Describe circulatory system of cockroach.

$\rightarrow$ The blood vascular system of cockroach is of open type. Means during circulation blood instead of passing from capillaries enters into space called hemocoel. So body organs and tissues have direct contact with blood.

$\rightarrow$ Blood is mainly made up of blood plasma and irregularly shaped cells.

$\rightarrow$ Blood has no respiratory pigment so it is colourless. It is called hemolymphs. The hemolymph is composed of blood plasma and hemocytes.

$\rightarrow$ The heart of cockroach consists of elongated muscular tube lying along mid dorsal line of thorax and abdomen. It is differentiated into funnel shaped chambers with ostia on either side. The first 3 segments are located in thorax region and remaining are located in abdomen region.

$\rightarrow$ Blood cells are of two types. Small sized proleucocytes and large sized phagocytes. Blood enters into heart from sinuses through ostia and is pumped anteriorly to sinuses again.