Gas exchange in insects.

What are insects covered in

Protective exoskeleton made of chitin, gases such as oxygen and carbon dioxide cannot easily pass through exoskeleton, so on surface of exoskeleton are small openings called spiracles.

What do spiracles do

They allow gases such as oxygen and carbon dioxide to diffuse into the body of the insect.

Where do spiracles lead

Into a network of tubes called tracheae, they are relatively wide tubes with diameter of around 1mm, they extend down and along insects body

Walls of tracheae reinforced with spirals of chitin, it prevents the tracheae from collapsing

What are tracheoles

Extend from tracheae, they are fine tubes

Diameter of 1 nanometre or less

Each tracheole is a single cell that has extended to form a hollow tube, a huge number of tracheoles extend down in between the cells of the insects body.

Large number of tracheoles provides large surface area for gas exchange, allows insects to maintain a rapid rate of aerobic respiratiob

What is tracheal fluid

Ends of tracheoles filled with tracheal fluid

During intense activity , cells around tracheoles undergo anaerobic respiration, this produces lactic acid, lowering water potential of cells

Causes water in the tracheal fluid to move into cells

How is gas exchange passive in insects

Oxygen diffuses down its concentration gradient from high conc in external air, into tracheoles where concentration is lower

Carbon dioxide diffuses down its concentration gradient from relatively high concentration in the tracheoles out to the external air. Rate of diffusion decreases with distance, so insects tend to be small

How do insects reduce water loss

By closing spiracles