RESPIRATION IN INSECT (COCKROACH) -

• Respiration is direct. So metabolic rate is high.
• This system is related to each cell of the body so respiratory pigment is absent.
• Unit of respiratory system is trachea. These are white thread like form net in body.
• Ectodermal in origin. In wall of trachea taenidia present.
• These are complete rings made up of cuticle, maintain diameter of trachea.
• Branches of trachea near organs are tracheoles in their wall rings are absent.
• Diameter is less. Walls are elastic. Lumen is narrow. Thin cuticle is tracheoline.
• At the point of origin of tracheoles, tracheole cell present.
• In the end of tracheoles, tracheole fluid is filled, helpfull in exchange of gases.
• All trachea are originated from 3 pairs of tracheal trunks D, V & L.
• Lateral tracheal trunk is thickest one only this opens out side by 10 pairs of spiracles or stigmeta.
• 2 pairs thoracic spiracles are present. 8 pairs abdominal spiracles are present.
• 1st pair thoracic spiracle present between prothorax and mesothorax.
• 2nd pair thoracic spiracle present between meso and metathorax.
• 8 pairs abdominal spiracle present in first 8 segments of abdomen. Spiracles are ectodermal in origin.
• All spiracles present on lateral side, except 1st abdominal spiracle or 3rd spiracle.
• Near to spiracle Peristigmetal gland present. Each spiracle is protected by a plate i.e., peritreme.
• Cavity of spiracle is atrium. In it bristles present to check dust particles.
• By the outgrowth of wall of atrium a valve is formed. Controls opening and closing of spiracle.
• 1st thoracic and 1st abdominal spiracles always remains open, rest open or close during process.