounded by veins to help conserve body heat in cold water. F. Dorsal fin. Like the flukes, the dorsal fin is made of dense, fibrous connective tissue, with no bones. The dorsal fin may act as a keel. It probably helps stabilize a dolphin as it swims, but is not necessarily essential to a dolphin's balance.