insect gas exchange

what are spiracles?

pores on abdomen surface that allow gases to enter and leave

structure of system?

internal air-filled tubes - trachea open to the outside via spiracles
trachea branch into smaller tubes - tracheoles that extend throughout body permeable for gas exchange

role of trachioles?

deliver oxygen directly to cells

how does gas exchange take place?

• oxygen from air enters via spiracles and passed into trachea

• trachea branches tracheoles, which extend directly to individual cells

• oxygen diffuses into cells down conc. gradient

• carbon dioxide diffuses out of cells via its own diffusion gradient, into tracheoles

how is the conc. gradient for gas exchange created?

cells respire and use oxygen, and produce carbon dioxide
conc. gradient formed as oxygen conc. is greater in tracheoles than in cells

adaptations for maximum gas exchange?

• lots of tracheoles; large SA

• tracheoles have thin walls; short diffusion pathway

• abdominal movements

• tracheoles directly reach individual cells; short diffusion pathway

• fluid in tracheole ends drawn into tissues by osmosis during exercise: fluid removed, air fills trachea so rate of diffusion increases as rate is faster in air

how do abdominal movement allow for maximum gas exchange?

create pressure changes in body which help force air in and out of the trachea, maintaining a steep conc. gradient

gas exchange during flight?

• high metabolic rate during flight, so oxygen demand increases

• abdominal movements maintain a steep conc. gradient

• low oxygen so anaerobic respiration

• produces lactic acid, decreasing WP

• water in tracheoles moves into cells by osmosis, leaving more air, increasing rate of gas diffusion

• reducing O2 diffusion pathway, making diffusion more efficient when O2 is limited

how do spiracles reduce water loss?

• close to prevent evaporation

• only open when gas exchange is needed

• some have hairs or valves around spiracles which trap moist air and reduce water potential gradient, limiting evaporation

how do insects reduce water loss?

• small SA to volume ratio where water can evaporate from

• waterproof exoskeleton

• spiracles open and close

how do insects compromise efficient gas exchange and reducing water loss?

• thick waxy cuticle → increases diffusion pathway, reducing evaporation

• spiracles open for gas exchange, close to prevent water loss

• hairs around spiracles → trap water vapour and decrease WP to prevent evaporation