Describe respiratory system of cockroach.

$\rightarrow$ The respiratory system consists of a network of trachea. They are main elements of respiratory system.
$\rightarrow$  Many branches of trachea are spread in the whole body. Its end branches are called tracheoles. It transports $\mathrm{O}_{2}$ in all parts of the body.
$\rightarrow$ Trachea possess direct contact with atmospheric air by spiracles.
$\rightarrow$ There are 10 pairs of spiracles present on the lateral side of the body. Among them two pairs in thorax region and eight pairs are located in abdomen region.
$\rightarrow$ The wall of spiracles is formed of funnel like structures.
$\rightarrow$ Funnel like structures prevent dust like substances into respiratory system. Valve controls opening of spiracles.

$\rightarrow$ During respiration oxygen enters into trachea by spiracles and from there comes into contact with tissue fluid through tracheoles and gets dissolved in it. Tissues of the body use this dissolved oxygen for procuring work energy. Carbon dioxide produced during it also gets dissolved in tissue fluid and comes out during exhalation.