Gas exchange in insects

Gases enter and leave the tracheal system through spiracles

Spiralling strands of chitin in the walls of the

trachea make these tubes fairly rigid and

thus protect them from being compressed by the

surrounding tissues

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CO2

• Large surface area provided by the extensive network of tracheoles, which is further increased when fluid is withdrawn from the tracheoles during periods of high metabolic activity

• Steep concentration gradients are maintained between the tracheoles and body cells due to tissue respirationIn larger, more active insects, the pumping movements of the abdomen increase the steepness of these diffusion gradients to meet the metabolic demands of the organism

• A short diffusion path exists between the thin tracheole walls and the tissues

• The continual flow of air through the tracheal system maintains the ventilation of the tissues

This image shows a stag beetle, one of the largest of all insects. It can grow to widths of 5cm. Using your knowledge of the insect respiratory system explain why insects do not get much bigger than this…

Lactic acid reduces the water potential ofthe cells and water diffuses from the tracheoles

by osmosis back into the cells.Air moves in to replace the fluid, and gases

diffuse more rapidly across the air-filled tracheoles

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CO2