The circulatory system of cockroach is of open type. The blood vessels are poorly developed and blood flows freely in the body cavity which is called haemocoel. Visceral organs located in the haemocoel are bathed in blood (haemolymph).
It contains colourless plasma and corpuscles called haemocytes.
Each heart chamber opens into next chamber through a ventricular valve. Each chamber has a pair of incurrent pores called ostia (which possess valvular mechanism to pass the blood only from haemocoel to the heart chambers).
The heart chambers contract one after the other rapidly. This pushes the blood into the anterior aorta as well as a few lateral or excurrent arteries. From aorta, blood passes into head sinuses and then into perivisceral and perineural sinuses.
