gas exchange in insects

Question 1

describe the process of gas exchange in insects

Answer 1

insects have a system of pipes called the tracheal system that connects the air outside the animal to the tissues of the body that require the oxygen

the opening of the tracheae to the air is through tiny holes on the insect’s surface called spiracles

the spiracles have valves so that they can close to reduce water loss via evaporation

each spiracle leads into tubes called tracheae, held open by spiral bands of cuticle

a trachea branches repeatedly to form finer and finer tubes called tracheoles. the numerous tracheoles increase the surface area over which gas exchange takes place.

oxygen diffuses from the air, through the spiracles along the trachea and tracheoles to the cells

the tracheoles are thin, providing a short diffusion distance and penetrate all body tissues

the oxygen then diffuses into the cells through the cell membrane of the tracheole. this is the gas exchange surface.

carbon dioxide leaves the insect’s cells and travels to the atmosphere by the reverse pathway.

Question 2

in what three ways do respiratory gases move in and out of the tracheal system?

Answer 2

1. down a diffusion gradient
2. mass transport : the contraction of muscles (abdominal pumping) in insects can squeeze the tracheae enabling mass movements of air in and out, further speeding up the exchange of respiratory gases
3. the ends of the tracheoles are filled with water. during periods of major activity, the muscle cells around the tracheoles respire and carry out some anaerobic respiration. this produces lactate, which is soluble and lowers the water potential of the muscle cells. water therefore moves into the cells from the tracheoles by osmosis. the water in the ends of the tracheoles decreases in volume and in doing so draws air further into them. this means the final diffusion pathway is in a gas rather than a liquid phase, and therefore diffusion is more rapid. this increases the rate at which air is moved in the tracheoles but leads to greater water evaporation.