Respiration in cockroach

Cockroach has specialized organs for repiration.The respiratory system of the cockroach is very specialized.It consists of branching systems of air tubules called tracheae lined by chitin.The main tracheal trunk communicates with exterior by 10 pairs of apertures called spiracles, present on the lateral sides of the body.Two pairs are in thorax while the rest eight are in each of the eight abdominal segments.The main tracheae divide and subdivide forming very fine thin-walled tubules called tracheoles.These tracheoles end into blind ducts partly filled with fluid, in which the oxygen dissolves.These surround the organs and the tissues and directly supply oxygen to the living cells.A concentration gradient is set up between them and the spiracular openings and oxygen diffuses into the trachea from the outside air.The movement of the air through the tracheal trunks transfers gases through inspiration and expiration.Air is pumped in and out of the tracheae by the expension and contraction of the abdominal muscles (Dorsoventral muscles).When abdomen expands, the first four pairs of spiracles open, air rushes in through these spiracles into tracheoles.Abdomen contracts, the anterior four pairs of spiracles close and posterior six pairs of spiracles open.This forces air through the tubes and eventually out of the body.In this way exhalation and inhilation take place.Air is directly supplied through tracheoles to the tissue cells.Blood is not involved in transport of gases.