Respiratory system :
It exhibits aerial respiration which is with the help of tracheal system. The tracheal system carries the oxygen directly upto the tissues. It includes spiracles & trachea.
Spiracles :
It has 10 pairs of spiracles which are also called as stigmata. First two pairs of the spiracles are found vento-laterally in pro/mesothrax and meso/metathorax. The first pair of the abdominal spiracles are found dorsolaterally on the 1st abdomen segments. The seven pairs of the spiracles are found ventro-laterally in 2nd to 8th segment on the pleurites
Each spiracle is oval and it is surrounded by a chitinous ring called peritreme. The spiracles are provided with ciliary brislles which filter the inspired air. The thoracic spiracles are comparatively large. The first thorasic & the first abdominal spiracles remain permanently open. Rest spiracles open only at the time of inspiration and they are provided with valves. Each spiracle leads into a small chamber, tire tracheal chamber or atrium. Hence, there are 10 pairs of atria.
Trachea :
The trachea is also called as wind pipe & it originates from ectoderm. It has three pairs of longitudinal tracheal trunks
- Dorso-lateral tracheal trunk—1 pair
- Latral tracheal trunk—1 pair
- Ventro-latral tracheal trunk—1 pair
The 10 atria of one side open into the ventro-lateral tracheal tracheal trunks of it’s own side. All the six longitudinal tracheal trunks remain connected by transverse connecting trachea in each segment. The tracheal trunks divide to form trachea. The trachea are thin-walled, elastic & silvery’ white tubes. Their walls are supported by spiral rings made up of chitin. Each trachea ends into a trachiole cell. The trachiole cell gives out 3 to 5 intracellular tubules which are called as trachioles. The trachioles are the tubules of 1 micron diameter. They are silvery white & their walls are supported by spiral rings made up of trachin protein, the inner ends of the trachioles are closed & are full of trachiole fluid. This trachiole fluid helps in the exchange of the gases. The lining of the trachiole is called as intima.
Mechanism of Respiration :
Respiration in cockroach is performed by the contraction & the relaxation of the tergosternal muscles.
As a result of the contraction of the tergosternal muscles, the air squeezed out which is called as expiration. The relaxation of the tergosternal muscles reduces the pressure on the trachea, as air result the air rushes into the body through the spiracles. It is called as inspiration. During rest the process of breathing in involuntary & during active phase, it a voluntary process. The exchange of gases takes place by diffusion between the trachiole fluid & tissue fluid. The route of air during breathing as follows-
