English II Albun 3er corte | Page 3

CIRCULATORY SYSTEM: DORSAL VESSEL It is defined as open or lagoon. Regardless of the number of vessels and how closed it may be, free blood always ends up in the general body cavity. RESPIRATORY SYSTEM The respiratory system of insects introduces respiratory gases into the body and performs gas exchange. The air enters through a series of external openings called spiracles that lead to a network of tubes called tracheas. These tracheas branch repeatedly until they reach the trachelas.