The circulatory system in insects consists of a simple dorsal vessel (heart) and open circulatory system. The dorsal vessel is a tubular structure composed of a single layer of contractile myocardial cells. It has openings called ostia that allow one-way flow of hemolymph into the heart. Contractions of the dorsal vessel pump hemolymph through the body. The ventral diaphragm and accessory pulsatile organs also aid circulation.
Hemolymph is the insect equivalent of blood and lymph. It is a fluid that contains ions, molecules, sugars, proteins and hemocytes (blood cells). The main functions of hemolymph are transport, protection, waste removal, thermal regulation and maintaining osm