Describe the respiratory system of cockroach with the help of neat and labeled diagram?

Respiratory system of cockroach consists of
a) Stigmata b) Trachea c) Tracheole
 

a) Stigmata:

• There are 10 pairs of stigmata in cockroach.
• Two pairs of stigmata are in thorax and eight pairs are in abdomen.
• There are more than two pairs of spiracles and all of them are functional.
• Therefore, the respiratory system is said to be polypneustic and holopneustic respectively.
• Spiracles are surrounded by chitinous ring called peritreme.
• They have hair like structures called trichome to filter dust particles.

b) Trachea:

• Spiracles open into atrium.
• From the atria of the thoracic spiracles many tracheae arise.
• They join to form tracheal trunks.
• These trunks enter all the organs of head as a cephalic tracheal trunk.
• From the atria of abdominal spiracles three tracheal tubes arise.
• These tubes join to form lateral, dorsal and ventral longitudinal trunks.
• The branches of these tracheal trunks enter different organs.
• Wall of trachea is formed by three layers - Outer basement membrane, middle epithelium, inner cuticular layer called intima. Intima has spiral thickenings called taenidia, which keeps the trachea open and prevents it from collapsing.

c) Tracheole:

• The tracheal branch ends in tracheole cell.
• They are formed of protein called trachein.
• Tracheole is filled with tracheolar fluid.
• It is more when insect is inactive.
• It is absorbed completely when the insect is active.